Patent Description:
<CIT>, which forms the closest prior art, proposes an arrangement for scanning a space by means of visible or invisible radiation. In a first variant, the arrangement comprises a movable element, a radiation source and a deflecting element along a central axis. The movable element comprises a MEMS mirror which is rotatable and/or tiltable with respect to the central axis. Alternatively, the radiation source can be integrated into the movable integrated in the movable element.

<CIT> proposes an omnidirectional antenna system for a radar device monitoring movement of an object in an area under surveillance comprising a dielectric rod projecting from a waveguide horn, the projecting end of the rod carrying a conical reflector whose tip is directed towards the horn, the edge of the horn having a flange at whose periphery there is a frusto-conical surface extending away from the reflector, the flange and surface forming part of the housing of the device. Said rod is graduated in step-wise manner within the waveguide and extends out of the horn in a portion which is of circular cross-section. At the free end of the rod there is a conical reflector.

<CIT> proposes a high power beamforming vehicle-mounted antenna with a two-stage structure, comprising a plurality of groups of symmetrically-arranged vehicle-mounted communication antennas with same structures, wherein each pair of vehicle-mounted communication antennas comprise a circular polarizer, a millimeter wave cone horn antenna arranged above the circular polarizer and mutually connected with the circular polarizer, a lens arranged horizontally above the millimeter wave cone horn antenna, and a reflection plate arranged obliquely above the lens.

A radar system typically has a limited field of view which does not cover a detection range of more than <NUM>° around the radar system with a single radar sensor. Besides, some applications may require a radar system to exclude certain parts of the field of view from detection. Hence, there may be a demand for improved radar sensing.

The demand may be satisfied by the subject matter of the appended claims.

An example relates to a radar system comprising a radar sensor. The radar sensor comprises an antenna configured to emit a radar beam towards a predefined region. The radar system further comprises a reflector spaced apart from the radar sensor and symmetrical with respect to a line of symmetry or a plane of symmetry. The line of symmetry or the plane of symmetry is parallel to a beam axis of the radar beam. The line of symmetry or the plane of symmetry is displaced with respect to a phase center of the antenna. The reflector is configured to redirect at least part of the radar beam towards a target region different from the predefined region. The reflector is further configured to redirect a reflection of the radar beam originating from the target region onto the radar sensor.

Another example relates to an electronic device comprising a radar system as described herein and control circuitry configured to control an operation of the electronic device based on an output signal of the radar system.

Another example relates to a method for operating a radar system comprising a radar sensor and a reflector spaced apart from the radar sensor and symmetrical with respect to a line of symmetry or a plane of symmetry. The method comprises emitting, at an antenna of the radar sensor, a radar beam towards a predefined region. The line of symmetry or the plane of symmetry is parallel to a beam axis of the radar beam. The line of symmetry or the plane of symmetry is displaced with respect to a phase center of the antenna. The method further comprises redirecting, using the reflector, the radar beam towards a target region different from the predefined region, and redirecting, using the reflector, a reflection of the radar beam originating from the target region onto the radar sensor.

Some examples of apparatuses and/or methods will be described in the following by way of example only, and with reference to the accompanying figures, in which in particular the embodiment of <FIG> and <FIG> form the embodiment of the invention as claimed; the embodiments in <FIG>, <FIG>, <FIG> are comparative examples useful for understanding the invention but not forming part of the invention as claimed.

When two elements A and B are combined using an "or", this is to be understood as disclosing all possible combinations, i.e., only A, only B as well as A and B, unless expressly defined otherwise in the individual case.

<FIG> illustrate a schematic representation of an example of a radar system <NUM>. The radar system <NUM> comprises a radar sensor <NUM>. The radar sensor <NUM> may be any device suitable for emitting and receiving a radio-frequency electromagnetic signal, i.e., a radar transceiver. The radar sensor <NUM> comprises an antenna <NUM> for radiating a radar beam <NUM>. The antenna <NUM> may be a conductor of any kind capable of converting wire-bound electric energy into a free-propagating radar wave. For instance, the antenna <NUM> may be a patch-antenna integrated into the radar sensor <NUM>.

The antenna <NUM> is configured to emit the radar beam <NUM> towards a predefined region. For instance, the antenna <NUM> may be a directional antenna such as a phased-array antenna, which allows the radiation power to be concentrated onto a certain direction, yielding an increased radar signal strength in a certain area (the predefined region) extending along the said direction. The predefined region may correspond to a field of view of the radar sensor <NUM> when operated as a standalone system. In other words, the predefined region may be considered a detection zone for which the radar sensor <NUM> per se (without the reflector explained below) exhibits a sufficient sensitivity to accomplish a certain radar task.

The radar beam <NUM> emitted by the antenna <NUM> shall not be understood as a beam in an optical sense. The radar beam <NUM> may rather correspond to a main lobe of the radar radiation, thus, describe a portion of the entire radar radiation emitted by the antenna <NUM> with a higher field strength compared to other lobes which appear in a radiation pattern of the antenna <NUM>. The radar beam <NUM> may exhibit any three-dimensional shape. For instance, the radar beam <NUM> may exhibit a conical shape or a cone section through which the radar radiation propagates. The antenna <NUM> may exhibit a phase center or apparent phase center from which the radar beam <NUM> spreads spherically outward. <FIG> illustrates an exemplary transmission path of the radar beam <NUM> and <FIG> illustrates an exemplary receiving path of a reflection of the radar beam <NUM>.

