Carrier phase offset correction in coherent distributed radar systems

Abstract

A first antenna in the first radar sensor receives a first signal transmitted by one or more second antennas in the second radar sensor and reflected by at least one object. A third antenna in the second radar sensor receives a second signal transmitted by one or more fourth antennas in the first radar sensor and reflected by the at least one object. A snapshot is generated that includes a complex value representative of a phase response of the first signal and the second signal, and a carrier phase offset between the first signal and the second signal is estimated based on the snapshot. In some cases, an output representative of the detection of the object is generated based on the carrier phase offset.

Description

Technical Field

[0001] This invention relates to a carrier phase offset correction method and device in a coherent distributed radar system. Background Technology

[0002] Advanced Driver Assistance Systems (ADAS) support human-machine interfaces for automobiles and other vehicles to reduce driver errors, collisions, and injuries. ADAS comprises cameras, sensors, and associated hardware and software that can detect obstacles or driver errors and then provide warnings or take action to avoid collisions. Examples of ADAS functionalities include forward collision warning, lane departure warning, rear cross-traffic alert, blind spot warning, automatic braking, automatic pedestrian emergency braking, rear braking, blind spot intervention, adaptive cruise control, lane centering assist, and lane keeping assist. The sensing technologies used in ADAS include light detection and ranging (LiDAR), cameras, ultrasound, and radar. Automotive radar sensors can simultaneously measure the distance, radial velocity, azimuth, and elevation angles of multiple objects.

[0003] Vehicle-mounted radar systems can include a single, co-located transmitter and receiver (monostatic), transmitters and receivers deployed at two locations (bistatic), and transmitters and receivers deployed at more than two locations (multistatic). Distributing transmitters and receivers across multiple locations can increase the system's signal-to-noise ratio (SNR), improve positioning accuracy, enhance velocity vector estimation, improve spatial resolution, and strengthen the signal volume. Multiple-input multiple-output (MIMO) configurations deploy multiple transmitter and receiver antennas at each location to improve the radar system's angular resolution and accuracy. Bistatic or multistatic radar sensors require time, frequency, and phase synchronization, as well as additional data transmission links, higher computational complexity, and more accurate site positioning. Summary of the Invention

[0004] According to a first aspect of this disclosure, a method is provided, the method comprising: receiving, by a first antenna in a first radar sensor, a first signal transmitted by at least one second antenna in a second radar sensor and reflected by at least one object; receiving, by a third antenna in the second radar sensor, a second signal transmitted by at least one fourth antenna in the first radar sensor and reflected by the at least one object; generating a snapshot including complex values ​​representing the phase responses of the first signal and the second signal; and estimating a carrier phase offset between the first signal and the second signal based on the snapshot.

[0005] In one or more embodiments, the snapshot includes first information indicating the relative phase of a first signal received by a first antenna and second information indicating the relative phase of a second signal received by a third antenna.

[0006] In one or more embodiments, the method further includes: generating a virtual array based on snapshots, the virtual array representing a functional relationship between the phase response of a first signal and the spacing between a first antenna and the at least one second antenna, and representing a functional relationship between the phase response of a second signal and the spacing between a third antenna and the at least one fourth antenna. The virtual array may include multiple piecewise linear phase relationships corresponding to the positions of the at least one second antenna and the at least one fourth antenna.

[0007] The method may further include: determining the slope of the plurality of piecewise linear phase relationships based on a first direction of arrival of the first signal and a second direction of arrival of the second signal; determining the offset between the plurality of piecewise linear phase relationships based on a first departure direction of the first signal and a second departure direction of the second signal; and estimating a carrier phase offset based on the slope and the offset.

[0008] In one or more embodiments, the first and second signals are reflected by a single object, and the estimation of carrier phase offset includes estimating the carrier phase offset based on the phase difference between the first and second signals. The virtual array may be symmetric, and the method further includes: generating a difference snapshot by multiplying the complex value of the first signal by the complex conjugate of the complex value of the second signal, which shares the position of a virtual antenna in the virtual array after folding; and estimating the carrier phase offset based on the difference snapshot. Estimating the carrier phase offset may include: determining a beamforming spectrum based on a Fourier transform of the difference snapshot; identifying peak locations and spectral peaks in the beamforming spectrum; and performing an inverse Fourier transform of the spectral peaks to estimate the carrier phase offset.

[0009] In one or more embodiments, the method further includes: generating an output representing the detection of the object based on a carrier phase offset.

