Patent Description:
Some features and functionalities have become available to many mobile devices that enable the mobile devices to be more useful, such as by displaying information (e.g., notifications, date and time, etc.) without requiring the user to press a button to turn on the display. A disadvantage of these features and functionalities is the additional power required for operation. Some systems can be "aware" of when the user is near the mobile device, such as by using a camera and processing image or video data to detect the user. Then, the display is turned on to present information based on that detection. However, the power consumed by continuously operating the camera and processing the image or video data may not be, in some cases, substantially less than simply leaving the display on. Accordingly, current power-saving techniques are inefficient for some mobile devices. Cited document <CIT> discloses a radar sub-system configured to be installed in a portable electronic device, having different power modes for different functionalities: a low power mode for simple detection, and higher power modes for object tracking and identification of objects and gestures.

<CIT> discloses utilizing proximity detection capabilities of a mobile device to determine, upon wakeup, if a user is within a detectable distance of the device to provide possible gesture input. When a positive detection comes in, the device may use the light intensity (e.g., brightness level) measuring capabilities to further determine whether the user is attempting to engage the device to provide gesture input or if the device was unintentionally engaged. Once determinations are made that a user is waiting to engage the gesture recognition capabilities of the mobile device, it may coincidentally notify the user (e.g., using LED notification) that the device is ready to accept gesture input from the user.

<CIT> discloses a mobile device having one or more display screens which utilizes a plurality of different states to determine which illumination and animation power management processes to utilize in order to optimize power consumption.

The proposed solution relates to a user device of claim <NUM> and a method of claim <NUM>. In this context, this document describes techniques and systems that enable a mobile device-based radar system for applying different power modes to a multi-mode interface. The techniques and systems use a radar field to enable a mobile device to accurately determine the presence or absence of a user near the mobile device and further determine movements of the user to implicitly interact, or communicate, with the mobile device. Using these techniques, the mobile device can account for the user's nonverbal communication cues to determine and maintain an awareness of the user in its environment, and respond to indirect interactions by the user to educate the user that the mobile device is aware of the user and the user's movements with respect to the mobile device. In addition, the mobile device can apply various power states to components of the mobile device to reduce power consumption depending on the level of interaction by the user with the mobile device.

For example, different power states (e.g., radar-power states) are applied to the radar system and corresponding power modes are applied to the multi-mode interface. The different radar-power states may be applied only in response to the level of the user's indirect (implicit) interaction with the mobile device in order to reduce power consumption while at the same time providing a system that is continuously "aware of' and responsive to the user's interactions with the mobile device. Responding to the user's indirect interactions can include providing visual feedback, using different power modes of the multi-mode interface, on a display of the mobile device based on the user's movements relative to the mobile device. The multi-mode interface operates and is provided as part of the mobile device's digital environment (e.g., the multi-mode interface may be considered as a "canvas" for the operating system of the mobile device), separate and independent of an application program executed by the mobile device.

This summary is provided to introduce simplified concepts concerning a mobile device-based radar system for applying different power modes to a multi-mode interface, which is further described below in the Detailed Description and Drawings. This summary is not intended to identify essential features of the claimed subject matter, nor is it intended for use in determining the scope of the claimed subject matter.

The details of one or more aspects of a mobile device-based radar system for applying different power modes to a multi-mode interface are described in this document with reference to the following drawings. The same numbers are used throughout the drawings to reference like features and components:.

This document describes techniques and systems that enable a mobile device-based radar system for applying different power modes to a multi-mode interface. By applying different power modes to the multi-mode interface, the mobile device-based radar system provides visual feedback, using the multi-mode interface, in response to implicit interactions by the user with the mobile device to reduce power consumption of the mobile device while educating the user that the mobile device is aware of the user's movements and can respond in subtle and interesting ways. Implicit interactions, or communications, include a user's presence, spatial relations, and hand movements around the mobile device. In particular, the implicit interactions by the user with the mobile device are movements of the user near the mobile device that are not intended to initiate or perform a function on the device, but that can nevertheless be harbingers of change in the user's state of usage with respect to the device. Accordingly, implicit interactions are not considered explicit or direct user input but are instead actions by the user that indirectly provide input to the mobile device. Put another way, implicit interactions include user actions near the mobile device that are not intended to provide direct input but which the mobile device can use to determine, or interpret as, an implied or indirect input. Example implicit interactions include a user entering an area (e.g., radar field) having a particular radius around the mobile device, a user's hand reaching toward (or away from) the mobile device, while in a dormant or other lower-power state, within a particular threshold distance to pick it up and use it, a user looking toward the mobile device, a user moving their head toward the mobile device within a specified distance such as to look more closely at the mobile device, a user nodding or shaking their head while facing the mobile device, a user exiting the radar field, and so forth. In contrast to implicit interactions, explicit user inputs may include touch input to a touchscreen of the mobile device, actuation of a button on the mobile device, a gesture such as a screen swipe, screen tap, or screen double tap, or reaching toward or making an air gesture such as a wave over the mobile device while already active or in a higher-power state, etc. so as to directly interact with the mobile device, or an application program or user-interface (UI) element of the mobile device, in a way that is intended by the user to initiate a particular function.

The described techniques and systems employ a radar system to provide a rich ambient multi-mode interface experience that enables limited functionality based on a power mode, of the multi-mode interface, corresponding to a user's implicit interactions with the mobile device. Rather than reacting only to explicit user input, these techniques provide feedback to the user to indicate that the device is aware of and is detecting the user's movements and can react in interesting ways. The user's implicit interaction may be discerned by determining an unauthenticated user's movements relative to the device (e.g., when the device is in a locked state).

The multi-mode interface includes several power modes including, for example, a dormant mode, an ambient mode, an alert mode, and an active mode. Varying levels of power are provided to, or consumed by, a display device of the mobile device based on which power mode of the multi-mode interface is currently being executed at least because of specific functionalities that are enabled by each power mode.

In an example, when the radar system is in a lower-power mode (e.g., idle mode), the mobile device can also be in a lower-power state by turning off or otherwise reducing the power consumption of various functions such as a display device, a touchscreen, a microphone, a voice assistant, and so forth. At the same time, the multi-mode interface may be in the dormant mode, such that the interface is in a dormant state and provides a black display e.g., a power-off display or power-on display using black pixels. In some cases, the display device is considered to be in an "OFF" state when the multi-mode interface is in the dormant mode such that the display device is turned off and no power is provided to the display device to illuminate pixels. In this way, the black display can include an electronic ink display that uses other ink colors (e.g., white) in addition to black ink. The dormant mode may be applied to the multi-mode interface when the user is not near the mobile device (e.g., user is not detected within a specified distance of the mobile device) or when the mobile device is placed in the user's pocket, purse, or bag where the device detects that it is within a dark location and the user is not interacting (implicitly or explicitly) with the mobile device.

When the radar system detects the user in the area, the user device autonomously transitions the radar system from an idle power mode to a low-power attention mode and correspondingly transitions the multi-mode interface from the dormant mode to the ambient mode. Here, the user device is aware of the user's presence within a specified distance of the device (e.g., within a radar field of the radar system). The device operates in the lower-power state and the display screen is set to a low luminosity to reduce power consumption based on the level of user interaction with the user device. Because the user is simply present, the user's interaction is low, but the user device can provide a low-luminosity display to indicate that the user device detects the user's presence and is monitoring for additional interactions. As described herein, luminosity refers to the perceived brightness of an object by a human. Modifying the luminosity may include modifying luminance (e.g., brightness), contrast, and/or opaqueness. A low-luminosity may refer to a luminosity level that is less than a predefined threshold level, such as approximately <NUM>%, <NUM>%, <NUM>%, <NUM>%, and so on. This predefined threshold may be set by a manufacturer or defined by a setting selected by the user. A high-luminosity may refer to a luminosity level that is greater than a predefined threshold level, e.g., approximately <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%. Any suitable number of luminosity levels can be implemented, such as three (e.g., low, medium, high), four, five, or more, to correlate with the number of modes of the multi-mode interface.

In some cases, one or more user-interface elements (e.g., a clock, a battery-charge level indicator, a home button, a lock button, etc.) are displayed on the display screen with low luminosity, such as low brightness. The display screen can also display an image with low luminosity and color saturation, such as a faded and/or dim, monochrome (e.g., greyscale) version of the image. Low-color saturation is not, however, limited to monochrome. Rather, the low-color saturation may include one or more colors with darkened tones or shades such that the perceived colorfulness of the display is muted.

In one aspect, when transitioning from the dormant mode to the ambient mode, additional power is provided to the multi-mode interface to reveal (e.g., fade in) the image for a specified duration of time to greet the user with moderate to high luminosity. In this way, the display informs the user that the device is aware of the user's presence and is prepared to respond to the user's movements. After the duration of time expires, the power may be adjusted to decrease the luminosity such that the image fades into a less prominent state. For example, power consumption may be reduced and the display screen may be darkened to hide the image or provide a dim, desaturated version of the image. In some implementations, the power consumption is further reduced by darkening and/or desaturating one or more of the user-interface elements. In the ambient mode, the device is periodically responsive to the user's movements (e.g., uses a low sample rate for detecting the user's movements). A low sample rate allows the mobile device to maintain low power-consumption.

The radar system can detect threshold movement by an object, such as the user's hand reaching toward the device, within a specified distance of the device (e.g., approximately <NUM> meters, <NUM> meters, <NUM> meters, <NUM> meters, etc.). When the radar system detects this threshold movement, the interaction manager can autonomously transition the multi-mode interface from the ambient mode to the alert mode. In the alert mode, the power provided to the multi-mode interface is dynamically adjustable to increase the luminosity of at least the image as the user reaches toward the device. For example, the luminosity is adjusted in proportion to an amount and/or rate of decrease in the distance between the user's hand and the device such that at least the image progressively becomes more visible as the user's hand approaches the device. In some instances, one or more shapes or objects may come out of the background and/or in from the sides of the display device, progressively growing in size and becoming more visible as the user's hand approaches the device. In aspects, the shapes or objects may move onscreen as the user's hand moves toward the device, such as toward or away from the user's hand, or toward or away from a specified onscreen-location. Another example includes the display screen transitioning from dark or low luminosity, with one or more UI elements displayed in a light color (e.g., white, yellow, orange, etc.), to high brightness with the one or more UI elements displayed in a dark color (e.g., black, brown, navy blue, etc.).

When an authentication system (e.g., radar-based authentication, facial recognition authentication, fingerprint recognition authentication, and so forth) of the mobile device recognizes the user as an authorized user, the interaction manager transitions the multi-mode interface to the active mode. The active mode is a fully operational state of the device and provides full rights to an authenticated user. This is in contrast to the dormant, ambient, and alert modes, which each provide less-than-full rights to the user. In the active mode, the device operates in a higher-power (or active) state in which the user has full access to the device. When transitioning from the alert mode to the active mode (e.g., when the device unlocks based on user recognition and authentication), the device provides additional power to the multi-mode interface to increase the color saturation of at least the displayed image. In this way, color flows into the image to provide visual feedback to the user to indicate that the user is recognized and authenticated and the device is unlocked. In some aspects, the luminosity can be further increased along with the increase in color saturation until reaching an appropriate level of luminosity, such as a preset luminosity level associated with operation of the device in an unlocked state.