An exemplary first trajectory <NUM>-<NUM> of the radar beam <NUM> is illustrated by the transmission path of <FIG>. The first trajectory <NUM>-<NUM> in the sense of the present disclosure may be considered a field vector of a partial energy flow of the radar beam <NUM> which is perpendicular to a radar wavefront of the radar beam <NUM>. The first trajectory <NUM>-<NUM> emanates from a phase center of the antenna <NUM> and points to a direction towards the predefined region.

The radar system <NUM> further comprises a reflector <NUM> spaced apart from the radar sensor <NUM>. The distance between the antenna <NUM> and the reflector <NUM> may be selected according to requirements of the target application, e.g., according to an operating frequency of the radar sensor <NUM>. On the one hand, a maximum distance (e.g., <NUM>) between the reflector <NUM> and the antenna <NUM> may be specified such that a size of the reflector <NUM> (which may be selected according to the distance) is suitable for the target application and that an efficiency loss of the radar sensor <NUM> is acceptable for the target application. On the other hand, the reflector <NUM> may be arranged relative to the antenna <NUM> such that a minimum distance between the antenna <NUM> and the reflector <NUM> is met. This minimum distance may be required to ensure that the reflector <NUM> is placed in the far field of the antenna <NUM>, i.e., to ensure that the radar beam <NUM> propagates in a certain free space without disturbance. The minimum distance may depend on the operating frequency of the radar sensor <NUM> and physical dimensions of the antenna <NUM>.

The reflector <NUM> may be any structure with a surface reflective for a partial or entire radar frequency range of the radar beam <NUM>. The reflector <NUM> may be selected according to a desired reflection behavior of its surface. For instance, the reflector <NUM> may comprise an outer surface configured to redirect the at least part of the radar beam <NUM>. At least the outer surface of the reflector <NUM> may be metallic. The surface may be metallic to cause a reflection of an incident part of the radar beam <NUM>. In some examples, the reflector <NUM> may be formed as a solid metal piece. For high-frequency radar applications, a thin metal layer may be sufficient to provide a suitable reflection behavior, i.e., the reflector <NUM> may be fabricated of any material such as a polymer by, e.g., 3D-printing or injection molding, and covered by a metallic coating or foil. This may reduce the weight and the production cost of the reflector <NUM>. The (outer) surface of the reflector <NUM> may preferably be even for improving the reflection behavior. In some examples, the surface of the reflector <NUM> may exhibit a metallic grid structure. This may be advantageous for applications where the reflector <NUM> is required to be partly optical transparent, e.g., in cases where the reflector <NUM> is implemented into a layer of a display.

The reflector <NUM> is configured to redirect at least part of the radar beam <NUM> towards a target region different from the predefined region. The reflector <NUM> redirects such parts of the beam which impinge on a surface of the reflector <NUM>. The share of radiation power being redirected by the reflector <NUM> may depend, among other things, on at least one of the extent of the reflector <NUM>, the distance between the reflector <NUM> and the phase center of the antenna <NUM>, and the beam width of the radar beam <NUM>. For instance, in cases where the reflector <NUM> - different from the one shown in <FIG> and Fig. ab - spatially covers only part of a beamwidth of the radar beam <NUM> (i.e., an extent of the radar beam <NUM> measured along a wavefront of the radar beam <NUM>), the reflector <NUM> may redirect only a certain portion of the radar beam <NUM> towards the target region, such as at least <NUM>% or <NUM>% of the entire power of the radar beam <NUM>, and let pass the remaining portion of the radar beam <NUM> towards the predefined region. This may lead to a remaining sensitivity of the radar system <NUM> for the predefined region which may be advantageous for applications where a target object located in the predefined region or the target region shall be detectable. However, in some examples such as the example shown in <FIG>, the reflector <NUM> spatially extends over an entire beamwidth of the radar beam <NUM> and may, therefore, redirect substantially the entire radar beam <NUM> towards the target region. The latter may especially be beneficial for applications where objects in the predefined region shall be explicitly excluded from detection or where the radiation power spread over the target region shall be increased.

The redirection of the radar beam <NUM> is based on reflection at a surface of the reflector <NUM>, thus, an angle of reflection between the surface of the reflector <NUM> and a redirected trajectory may correspond to an angle of incidence between the surface of the reflector <NUM> and an impinging trajectory. Consequently, the shape of the reflector <NUM> and the position of the reflector <NUM> relative to the radar beam <NUM> may be selected according to a desired shape and position of the target region. The selection of the reflector <NUM> for matching a certain application may be independent of an operating frequency of the radar sensor <NUM>. The reflector <NUM> may, therefore, introduce no limitations regarding a bandwidth and may be used in wideband operations. The design of the reflector <NUM> may easily be transferred to any other configuration of a radar system according to the present disclosure. The shape of the reflector <NUM> may be independent of a specific antenna type. Thus, the radar system <NUM> may be adjustable to a wide variety of applications requiring different operation frequencies or antenna types.

By way of illustration, the reflector <NUM> is illustrated by a triangular symbol in <FIG>. It is to be noted that, independently from the illustration of <FIG>, the reflector <NUM> may be of any shape suitable for redirecting the radar beam <NUM> to the target region. In some examples, the reflector <NUM> tapers towards the radar sensor <NUM>. The reflector <NUM> may taper in an apex or edge towards the radar sensor <NUM> such that, ideally, no part of the initial radar beam <NUM> or only a negligibly small portion of the radar beam <NUM> (e.g., less than <NUM>%) impinging on the surface of the reflector <NUM> is directly reflected back to the radar sensor <NUM>. In other words, an angle of incidence between the radar beam <NUM> and the surface of the reflector <NUM> may differ, e.g., by more than <NUM>,<NUM>% from <NUM>°. This may prevent direct reflections and, thus, a potentially undesirable increase of sensitivity of the radar system <NUM> to false targets or vibrations, or a reduction of sensitivity to the actual target.