[0010] According to a second aspect of this disclosure, an apparatus is provided, the apparatus comprising: a first radar sensor including a plurality of first antennas and at least one second antenna; a second radar sensor including a plurality of third antennas and at least one fourth antenna, the first antennas being configured to receive a first signal transmitted by the at least one fourth antenna and reflected by at least one object, the third antennas being configured to receive a second signal transmitted by the at least one second antenna and reflected by the at least one object; and at least one processing unit configured to generate a snapshot including complex values ​​representing the phase responses of the first signal and the second signal, and to estimate a carrier phase offset between the first signal and the second signal based on the snapshot.

[0011] In one or more embodiments, the snapshot includes first information indicating the relative phase of a first signal received by a first antenna and second information indicating the relative phase of a second signal received by a third antenna.

[0012] In one or more embodiments, the processing unit is configured to generate a virtual array based on snapshots, the virtual array representing a function of the phase response of a first signal and the spacing between a first antenna and the at least one fourth antenna, and representing a function of the phase response of a second signal and the spacing between a third antenna and the at least one second antenna. The virtual array may include multiple piecewise linear phase relationships corresponding to the positions of the at least one second antenna and the at least one fourth antenna. The processing unit may be configured to: determine the slope of the multiple piecewise linear phase relationships based on a first direction of arrival of the first signal and a second direction of arrival of the second signal; determine the offset between the multiple piecewise linear phase relationships based on a first departure direction of the first signal and a second departure direction of the second signal; and estimate a carrier phase offset based on the slope and the offset. The processing unit may be configured to determine the slope and the offset using a least squares method.

[0013] In one or more embodiments, the first and second signals are reflected by a single object, and a processing unit is configured to estimate a carrier phase offset based on the phase difference between the first and second signals. The virtual array may be symmetric, and the processing unit may be configured to: generate a difference snapshot by multiplying the complex value of the first signal by the complex conjugate of the complex value of the second signal, which shares the virtual antenna position in the folded virtual array; and estimate the carrier phase offset based on the difference snapshot. The processing unit may be configured to: determine a beamforming spectrum based on the Fourier transform of the difference snapshot; identify peak locations and spectral peaks in the beamforming spectrum; and perform an inverse Fourier transform of the spectral peaks to estimate the carrier phase offset.

[0014] According to a first aspect of this disclosure, an apparatus is provided, the apparatus comprising: a plurality of radar sensors, each of the plurality of radar sensors including a plurality of receiving antennas and at least one transmitting antenna, the receiving antennas in a first subgroup of the radar sensors being configured to receive a first signal transmitted by a transmitting antenna in a second subgroup of the radar sensors and reflected by at least one object, the receiving antennas in the second subgroup of the radar sensors being configured to receive a second signal transmitted by the at least one transmitting antenna in the first subgroup of the radar sensors and reflected by at least one object; and at least one processing unit configured to generate a snapshot including complex values ​​representing the phase responses of the first signal and the second signal, and to estimate a carrier phase offset between the first signal and the second signal based on the snapshot. The at least one processing unit may be configured to estimate the carrier phase offset based on an offset between piecewise linear phase relationships in the phase responses of the first signal and the second signal, the piecewise linear phase relationships corresponding to at least one position of the at least one transmitting antenna. Attached Figure Description

[0015] This disclosure will be better understood by referring to the accompanying drawings, which will make its numerous features and advantages clear to those skilled in the art. The same reference numerals are used in different drawings to indicate similar or identical items.

[0016] Figure 1 A coherent distributed radar system according to some embodiments is shown, the coherent distributed radar system comprising two or more radar sensors that use reflected coherent radiation to detect an object.

[0017] Figure 2 The path length difference between reflected signals in a portion of a coherent distributed radar system according to some embodiments is shown.

[0018] Figure 3 Piecewise linear phase relationships and linear phase relationships after correcting for carrier phase offsets are shown according to some embodiments.

[0019] Figure 4 A bistatic virtual array representing the transmission path between the transmitting and receiving antennas in two radar sensors is shown according to some embodiments.

[0020] Figure 5 The phase response of a bistatic virtual array to a signal generated by two radar sensors, reflected from a single object, and received by the two radar sensors, according to some embodiments, is shown.

[0021] Figure 6 A method for performing coherent distributed radar detection, including correcting carrier phase offset, is illustrated according to some embodiments.

[0022] Figure 7 A piecewise linear model of the phase in a snapshot of a bistatic array according to some embodiments is shown.