Some conventional mobile devices may use cameras or proximity sensors (e.g., capacitive sensors) to determine the location of the user and adjust various functions of the mobile device based on the proximity of the user. For example, the mobile device may provide additional privacy or aesthetic value by turning off a display unless the user is within a predetermined distance. The conventional mobile device, however, typically cannot provide a rich ambient experience to a user that can educate the user that the device is aware of the user's movements and can react in interesting ways, particularly when the user device is in a locked state.

Further, power consumption of the radar system and the mobile device itself can be substantially less than some conventional techniques that may use an always-on camera (or other sensors or combinations of sensors) to control some display features. Less power is consumed when the user is only implicitly or indirectly interacting with the user device, and additional power is provided to the radar system and the multi-mode interface only when the level of indirect user interaction increases. Further, the power consumption is reduced when the level of indirect user interaction decreases. These are but a few examples of how the described techniques and devices may be used to enable a low-power mobile device-based radar system for applying different power modes to a multi-mode interface. Other examples and implementations of which are described throughout this document. The document now turns to an example operating environment, after which example devices, methods, and systems are described.

<FIG> illustrates an example environment <NUM> in which techniques enabling a mobile device-based radar system for applying different power modes to a multi-mode interface can be implemented. The example environment <NUM> includes a user device <NUM> (e.g., electronic device), which includes, or is associated with, a radar system <NUM>, a persistent radar-based interaction manager <NUM> (interaction manager <NUM>), and, optionally, one or more non-radar sensors <NUM> (non-radar sensor <NUM>). The non-radar sensor <NUM> can be any of a variety of devices, such as an audio sensor (e.g., a microphone), a touch-input sensor (e.g., a touchscreen), or an image-capture device (e.g., a camera or video-camera).

In the example environment <NUM>, the radar system <NUM> provides a radar field <NUM> by transmitting one or more radar signals or waveforms as described below with reference to <FIG>. The radar field <NUM> is a volume of space from which the radar system <NUM> can detect reflections of the radar signals and waveforms (e.g., radar signals and waveforms reflected from objects in the volume of space). The radar system <NUM> also enables the user device <NUM>, or another electronic device, to sense and analyze reflections from an object (e.g., user <NUM>) in the radar field <NUM>. Some implementations of the radar system <NUM> are particularly advantageous as applied in the context of smartphones, such as the user device <NUM>, for which there is a convergence of issues such as a need for low power, a need for processing efficiency, limitations in a spacing and layout of antenna elements, and other issues, and are even further advantageous in the particular context of smartphones for which radar detection of fine hand air gestures is desired. Although the embodiments are particularly advantageous in the described context of the smartphone for which fine radar-detected hand air gestures is required, it is to be appreciated that the applicability of the features and advantages of the present invention is not necessarily so limited, and other embodiments involving other types of electronic devices may also be within the scope of the present teachings.

The object may be any of a variety of objects from which the radar system <NUM> can sense and analyze radar reflections, such as wood, plastic, metal, fabric, a human body, or human body parts (e.g., a foot, hand, or finger of a user of the user device <NUM>). As shown in <FIG>, the object is a user (e.g., user <NUM>) of the user device <NUM>. Based on the analysis of the reflections, the radar system <NUM> can provide radar data that includes various types of information associated with the radar field <NUM> and the reflections from the user <NUM>, as described with reference to <FIG> (e.g., the radar system <NUM> can pass the radar data to other entities, such as the interaction manager <NUM>).

It should be noted that the radar data may be continuously or periodically provided over time, based on the sensed and analyzed reflections from the user <NUM> in the radar field <NUM>. A position of the user <NUM> can change over time (e.g., the user <NUM> may move within the radar field <NUM>) and the radar data can thus vary over time corresponding to the changed positions, reflections, and analyses. Because the radar data may vary over time, the radar system <NUM> may provide radar data that includes one or more subsets of radar data that correspond to different periods of time. For example, the radar system <NUM> may provide a first subset of the radar data corresponding to a first time-period, a second subset of the radar data corresponding to a second time-period, and so forth.

The interaction manager <NUM> can be used to interact with or control various components of the user device <NUM> (e.g., modules, managers, systems, or interfaces). For instance, the interaction manager <NUM> can interact with, or implement, a multi-mode interface <NUM>. The interaction manager <NUM> can maintain the multi-mode interface <NUM> in a particular mode or cause the multi-mode interface <NUM> to change modes, based on radar data obtained from the radar system <NUM>. These modes are described in further detail below with respect to <FIG>.

The interaction manager <NUM> can be used to interact with or control various components of the user device <NUM> (e.g., modules, managers, systems, or interfaces). For example, the interaction manager <NUM> can be used to maintain the radar system <NUM> in an idle mode. The idle mode is a persistent lower-power radar mode that allows the radar system <NUM> to scan an environment external to the user device <NUM> and determine a presence of the user <NUM>. The term "persistent," with reference to the interaction manager <NUM>, and to the idle mode of the radar system <NUM>, means that no user interaction is required to maintain the radar system <NUM> in the idle mode or to activate the interaction manager <NUM>. In some implementations, the "persistent" state may be paused or turned off (e.g., by the user <NUM>). In other implementations, the "persistent" state may be scheduled or otherwise managed in accordance with one or more parameters of the user device <NUM> (or other electronic device). For example, the user <NUM> may schedule the "persistent" state such that it is only operational during daylight hours, even though the user device <NUM> is on both at night and during the day. In another example, the user <NUM> may coordinate the "persistent" state with a power-saving mode of the user device <NUM>.

In the idle mode, the interaction manager <NUM> can determine the presence of the user <NUM> without verbal, touch, or other input by the user. For example, while in the idle mode, the interaction manager <NUM> may use one or more subsets of the radar data (as described herein), provided by the radar system <NUM>, to determine the presence of the user <NUM> or of other objects that may be within a range of the radar field <NUM> of the user device <NUM>. In this way, the interaction manager <NUM> can provide seamless power management without requiring explicit user input.

In some implementations, the idle mode requires no more than approximately <NUM> milliwatts (mW) of power. In other implementations, the idle mode may require a different amount of power, such as approximately two mW or approximately eight mW. Further, when the interaction manager <NUM> is maintaining the radar system <NUM> in the idle mode, the interaction manager <NUM> may also maintain the user device <NUM> in a lower-power state (e.g., a sleep mode or other power-saving mode). In this way, by determining whether the user <NUM> (or another person) is near the user device <NUM>, the interaction manager can help preserve battery power by reducing power consumption when no user is near the user device <NUM>.

The radar field <NUM> is an area around the radar system <NUM> within which the interaction manager <NUM> can accurately determine the presence of the user <NUM>. The radar field <NUM> may take any of a variety of shapes and forms. For example, radar field <NUM> may have a shape as described with reference to <FIG> and <FIG>. In other cases, the radar field <NUM> may take a shape such as a radius extending from the radar system <NUM>, a volume around the radar system <NUM> (e.g., a sphere, a hemisphere, a partial sphere, a beam, or a cone), or a non-uniform shape (e.g., to accommodate interference from obstructions in the radar field <NUM>). The radar field <NUM> may extend any of a variety of distances from the radar system <NUM> such as three, seven, ten, or fourteen feet (or one, two, three, or four meters). The radar field <NUM> may be predefined, user-selectable, or determined via another method (e.g., based on power requirements, remaining battery life, or another factor). In some implementations, when the interaction manager <NUM> determines the presence of the user <NUM> (or another object) within the radar field <NUM>, the interaction manager <NUM> can cause the radar system <NUM> to exit the idle mode and enter an interaction mode, which is described in detail below.

Optionally, or in other implementations, when the interaction manager <NUM> determines the presence of the user <NUM> (or another object) within the radar field <NUM>, the interaction manager <NUM> can cause the radar system <NUM> to enter an attention mode. The attention mode is a radar mode that allows the radar system <NUM> to provide other information about objects within the radar field <NUM>. For example, while in the attention mode, the radar system <NUM> can provide other radar data (including one or more other subsets of the radar data, as described herein) that can be used to determine an implicit interaction by the user <NUM> with the user device, such as the user <NUM> reaching a hand toward the user device <NUM>.

In some implementations, the attention mode requires no more than approximately <NUM> mW of power. In other implementations, the attention mode may require a different amount of power, such as between approximately <NUM> mW and approximately <NUM> mW or between approximately <NUM> mW and approximately <NUM> mW. When the interaction manager <NUM> is maintaining the radar system <NUM> in the attention mode, the interaction manager <NUM> may also maintain the user device <NUM> in the lower-power state that may be used with the idle mode, or the interaction manager <NUM> may cause the user device <NUM> to exit the lower-power state and enter another state (e.g., a wake mode, an active mode, and so forth).

The interaction manager <NUM> (or another module or entity) can use the radar data to determine implicit interactions by the user <NUM> with the user device <NUM>. The implicit interactions level can be determined from a variety of information about the user <NUM> (within the radar field <NUM>) that can be determined based on the other radar data. The interaction manager <NUM> can determine the implicit interaction by the user <NUM> without verbal, touch, or other input by the user. For example, the interaction manager <NUM> may use the other radar data, or one or more other subsets of the other radar data, to determine a body position or posture of the user <NUM> in relation to the user device <NUM>.

The determination of the body position and posture of the user <NUM> may include determining one or more of a variety of different nonverbal body language cues, body positions, or body postures. The cues, positions and postures may include an absolute position or distance of the user <NUM> with reference to the user device <NUM>, a change in the position or distance of the user <NUM> with reference to the user device <NUM>.

(e.g., whether the user <NUM> (or the user's hand or object held by the user <NUM>) is moving closer to or farther from the user device <NUM>), the velocity of the user <NUM> (or hand or object) when moving toward or away from the user device <NUM>, whether the user <NUM> turns toward or away from the user device <NUM>, whether the user <NUM> leans toward, waves toward, reaches for, or points at the user device <NUM>, and so forth.

In some implementations, the interaction mode requires no more than approximately <NUM> mW of power. In other implementations, the interaction mode may require a different amount of power, such as approximately <NUM> mW or approximately <NUM> mW. Further, when the interaction manager <NUM> maintains the radar system <NUM> in the interaction mode, while the user <NUM> interacts with the user device <NUM>, the interaction manager <NUM> may also maintain the user device <NUM> in an appropriate power state (e.g., a full-power state, the wake mode or active mode as described with reference to the attention mode, the sleep state as described with reference to the idle mode, or another power state). In this way, by determining implicit interactions by the user <NUM> (or another person) with the user device <NUM>, the interaction manager can help preserve battery power by inducing an appropriate radar-power state for the radar system <NUM>, and optionally for the user device <NUM>, that is appropriate to the level of interaction by the user <NUM>.

The power consumed by the radar system <NUM> in the idle mode, the attention mode, and the interaction mode can be adjusted using various techniques. For example, the radar system <NUM> can reduce power consumption by collecting radar data at different duty cycles (e.g., lower frequencies may use less power and higher frequencies may use more power), turning various components off when the components are not active, or adjusting a power amplification level. Additional details regarding power management of the radar system <NUM> (and the user device <NUM>) are described with reference to <FIG>.