In some examples, the reflector <NUM> tapers towards an apex or an edge oriented towards the radar sensor <NUM>. For instance, the reflector <NUM> may exhibit a conical or pyramidal shape with an apex or a prismatic shape with an edge pointing towards the radar sensor <NUM>. The reflector <NUM> may be designed such that the tapering, i.e., a tip or edge pointing towards the radar sensor <NUM>, is sharp enough to prevent or sufficiently reduce the aforesaid direct reflections.

The reflector <NUM> or, in particular, a surface of the reflector <NUM> may be symmetrical with respect to a line of symmetry or a plane of symmetry. The reflector <NUM> may exhibit a shape of, e.g., a cone, pyramid, or prism with a symmetrical base plane such as provided by a regular pyramid, a regular prism, or a circular cone. The line of symmetry or the plane of symmetry may run through a point of symmetry of the base plane and an apex or edge of the reflector <NUM>. The line of symmetry or the plane of symmetry is parallel to a beam axis of the radar beam <NUM>. The beam axis may be understood as imaginary line through the phase center of the antenna <NUM> and the centroid of a wavefront of the radar beam <NUM>. Such a symmetrical structure of the reflector <NUM> may enable a uniform distribution of radiation power over the target region.

An orientation or position of the reflector <NUM> differs from the one shown in <FIG>, i.e., a line of symmetry or plane of symmetry of the reflector <NUM> is displaced with respect to the phase center of the antenna <NUM>. The latter may lead to a spreading of radiation power outwards from a certain side of the apex or edge of the reflector <NUM>, i.e., the target region may be restricted to said side.

It is to be noted that any feature of the radar system <NUM> referring to a geometric concept, such as symmetry, parallelism, orthogonality, flatness, straightness, or to a geometric shape is to be understood within the limits of manufacturing or mounting tolerances.

For further elaborating on the shape, size, and position of a reflector in accordance with the present disclosure, further examples are explained with reference to figures below such as <FIG>, <FIG>.

Referring back to <FIG>, the reflector <NUM> deviates the first trajectory <NUM>-<NUM> towards the predefined region when it impinges on the surface of the reflector <NUM>. The deviation causes the first trajectory <NUM>-<NUM> to continue the transmission path along a second trajectory <NUM>-<NUM>. The second trajectory <NUM>-<NUM> emanates from an impact point on the surface of the reflector <NUM> (where the first trajectory <NUM>-<NUM> impinges) and points to the target region.

The target region may be considered a synthetic field of view of the radar system <NUM> which differs from the original field of view of the radar sensor <NUM>. The synthetic field of view results from the redirection of the part of the radar beam <NUM>. The redirection of the radar beam <NUM> may enable a spatial shift of the detectable region of the radar sensor <NUM>. The target region may be considered a detection zone for which the radar sensor <NUM> in combination with the reflector <NUM> exhibits a desirable sensitivity or accuracy for accomplishing a certain radar task. In case only part of the radar beam <NUM> is redirected by the reflector <NUM>, the radar system <NUM> may maintain a sensitivity for at least part of the original field of view of the radar sensor <NUM>.

The target region is different from the predefined region in a sense that the target region at least includes any region outside the predefined region. In other words, the target region may be partly overlapping or may entirely be outside the predefined region. The target region may be of any shape or size and may include several separated subregions. For instance, the target region may comprise two subregions which are opposing with respect to a phase center of the antenna <NUM>. In some examples, the target region may extend over at least <NUM>° along a plane parallel to an emitting surface of the antenna <NUM> when viewed from a phase center of the antenna <NUM>. The emitting surface may correspond to an orientation of the radar sensor <NUM>, e.g., a radar sensor facing vertically upwards may have a horizontal emitting surface. A typical radar sensor may have a field of view limited to an angular range of up to approximately <NUM>° which may be mainly due to the antenna design. The radar sensor <NUM> combined with the reflector <NUM> may widen up this limited angular range. In radar applications where an angular range of more than <NUM>° shall be covered, the radar system <NUM> be a more cost-effective alternative to using multiple radar sensors.

In a concrete application, the radar sensor <NUM> may be placed along a horizontal plane and facing upwards causing the main radiation of the radar beam <NUM> accordingly facing upwards. The predefined region would then be located above the radar sensor <NUM>. However, the application may require a detection of objects in an angular range of <NUM>° horizontally around the radar sensor <NUM>. A shape, material, and position of the reflector <NUM> may be designed for matching this requirement of the application. For instance, the reflector <NUM> may be placed centered above the phase center of the radar sensor <NUM>. Additionally, the reflector <NUM> may be constructed symmetrically with respect to the phase center to evenly distribute the radar power of the redirected radar radiation over the angular range of <NUM>°. The latter may ensure that no spatial angle will be preferred.

In the example of <FIG>, the second trajectory <NUM>-<NUM> is tilted by approximately <NUM>° with respect to the first trajectory <NUM>-<NUM> which may lead to a thereto corresponding spatial shift of the target region. Hence, an imaginary line between the phase center of the antenna <NUM> and the tip of the first trajectory <NUM>-<NUM> (pointing towards the predefined region) may be tilted by approximately <NUM>° degrees with respect to an imaginary line between the phase center and the tip of the second trajectory <NUM>-<NUM> (pointing towards the target region).

