Patent Description:
RF ranging systems employ a Time-Of-Flight (TOF) principle to determine a distance between a transmitter and a target. Typically, a transmitter transmits a waveform towards the target. The waveform is then reflected or retransmitted by the target towards a receiver. The duration of time for the reflection or retransmission to reach the receiver, determines the distance between the transmitter and the target.

Examples of targets include distant targets, with relatively weak reflectivity, and nearby targets, which reflect a stronger signal towards the receiver. Monostatic radars combine the transmitter and receiver antennas to reduce a cost of an RF ranging system. However, monostatic radars have not been able to operate in both long-range and short-range modes, thus limiting their application.

<CIT> discloses an apparatus and a method for controlling a radar, the method including setting detection modes of a radar mounted to a vehicle and controlling radar transmission signals according to the detection modes. An apparatus for controlling a radar includes: a target detector configured to detect targets around a vehicle and classify the detected targets; a transmission pattern setter configured to set a transmission pattern of transmission signals, based on at least one piece of detection distance information of the detected targets, detection location information, detection height information, and information on a number of detected targets; and a transmission signal controller configured to select at least one array antenna from a plurality of array antennas according to the transmission pattern and radiate the transmission signals through the selected array antenna.

<CIT> discloses a radar apparatus supporting short range and long range radar operations, wherein a plurality of short range transmitting chirp signals and a plurality of long range transmitting chirp signals are generated by a predetermined modulation scheme and is transmitted to an object through at least one transmitting array antenna and signals reflected from the object is received through at least one receiving array antenna, and the plurality of long range transmitting chirp signals have transmission power larger than that for the plurality of short range transmitting chirp signals.

<CIT> discloses a hybrid radar that combined Frequency-Modulated Continuous-Wave (FMCW) radar and pulsed radar in a single radar wave-train.

In a first aspect, there is provided an apparatus comprising the features of claim <NUM>.

In one or more embodiments, the ranging cycle may further comprise a third duration of a deactivated mode, wherein the deactivated mode comprises deactivating the transmitter.

In one or more embodiments, the apparatus may be temporally shared for a plurality of ranging applications.

In one or more embodiments, the controller may comprise machine-learning circuitry configured to identify a target classification of one or more targets within a range of the apparatus.

In another aspect, there is provided a system comprising the apparatus of the first aspect defined above and a passive target capable of reflecting the transmission towards the antenna.

In another aspect, there is provided a system comprising the apparatus of the first aspect defined above and an active target configured to receive the transmission from the transmitter and to transmit a second transmission towards the antenna.

In another aspect, there is provided a method for operating an impulse radar using variable pulse repetition frequency, the method comprising the steps of claim <NUM>.

In one or more embodiments, the method may further comprise temporally sharing the impulse radar for a plurality of ranging targets.

In one or more embodiments, the method may further comprise adjusting at least one of the first duration and the second duration based on a detected first number of short-range targets and a detected second number of long-range targets.

In one or more embodiments, the method may further comprise adjusting at least one of the first duration and the second duration based on one or more predefined parameters.

In one or more embodiments, the method may further comprise adjusting at least one of the first duration and the second duration based on an inferred classification of the at least one target.

In one or more embodiments, the method may further comprise inferring the inferred classification of the at least one target using machine learning of a relative movement of the at least one target and another target.

Embodiments described herein provide for a pulsed radar system alternatively operating in both a long-range (e.g., gated mode), and a short-range (e.g., non-gated mode). In the long-range mode, receiver blindness is supported for higher available Signal to Noise Ratio (SNR). In the short-range mode, the receiver detects target reflections or retransmissions overlapping with a direct feed-through signal from the mono-static transmitter to the receiver. Accordingly, the pulsed (e.g., impulse), radar systems described herein offer cost competitive detection of both short-range and long-range targets, as well as a dynamic means to tune operating modes of the radar system based on a combination of target characteristics.