The user device <NUM> can also include a display device, such as display <NUM>. The display <NUM> can include any suitable display device, such as a touchscreen, a liquid crystal display (LCD), thin film transistor (TFT) LCD, an in-place switching (IPS) LCD, a capacitive touchscreen display, an organic light emitting diode (OLED) display, an active-matrix organic light-emitting diode (AMOLED) display, super AMOLED display, and so forth. The display <NUM> is used to display the multi-mode interface <NUM> in any of its various modes.

The radar-based interaction manager <NUM> can determine movements made by the user or the user's hand based on radar data provided by the radar system <NUM>. The interaction manager <NUM> then processes the movements in a way that enables the user to implicitly interact with the user device <NUM> via the movements. For example, as described with reference to <FIG>, the radar system can use the radar field to sense and analyze reflections from objects in the radar field in ways that enable high resolution and accuracy for movement recognition of the user.

Some implementations of the radar system <NUM> are particularly advantageous as applied in the context of smart devices (e.g., user device <NUM>), for which there is a convergence of issues. This can include a need for limitations in a spacing and layout of the radar system <NUM> and low power. Exemplary overall lateral dimensions of the smart device can be, for example, approximately eight centimeters by approximately fifteen centimeters. Exemplary footprints of the radar system can be even more limited, such as approximately four millimeters by six millimeters with antennas included. Exemplary power consumption of the radar system <NUM> may be on the order of a few milliwatts to tens of milliwatts (e.g., between approximately two milliwatts and twenty milliwatts). The requirement of such a limited footprint and power consumption for the radar system <NUM> enables the smart device to include other desirable features in a space-limited package (e.g., a camera sensor, a fingerprint sensor, a display, and so forth).

Exemplary overall lateral dimensions of the smart device can be, for example, approximately eight centimeters by approximately fifteen centimeters. Exemplary footprints of the radar system <NUM> can be even more limited, such as approximately four millimeters by six millimeters with antennas included. Exemplary power consumption of the radar system <NUM> may be on the order of a few milliwatts to several milliwatts (e.g., between approximately two milliwatts and twenty milliwatts). The requirement of such a limited footprint and power consumption for the radar system <NUM>, enables the smart device to include other desirable features in such a space-limited package (e.g., a camera sensor, a fingerprint sensor, a display, and so forth). The smart device and the radar system <NUM> are further described with respect to <FIG>.

In more detail, consider <FIG>, which illustrates an example implementation <NUM> of the user device <NUM> (including the radar system <NUM>, the interaction manager <NUM>, and the non-radar sensor <NUM>) that can implement a mobile device-based radar system for applying different power modes to a multi-mode interface. The user device <NUM> of <FIG> is illustrated with a variety of example devices, including a user device <NUM>-<NUM>, a tablet <NUM>-<NUM>, a laptop <NUM>-<NUM>, a desktop computer <NUM>-<NUM>, a computing watch <NUM>-<NUM>, computing spectacles <NUM>-<NUM>, a gaming system <NUM>-<NUM>, a home-automation and control system <NUM>-<NUM>, and a microwave <NUM>-<NUM>. The user device <NUM> can also include other devices, such as televisions, entertainment systems, audio systems, automobiles, drones, track pads, drawing pads, netbooks, e-readers, home security systems, and other home appliances. Note that the user device <NUM> can be wearable, non-wearable but mobile, or relatively immobile (e.g., desktops and appliances).

Exemplary overall lateral dimensions of the user device <NUM> can be, for example, approximately eight centimeters by approximately fifteen centimeters. Exemplary footprints of the radar system <NUM> can be even more limited, such as approximately four millimeters by six millimeters with antennas included. The requirement of such a limited footprint for the radar system <NUM>, which is needed to accommodate the many other desirable features of the user device <NUM> in such a space-limited package (e.g., a fingerprint sensor, the non-radar sensor <NUM>, and so forth) combined with power and processing limitations, can lead to compromises in the accuracy and efficacy of radar gesture detection, at least some of which can be overcome in view of the teachings herein.

The user device <NUM> also includes one or more computer processors <NUM> and one or more computer-readable media <NUM>, which includes memory media and storage media. Applications and/or an operating system (not shown) implemented as computer-readable instructions on the computer-readable media <NUM> can be executed by the computer processors <NUM> to provide some or all of the functionalities described herein. The computer-readable media <NUM> also includes a radar-based application <NUM>, which uses radar data generated by the radar system <NUM> to perform a function, such as detect a presence of a user or track the user's air gestures for touch-free control.

The user device <NUM> may also include a network interface <NUM>. The user device <NUM> can use the network interface <NUM> for communicating data over wired, wireless, or optical networks. By way of example and not limitation, the network interface <NUM> may communicate data over a local-area-network (LAN), a wireless local-area-network (WLAN), a personal-area-network (PAN), a wide-area-network (WAN), an intranet, the Internet, a peer-to-peer network, point-to-point network, or a mesh network.

In aspects, the radar system <NUM> is implemented at least partially in hardware. Various implementations of the radar system <NUM> can include a System-on-Chip (SoC), one or more Integrated Circuits (ICs), a processor with embedded processor instructions or configured to access processor instructions stored in memory, hardware with embedded firmware, a printed circuit board with various hardware components, or any combination thereof. The radar system <NUM> operates as a monostatic radar by transmitting and receiving its own radar signals. In some implementations, the radar system <NUM> may also cooperate with other radar systems <NUM> that are within an external environment to implement a bistatic radar, a multistatic radar, or a network radar. Constraints or limitations of the user device <NUM>, however, may impact a design of the radar system <NUM>. The user device <NUM>, for example, may have limited power available to operate the radar, limited computational capability, size constraints, layout restrictions, an exterior housing that attenuates or distorts radar signals, and so forth. The radar system <NUM> includes several features that enable advanced radar functionality and high performance to be realized in the presence of these constraints, as further described below with respect to <FIG>. Note that in <FIG>, the radar system <NUM> and the interaction manager <NUM> are illustrated as part of the user device <NUM>. In other implementations, either or both of the radar system <NUM> and the interaction manager <NUM> may be separate or remote from the user device <NUM>.

<FIG> illustrates an example transceiver <NUM> and processor <NUM>. The transceiver <NUM> includes multiple components that can be individually turned on or off via the power management module <NUM> in accordance with an operational state of the radar system <NUM>. The transceiver <NUM> is shown to include at least one of each of the following components: an active component <NUM>, a voltage-controlled oscillator (VCO) and voltage-controlled buffer <NUM>, a multiplexer <NUM>, an analog-to-digital converter (ADC) <NUM>, a phase lock loop (PLL) <NUM>, and a crystal oscillator <NUM>. If turned on, each of these components consume power, even if the radar system <NUM> is not actively using these components to transmit or receive radar signals. The active component <NUM>, for example, can include an amplifier or filter that is coupled to a supply voltage. The voltage-controlled oscillator <NUM> generates a frequency-modulated radar signal based on a control voltage that is provided by the phase lock loop <NUM>. The crystal oscillator <NUM> generates a reference signal for signal generation, frequency conversion (e.g., upconversion or downconversion), or timing operations within the radar system <NUM>. By turning these components on or off, the power management module <NUM> enables the radar system <NUM> to quickly switch between active and inactive operational states and conserve power during various inactive time periods. These inactive time periods may be on the order of microseconds (µs), milliseconds (ms), or seconds (s).

The processor <NUM> is shown to include multiple processors that consume different amounts of power, such as a low-power processor <NUM>-<NUM> and a high-power processor <NUM>-<NUM>. As an example, the low-power processor <NUM>-<NUM> can include a processor that is embedded within the radar system <NUM> and the high-power processor can include the computer processor <NUM> or some other processor that is external to the radar system <NUM>. The differences in power consumption can result from different amounts of available memory or computational ability. For instance, the low-power processor <NUM>-<NUM> may utilize less memory, perform fewer computations, or utilize simpler algorithms relative to the high-power processor <NUM>-<NUM>. Despite these limitations, the low-power processor <NUM>-<NUM> can process data for less complex radar-based applications <NUM>, such as proximity detection or motion detection. The high-power processor <NUM>-<NUM>, in contrast, may utilize a large amount of memory, perform a large amount of computations, or execute complex signal processing, tracking, or machine learning algorithms. The high-power processor <NUM>-<NUM> may process data for high-profile radar-based applications <NUM>, such as air gesture recognition, and provide accurate, high-resolution data through the resolution of angular ambiguities or distinguishing of multiple users <NUM>.

To conserve power, the power management module <NUM> can control whether the low-power processor <NUM>-<NUM> or the high-power processor <NUM>-<NUM> are used to process the radar data. In some cases, the low-power processor <NUM>-<NUM> can perform a portion of the analysis and pass data onto the high-power processor <NUM>-<NUM>. Example data may include a clutter map, raw or minimally processed radar data (e.g., in-phase and quadrature data or range-Doppler data), or digital beamforming data. The low-power processor <NUM>-<NUM> may also perform some low-level analysis to determine whether there is anything of interest in the environment for the high-power processor <NUM>-<NUM> to analyze. In this way, power can be conserved by limiting operation of the high-power processor <NUM>-<NUM> while utilizing the high-power processor <NUM>-<NUM> for situations in which high-fidelity or accurate radar data is requested by the radar-based application <NUM>. Other factors that can impact power consumption within the radar system <NUM> are further described with respect to <FIG>.

These and other capabilities and configurations, as well as ways in which entities of <FIG> act and interact, are set forth in greater detail below. These entities may be further divided, combined, and so on. The environment <NUM> of <FIG> and the detailed illustrations of FIG. <NUM> through FIG. <NUM> illustrate some of many possible environments and devices capable of employing the described techniques. <FIG> describe additional details and features of the radar system <NUM>. In <FIG>, the radar system <NUM> is described in the context of the user device <NUM>, but as noted above, the applicability of the features and advantages of the described systems and techniques are not necessarily so limited, and other embodiments involving other types of electronic devices may also be within the scope of the present teachings.

<FIG> illustrates an example implementation <NUM> of the radar system <NUM> that can be used to enable and control different power modes of a multi-mode interface. In the example <NUM>, the radar system <NUM> includes at least one of each of the following components: a communication interface <NUM>, an antenna array <NUM>, a transceiver <NUM>, a processor <NUM>, and a system media <NUM> (e.g., one or more computer-readable storage media). The processor <NUM> can be implemented as a digital signal processor, a controller, an application processor, another processor (e.g., the computer processor <NUM> of the user device <NUM>) or some combination thereof. The system media <NUM>, which may be included within, or be separate from, the computer-readable media <NUM> of the user device <NUM>, includes one or more of the following modules: an attenuation mitigator <NUM>, a digital beamformer <NUM>, an angle estimator <NUM>, or a power management module <NUM>. These modules can compensate for, or mitigate the effects of, integrating the radar system <NUM> within the user device <NUM>, thereby enabling the radar system <NUM> to recognize small or complex air gestures, distinguish between different orientations of the user, continuously monitor an external environment, or realize a target false-alarm rate. With these features, the radar system <NUM> can be implemented within a variety of different devices, such as the devices illustrated in <FIG>.