In other examples, the tilt angle between a trajectory of the radar beam <NUM> and the redirected counterpart of the trajectory may be different than the one shown in <FIG>. In some examples, an imaginary line between the phase center of the antenna <NUM> and any boundary point of the predefined region is tilted by at least <NUM> degrees with respect to an imaginary line between the phase center and any boundary point of the target region. The tilt angle may be determined by the angle of incidence for trajectories of the radar beam <NUM> impinging on the reflector <NUM>. More specifically, the tilt angle may be (mainly) determined by a shape and position of the reflector <NUM> relative to the phase center of the antenna <NUM>. The tilt angle of the target region with respect to the predefined region may, on the one hand, exclude from detection a first solid angle (at least parts of the predefined region) viewed from the phase center of the antenna <NUM> and, on the other hand, include a second solid angle range (the target region) into detection. Thus, the detectable region of the radar system <NUM> may be shifted beyond the boundary of the original field of view of the radar sensor <NUM>.

The reflector <NUM> is further configured to redirect a reflection of the radar beam <NUM> originating from the target region onto the radar sensor <NUM>. This is illustrated by the receiving path of <FIG>. Assuming the second trajectory <NUM>-<NUM> of <FIG> (or any other trajectory of the radar beam <NUM>) impinges on an object within the target region, the trajectory <NUM>-<NUM> may reflect off of the object, yielding a third trajectory <NUM>-<NUM> which represents said reflection. Thus, the third trajectory <NUM>-<NUM> emanates from the impact point on a surface of the object and points back to the reflector <NUM>. When the third trajectory <NUM>-<NUM> impinges on the reflector <NUM>, it is, in turn, deviated by the reflector <NUM> towards the radar sensor <NUM>, yielding a fourth trajectory <NUM>-<NUM> representing said deviation. The trajectories <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> of <FIG> are used for illustrative purposes. In other examples, the second trajectory <NUM>-<NUM> may cross the target region without impinging on a target, thus, no reflection or redirection in form of the third and fourth trajectory <NUM>-<NUM>, <NUM>-<NUM> may occur. The radar beam <NUM> may, furthermore, include further trajectories pointing towards the predefined region in different directions than the one of the first trajectory <NUM>-<NUM>. Even though the transmission path and the receiving path of the radar system <NUM> are illustrated separately in <FIG>, the radar system <NUM> may simultaneously transmit and receive the radar beam <NUM> and its reflection.

For receiving the reflection of the radar beam <NUM>, the radar system <NUM> may comprise a second antenna, i.e., the radar sensor <NUM> may be a bistatic radar sensor, or the emitting antenna <NUM> additionally serves as receiving antenna, i.e., the radar sensor <NUM> may be a monostatic radar sensor. In the latter case, the reflector <NUM> would redirect the reflection of the radar beam <NUM> onto the aforesaid emitting antenna <NUM>.

In case of a bistatic concept with two separate antennas for transmitting the radar beam <NUM> and receiving its reflection, it may be necessary to adapt the shape and position of the reflector <NUM> to prevent that a mismatch between the transmission path and the receiving path occurs. This issue may be solved by placing the reflector <NUM> in a larger distance to the radar sensor <NUM> such that a distance of the receiving antenna <NUM> and the transmitting antenna is negligible compared to the distance between the radar sensor <NUM> and the reflector <NUM>, i.e., the position of both antennas may be approximately equal. It may be necessary in such cases to select a larger reflector compared to one of a monostatic concept. Consequently, a monostatic radar sensor may be preferable for applications requiring compactness.

The radar system <NUM> may be applicable to several radar scenarios. For instance, the radar sensor <NUM> may be configured to determine, based on the reflection of the radar beam <NUM>, at least one of presence, a movement (e.g., a velocity), and a distance of an object in an environment of the radar system <NUM>. The radar sensor <NUM> may, e.g., detect presence or motion of a person in a surrounding of the radar system <NUM>. A distance between the radar system <NUM> and an object may be determined, e.g., by using FSK (frequency-shift keying) or FMCW (frequency-modulated continuous wave) modulation.

The radar system <NUM> may enable a simple and cost-effective adjustment of a field of view of the radar sensor <NUM> to requirements of a particular radar application. For example, in applications where an angular range of detection, e.g., over <NUM>°, is desirable, the radar system <NUM> may provide a low-cost solution for widening up the original angular range of the radar sensor <NUM>. Or, in case the radar sensor <NUM> is integrated into a device and - due to design considerations of the device - exhibits an orientation or position which by itself is impractical for the radar task, e.g., when objects in a region outside a field of view of the radar sensor <NUM> shall be detected, a suitable deployment of the reflector <NUM> may, however, enable the fulfillment of the radar task. In particular, the radar system <NUM> may enable a lateral detection of objects, i.e., a detection of objects which are located to a side of the radar sensor <NUM> with respect to its orientation. In simple terms, the radar system <NUM> may detect objects which are located in a "blind spot" of the radar sensor <NUM>, thus, in a region which is not directly available for detection by the radar sensor <NUM> itself. Additionally, the radar system <NUM> may explicitly exclude parts of the field of view of the radar sensor <NUM> from detection without substantially worsen its power efficiency.

<FIG> illustrate an example of a radar system <NUM> wherein <FIG> and <FIG> show an oblique top view of the radar system <NUM> and <FIG> show a side view of the radar system <NUM>. The radar system <NUM> comprises a radar sensor <NUM> which is mounted on a printed circuit board <NUM>. The radar sensor <NUM> comprises a monostatic antenna <NUM> configured to emit a radar beam towards a predefined region. The radar sensor <NUM> comprises an emitting surface which is configured to emit the radar beam. The emitting surface is a surface of the radar sensor <NUM> from which the antenna <NUM> radiates the radar beam. In <FIG>, the emitting surface faces vertically upwards.