<FIG> shows an example embodiment <NUM> of an RF ranging system, wherein a target retransmits a received waveform from a radar. It should be appreciated that the teachings of this disclosure apply to both monostatic radars having a collocated transmitter and receiver, and bistatic radars having a transmitter and receiver having a substantial separation therebetween. Furthermore, this disclosure is contemplated to be implemented in either monostatic or bistatic radar embodiments with either passive targets (e.g., reflecting a received signal), or active targets (e. g, actively retransmitting the received signal). The embodiment <NUM> employs the TOF principle to determine a distance between two objects, or markers on objects. Specifically, the embodiment <NUM> includes a radar <NUM> and a target <NUM>. The radar <NUM> transmits, with a transmitter <NUM>, a waveform (e.g., a chirp or a pulse) over a path <NUM> to a receiver <NUM>. The waveform travels across the path <NUM> as a "challenge" to the target <NUM> and with an elapsed transit time equal to "TOF-<NUM>. " The receiver <NUM> transfers a request over a net <NUM> to a transmitter <NUM>, with an elapsed processing time equal to "Tproc. " The transmitter <NUM> transmits a second transmission over a path <NUM> to a receiver <NUM> of the radar <NUM>. The second transmission is a "response" to the challenge of the radar <NUM> and transits the path <NUM> with a transit time equal to "TOF-<NUM>.

A controller <NUM> controls the operations of the transmitter <NUM> and the receive <NUM> over respective nets <NUM> and <NUM>. Specifically, the controller initiates a transmission from the transmitter <NUM>, and starts the calculation of the distance between the radar <NUM> and the target <NUM> with a Round-Trip Time of Flight ("RTToF") counter <NUM>. The transmitter <NUM> starts the counter <NUM> with a start request on net <NUM> to establish a start time <NUM>. The receiver <NUM> stops the counter <NUM> with a stop request on net <NUM> to establish a stop time <NUM>. The time difference between the start time <NUM> and the stop time <NUM> is a measured time (Tmeas). Similarly, the target <NUM> measures a processing time (Tproc) with a counter <NUM>, by measuring a time difference between a time <NUM>, when the receiver <NUM> receives the waveform from the transmitter <NUM>, and a time <NUM>, when the transmitter <NUM> transmits the second waveform to the receiver <NUM>. Accordingly, the distance (D) between the radar <NUM> and the target <NUM> is given by the following equation (<NUM>), wherein "c" is the speed of light in the medium comprising the paths <NUM> and <NUM>.

In another embodiment, wherein the target <NUM> passively reflects the waveform transmitted by the transmitter <NUM>, the processing time Tproc is zero, hence in equation <NUM>. In example embodiments of a radar based on an Impulse-Radio Ultra-Wide Band ("IR UWB") protocol based on IEEE <NUM>. <NUM> High Rate Pulse (HRP) repetition frequency UWB operating between approximately <NUM> and <NUM>, the radar transceiver operates either as a bistatic or a monostatic radar. <FIG> shows an example embodiment <NUM> including a transceiver <NUM> and a target <NUM>. The embodiment <NUM> is configured as a monostatic radar, wherein a collocated transmitter and receiver form a transceiver <NUM>. In one embodiment, the transceiver <NUM> includes a transmitter and a receiver having respective antennas in close proximity. In another embodiment, the transmitter and receiver share the same antenna <NUM>, the reduce the cost of the RF ranging system.

In the embodiment <NUM> of the monostatic radar, a pulse is transmitted by the transceiver <NUM> towards the target <NUM>, and then a reflected pulse (e.g., second transmission) <NUM> is reflected by the target <NUM>. A distance (or range) <NUM> between the transceiver <NUM> and the target <NUM> is calculated using the methods described for <FIG>. For targets that are physically close to the transceiver <NUM>, a radar blind range <NUM> exists, when the transceiver <NUM> transmits in a gated mode, because the reflected pulse <NUM> returns to the transceiver <NUM> while the receiving portion of the transceiver <NUM> is blinded. The term "blinded" in this context means that the receiver ignores received waveforms through one or more techniques, including but not limited to, deactivating an amplifier of the receiver, or gating an output of the amplifier.

In one example embodiment of a monostatic radar, as shown in <FIG>, a relatively low-cost radar is implemented to perform functions such as (human) presence detection, respiration rate monitoring or heartbeat monitoring. As a specific case, where an IR-UWB radio is primarily used for vehicular access, a radar mode of an externally mounted transceiver allows the re-use of the same hardware to act as a parking sensor (e.g., to be used for autonomous remote parking). Similarly, in another embodiment, an internally mounted IR-UWB transceiver is used for in-cabin radar monitoring or gesture control in an automobile.