[0023] Figure 8 A method for estimating the carrier phase offset between two radar sensors in a coherent distributed radar system using the least squares method, according to some embodiments, is shown.

[0024] Figure 9 A method is shown, according to some embodiments, for estimating the carrier phase offset between two radar sensors in a coherent distributed radar system using a spectrum-based technique applied to the phase difference between signal pairs. Detailed Implementation

[0025] To locate an object, the vehicle radar system transmits coherent phase-aligned signals from one or more transmitting antennas. The transmitted signals are reflected by the object and return to the receiver antenna in the vehicle radar system. For a monostatic radar system, the direction of departure (DoD) of the signal transmitted by the transmitting antenna is equal to the direction of arrival (DoA) of the reflected signal received by the receiver antenna. Therefore, the path length difference from the transmitting antenna to the juxtaposed receiver antenna is... A proportional quantity, where d is the distance between the receiver antennas, and The DoA (DoD) of the reflected signal at the receiver antenna is the phase difference between the signals received at the receiver antenna. Different path lengths introduce a phase difference between the signals received at the receiver antenna, and the relationship between the phases of the signals received at different receiver antennas is characterized as a linear phase slope determined by the DoA. In contrast, a bistatic radar system combines signals transmitted by one radar sensor and received in another. For example, the DoD of a signal transmitted from the transmit antenna of the first radar sensor in a bistatic radar system is not necessarily the same as the DoA of a signal received at the receiver antenna of the second radar sensor in the same system. Target angular estimation in a bistatic radar system is accomplished by analyzing the phase difference between the received signals. These phases are determined by the path length differences between the transmitter, target, and receiver. In a bistatic radar system, the phase difference has an additional phase offset caused by the difference in carrier frequencies of the two or more radar sensors. This carrier phase offset must be estimated and corrected before the phase difference due to the path length difference can be analyzed.

[0026] Figure 1-9A system, apparatus, and method are illustrated for estimating carrier phase offsets between multiple radar sensors by comparing the phase difference between a signal transmitted by an antenna in one radar sensor and a signal received by an antenna in a different radar sensor. In some cases, the radar system uses a first radar sensor and a second radar sensor to detect objects, each of which includes one or more transmitting antennas and one or more receiving antennas. The radar system generates snapshots that include a set of complex values ​​representing, in particular, the phase response of the signal transmitted between the combinations of transmitting and receiving antennas.

[0027] A bistatic virtual array represents the phase response of a corresponding signal as a function of the spacing between the transmitting and receiving antennas. For example, a snapshot may include first information indicating the relative phase of signals transmitted by the transmitting antenna in a first radar sensor and received by the receiving antenna in a second radar sensor. A snapshot may also include second information indicating the relative phase of signals transmitted by the transmitting antenna in the second radar sensor and received by the receiving antenna in the first radar sensor. In this case, the bistatic virtual array includes a piecewise linear phase relationship corresponding to the positions of the transmitting antennas.

[0028] The slope of the linear phase relationship is determined by the direction of arrival of the signal at the corresponding receiving antenna. The offset between the linear phase relationships is determined by the direction of departure of the signal at the corresponding transmitting antenna. In one embodiment, the parameters of the linear phase relationship are estimated using a least-squares method, and then these parameters are used to estimate the carrier phase offset between the first and second radar sensors. If the snapshot contains a single object and the corresponding bistatic array is symmetrical, the carrier phase offset can be determined based on the phase difference between the signal transmitted from the first radar sensor to the second radar sensor and the signal transmitted from the second radar sensor to the first radar sensor. However, as discussed herein, symmetry of the bistatic array is not required in all embodiments.

[0029] Figure 1 A coherent distributed radar system 100 according to some embodiments is shown, comprising two or more radar sensors 102, 104 that use reflected coherent radiation to detect an object 106. The illustrated embodiment of the coherent distributed radar system 100 is implemented in a vehicle 108 and can therefore be used as part of an advanced driver assistance system (ADAS). However, the coherent distributed radar system 100 can also be implemented in other scenarios or environments, such as industrial applications requiring dynamic, real-time identification of objects approaching the coherent distributed radar system 100.

[0030] The coherent distributed radar system 100 also includes one or more processing units 110 and one or more memories 112. The processing unit 110 implements multiple processor cores, for example, that execute instructions simultaneously or in parallel (for clarity, ...). Figure 1 Circuitry systems such as those not shown in the diagram. In some embodiments, one or more processor cores operate as Single Instruction Multiple Data (SIMD) units, which perform the same operation on different datasets simultaneously or in parallel. Processing unit 110 is configured to execute instructions stored in memory 112, such as program code for one or more applications. Data consumed by processing unit 110 in executing instructions and results produced by processing unit 110 may also be stored in memory 112.