Using the communication interface <NUM>, the radar system <NUM> can provide radar data to the interaction manager <NUM>. The communication interface <NUM> may be a wireless or wired interface based on the radar system <NUM> being implemented separate from, or integrated within, the user device <NUM>. Depending on the application, the radar data may include raw or minimally processed data, in-phase and quadrature (I/Q) data, range-Doppler data, processed data including target location information (e.g., range, azimuth, elevation), clutter map data, and so forth. Generally, the radar data contains information that is usable by the interaction manager <NUM> for a mobile device-based radar system for applying different power modes to a multi-mode interface.

The antenna array <NUM> includes at least one transmitting antenna element (not shown) and at least two receiving antenna elements (as shown in <FIG>). In some cases, the antenna array <NUM> may include multiple transmitting antenna elements to implement a multiple-input multiple-output (MIMO) radar capable of transmitting multiple distinct waveforms at a time (e.g., a different waveform per transmitting antenna element). The use of multiple waveforms can increase a measurement accuracy of the radar system <NUM>. The receiving antenna elements can be positioned in a one-dimensional shape (e.g., a line) or a two-dimensional shape for implementations that include three or more receiving antenna elements. The one-dimensional shape enables the radar system <NUM> to measure one angular dimension (e.g., an azimuth or an elevation) while the two-dimensional shape enables two angular dimensions to be measured (e.g., both azimuth and elevation). Example two-dimensional arrangements of the receiving antenna elements are further described with respect to <FIG>.

<FIG> illustrates example arrangements <NUM> of receiving antenna elements <NUM>. If the antenna array <NUM> includes at least four receiving antenna elements <NUM>, for example, the receiving antenna elements <NUM> can be arranged in a rectangular arrangement <NUM>-<NUM> as depicted in the middle of <FIG>. Alternatively, a triangular arrangement <NUM>-<NUM> or an L-shape arrangement <NUM>-<NUM> may be used if the antenna array <NUM> includes at least three receiving antenna elements <NUM>.

Due to a size or layout constraint of the user device <NUM>, an element spacing between the receiving antenna elements <NUM> or a quantity of the receiving antenna elements <NUM> may not be ideal for the angles at which the radar system <NUM> is to monitor. In particular, the element spacing may cause angular ambiguities to be present that make it challenging for conventional radars to estimate an angular position of a target. Conventional radars may therefore limit a field of view (e.g., angles that are to be monitored) to avoid an ambiguous zone, which has the angular ambiguities, and thereby reduce false detections. For example, conventional radars may limit the field of view to angles between approximately -<NUM> degrees to <NUM> degrees to avoid angular ambiguities that occur using a wavelength of <NUM> millimeters (mm) and an element spacing of <NUM> (e.g., the element spacing being <NUM>% of the wavelength). Consequently, the conventional radar may be unable to detect targets that are beyond the <NUM>-degree limits of the field of view. In contrast, the radar system <NUM> includes the digital beamformer <NUM> and the angle estimator <NUM>, which resolve the angular ambiguities and enable the radar system <NUM> to monitor angles beyond the <NUM>-degree limit, such as angles between approximately -<NUM> degrees to <NUM> degrees, or up to approximately -<NUM> degrees and <NUM> degrees. These angular ranges can be applied across one or more directions (e.g., azimuth and/or elevation). Accordingly, the radar system <NUM> can realize low false-alarm rates for a variety of different antenna array designs, including element spacings that are less than, greater than, or equal to half a center wavelength of the radar signal.

Using the antenna array <NUM>, the radar system <NUM> can form beams that are steered or un-steered, wide or narrow, or shaped (e.g., as a hemisphere, cube, fan, cone, or cylinder). As an example, the one or more transmitting antenna elements (not shown) may have an un-steered omnidirectional radiation pattern or may be able to produce a wide beam, such as the wide transmit beam <NUM>. Either of these techniques enable the radar system <NUM> to illuminate a large volume of space. To achieve target angular accuracies and angular resolutions, however, the receiving antenna elements <NUM> and the digital beamformer <NUM> can be used to generate thousands of narrow and steered beams (e.g., <NUM> beams, <NUM> beams, or <NUM> beams), such as the narrow receive beam <NUM>. In this way, the radar system <NUM> can efficiently monitor the external environment and accurately determine arrival angles of reflections within the external environment.

Returning to <FIG>, the transceiver <NUM> includes circuitry and logic for transmitting and receiving radar signals via the antenna array <NUM>. Components of the transceiver <NUM> can include amplifiers, mixers, switches, analog-to-digital converters, filters, and so forth for conditioning the radar signals. The transceiver <NUM> can also include logic to perform in-phase/quadrature (I/Q) operations, such as modulation or demodulation. The transceiver <NUM> can be configured for continuous wave radar operations or pulsed radar operations. A variety of modulations can be used to produce the radar signals, including linear frequency modulations, triangular frequency modulations, stepped frequency modulations, or phase modulations.

The transceiver <NUM> can generate radar signals within a range of frequencies (e.g., a frequency spectrum), such as between <NUM> gigahertz (GHz) and <NUM>, between <NUM> and <NUM>, or between <NUM> and <NUM>. The frequency spectrum can be divided into multiple sub-spectra that have a similar bandwidth or different bandwidths. The bandwidths can be on the order of <NUM> megahertz (MHz), <NUM>, <NUM>, and so forth. As an example, different frequency sub-spectra may include frequencies between approximately <NUM> and <NUM>, <NUM> and <NUM>, or <NUM> and <NUM>. Multiple frequency sub-spectra that have a same bandwidth and may be contiguous or non-contiguous may also be chosen for coherence. The multiple frequency sub-spectra can be transmitted simultaneously or separated in time using a single radar signal or multiple radar signals. The contiguous frequency sub-spectra enable the radar signal to have a wider bandwidth while the non-contiguous frequency sub-spectra can further emphasize amplitude and phase differences that enable the angle estimator <NUM> to resolve angular ambiguities. The attenuation mitigator <NUM> or the angle estimator <NUM> may cause the transceiver <NUM> to utilize one or more frequency sub-spectra to improve performance of the radar system <NUM>, as further described with respect to <FIG> and <FIG>.

A power management module <NUM> enables the radar system <NUM> to conserve power internally or externally within the user device <NUM>. In some implementations, the power management module <NUM> communicates with the interaction manager <NUM> to conserve power within either or both of the radar system <NUM> or the user device <NUM>. Internally, for example, the power management module <NUM> can cause the radar system <NUM> to collect data using a predefined radar-power state or a specific duty cycle (e.g., a lower duty cycle uses a slower update rate and a higher duty cycle uses a faster update rate). In this case, the power management module <NUM> dynamically switches between different radar-power states such that response delay and power consumption are managed together based on the activity within the environment. In general, the power management module <NUM> determines when and how power can be conserved, and incrementally adjusts power consumption to enable the radar system <NUM> to operate within power limitations of the user device <NUM>. In some cases, the power management module <NUM> may monitor an amount of available power remaining and adjust operations of the radar system <NUM> accordingly. For example, if the remaining amount of power is low, the power management module <NUM> may continue operating in a lower-power mode instead of switching to a higher-power mode.

The low-power mode, for example, may use a low duty cycle on the order of a few hertz (e.g., approximately <NUM> or less than <NUM>), which reduces power consumption to a few milliwatts (mW) (e.g., between approximately <NUM> mW and <NUM> mW). The high-power mode, on the other hand, may use a high duty cycle on the order of tens of hertz (Hz) (e.g., approximately <NUM> or greater than <NUM>), which causes the radar system <NUM> to consume power on the order of several milliwatts (e.g., between approximately <NUM> mW and <NUM> mW). While the low-power mode can be used to monitor the external environment or detect an approaching user, the power management module <NUM> may switch to the high-power mode if the radar system <NUM> determines the user is starting to perform an air gesture. Different triggers may cause the power management module <NUM> to switch between the different radar-power states. Example triggers include motion or the lack of motion, appearance or disappearance of the user, the user moving into or out of a designated region (e.g., a region defined by range, azimuth, or elevation), a change in velocity of a motion associated with the user, or a change in reflected signal strength (e.g., due to changes in radar cross section). In general, the triggers that indicate a lower probability of the user interacting with the electronic device <NUM> or a preference to collect data using a longer response delay may cause a lower-power mode to be activated to conserve power.

The power management module <NUM> can also conserve power by turning off one or more components within the transceiver <NUM> (e.g., a voltage-controlled oscillator, a multiplexer, an analog-to-digital converter, a phase lock loop, or a crystal oscillator) during inactive time periods. These inactive time periods occur if the radar system <NUM> is not actively transmitting or receiving radar signals, which may be on the order of microseconds (µs), milliseconds (ms), or seconds (s). Further, the power management module <NUM> can modify transmission power of the radar signals by adjusting an amount of amplification provided by a signal amplifier. Additionally, the power management module <NUM> can control the use of different hardware components within the radar system <NUM> to conserve power. If the processor <NUM> comprises a lower-power processor and a higher-power processor (e.g., processors with different amounts of memory and computational capability), for example, the power management module <NUM> can switch between utilizing the lower-power processor for low-level analysis (e.g., implementing the idle mode, detecting motion, determining a location of a user, or monitoring the environment) and the higher-power processor for situations in which high-fidelity or accurate radar data is requested by the interaction manager <NUM> (e.g., for implementing the attention mode or the interaction mode, air gesture recognition or user orientation).

In addition to the internal power-saving techniques described above, the power management module <NUM> can also conserve power within the electronic device <NUM> by activating or deactivating other external components or sensors that are within the electronic device <NUM>. These external components may include speakers, a camera sensor, a global positioning system, a wireless communication transceiver, a display, a gyroscope, or an accelerometer. Because the radar system <NUM> can monitor the environment using a small amount of power, the power management module <NUM> can appropriately turn these external components on or off based on where the user is located or what the user is doing. In this way, the electronic device <NUM> can seamlessly respond to the user and conserve power without the use of automatic shut-off timers or the user physically touching or verbally controlling the electronic device <NUM>.

<FIG> illustrates additional details of an example implementation <NUM> of the radar system <NUM> within the user device <NUM>. In the example <NUM>, the antenna array <NUM> is positioned underneath an exterior housing of the user device <NUM>, such as a glass cover or an external case. Depending on its material properties, the exterior housing may act as an attenuator <NUM>, which attenuates or distorts radar signals that are transmitted and received by the radar system <NUM>. The attenuator <NUM> may include different types of glass or plastics, some of which may be found within display screens, exterior housings, or other components of the user device <NUM> and have a dielectric constant (e.g., relative permittivity) between approximately four and ten. Accordingly, the attenuator <NUM> is opaque or semi-transparent to a radar signal <NUM> and may cause a portion of a transmitted or received radar signal <NUM> to be reflected (as shown by a reflected portion <NUM>). For conventional radars, the attenuator <NUM> may decrease an effective range that can be monitored, prevent small targets from being detected, or reduce overall accuracy.