In embodiments of RF ranging systems, such as the one described in <FIG> and <FIG>, it is desirable to maximize security and link budget while minimizing current consumption, latency, and system cost. Accordingly, in one example embodiment, the RF ranging system is based on an IR-UWB transceiver (e.g., using a protocol based on IEEE <NUM>. <NUM> HRP UWB). IR-UWB transceivers offer a means to support pulse radar functionality, with pulse transmitters, receivers that are designed to provide accurate estimates of the Channel Impulse Response (CIR), and the ability to support both transmit and receive functions using a single antenna <NUM>.

With efficient Digital Signal Processor (DSP) algorithms, included for example in the controller <NUM>, the link budget is primarily determined by receiver sensitivity, as the transmitter tends to be limited by the average or mean power spectral density regulations (e.g., -<NUM> dBm/MHz for UWB devices under FCC Part <NUM> and/or ETSI EN <NUM><NUM>).

In a traditional pulse radar using a gated mode, the receiver can be blind during transmission, meaning that a monostatic pulse radar, unlike its Continuous-Wave (CW) counterpart, need not reduce the receiver gain during signal reception due to signals from the transmitter reaching the receiver with large amplitudes (e.g., from direct transmitter to receiver feed-through coupling). This larger receiver gain afforded by the gated mode, results in better receiver sensitivity (e.g., it allows a pulse radar to achieve a larger link budget than a CW radar at equal average transmit power).

For an example embodiment of a short-range radar, receiver blindness is not allowed, as reflections of interest may (partially) overlap with (direct-feedthrough) signals from the transmitter appearing at the receiver. For example, with a typical UWB pulse shape, a typical pulse duration of approximately <NUM> ns would impose a blind time corresponding to approximately <NUM> meters round-trip time-of-flight (e.g., targets closer than <NUM> meters would not be detected, as shown by the radar blind range <NUM> of <FIG>). This scenario is worse if blinding the receiver requires additional time for mode-switching, which is typically the case. A typical radar blind range <NUM> of several meters is common when mode-switching is considered in a gated mode RF ranging system. The embodiments described herein, alternate the mode of operation of a pulse radar between a gated (e.g., long-range) mode and a non-gated (e.g., short-range) mode. The characteristics of a gated mode and a non-gated mode radar system are compared in Table <NUM> below.

Example embodiments of RF ranging systems described herein adjust the relative durations of a gated mode and a non-gated mode (and in some embodiments, also a deactivated mode). Adjusting the relative durations of these modes occurs dynamically based on one or more of the following criteria. In one example embodiment, the relative duration (or duty cycle) of the gated and non-gated modes is adjusted based on the number of detected short-range targets relative to the number of long-range targets. For example, when a majority of the detected targets are short-range, additional time is allocated to a non-gate mode operation. In another example embodiment, the SNR margin of short-range targets relative to the SNR margin of long-range targets is used. The required SNR for short-range targets is typically less than for long-range targets because short-range targets reflect more signal power. In another example embodiment, a predefined ratio of gated mode duration and non-gated mode duration is defined for a programmed or set use case. For example, a radar used for gesture control prioritizes short-range detection of hand movements.

In another example embodiment, the target type or classification is inferred based on observed target characteristics, including but not limited to, reflected signal strength and relative movements between two or more detected targets or between a detected target and the RF transceiver. In another example embodiment, inferring target classifications or types include using machine learning and/or artificial intelligence.

<FIG> shows the sequential modes of operation of an impulse radar, (e.g., for RF ranging) allocating the maximum time for radar transmission, in a repeating sequence of two modes. <FIG> also shows a "duty-cycle" optimization, where duty-cycle refers to the ratio of the gated modes to the non-gated modes. In <FIG> a gated mode <NUM> is interleaved with a non-gated mode <NUM>, each with an equal duration (e.g., <NUM>). <FIG> shows an embodiment favoring short-range targets, at the expense of SNR for long-range targets. Here, the duration of the gated mode <NUM> (e.g., <NUM>) is less than the duration of the non-gated mode <NUM> (e.g., <NUM>). <FIG> shows an embodiment favoring long-range targets, at the expense of SNR for short-range targets. Here, the duration of the gated mode <NUM> (e.g., <NUM>) is greater than the duration of the non-gated mode <NUM> (e.g., <NUM>).