For illustrating the effect of the deployment of a reflector <NUM> on the operation of the radar system <NUM>, <FIG> show the radar system <NUM> without the reflector <NUM> whereas <FIG> and <FIG> show the radar system <NUM> with the reflector <NUM>. The reflector <NUM> is a rotationally symmetrical cone placed in a centered position above the antenna <NUM> and tapering towards the antenna <NUM>. A minimum distance between the reflector <NUM> and the antenna <NUM> may be, e.g., <NUM>,<NUM>. A maximum distance between the reflector <NUM> and the antenna <NUM> may be <NUM>. The cone angle β may be approximately <NUM>°. The reflector <NUM> is configured to redirect part of the radar beam, e.g., a vertical trajectory <NUM>-<NUM> of the radar beam, towards a target region. The reflector <NUM> deviates the trajectory <NUM>-<NUM> in an angle of approximately <NUM>° towards the target region, yielding a horizontal trajectory <NUM>-<NUM>. The target region may, thus, extend in a horizontal plane around the radar sensor <NUM>. The reflector <NUM> is further configured to redirect a reflection (not shown) of the radar beam originating from the target region onto the radar sensor <NUM>.

<FIG> and <FIG> show an example of a three-dimensional radiation pattern <NUM> of the radar sensor <NUM> for an operating frequency of <NUM>. The radiation pattern <NUM> is a simulation of the dependence of the field strength of the radar beam on the direction of its spatial power flow starting from an origin of the radar beam (the phase center of the antenna <NUM>). It is to be noted that the latter applies similarly to the radiation patterns illustrated by <FIG> and <FIG>. The radiation pattern <NUM> illustrates said dependence by means of a grayscale. The intensity strength (darkness) of the gray in a point of the surface indicates the field strength of radiation emitted by the antenna towards said point. The darker the gray, the higher is the field strength.

In <FIG>, the radiation pattern <NUM> for the radar system <NUM> as a standalone system, i.e., without the reflector <NUM>, is shown. Thereby, the radiation pattern <NUM> exhibits a nearly spherical surface encompassing the phase center of the antenna <NUM>. In <FIG>, the field strength of the radar beam is highest in a circular area around a vertical projection of the phase center onto the spherical surface, i.e., most of the radiation power is emitted upwards. This is also shown by <FIG> which illustrates a polar diagram <NUM> of a first directive gain <NUM> and a second directive gain <NUM> of the radar sensor <NUM> without reflector <NUM> in two vertical planes through the phase center orthogonal to one another, i.e., the polar diagram <NUM> of <FIG> represents two vertical cross sections of the radiation pattern <NUM> of <FIG>. A radial distance of a boundary point of the first directive gain <NUM> and the second directive gain <NUM> from the origin of the polar diagram <NUM> in any direction represents the field strength of radiation emitted in that direction. The higher the radial distance, the higher is the field strength for the corresponding direction. The field strength is represented logarithmically along the axis of the polar diagram <NUM>, i.e., the polar diagram <NUM> has a logarithmic scale. It is to be noted, that the latter similarly applies to the polar diagrams illustrated by <FIG>, <FIG> and <FIG>.

The first directive gain <NUM> and the second directive gain <NUM> exhibit a main lobe whose extent mainly covers a range between -<NUM>° to +<NUM>° and elongates upwards (<NUM>°), i.e., most of the radiation power is emitted upwards and only little radiation power is distributed horizontally.

In <FIG>, the radiation pattern <NUM> for the radar system <NUM> with the reflector <NUM> is shown. The radiation pattern <NUM> is a spherical segment centered above the phase center and cut off by the surface of the reflector <NUM>, i.e., the radiation pattern <NUM> forms a ring which circulates the phase center and is opened upwards. The field strength is highest in a horizontal plane through the tip of the reflector <NUM> and decreases with increasing distance to said horizontal plane. Since the reflector <NUM> has a rotationally symmetrical shape, the radiation power of the radar beam is distributed (nearly) uniformly over an angular range of <NUM>° along the horizontal plane viewed from the phase center. The reflector <NUM>, thus, enables a redirection of the radiation power towards the sides of the radar sensor <NUM>. This is also shown by <FIG> which illustrates a polar diagram <NUM> of the first directive gain <NUM> and the second directive gain <NUM> of <FIG> and, additionally, of a third directive gain <NUM> and a fourth directive gain <NUM> of the radar sensor <NUM> with reflector <NUM> in the same two vertical planes like the ones of <FIG>. The third directive gain <NUM> and the fourth directive gain <NUM> show two similarly sized and shaped main lobes on opposing sides relative to a zero axis of the polar diagram <NUM>. The main lobes extend mainly towards a range from +<NUM>° to +<NUM>° and -<NUM>° to -<NUM>°, i.e., the radiation power is mainly emitted laterally.

By using the reflector <NUM>, the radar system <NUM> may increase a detection range in a horizontal plane around the radar sensor <NUM>. Additionally, the radar system <NUM> may decrease a sensitivity of the radar sensor <NUM> for the main radiation direction of a setup without the reflector <NUM> (<FIG>).

A direction of the reflected radar signal and, consequently, a position and shape of the target region may be mainly dependent on a shape and position of the reflector <NUM>. Conversely, the shape and position of the reflector <NUM> may be modified to obtain an intended radiation pattern. In the example of <FIG>, the tilt angle between a trajectory outgoing from the reflector <NUM> and a trajectory of the initial radar beam is approximately <NUM>°, resulting in a target region mainly extending along a horizontal plane around the radar sensor <NUM>. Depending on requirements of a radar application, the preferred tilt angle may differ from <NUM>°. The tilt angle may be adjusted by a suitable selection of a shape of the reflector <NUM>, or more specifically, of an opening angle with which the reflector <NUM> tapers towards the radar sensor <NUM>. This is further explained with reference to <FIG>. The shape and position of the target region may further be adjusted based on a suitable selection of the geometric shape and position of the reflector <NUM>. The latter is further explained with reference to <FIG> and <FIG>.