[0031] Radar sensors 102 and 104 include one or more transmitting antennas for emitting coherent radiation and one or more receiving antennas for receiving coherent radiation reflected from object 106. For clarity, Figure 1 Individual antennas are not shown. In the illustrated embodiment, radar sensor 102 emits radiation toward object 106 along path 114, and radar sensor 104 emits radiation toward object 106 along path 116. A portion of the radiation emitted by radar sensor 102 is reflected by object 106 and returns to sensor 102 along path 118; another portion of the radiation emitted by radar sensor 102 is reflected by object 106 and returns to radar sensor 104 along path 120. A portion of the radiation emitted by radar sensor 104 is reflected by object 106 and returns to radar sensor 104 along path 122; another portion of the radiation emitted by radar sensor 104 is reflected by object 106 and returns to sensor 102 along path 124.

[0032] As discussed herein, the different path lengths between the transmitting and receiving antennas in radar sensors 102 and 104 generate phase differences between the signals received at radar sensors 102 and 104. These phase differences can be used to determine, in particular, the position (location) and velocity of object 106. In some cases, velocity may be referred to as Doppler velocity because velocity can be determined based on the Doppler shift of the signal's frequency. However, the difference between the carrier phases of the carriers used by the front ends of radar sensors 102 and 104 produces a carrier phase offset between the signals transmitted by one of radar sensors 102 and 104 and received by the other. In the illustrated embodiment, even if paths 120 and 124 have the same path length, a carrier phase offset is generated between the signal received at radar sensor 102 along path 124 (i.e., the signal transmitted by radar sensor 104) and the signal received at radar sensor 104 along path 120 (i.e., the signal transmitted by radar sensor 102). Carrier phase offset reduces the accuracy of position determination for object 106 because the phase difference is inconsistent with the lengths of paths 120 and 124.

[0033] The carrier phase offset can be estimated and corrected based on signals transmitted by each of radar sensors 102, 104 and received by a different radar sensor among radar sensors 102, 104. In some embodiments, one or more receiving antennas in radar sensor 102 (on path 124) receive signals transmitted by one or more transmitting antennas in radar sensor 104, and one or more receiving antennas in radar sensor 104 (on path 120) receive signals transmitted by one or more transmitting antennas in radar sensor 102. Processing unit 110 generates a snapshot including complex values ​​representing the phase response of the signals received by the receiving antennas in radar sensors 102, 104. Processing unit 110 then estimates the carrier phase offset between the signals received by the receiving antennas in radar sensors 102, 104 based on the snapshot.

[0034] Figure 2 The difference in path length between reflected signals in section 200 of a coherent distributed radar system according to some embodiments is shown. Section 200 in Figure 1This is implemented in some embodiments of the coherent distributed radar system 100 shown. Part 200 includes radar sensors 202 and 204 that transmit and receive coherent electromagnetic radiation that can be reflected from one or more objects, such as object 206. In the illustrated embodiment, radar sensor 202 includes antennas 210, 211, 212, 213, and 214 (collectively referred to herein as "antennas 210-214"), and radar sensor 204 includes antennas 220, 221, 222, 223, and 224 (collectively referred to herein as "antennas 220-224"). Antennas 210 and 211 in radar sensor 202 and antennas 220 and 221 in radar sensor 204 are configured to transmit signals including coherent electromagnetic radiation. Antennas 212-214 in radar sensor 202 and antennas 222-224 in radar sensor 204 are configured to receive signals including coherent electromagnetic radiation reflected from object 206. In some embodiments, antennas 214, 224 are also configured to transmit signals including coherent electromagnetic radiation.