Assuming a transmit power of the radar system <NUM> is limited, and re-designing the exterior housing is not desirable, one or more attenuation-dependent properties of the radar signal <NUM> (e.g., a frequency sub-spectrum <NUM> or a steering angle <NUM>) or attenuation-dependent characteristics of the attenuator <NUM> (e.g., a distance <NUM> between the attenuator <NUM> and the radar system <NUM> or a thickness <NUM> of the attenuator <NUM>) are adjusted to mitigate the effects of the attenuator <NUM>. Some of these characteristics can be set during manufacturing or adjusted by the attenuation mitigator <NUM> during operation of the radar system <NUM>. The attenuation mitigator <NUM>, for example, can cause the transceiver <NUM> to transmit the radar signal <NUM> using the selected frequency sub-spectrum <NUM> or the steering angle <NUM>, cause a platform to move the radar system <NUM> closer or farther from the attenuator <NUM> to change the distance <NUM>, or prompt the user to apply another attenuator to increase the thickness <NUM> of the attenuator <NUM>.

Appropriate adjustments can be made by the attenuation mitigator <NUM> based on pre-determined characteristics of the attenuator <NUM> (e.g., characteristics stored in the computer-readable media <NUM> of the user device <NUM> or within the system media <NUM>) or by processing returns of the radar signal <NUM> to measure one or more characteristics of the attenuator <NUM>. Even if some of the attenuation-dependent characteristics are fixed or constrained, the attenuation mitigator <NUM> can take these limitations into account to balance each parameter and achieve a target radar performance. As a result, the attenuation mitigator <NUM> enables the radar system <NUM> to realize enhanced accuracy and larger effective ranges for detecting and tracking the user that is located on an opposite side of the attenuator <NUM>. These techniques provide alternatives to increasing transmit power, which increases power consumption of the radar system <NUM>, or changing material properties of the attenuator <NUM>, which can be difficult and expensive once a device is in production.

<FIG> illustrates an example scheme <NUM> implemented by the radar system <NUM>. Portions of the scheme <NUM> may be performed by the processor <NUM>, the computer processors <NUM>, or other hardware circuitry. The scheme <NUM> can be customized to support different types of electronic devices and radar-based applications (e.g., the interaction manager <NUM>), and also enables the radar system <NUM> to achieve target angular accuracies despite design constraints.

The transceiver <NUM> produces raw data <NUM> based on individual responses of the receiving antenna elements <NUM> to a received radar signal. The received radar signal may be associated with one or more frequency sub-spectra <NUM> that were selected by the angle estimator <NUM> to facilitate angular ambiguity resolution. The frequency sub-spectra <NUM>, for example, may be chosen to reduce a quantity of sidelobes or reduce an amplitude of the sidelobes (e.g., reduce the amplitude by <NUM> dB, <NUM> dB, or more). A quantity of frequency sub-spectra can be determined based on a target angular accuracy or computational limitations of the radar system <NUM>.

The raw data <NUM> contains digital information (e.g., in-phase and quadrature data) for a period of time, different wavenumbers, and multiple channels respectively associated with the receiving antenna elements <NUM>. A Fast-Fourier Transform (FFT) <NUM> is performed on the raw data <NUM> to generate pre-processed data <NUM>. The pre-processed data <NUM> includes digital information across the period of time, for different ranges (e.g., range bins), and for the multiple channels. A Doppler filtering process <NUM> is performed on the pre-processed data <NUM> to generate range-Doppler data <NUM>. The Doppler filtering process <NUM> may comprise another FFT that generates amplitude and phase information for multiple range bins, multiple Doppler frequencies, and for the multiple channels. The digital beamformer <NUM> produces beamforming data <NUM> based on the range-Doppler data <NUM>. The beamforming data <NUM> contains digital information for a set of azimuths and/or elevations, which represents the field of view for which different steering angles or beams are formed by the digital beamformer <NUM>. Although not depicted, the digital beamformer <NUM> may alternatively generate the beamforming data <NUM> based on the pre-processed data <NUM> and the Doppler filtering process <NUM> may generate the range-Doppler data <NUM> based on the beamforming data <NUM>. To reduce a quantity of computations, the digital beamformer <NUM> may process a portion of the range-Doppler data <NUM> or the pre-processed data <NUM> based on a range, time, or Doppler frequency interval of interest.

The digital beamformer <NUM> can be implemented using a single-look beamformer <NUM>, a multi-look interferometer <NUM>, or a multi-look beamformer <NUM>. In general, the single-look beamformer <NUM> can be used for deterministic objects (e.g., point-source targets having a single phase center). For non-deterministic targets (e.g., targets having multiple phase centers), the multi-look interferometer <NUM> or the multi-look beamformer <NUM> are used to improve accuracies relative to the single-look beamformer <NUM>. Humans are an example of a non-deterministic target and have multiple phase centers <NUM> that can change based on different aspect angles, as shown at <NUM>-<NUM> and <NUM>-<NUM>. Variations in the constructive or destructive interference generated by the multiple phase centers <NUM> can make it challenging for conventional radars to accurately determine angular positions. The multi-look interferometer <NUM> or the multi-look beamformer <NUM>, however, perform coherent averaging to increase an accuracy of the beamforming data <NUM>. The multi-look interferometer <NUM> coherently averages two channels to generate phase information that can be used to accurately determine the angular information. The multi-look beamformer <NUM>, on the other hand, can coherently average two or more channels using linear or non-linear beamformers, such as Fourier, Capon, multiple signal classification (MUSIC), or minimum variance distortion less response (MVDR). The increased accuracies provided via the multi-look beamformer <NUM> or the multi-look interferometer <NUM> enable the radar system <NUM> to recognize small air gestures or distinguish between multiple portions of the user.

The angle estimator <NUM> analyzes the beamforming data <NUM> to estimate one or more angular positions. The angle estimator <NUM> may utilize signal processing techniques, pattern matching techniques, or machine learning. The angle estimator <NUM> also resolves angular ambiguities that may result from a design of the radar system <NUM> or the field of view the radar system <NUM> monitors. An example angular ambiguity is shown within an amplitude plot <NUM> (e.g., amplitude response).

The amplitude plot <NUM> depicts amplitude differences that can occur for different angular positions of the target and for different steering angles <NUM>. A first amplitude response <NUM>-<NUM> (illustrated with a solid line) is shown for a target positioned at a first angular position <NUM>-<NUM>. Likewise, a second amplitude response <NUM>-<NUM> (illustrated with a dotted-line) is shown for the target positioned at a second angular position <NUM>-<NUM>. In this example, the differences are considered across angles between -<NUM> degrees and <NUM> degrees.

As shown in the amplitude plot <NUM>, an ambiguous zone exists for the two angular positions <NUM>-<NUM> and <NUM>-<NUM>. The first amplitude response <NUM>-<NUM> has a highest peak at the first angular position <NUM>-<NUM> and a lesser peak at the second angular position <NUM>-<NUM>. While the highest peak corresponds to the actual position of the target, the lesser peak causes the first angular position <NUM>-<NUM> to be ambiguous because it is within some threshold for which conventional radars may be unable to confidently determine whether the target is at the first angular position <NUM>-<NUM> or the second angular position <NUM>-<NUM>. In contrast, the second amplitude response <NUM>-<NUM> has a lesser peak at the second angular position <NUM>-<NUM> and a higher peak at the first angular position <NUM>-<NUM>. In this case, the lesser peak corresponds to the target's location.

While conventional radars may be limited to using a highest peak amplitude to determine the angular positions, the angle estimator <NUM> instead analyzes subtle differences in shapes of the amplitude responses <NUM>-<NUM> and <NUM>-<NUM>. Characteristics of the shapes can include, for example, roll-offs, peak or null widths, an angular location of the peaks or nulls, a height or depth of the peaks and nulls, shapes of sidelobes, symmetry within the amplitude response <NUM>-<NUM> or <NUM>-<NUM>, or the lack of symmetry within the amplitude response <NUM>-<NUM> or <NUM>-<NUM>. Similar shape characteristics can be analyzed in a phase response, which can provide additional information for resolving the angular ambiguity. The angle estimator <NUM> therefore maps the unique angular signature or pattern to an angular position.

The angle estimator <NUM> can include a suite of algorithms or tools that can be selected according to the type of user device <NUM> (e.g., computational capability or power constraints) or a target angular resolution for the interaction manager <NUM>. In some implementations, the angle estimator <NUM> can include a neural network <NUM>, a convolutional neural network (CNN) <NUM>, or a long short-term memory (LSTM) network <NUM>. The neural network <NUM> can have various depths or quantities of hidden layers (e.g., three hidden layers, five hidden layers, or ten hidden layers) and can also include different quantities of connections (e.g., the neural network <NUM> can comprise a fully-connected neural network or a partially-connected neural network). In some cases, the CNN <NUM> can be used to increase computational speed of the angle estimator <NUM>. The LSTM network <NUM> can be used to enable the angle estimator <NUM> to track the target. Using machine learning techniques, the angle estimator <NUM> employs non-linear functions to analyze the shape of the amplitude response <NUM>-<NUM> or <NUM>-<NUM> and generate angular probability data <NUM>, which indicates a likelihood that the user or a portion of the user is within an angular bin. The angle estimator <NUM> may provide the angular probability data <NUM> for a few angular bins, such as two angular bins to provide probabilities of a target being to the left or right of the user device <NUM>, or for thousands of angular bins (e.g., to provide the angular probability data <NUM> for a continuous angular measurement).

Based on the angular probability data <NUM>, a tracker module <NUM> produces angular position data <NUM>, which identifies an angular location of the target. The tracker module <NUM> may determine the angular location of the target based on the angular bin that has a highest probability in the angular probability data <NUM> or based on prediction information (e.g., previously-measured angular position information). The tracker module <NUM> may also keep track of one or more moving targets to enable the radar system <NUM> to confidently distinguish or identify the targets. Other data can also be used to determine the angular position, including range, Doppler, velocity, or acceleration. In some cases, the tracker module <NUM> can include an alpha-beta tracker, a Kalman filter, a multiple hypothesis tracker (MHT), and so forth.

A quantizer module <NUM> obtains the angular position data <NUM> and quantizes the data to produce quantized angular position data <NUM>. The quantization can be performed based on a target angular resolution for the interaction manager <NUM>. In some situations, fewer quantization levels can be used such that the quantized angular position data <NUM> indicates whether the target is to the right or to the left of the user device <NUM> or identifies a <NUM>-degree quadrant the target is located within. This may be sufficient for some radar-based applications, such as user proximity detection. In other situations, a larger number of quantization levels can be used such that the quantized angular position data <NUM> indicates an angular position of the target within an accuracy of a fraction of a degree, one degree, five degrees, and so forth. This resolution can be used for higher-resolution radar-based applications, such as air gesture recognition, or in implementations of the attention mode or the interaction mode as described herein. In some implementations, the digital beamformer <NUM>, the angle estimator <NUM>, the tracker module <NUM>, and the quantizer module <NUM> are together implemented in a single machine learning module.