<FIG> illustrate a sectional view of an example of a radar system <NUM> with different redirection angles between a radar beam <NUM> emitted by a radar sensor <NUM> and a reflected radar signal <NUM> after impinging on a reflector <NUM>. The radar sensor <NUM> comprises an antenna configured to emit the radar beam <NUM> towards a predefined region. The reflector <NUM> is configured to redirect at least part of the radar beam <NUM> towards a target region different from the predefined region and to redirect a reflection of the radar beam <NUM> originating from the target region onto the radar sensor <NUM>.

In <FIG>, a cross section of the reflector <NUM> is illustrated by a triangle, i.e., the reflector <NUM> may exhibit, e.g., a pyramidal, prismatic, or conic shape. In <FIG>, an opening angle of a tapering of the reflector <NUM> towards the radar sensor <NUM> may cause the redirection angle to range between approximately <NUM>° to <NUM>°, thus, causing the reflected radar signal <NUM> spreading mainly over a plane parallel to an emitting surface of the radar sensor <NUM>. In <FIG>, the tapering is less pointed than that of <FIG>, i.e., the opening angle of the tapering is bigger, which causes the reflected radar signal <NUM> to be tilted towards a plane along the emitting surface (more downwards). In <FIG>, the tapering is more pointed than that of <FIG>, i.e., the opening angle of the tapering is smaller, which causes the reflected radar signal <NUM> to be tilted away from the plane along the emitting surface (more upwards).

By selecting a suitable shape of the reflector <NUM>, any redirection angle may be realized. The redirection angle may define a position of the target region in a way that an imaginary line between a phase center of the antenna and any boundary point of the predefined region may be tilted with respect to an imaginary line between the phase center and any boundary point of the target region by an angle corresponding to the redirection angle. For instance, the imaginary line between the phase center of the antenna and any boundary point of the predefined region may be tilted by at least <NUM>° with respect to the imaginary line between the phase center and any boundary point of the target region.

The radar system <NUM> may allow a redirection of the radar beam <NUM> towards a target region matching a particular radar application. The radar system <NUM> may provide simple means -by selecting a suitable shape of the reflector <NUM> - to adapt the target region to the radar application. The radar system <NUM> may enable detection of objects lateral to the radar sensor <NUM>, e.g., along a plane parallel to an emitting surface of the radar sensor <NUM>.

<FIG> illustrates a sectional view of an example of a radar system <NUM>. The radar system <NUM> comprises a radar sensor <NUM> configured to emit a radar beam <NUM> towards a predefined region. The radar system <NUM> comprises a reflector <NUM> configured to redirect at least part of the radar beam <NUM> towards a target region different from the predefined region.

Since the reflector <NUM> does not cover an entire beamwidth (extent) of the radar beam <NUM>, some parts of the radar beam <NUM>, e.g., a first trajectory <NUM>-<NUM> of the radar beam <NUM>, partially passes the reflector <NUM> without being redirected, thus, the first trajectory <NUM>-<NUM> is not affected by the reflector <NUM> and points to the predefined region. Consequently, the radar system <NUM> may exhibit a sensitivity for the target region as well as for parts of the predefined region. In the example of <FIG>, the radar system <NUM> may still be able to detect objects above the radar sensor <NUM>, e.g., in a boundary area of the radar beam <NUM> protruding over the reflector <NUM>.

The radar system <NUM> may allow a modification of a region for which the radar sensor <NUM> would - as a standalone system - be sensitive, i.e., the radar system <NUM> may enable an alignment of the field of view of the radar sensor <NUM> to a particular application. The radar system <NUM> may exclude entirely or partially an original field of view of the radar sensor <NUM> from detection and include a customizable target region into detection.

<FIG> and <FIG> illustrate a side view and an oblique top view, respectively, of an example of a radar system <NUM>. The radar system <NUM> comprises a radar sensor <NUM> comprising an antenna configured to emit a radar beam towards a predefined region. The radar system <NUM> comprises a reflector <NUM> configured to redirect at least part of the radar beam towards a target region different from the predefined region.

The radar system <NUM> exhibits a configuration similar to the radar system <NUM> described above except that the reflector <NUM> is displaced with respect to a phase center of the antenna. More specifically, the reflector <NUM> is symmetrical with respect to a line of symmetry <NUM> and the line of symmetry <NUM> is displaced, e.g., by <NUM>, with respect to a beam axis <NUM> through the phase center of the antenna. The reflector <NUM> is only slightly displaced such that it is at least partly placed in the predefined region, i.e., such that at least part of the radar beam impinges on the surface of the reflector <NUM>.

<FIG> additionally illustrates a three-dimensional radiation pattern <NUM> of the radar sensor <NUM>. The radiation pattern <NUM> appears as a segment of a sphere encompassing the phase center and cut off by a surface of the reflector <NUM>. The field strength of the radiation is especially high along a horizontal plane through the phase center, i.e., a radiation power of the radar beam is mainly focused on one side of the radar sensor <NUM>. This is also shown by <FIG> which illustrates a polar diagram <NUM> of a first directive gain <NUM> of the radar sensor <NUM> of <FIG> with a centered reflector and a second directive gain <NUM> of the radar sensor <NUM> with the displaced reflector <NUM>. The polar diagram <NUM> represents a horizontal plane through the phase center of the respective antenna. The first directive gain <NUM> shows an approximately uniform distribution of the radiation power over the entire angular range whereas the second directive gain <NUM> has a limited angular range from -<NUM>° to <NUM>°.