[0035] The departure direction of coherent electromagnetic radiation from radar sensors 202 and 204 and the arrival direction of coherent electromagnetic radiation at radar sensors 202 and 204 depend on the relative positions of object 206 and sensors 202 and 204. Therefore, the angles indicating the departure and arrival directions differ at radar sensors 202 and 204. In the illustrated embodiment, angle 226 (also referred to herein) The direction of departure and direction of arrival at radar sensor 202 are indicated, and the angle 228 (also referred to herein) The directions of departure and arrival at radar sensor 204 are indicated. Angles 226 and 228 result in corresponding path length differences 230 and 232 between the coherent electromagnetic radiation transmitted and / or received by antennas 210-214 and 220-224. Path length differences 230 and 232 introduce a phase difference between the transmitted and / or received signals. If the spacing between antennas 210-214 and 220-224 (e.g., distance 234) is denoted as d, then the phase difference between adjacent antennas 210-214 in radar sensor 202 is related to the value... The phase difference and value between adjacent antennas 220-224 in radar sensor 204 are linearly related. A linear relationship exists. The carrier phase offset will also exist between the linear phase relationship of antennas 210-214 in radar sensor 202 and antennas 220-224 in radar sensor 204. Subgroups of antennas 210-214 in radar sensor 202 and antennas 220-224 in radar sensor 204 are used to estimate the carrier phase offset, as discussed herein.

[0036] Figure 3 Piecewise linear phase relationship 300 and linear phase relationship 302 after carrier phase offset correction are illustrated according to some embodiments. The horizontal axis represents the spacing between the antennas in the two sensors, which can be measured as a multiple of the wavelength of the coherent signals transmitted from and received by the sensors. The vertical axis represents the relative phase of the signals received at the corresponding antennas. In some embodiments, piecewise linear phase relationship 300 and linear phase relationship 302 represent the phase of the signals received at the corresponding antennas. Figure 1 The radar sensors 102, 104 and shown are Figure 2 The phase relationship between the signals received by the antennas in sensors 202 and 204 is shown.

[0037] As described herein, the slopes of portions of piecewise linear phase relationships 300 and 302 are related to the direction of arrival and / or departure of the signal. Although the slopes in the illustrated embodiments are the same for both piecewise linear phase relationships 300 and 302, in some embodiments, portions of piecewise linear phase relationships 300 and / or 302 may have different slopes because the spacing between the sensors creates differences in the direction of arrival and / or departure of the signal at different sensors.

[0038] Before correcting for carrier phase shift, the piecewise linear phase relationship 300 comprises two parts 304 and 306 representing the linear phase relationship between signals received at antennas in different sensors. For example, part 304 of the piecewise linear phase relationship 300 represents the relationship between signals received at antennas in a first sensor, and part 306 represents the relationship between signals received at antennas in a second sensor. The discontinuity 310 between parts 304 and 306 at the origin (i.e., the midpoint or zero point between antennas) represents the carrier phase shift between signals received by different antennas.

[0039] After correcting for the carrier phase offset, the linear phase relationship 302 is generally continuous and linear, with a slope corresponding to the slopes of portions 304 and 306. As discussed herein, the carrier phase offset is estimated by extrapolating the phase, representing the complex value of the received signal, to the center of the virtual antenna array. The complex value of the phase corresponds to the independent variable representing the phasor of the received signal. In some embodiments, the phase is extrapolated based on least squares. In other embodiments, the phase is extrapolated based on the Fast Fourier Transform (FFT) of the product of complex value pairs associated with the same antenna. The extrapolation process can also provide information indicating whether the signal was generated by a single bounce reflection or a multipath reflection.

[0040] Figure 4A bistatic virtual array 400, according to some embodiments, represents the transmission path between the transmitting and receiving antennas in two radar sensors. The bistatic array corresponding to some embodiments of the bistatic virtual array 400 can be configured to represent the transmission path between antennas 210-214 in radar sensor 202 and antennas 220-224 in radar sensor 204.

[0041] In the illustrated embodiment, the bistatic virtual array 400 includes two sets of elements corresponding to transmission paths originating from two different radar sensors. The first set of elements represents the path received at the receiving antenna in the second radar sensor from the transmitting antenna in the first radar sensor. The second set of elements represents the path received by the receiving antenna in the first radar sensor from the transmitting antenna in the second radar sensor. The first radar sensor is implemented to include elements placed in relative positions. The four receiving antenna elements at the location and the position relative to the first receiving antenna element are placed at the location A monostatic radar array with two transmitting antenna elements, wherein λ is the wavelength of coherent radiation emitted from the first and second radar sensors. The second radar sensor is implemented to include elements placed at a relative position. The four receiving antenna elements at the location and the position relative to the first receiving antenna element are placed at the location A monostatic radar array with two transmitting antenna elements at a location. Therefore, the antenna pattern in the first radar sensor is mirrored by the antenna pattern in the second radar sensor.