<FIG> illustrates four example radar pipelines <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>. Each of the radar pipelines <NUM> perform radar operations associated with respective radar-power states <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>. The pre-presence pipeline <NUM>-<NUM>, for example, is employed if a presence of the user <NUM> is not known for certain. The pre-presence pipeline <NUM>-<NUM> can monitor the environment and determine whether the user device <NUM> moves or whether there is motion within the environment, which may indicate a presence of the user <NUM>. The presence pipeline <NUM>-<NUM> is used to confidently determine a presence of the user <NUM>. If the user <NUM> moves closer to the radar system <NUM> or performs some sort of motion that is advantageous to monitor using a higher duty cycle (e.g., fast update rate), the awareness pipeline <NUM>-<NUM> is activated. The awareness pipeline <NUM>-<NUM> may track the user <NUM> and monitor a distance between the user <NUM> and the user device <NUM>. Likewise, the engagement pipeline <NUM>-<NUM> is employed to collect radar data at a highest duty cycle, which may support advanced radar techniques such as air gesture recognition. While the engagement pipeline <NUM>-<NUM> consumes more power than the other radar pipelines <NUM>, the higher power consumption enables small or fast motions of the user <NUM> to be recognized, which the other radar pipelines <NUM> may be unable to confidently or accurately evaluate.

Each of the radar pipelines <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> employ a respective radar operation, such as a pre-presence operation <NUM>, a presence operation <NUM>, an awareness operation <NUM>, and an engagement operation <NUM>. Each of these radar operations may utilize a particular duty cycle, framing structure, transmit power, or hardware according to the radar-power state <NUM>. In general, the radar operations monitor the environment and detect triggers that activate a lower-power or a higher-power radar pipeline <NUM>. Although not shown, the radar operations may utilize more than one radar-power state <NUM> to monitor the environment and detect a trigger. Example triggers include motion or the lack of motion, appearance or disappearance of a user, a user moving into or out of a designated region (e.g., a region defined by range, azimuth, or elevation), a change in velocity of a motion associated with the user, or a change in reflected signal strength (e.g., due to changes in radar cross section). In general, the triggers that indicate a higher probability of a user (e.g., the user <NUM>) interacting with the user device <NUM> or a preference for a shorter response delay may cause a higher-power radar pipeline <NUM> to be activated.

The duty cycle represents how often the radar system <NUM> is active (e.g., actively transmitting or receiving radar signals). The framing structure specifies a configuration, scheduling, and signal characteristics associated with the transmission and reception of the radar signals. In general, the framing structure is set up such that the appropriate radar data can be collected based on the external environment. The framing structure can be customized to facilitate collection of different types of radar data for different applications (e.g., proximity detection, feature recognition, or air gesture recognition). Based on the framing structure, the power management module <NUM> can turn off the components within the transceiver <NUM> in <FIG> and <FIG> to conserve power.

The radar-power state <NUM> can also be associated with a transmit power, which can vary based on a range or distance that the radar system <NUM> is monitoring. If the user <NUM> is farther from the computing device <NUM>, for example, a higher transmit power may be used to detect the user <NUM>. Alternatively, if the user <NUM> is closer to the computing device <NUM>, a lower transmit power may be used to conserve power. The hardware can include components whose power consumption can be individually controlled (e.g., the components of the transceiver <NUM> in <FIG> and <FIG>) or components that consume different amounts of power during operation (e.g., the low-power processor <NUM>-<NUM> and the high-power processor <NUM>-<NUM> in <FIG>).

<FIG> illustrates an example sequence flow diagram <NUM> for triggering different radar pipelines <NUM>, with time elapsing in a downward direction. At <NUM>, the user <NUM> is not present or is outside a detectable range. For example, the user <NUM> may be on the order of several meters (m) from the user device <NUM> (e.g., at distances greater than <NUM>). Therefore, the pre-presence pipeline <NUM>-<NUM> is employed to conserve power via a low duty cycle associated with the radar-power state <NUM>-<NUM> (e.g., idle mode). The pre-presence pipeline <NUM>-<NUM> may also utilize the low-power processor <NUM>-<NUM> to monitor the environment and detect motion, which may be indicative of a presence of the user <NUM>.

At <NUM>, the user <NUM> approaches the user device <NUM> and the pre-presence pipeline <NUM>-<NUM> triggers the presence pipeline <NUM>-<NUM> to confirm a presence of the user <NUM>. As an example, the user <NUM> may be within a few meters from the user device <NUM> (e.g., between approximately <NUM> and <NUM>). The presence pipeline <NUM>-<NUM> uses a medium-low duty cycle associated with the radar-power state <NUM>-<NUM> (e.g., attention mode). As the user <NUM> moves around in the environment, if the user <NUM> comes within a specified range to the user device <NUM>, the presence pipeline <NUM>-<NUM> triggers the awareness pipeline <NUM>-<NUM>. For example, the awareness pipeline <NUM>-<NUM> may be triggered if the user <NUM> comes within a close distance, such as within a meter, from the user device <NUM>. Due to a proximity of the user <NUM>, the presence pipeline <NUM>-<NUM> may also activate the display <NUM> on the user device <NUM> or turn on other non-radar sensors <NUM> that may be utilized by the user device <NUM>. A camera sensor, for example, may be activated for capturing an image of the user <NUM>. In other examples, a gyroscope or an accelerometer may be activated to determine an orientation of the user device <NUM> or speakers may be activated to provide an audible tone if the user <NUM> has a missed call or a new communication (e.g., a text message) is available.

At <NUM>, the awareness pipeline <NUM>-<NUM> tracks and monitors a location or motion of at least one appendage of the user <NUM> using a medium-high duty cycle associated with the radar-power state <NUM>-<NUM> (e.g., attention mode). Although the user <NUM> is near the user device <NUM>, the user <NUM> may be relatively motionless or performing other tasks that are not associated with the user device <NUM>. Thus, the medium-high duty cycle enables the radar system <NUM> to conserve power while enabling the radar system <NUM> to detect changes that may be indicative of the user <NUM> preparing to interact with the user device <NUM>. At <NUM>, the user <NUM> raises a hand. The awareness pipeline <NUM>-<NUM> determines that this motion is indicative of the user <NUM> moving the hand in position to make an air gesture, such as by reaching toward the user device <NUM>. Therefore, the engagement trigger activates the engagement pipeline <NUM>-<NUM>. This motion may also cause a portion of the user <NUM> to come within a closer distance, such as within several centimeters (cm) from the user device <NUM> (e.g., within approximately <NUM>). This proximity may be another engagement trigger that activates the engagement pipeline <NUM>-<NUM>.

At <NUM>, the engagement pipeline <NUM>-<NUM> collects the radar data at a high duty cycle associated with the radar-power state <NUM>-<NUM> (e.g., interaction mode). This duty cycle enables the radar system <NUM> to recognize the air gesture, which can be used to control the user device <NUM> via the radar-based application <NUM>. Although the radar pipelines <NUM> are shown in a cascaded form in <FIG> or sequentially activated in <FIG>, some of the radar pipelines <NUM> can operate in parallel.

These and other capabilities and configurations, as well as ways in which entities of <FIG> act and interact, are set forth below. The described entities may be further divided, combined, used along with other sensors or components, and so on. In this way, different implementations of the user device <NUM>, with different configurations of the radar system <NUM> and non-radar sensors, can be used to implement a mobile device-based radar system for applying different power modes to a multi-mode interface. The example operating environment <NUM> of <FIG> and the detailed illustrations of <FIG> illustrate but some of many possible environments and devices capable of employing the described techniques.

As noted, the techniques and systems described herein can also enable the user device <NUM> to provide functionality based on a user's implicit interactions with the device. <FIG> and <FIG> illustrate example implementations <NUM> and <NUM> of a multi-mode interface that changes modes based on radar data indicating a user's implicit interactions with a mobile device. The example implementations <NUM> and <NUM> illustrate a user device <NUM> (e.g., the user device <NUM>) in different instances <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>. When the user <NUM> is not detected within the radar field <NUM>, the multi-mode interface <NUM> operates in a dormant mode <NUM>. In the dormant mode <NUM>, the multi-mode interface <NUM> is dormant such that no image(s) or object(s) are displayed via the display <NUM> of the user device <NUM>-<NUM>. In addition, the display <NUM> may be in an off state and the radar system <NUM> from <FIG> may be in an idle mode. These modes and states are low-power operational modes and states.

When the user <NUM> enters the radar field <NUM>, the radar system <NUM> detects the user <NUM> based on reflected radar signals from the user <NUM>. The interaction manager <NUM> uses this radar data to determine the presence of the user <NUM> within the radar field <NUM>. In response to detecting the presence of the user <NUM>, the interaction manager <NUM> causes the multi-mode interface <NUM> to change modes. In this instance, the multi-mode interface <NUM> exits the dormant mode <NUM> and enters an ambient mode <NUM>. When the multi-mode interface <NUM> enters the ambient mode <NUM>, default or predefined display parameters (e.g., luminosity, color saturation) may be applied for a short duration of time (e.g., <NUM> seconds, <NUM> second, <NUM> seconds, <NUM> seconds, <NUM> seconds, and so on) such that the display screen lights up with moderate to high luminosity, revealing (e.g., fading in) the image for a specified duration of time to greet the user. In this way, the display informs the user that the device is aware of the user's presence and is prepared to respond to the user's movements. After the duration of time expires, the luminosity may decrease such that the image fades into a less prominent state. For example, the display screen may be darkened to hide the image or provide a dim, desaturated version of the image so as to reduce power consumption. In some implementations, one or more of the user-interface elements may also be darkened and/or desaturated to reduce power consumption. In the ambient mode, the device is periodically responsive to the user's movements (e.g., uses a low sample rate for detecting the user's movements). A low sample rate allows the mobile device to maintain low power-consumption.

In <FIG>, one or more objects and/or images, including an image <NUM> of a star and a lock icon <NUM> are presented with partial or full luminosity for the duration of time. A background of the multi-mode interface <NUM> may also be provided at a default or predefined luminosity and color saturation. Other elements may also be included, such as a clock element <NUM> (showing time and/or calendar date) or other items (not shown) including a notification item (e.g., icon, badge, banner, etc.), an access tool to a particular application such as a camera application, and so forth.

In response to expiration of the duration of time, the interaction manager <NUM> adjusts one or more display parameters (e.g., luminosity, color saturation) to darken the multi-mode interface <NUM>, which reduces power consumption. This is based on the user device <NUM> not detecting any explicit interaction by the user <NUM> with the user device <NUM>. In this darkened state of the ambient mode of the multi-mode interface <NUM>, displayed objects and images may be maintained at a low luminosity and zero or low color-saturation (e.g., black and white, grayscale). As shown in the user device <NUM>-<NUM>, for example, the clock element <NUM> remains displayed while the lock icon <NUM> is removed. The lock icon <NUM> (or any other element), however, may remain displayed. The background of the multi-mode interface <NUM> is darkened as part of the decreased luminosity. Further, the image <NUM> is faded to a low-luminosity version (including low brightness, zero or low saturation, high or low contrast, or any combination thereof). Optionally, the image <NUM> may be sufficiently darkened so as to not be visible by the user <NUM>. The multi-mode interface <NUM> may remain in the ambient mode <NUM> while the user <NUM> is present within the radar field <NUM> and not explicitly interacting with the user device <NUM>, either by touch gestures or air gestures. Rather, the user's presence is considered to be an implicit interaction because the user is not actively interacting with the user device <NUM> to enter user input.