A displacement of the reflector <NUM> relative to the phase center may cause a radiation power of the radar beam to be focused more on a particular side of the radar sensor <NUM>. This effect may be used to shape the radiation pattern as desired. For example, in an application where an angular range of, e.g., <NUM>° viewed from the phase center is required, the reflector <NUM> may be placed outside a centered position relative to the phase center. The radar system <NUM> may be useful for applications where a device comprising the radar system <NUM> has a fixed position and is placed close to an obstacle. Then, a focus of the radiation power away from the obstacle may be beneficial to increase a detection distance for a side of the radar sensor <NUM> opposing the obstacle.

<FIG> and <FIG> illustrate an oblique top view of an example of a radar system <NUM>. The radar system <NUM> comprises a radar sensor <NUM> comprising an antenna configured to emit a radar beam towards a predefined region. The radar system <NUM> comprises a reflector <NUM> configured to redirect at least part of the radar beam towards a target region different from the predefined region.

The radar system <NUM> exhibits a configuration similar to the radar system <NUM> of <FIG> except that the reflector <NUM> exhibits a prismatic shape (shape of a triangular prism) centered above a phase center of the antenna. The tapering of the reflector <NUM> is an edge pointing towards the antenna. More specifically, the reflector <NUM> is symmetrical with respect to a line of symmetry and the line of symmetry extends through the phase center of the antenna.

<FIG> additionally illustrates a three-dimensional radiation pattern <NUM> of the radar sensor <NUM>. The radiation pattern <NUM> exhibits two separated spherical segments which are opposing with respect to the radar sensor <NUM>. Accordingly, the resulting target region may comprise two subregions which are opposing with respect to the phase center of the antenna. This is also shown by <FIG> which illustrates a polar diagram <NUM> of a first directive gain <NUM> of the radar sensor <NUM> of <FIG> with a conical reflector and a second directive gain <NUM> of the radar sensor <NUM> with the prismatic reflector <NUM>. The polar diagram <NUM> represents a horizontal plane through the phase center of the respective antenna. The first directive gain <NUM> shows an approximately uniform distribution of the radiation power over the entire angular range whereas the second directive gain <NUM> exhibits two opposing lobes with an angular range from approximately -<NUM>° to -<NUM>° and from +<NUM>° to +<NUM>°, respectively, thus, an angular range from -<NUM>° to +<NUM>° and from + <NUM> to -<NUM>° (clockwise) is excluded from detection.

The radar system <NUM> creates separated areas of radar coverage based on a geometry of the reflector <NUM>. In other examples, a radar system according to the present disclosure may create any number of separated subregions for detection with any respective angular range. This may be advantageous for applications requiring certain regions to be excluded from detection or to focus radar power on certain regions of interest.

<FIG> illustrates an electronic device <NUM> comprising a radar system <NUM> and control circuitry <NUM> configured to control an operation of the electronic device <NUM> based on an output signal of the radar system <NUM>. The radar system <NUM> comprises a radar sensor and a reflector as described above, e.g., with reference to <FIG>. The radar sensor is configured to emit a radar beam to a predefined region. The reflector is configured to redirect at least part of the radar beam towards a target region.

The control circuitry <NUM> may be a single dedicated processor, a single shared processor, or a plurality of individual processors, some of which or all of which may be shared, a digital signal processor (DSP) hardware, an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). The control circuitry <NUM> may optionally be coupled to, e.g., read only memory (ROM) for storing software, random access memory (RAM) and/or non-volatile memory. The processing circuitry <NUM> is communicatively coupled to the radar system <NUM>.

The electronic device <NUM> may be any device with a radar function. The electronic device <NUM> may be, e.g., a consumer device. The electronic device <NUM> may be, e.g., an audio equipment such as a speaker or a telecommunication device such as a television receiver.

The radar system <NUM> may be configured to determine at least one of presence, a movement, and a distance of an object in an environment of the electronic device <NUM>. For instance, the redirected radar beam may impinge on the object and reflect back to the reflector which, then, redirects the reflection to the radar sensor. An antenna of the radar sensor may receive the reflection and generate the output signal based on the received reflection. The radar system <NUM> may, then, transfer the output signal to the control circuitry <NUM> for further processing.

The radar system <NUM> may be configured to determine the at least one of presence, the movement, and the distance of the object in an immediate surrounding of the electronic device <NUM>, e.g., in a distance of up to a few meters (e.g., <NUM> or <NUM> meters) to the electronic device <NUM>. The radar system <NUM> may be configured to detect presence of a user of the electronic device <NUM>. For instance, the radar system <NUM> may be configured to determine whether a person is present in a certain area around the electronic device <NUM> and, optionally, determine whether that person approaches the electronic device <NUM> or moves away from the electronic device <NUM>.

The control circuitry <NUM> may control the operation of the electronic device <NUM>, e.g., by activating or deactivating a certain function of the electronic device <NUM> based on the output signal, e.g., a certain function may be activated if it is determined that a user of the electronic device <NUM> is present. For instance, the control circuitry <NUM> may, if it is determined that a user is close, skip key word activation or automatically play music, activate air-conditioning, heating or alike. The control circuitry <NUM> may monitor a distance to a user based on the output signal (follow-me function). The electronic device <NUM> may have a (wireless) connection to other electronic devices in its surrounding and communicate the distance to the other electronic devices in order to determine which of the electronic devices is closest to the user, e.g., for connecting a microphone of the determined electronic device with a mobile phone of the user for phone calls. The electronic device <NUM> may be a speaker and be connected to other speakers in its surrounding to enable a dynamic handover of an audio output to one of the speakers closest to the user.