In one embodiment, the relative durations of the gated mode and the non-gated mode is dynamically adjusted based on a variety of criteria as discussed above. It should be appreciated that the durations of the gated modes, non-gated modes and deactivated modes of <FIG> are shown as example embodiments and not to limit the disclosure to other embodiments having different durations of the these modes.

<FIG> shows the sequential modes of operation of an impulse radar, (e.g., for RF ranging) for a reduced energy operation, in a repeating sequence of three modes. In <FIG> a gated mode <NUM> is interleaved with a non-gated mode <NUM> and a deactivated mode <NUM>. While both the gated mode <NUM> and non-gated modes <NUM> have an equal duration of <NUM>, (and thus equal weighting for long-range and short-range targets), the deactivated mode <NUM> is substantially longer at <NUM> to reduce energy consumption. In one embodiment, the deactivated mode <NUM> reduces energy consumption by deactivating the transceiver. <FIG> shows an embodiment favoring short-range targets, at the expense of SNR for long-range targets. Here, the duration of the gated mode <NUM> (e.g., <NUM>) is less than the duration of the non-gated mode <NUM> (e.g., <NUM>). Similar to <FIG>, the deactivated mode <NUM> is substantially longer at <NUM> to reduce energy consumption. <FIG> shows an embodiment favoring long-range targets, at the expense of SNR for short-range targets. Here, the duration of the gated mode <NUM> (e.g., <NUM>) is greater than the duration of the non-gated mode <NUM> (e.g., <NUM>). Similar to <FIG>, the deactivated mode <NUM> is substantially longer at <NUM> to reduce energy consumption.

In one embodiment, the relative durations of the gated mode and the non-gated mode are dynamically adjusted based on a variety of criteria as discussed above. It should be appreciated that the durations of the gated modes, non-gated modes and deactivated modes are shown as example embodiments and not to limit the disclosure to other embodiments having different durations of the these modes.

<FIG> with reference to <FIG> shows a method <NUM> for operating an impulse radar using variable pulse repetition frequency. At <NUM>, an RF pulse is transmitted (e.g., with a transmitter <NUM>), during a gated mode. At <NUM>, an RF pulse is transmitted during a non-gated mode. At <NUM>, a returned transmission is received (e.g., with a receiver <NUM>). The amplifier of the receiver is blinded during the gated mode. A gain of the amplifier of the receiver is reduced during the non-gated mode. At <NUM>, a first duration of the gated mode and/or a second duration of the non-gated mode (e.g., <FIG>) is adjusted (e.g., with a controller <NUM>), in response to a maximum duty-cycle operation.

Claim 1:
An apparatus (<NUM>, <NUM>) comprising:
a transmitter (<NUM>, <NUM>) comprising a pulsed Radio Frequency (RF) source coupled to an antenna (<NUM>), the transmitter (<NUM>, <NUM>) being configured to transmit a Radio Frequency (RF) pulse (<NUM>) during each of a gated mode and a non-gated mode;
a receiver (<NUM>, <NUM>) comprising an amplifier coupled to the antenna, the receiver (<NUM>, <NUM>) being configured to receive a returned transmission (<NUM>, <NUM>) from at least one target (<NUM>, <NUM>); and
a controller (<NUM>) configured to adjust one or more durations of a ranging cycle of the apparatus, wherein the ranging cycle comprises a first duration of the gated mode and a second duration of the non-gated mode, the gated mode blinding the amplifier during a transmission of the pulse (<NUM>) by the transmitter, and the non-gated mode reducing a gain of the amplifier during the transmission of the pulse (<NUM>); wherein the controller (<NUM>) is configured to adjust at least one of the first duration and the second duration in response to a maximum duty-cycle operation and based on at least one of a required first Signal to Noise Ratio (SNR) margin of the at least one target (<NUM>, <NUM>) being a short-range target and a required second SNR margin of the at least one target (<NUM>, <NUM>) being a long-range target.