Continuing to <FIG>, when the user <NUM> reaches toward the user device <NUM> while in the ambient mode <NUM>, the interaction manager <NUM> causes the multi-mode interface to exit the ambient mode <NUM> and enter an alert mode <NUM>. As the user's hand <NUM> moves toward the user device <NUM>, the interaction manager <NUM> adjusts one or more parameters, including at least the luminosity of the multi-mode interface <NUM>. The rate of adjustment of these parameters is based on the change of the position of the user's hand <NUM> relative to the user device <NUM>, and may further be based on various factors associated with the user's hand <NUM> and its movement, including the distance between the user's hand <NUM> and the user device <NUM>, the speed at which that distance decreases. In the alert mode <NUM>, the multi-mode interface <NUM> provides continuously responsive visual feedback corresponding to the movements of the user's hand <NUM>.

In the illustrated example, only highly luminous portions of the image <NUM> are visible in the multi-mode interface <NUM> when the user's hand <NUM> begins to reach toward the user device <NUM>-<NUM>. A dim version of the lock icon <NUM> is also maintained on the multi-mode interface <NUM>. As the user's hand <NUM> gets closer to the user device <NUM> (e.g., <NUM>-<NUM>), the image <NUM> is gradually revealed based on luminosity or other display parameters. Various portions of the image <NUM> (and other objects such as the lock icon <NUM>) become more and more visible and luminous. The rate at which this occurs may be directly proportional to the rate of decrease in the distance between the user's hand <NUM> and the user device <NUM> (e.g., how quickly the user's hand <NUM> moves toward the user device <NUM> while the radar system is in the awareness pipeline and/or the multi-mode interface <NUM> is in the alert mode <NUM>). In aspects, the image <NUM> remains in a desaturated state (e.g., grayscale) and more tones (e.g., shades of gray) are applied to the image <NUM> as the user's hand <NUM> moves closer to the user device <NUM>-<NUM>. Optionally, one or more parameters may also be adjusted to brighten the background of the multi-mode interface <NUM>. However, the alert mode <NUM> of the multi-mode interface <NUM> is associated with a low-power operational state of the user device <NUM>, so maintaining a dark background may help minimize power consumption when increasing the luminosity and/or other display parameters of the multi-mode interface <NUM>.

If, at this point, the user <NUM> moves their hand <NUM> away from the user device <NUM>-<NUM>, the interaction manager <NUM> applies the above-described effects in reverse, such that the image <NUM> is gradually darkened (e.g., luminosity is gradually decreased) to return the multi-mode interface <NUM> to the darkened state of the alert mode <NUM> (shown at user device <NUM>-<NUM>). If the distance between the user's hand <NUM> and the user device <NUM> becomes greater than a threshold distance, the interaction manager <NUM> may cause the multi-mode interface <NUM> to exit the alert mode <NUM> and re-enter the ambient mode <NUM>.

In this way, the multi-mode interface <NUM> provides continuously-responsive visual feedback corresponding positional information and the movements of the user's hand <NUM> as the user <NUM> reaches toward (or away from) the user device <NUM>. This continual responsiveness presented in the form of visual feedback allows the user <NUM> to know that the user device <NUM> is aware of the user's movements, which serves to educate the user <NUM> about the user device's awareness and capabilities while in a low-power or locked state.

To further enhance the user experience in regards to the user device's responsiveness to the user's movements relative to the user device <NUM>, the interaction manager <NUM> may cause the multi-mode interface <NUM> to enter an active mode <NUM> in response to the user <NUM> being authenticated by the user device <NUM>. When transitioning from the alert mode <NUM> to the active mode <NUM>, color-saturation of the multi-mode interface <NUM> is increased such that the image <NUM> is gradually filled with color. Accordingly, the user device <NUM>-<NUM> provides visual feedback, through the use of color, to indicate that the user <NUM> has been authenticated and is provided full access rights to the user device <NUM> by providing a high-luminosity and color saturation display. In addition the multi-mode interface <NUM> provides continuously-responsive visual feedback corresponding to positional information and movements of the user or the user's hand relative to the user device. The multi-mode interface <NUM> can also be adjusted in other aspects based on authentication of the user <NUM>, such as by changing a position of or replacing one or more displayed elements (e.g., replacing the lock icon <NUM> with an unlock icon <NUM>). These modifications can occur prior to presenting a home screen of the user device <NUM> or as part of the presentation of the home screen. The home screen, and additional pages, may be presented via the multi-mode interface <NUM> in the active mode <NUM>. The image <NUM> and/or other objects or elements may be maintained on the multi-mode interface <NUM> simultaneously with user-interface elements that are displayed on the home screen and additional pages.

The image <NUM> described with respect to <FIG> and <FIG> may be a still image selected as part of a theme package of the operating system of the user device <NUM>. Alternatively, the image <NUM> may be a user-selected still image, such as a digital photo or drawing, stored in the computer-readable media <NUM>. In this way, the user <NUM> may customize the image displayed via the multi-mode interface <NUM> of the user device <NUM>. Each image may be unique in how it is gradually revealed based on luminosity changes. Further, each image may be unique in how it is filled with color based on saturation changes when the user <NUM> is authenticated to the user device <NUM>.

Other visual effects of the multi-mode interface <NUM> that correspond to radar-detected movements of the user <NUM> relative to the user device <NUM> are also contemplated. For example, rather than a still image, the image <NUM> may include a curated collection of images, a family of related images, or a sequence of images (e.g., video). A collection of images can be used to produce one or more objects or images that respond to the user's implicit interactions with the user device <NUM>, such as by moving in subtle ways in association with the user's hand <NUM> movements and position relative to the user device <NUM>. One example of this is shown in <FIG>.

<FIG> illustrates an example implementation <NUM> of the multi-mode interface that changes modes based on radar data indicating a user's implicit interactions with a mobile device. Here, the user device <NUM>-<NUM> is illustrated with the multi-mode interface <NUM> in the ambient mode <NUM> (e.g., darkened state) based on the user's <NUM> presence being detected within the radar field <NUM> (not shown). In this example, no objects are displayed via the multi-mode interface <NUM>. When the user <NUM> begins to reach toward the user device <NUM>-<NUM>, the interaction manager <NUM> causes the multi-mode interface <NUM> to exit the ambient mode <NUM> and enter the alert mode <NUM>. In the alert mode <NUM>, one or more objects, such as small bubbles <NUM>, start coming into view from the sides of the multi-mode interface <NUM>. As the user's hand <NUM> gets closer to the user device <NUM>-<NUM>, the bubbles <NUM> progressively move toward a specified location. The rate at which the bubbles move may directly correspond to the rate at which the distance between the user's hand <NUM> and the user device <NUM> decreases. In some aspects, as the user's hand <NUM> gets closer to the user device <NUM>, the bubbles <NUM> combine with one another and grow in size (shown as combining bubbles <NUM>) until there is only one large bubble <NUM> at the specified location. During this movement towards the specified location, the bubbles <NUM>, <NUM> may become more luminous, particular as they combine with one another. If the user's hand <NUM> moves away from the user device <NUM>-<NUM>, the bubbles <NUM> start to pull apart from one another and move back toward the sides of the multi-mode interface <NUM>. The luminosity of the bubbles <NUM>, <NUM> may also decrease as they move away from each other.

At some point, the user <NUM> may be authenticated to the user device <NUM> by a user-recognition system (e.g., based on a password, a passcode, a fingerprint, and so on). In response to the user <NUM> being authenticated, the multi-mode interface <NUM> enters the active mode <NUM>. Upon entering the active mode <NUM>, the interaction manager <NUM> adjusts display parameters of the multi-mode interface <NUM>, such as color saturation. Here, the one large bubble <NUM> gradually progresses from grayscale to color to provide an indication that the user <NUM> has been authenticated to full rights. Additional lighting effects may be applied based on the position of the user's hand <NUM> relative to the user device <NUM>. Here, the user's hand <NUM> is located to the lower right side of the user device <NUM> (when in a portrait mode orientation) and based on this positioning, lighting effects are applied to the bubble <NUM> as if the user's hand <NUM> were a light source shining light onto the bubble <NUM>. Alternatively, the positioning of the user's hand <NUM> can be used to apply lighting effects in the opposite direction to produce the visual effect that the light source is shining toward the user's hand <NUM>. Of course, a lighting effect(s) can be applied in any suitable direction based on the relative positioning of the user's hand <NUM>.

As part of the applied visual effects that indicate that the user <NUM> has been authenticated, the bubble <NUM> may move to a different location. For example, the bubble <NUM> may quickly move toward or away from the user's hand <NUM>. The bubble <NUM> may move toward and collide with the lock icon <NUM>, causing the lock icon <NUM> to be replaced with the unlock icon <NUM>. This may produce a dramatic effect of the lock being broken open by the bubble <NUM>. In some aspects, the bubble <NUM> may change shape, size, or color. Accordingly, a variety of changes may occur in response to the multi-mode interface <NUM> entering the active mode <NUM>.

In another example, the curated collection of images can include abstract shapes that, during the alert mode <NUM> of the multi-mode interface <NUM>, move, bend, and/or reshape based on the user's hand <NUM> movements and relative positioning. This may be in addition to the change in luminosity as described above. Each of the images may be associated with unique positioning information corresponding to a position of the user's hand <NUM> relative to the user device <NUM> (e.g., distance between the user device <NUM> and the user's hand <NUM> combined with a location of the user's hand <NUM> relative to an orientation of the user device <NUM>). This allows a different image to be presented based on where the user's hand <NUM> is positioned (proximity and direction) relative to the user device <NUM>. In this way, the abstract shapes or other displayed objects may appear to react to the user's hand movements around the user device <NUM> in subtle and interesting ways, while the user device <NUM> is in a locked state. An example of this is described below in relation to <FIG>.

<FIG> illustrates another example implementation <NUM> of a multi-mode interface that changes modes based on radar data indicating a user's implicit interactions with a mobile device. Here, the user device <NUM>-<NUM> is illustrated with the multi-mode interface <NUM> in the ambient mode <NUM> based on the user's presence being detected within the radar field <NUM> (not shown). In this example, objects <NUM> are provided in a low-luminosity display by the multi-mode interface <NUM>. The objects are rendered via the display <NUM>. The objects <NUM> can be any object, shape, or image. The objects <NUM> have an initial position during the ambient mode <NUM> of the multi-mode interface <NUM>, an example of which is illustrated on the display <NUM> of user device <NUM>-<NUM>.