The electronic device <NUM> may have a fixed orientation, e.g., a certain surface area of the electronic device <NUM> may be designed for an orientation to a certain direction, e.g., vertically upwards or downwards, or horizontally to a certain side. The orientation may be dependent on a surrounding where the electronic device <NUM> is operated, e.g., the electronic device <NUM> may be designed for an orientation away from an obstacle such as a wall or towards an area of interest inside a room. The radar system <NUM> may be integrated into a certain side of the electronic device <NUM>, thus, the fixed orientation of the electronic device <NUM> may imply a similarly fixed orientation of the radar sensor.

The integration of the radar system <NUM> may be selected according to design considerations which may be opposed to the radar function, i.e., the orientation of the radar sensor may, per se, be impractical for the radar application. For instance, the radar system <NUM> may be integrated into a top side of the electronic device <NUM> resulting in an upward orientation of the radar sensor even though objects lateral to the electronic device <NUM> shall be detected. Or the radar function may require a target region differing from a field of view of the radar sensor, e.g., with an angular range of more than <NUM>°. In such cases, the radar system <NUM> may overcome a limitation of a conventional radar system by providing the possibility to freely define the target region for matching the requirements of the radar function.

For instance, the radar system <NUM> may be configured to detect presence of a user in a proximity to the electronic device <NUM>. The radar system <NUM> may be integrated into a top side of the electronic device <NUM>, i.e., facing upwards. The reflector of the radar system <NUM> may provide a coverage of <NUM>° around the electronic device <NUM>, i.e., it may be capable of detecting a user lateral to the electronic device <NUM> in any direction.

In some scenarios, a position of the electronic device <NUM> may be intended to be mostly fixed and a limited target region in front of the electronic device <NUM> may be relevant for monitoring presence of a user. In other scenarios, the electronic device <NUM> may be expected to be placed centered inside a room or, potentially, be moved with respect to its position and orientation. For any of those scenarios, the radar system <NUM> may provide a suitable method for detection of an object in an area of interest without the use of multiple sensors, reducing costs and power consumption of the electronic device <NUM>.

The radar system <NUM> may also prevent unwanted detection of objects by excluding certain regions around the electronic device <NUM> from detection. For instance, the radar system <NUM> may suppress an unwanted detection of movements of, e.g., a fan on the ceiling or a cleaning robot and pet on the floor, without extensive data processing effort or efficiency loss. The radar system <NUM> may allow immunity to detection of objects in an original field of view of the radar sensor. Besides, the radar system <NUM> may increase a sensitivity of the radar sensor for a desired target region different from a field of view of the radar sensor.

Using the radar system <NUM> may especially be beneficial for applications requiring a wide detection range over a solid angle of more than <NUM>° with a high sensitivity for the boundary area of the detection range. A conventional approach to fulfill this requirement may be the use of multiple radar sensors, e.g., <NUM> or <NUM> sensors: Each of the radar sensors may cover a limited part of the total target region. Another conventional approach may be the use of a sensor with multiple channels where each channel is connected to a respective antenna. The antennas may be placed such that each of the antenna may cover a limited part of the total target region. In contrast to the conventional approach, the radar system <NUM> may decrease hardware costs, space inside the electronic device <NUM> and power consumption. Since only one antenna may be required, a use of a monostatic radar sensor may additionally be advantageous for saving space, e.g., in high-frequency application and when the radar sensor is integrated into a package or chip. A simple geometry of the reflector may be suitable for most applications; thus, the fabrication of the reflector may be fast and cost-effective.

Another approach to fulfill the aforementioned requirement could be a radar sensor coupled to a dielectric or metallic waveguide. The dielectric waveguide may redirect the radar beam to a target region. Compared to the latter approach, the reflector of the radar system <NUM> may be simpler to fabricate. Besides, the radar system <NUM> may be operable with a common radar sensor whereas matching issues may occur when using the waveguide.

<FIG> illustrates a flowchart of an example of a method <NUM> for operating a radar system, such as the radar system <NUM> described above, comprising a radar sensor and a reflector spaced apart from the radar sensor and symmetrical with respect to a line of symmetry or a plane of symmetry. The line of symmetry or the plane of symmetry is parallel to a beam axis of a radar beam The line of symmetry or the plane of symmetry is displaced with respect to a phase center of the antenna. The method <NUM> comprises emitting <NUM>, at an antenna of the radar sensor, the radar beam towards a predefined region, redirecting <NUM>, using the reflector, the radar beam towards a target region different from the predefined region, and redirecting <NUM>, using the reflector, a reflection of the radar beam originating from the target region onto the radar sensor.

More details and aspects of the method <NUM> are explained in connection with the proposed technique or one or more examples described above, e.g., with reference to <FIG>. The method <NUM> may comprise one or more additional optional features corresponding to one or more aspects of the proposed technique, or one or more examples described above.

Claim 1:
A radar system (<NUM>) comprising:
a radar sensor (<NUM>) comprising an antenna configured to emit a radar beam (<NUM>) towards a predefined region; and
a reflector (<NUM>) spaced apart from the radar sensor (<NUM>) and symmetrical with respect to a line of symmetry or a plane of symmetry, wherein the line of symmetry or the plane of symmetry is parallel to a beam axis of the radar beam (<NUM>), wherein the reflector (<NUM>) is configured to:
redirect at least part of the radar beam (<NUM>) towards a target region different from the predefined region; and
redirect a reflection of the radar beam (<NUM>) originating from the target region onto the radar sensor (<NUM>);
the radar system (<NUM>) being characterized by the line of symmetry or the plane of symmetry being displaced with respect to a phase center of the antenna.