When the user <NUM> begins to reach toward the user device <NUM>-<NUM>, the interaction manager <NUM> causes the multi-mode interface <NUM> to exit the ambient mode <NUM> and enter the alert mode <NUM>. In the alert mode <NUM>, one or more of the objects <NUM> move. As the user's hand <NUM> gets closer to the user device <NUM>-<NUM>, the objects <NUM> continue to move. The rate and/or distance that the objects <NUM> move may directly correspond to the rate at which the distance between the user's hand <NUM> and the user device <NUM> decreases. The objects <NUM> can move in any direction and can change directions based on how close the user's hand <NUM> is to the user device <NUM>. In addition to, or alternative to, shifting in a certain direction, the movement of the objects <NUM> may include 3D rotation in any direction. Further, each object <NUM> may move independently of the other objects <NUM>. One or more of the objects <NUM> may also change its shape or size as the user's hand <NUM> approaches the user device <NUM>.

Similar to the above-described implementations, the multi-mode interface <NUM> may provide a low-luminosity display during the ambient mode <NUM> and initially during the alert mode <NUM>. The luminosity during the alert mode <NUM> is adjustable based on the changing distance between the user device <NUM> and the user's hand <NUM>. In some aspects, the multi-mode interface <NUM> provides a monochrome display during the ambient mode <NUM> and the alert mode <NUM>. Alternatively, the multi-mode interface <NUM> can provide a low color saturation display during these modes.

In response to the user being authenticated to the user device <NUM>, the multi-mode interface <NUM> enters the active mode <NUM>. Upon entering the active mode <NUM>, the interaction manager <NUM> adjusts display parameters of the multi-mode interface <NUM>, such as color saturation. Here, the objects <NUM> progress from grayscale to color to provide a visual indication that the user <NUM> has been authenticated to full rights. For example, as shown on user device <NUM>-<NUM>, the multi-mode interface <NUM> provides a high-luminosity and high-saturation display. As in the other described implementations, additional lighting effects can be applied to the objects <NUM> in any suitable way. The objects <NUM> an also move further in response to the authentication. Here, the objects <NUM> moved back toward their original positions in the ambient mode <NUM>. However, the objects <NUM> may or may not reach those original positions.

<FIG> depicts an example method <NUM> for managing power modes of a multi-mode interface based on radar-power states of a radar system of the user device. In aspects, the power modes are managed based on a level of implicit interaction by a user with the user device. The method <NUM> can be performed by the user device <NUM>, which uses the radar system <NUM> to provide a radar field. The radar field is used to determine implicit interactions of the user with the user device, such as a presence of the user within the radar field and movement of the user relative to the user device. Based on the determination of the user's presence and movements, the electronic device can apply a radar-power state to the radar system and apply a corresponding power mode to a multi-mode interface to enter and exit different modes of functionality.

The method <NUM> is shown as a set of blocks that specify operations performed but are not necessarily limited to the order or combinations shown for performing the operations by the respective blocks. Further, any of one or more of the operations may be repeated, combined, reorganized, or linked to provide a wide array of additional and/or alternate methods. In portions of the following discussion, reference may be made to the example operating environment <NUM> of <FIG> or to entities or processes as detailed in <FIG>, reference to which is made for example only. The techniques are not limited to performance by one entity or multiple entities operating on one device.

At <NUM>, a power management module maintains a radar system of the user device in a first radar-power state of a plurality of radar-power states. This power management module (e.g., power management module <NUM>) controls the radar-power state of the radar system (e.g., the radar system <NUM>) based on the level of interaction by a user with the user device, to reduce power consumption when the user is not fully engaged with the user device. Each of the radar-power states have a different maximum power-usage limit. In aspects, each radar-power state uses a different duty cycle. The first radar-power state described above is sufficient to generate a radar field (e.g., the radar field <NUM>) and sense reflections from a user (e.g., the user <NUM>) within the radar field.

At <NUM>, an interaction manager determines a presence or movement of the user within the radar field based on the sensed reflections. The interaction manager (e.g., the interaction manager <NUM>, which may also include the multi-mode interface <NUM>) can obtain radar data representing the sensed reflections from the radar system <NUM>. Using this radar data, the interaction manager can detect that: the user is entering the radar field, the user is present or moving within the radar field without explicitly interacting with the user device, the movement of the user includes the user's hand moving toward or away from the user device, or the user is exiting the radar field.

At <NUM>, responsive to the determining of the presence or movement of the user within the radar field, the power management module causes the radar system to change to a second radar-power state of the plurality of radar-power states. In aspects, the second radar-power state enables different functionality than that of the first radar-power state. For example, the power management module can enable the radar system to execute a presence operation corresponding to the second radar-power state. The presence operation may be configured to provide the radar data for detecting at least the presence of the user within the radar field and other data usable to determine implicit interaction by the user with the user device. Further, the presence operation may correspond to an ambient mode of the multi-mode interface. In another example, the power management module can enable the radar system to execute an awareness operation corresponding to the second radar-power state. The awareness operation may be configured to provide the radar data for detecting the presence of the user within the radar field and other radar data usable to determine implicit interaction by the user with the user device. Further, the awareness operation may correspond to an alert mode of the multi-mode interface. In yet another example, if the user is also authenticated to the user device, the power management module can enable the radar system to execute an engagement operation corresponding to the second radar-power state. The engagement operation enables the radar system to provide other radar data usable to detect and process radar-based air gestures that enable the user to explicitly interact with the user device.

At <NUM>, responsive to or incident with the radar system changing to the second radar-power state, the interaction manager module selects a power mode from a plurality of power modes for a multi-mode interface. The interaction manager module can use the radar data to determine a level of interaction by the user with the user device and then select which power mode of the plurality of power modes for the multi-mode interface is best-suited for the level of interaction. In aspects, at least two of the plurality of power modes may correspond to different radar-power states of the plurality of radar-power states of the radar system. For example, the dormant mode of the multi-mode interface may correspond to the idle mode (e.g., using a low duty cycle in the pre-presence pipeline) of the radar system. The ambient mode of the multi-mode interface may correspond to the attention mode (e.g., using a medium-low duty cycle in the presence pipeline) of the radar system. The alert mode of the multi-mode interface may correspond to the attention mode (e.g., using a medium-high duty cycle in the awareness pipeline) of the radar system. The active mode of the multi-mode interface may correspond to the interaction mode (e.g., using a high duty cycle in the engagement pipeline) of the radar system.

At <NUM>, the interaction manager applies the selected power mode to the multi-mode interface to provide a corresponding display. The interaction manager can provide any suitable display via the multi-mode interface, including a black display, a low-luminosity display, a monochrome display, or a high-luminosity and color saturation display. In aspects, the interaction manager provides the low-luminosity display responsive to the selected power mode for the multi-mode interface being the ambient mode. If the selected power mode is the alert mode, the interaction manager provides the monochrome display with a dynamically-adjustable luminosity that is adjustable based on changes to a position of the user's hand relative to the user device. If the selected power mode is the active mode, the interaction manager provides the high-luminosity and color saturation display. If the selected power mode is the dormant mode, the multi-mode interface provides the black display.

<FIG> illustrates various components of an example computing system <NUM> that can be implemented as any type of client, server, and/or electronic device as described with reference to the previous <FIG> to implement a mobile device-based radar system for applying different power modes to a multi-mode interface.

The computing system <NUM> includes communication devices <NUM> that enable wired and/or wireless communication of device data <NUM> (e.g., radar data, authentication data, reference data, received data, data that is being received, data scheduled for broadcast, and data packets of the data). The device data <NUM> or other device content can include configuration settings of the device, media content stored on the device, and/or information associated with a user of the device (e.g., an identity of a person within a radar field or customized air gesture data). Media content stored on the computing system <NUM> can include any type of radar, biometric, audio, video, and/or image data. The computing system <NUM> includes one or more data inputs <NUM> via which any type of data, media content, and/or inputs can be received, such as human utterances, interactions with a radar field, touch inputs, user-selectable inputs or interactions (explicit or implicit), messages, music, television media content, recorded video content, and any other type of audio, video, and/or image data received from any content and/or data source.

The computing system <NUM> also includes communication interfaces <NUM>, which can be implemented as any one or more of a serial and/or a parallel interface, a wireless interface, any type of network interface, a modem, and as any other type of communication interface. The communication interfaces <NUM> provide a connection and/or communication links between the computing system <NUM> and a communication network by which other electronic, computing, and communication devices communicate data with the computing system <NUM>.

The computing system <NUM> includes one or more processors <NUM> (e.g., any of microprocessors, controllers, or other controllers) that can process various computer-executable instructions to control the operation of the computing system <NUM> and to enable techniques for, or in which can be implemented, a mobile device-based radar system for applying different power modes to a multi-mode interface. Alternatively or additionally, the computing system <NUM> can be implemented with any one or combination of hardware, firmware, or fixed logic circuitry that is implemented in connection with processing and control circuits, which are generally identified at <NUM>. Although not shown, the computing system <NUM> can include a system bus or data transfer system that couples the various components within the device. A system bus can include any one or combination of different bus structures, such as a memory bus or memory controller, a peripheral bus, a universal serial bus, and/or a processor or local bus that utilizes any of a variety of bus architectures.

The computing system <NUM> also includes computer-readable media <NUM>, such as one or more memory devices that enable persistent and/or non-transitory data storage (i.e., in contrast to mere signal transmission), examples of which include random access memory (RAM), non-volatile memory (e.g., any one or more of a read-only memory (ROM), flash memory, EPROM, EEPROM, etc.), and a disk storage device. A disk storage device may be implemented as any type of magnetic or optical storage device, such as a hard disk drive, a recordable and/or rewriteable compact disc (CD), any type of a digital versatile disc (DVD), and the like. The computing system <NUM> can also include a mass storage media device (storage media) <NUM>.

Claim 1:
A user device comprising:
a display device (<NUM>); and
a radar system (<NUM>) implemented at least partially in hardware, the radar system configured to:
generate a radar field (<NUM>) and provide radar data corresponding to reflections from a user (<NUM>) within the radar field; and
operate at one of a plurality of radar-power states (<NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>) including a first radar-power state and a second radar-power state, the plurality of radar-power states each having a different maximum power-usage limit;
a processor (<NUM>) configured to analyze the radar data to detect a presence or movement of the user within the radar field;
a power management module (<NUM>) configured to:
maintain the radar system in the first radar-power state, the first radar-power state sufficient to at least detect the presence or movement of the user within the radar field; and
based on a determination of the user's presence or movement, cause the radar system to change to the second radar-power state; and
an interaction manager module (<NUM>) configured to, in response to or incident with the radar system changing to the second radar-power state:
determine a level of interaction by the user with the user device (<NUM>, <NUM>) based on the radar data;
select, based on the determination of the level of interaction, a power mode (<NUM>, <NUM>, <NUM>, <NUM>) of a multi-mode interface (<NUM>) from a plurality of power modes that correspond to different radar-power states of the plurality of radar-power states of the radar system; and
apply the selected power mode to the multi-mode interface to provide a display on the display device including a black display, a low-luminosity display, a monochrome display, and a high-luminosity and color saturation display of which each display corresponds to one selected power mode, wherein two of the power modes are an ambient mode (<NUM>) and an alert mode (<NUM>), wherein the ambient mode is exited and the alert mode is entered when a user reaches toward the user device while in the ambient mode, and wherein in the alert mode the monochrome display is provided with a dynamically adjustable luminosity that is adjustable based on the changes to a position of the user's hand relative to the user device.