[0042] A bistatic virtual array 400 is created by combining the relative positions of the transmitting antenna elements in one radar sensor with the relative positions of the receiving antenna elements in another radar sensor. Therefore, the bistatic virtual array 400 is represented as... The location of the virtual antenna element 405 is indicated by the reference numerals (only one is indicated by the reference numerals for clarity). The bistatic virtual array 400 is located in relative positions. A midpoint 410 is located at the point. In some embodiments, the first and second radar sensors are deployed with a baseline spacing B, and in this case, the relative antenna position of the first radar sensor is shifted by -B / 2, and the relative antenna position of the second radar sensor is shifted by +B / 2. If coherent electromagnetic radiation is reflected from a single object, the phase relationship between the signals received at the virtual antenna element 405 in the bistatic virtual array 400 will be piecewise linear and have linear phase characteristics related to the arrival and departure directions of the coherent electromagnetic radiation.

[0043] Figure 5The diagram illustrates the phase response 500 of a bistatic virtual array to a signal generated by two radar sensors, reflected from a single object, and received by the two radar sensors, according to some embodiments. The horizontal axis indicates the relative position of the virtual antenna element 502 (only one is indicated by reference numerals for clarity). In the illustrated embodiment, the virtual antenna element 502 is shifted one position to the right, which has no effect on subsequent analysis. The vertical axis indicates the angle relative to the phase response. In the illustrated embodiment, for... Figure 4 The elements of the bistatic virtual array 400 shown determine the phase response 500.

[0044] At the first radar sensor, a reflected signal is received in a first direction of arrival, and the first direction of arrival determining element... and The slope of the phase response; these two elements correspond to the two transmitting antennas at the second radar sensor. Note that... Figure 4 The component positions shown are relative to Figure 4 The component position shift shown This does not affect the carrier phase offset estimation. Lines 504 and 506 indicate the slope determined by the first direction of arrival. The second radar sensor receives the reflected signal with a second direction of arrival, and the second direction of arrival determining element... and The two elements correspond to the two transmitting antennas at the first radar sensor, and the different slopes of their phase responses are indicated by lines 508 and 510. Lines 508 and 510 indicate slopes determined by the second direction of arrival. The first direction of arrival at the first radar sensor corresponds to the departure direction of the signal transmitted by the second radar sensor, and the second direction of arrival at the second radar sensor corresponds to the departure direction of the signal transmitted by the first radar sensor. Therefore, the slopes of lines 504 and 506 are the same as the slopes of lines 512 and 514, which indicate the offset between the phase responses associated with the different transmitting antennas. Similarly, the slopes of lines 508 and 510 are the same as the slopes of lines 516 and 518.

[0045] The carrier phase offset 520 between the first and second radar sensors is estimated by extrapolating the lines 504, 506, 508, 510, which represent the phase responses associated with the two radar sensors. Figure 5 In the illustrated embodiment, lines 504, 506, 508, and 510 are extrapolated to a location... The assumed central element is 522.

[0046] Figure 6 A method 600 for performing coherent distributed radar detection, including correcting carrier phase offset, is illustrated according to some embodiments. Method 600 in... Figure 1 The coherent distributed radar system 100 shown and Figure 2This is implemented in some embodiments of part 200 of the coherent distributed radar system shown. Prior to the start method 600, the distributed radar system performs range and Doppler processing on the signal generated by transmitting coherent electromagnetic signals and receiving the reflected portion of the transmitted signals.

[0047] At box 605, for example Figure 1 The processing unit 110 and other processing units shown use detection algorithms, such as the Constant False Alarm Rate (CFAR) detection algorithm, to compile a detection list of candidate objects. Detected objects are labeled with tags that include the detected range, the detected velocity, and other tags generated by the detection algorithm. Output indicating or indicating that one or more of the objects have been detected can be generated by the processing unit.

[0048] At box 610, the processing unit performs spatial processing to generate a “snapshot” of each detection. A snapshot represents a set of complex values, and there is one complex value for each combination of the transmit and receive antennas.

[0049] At box 615, the processing unit calibrates a snapshot to account for receiver defects. In some embodiments, the calibration considers and / or corrects defects including differences in antenna feed length, differences in antenna response, differences in transmission at the receiving antenna, etc.

[0050] At block 620, the processing unit filters snapshots from the available snapshots to select those containing a single object. In the illustrated embodiment, the carrier phase offset estimation algorithm uses only snapshots that include a single object. In some embodiments, the filtering at block 620 is performed based on signal amplitude, as single-object snapshots are expected to have snapshot values ​​with approximately the same amplitude. Prior knowledge from snapshots of previous radar frames can also be used to assist in filtering or selecting snapshots.

[0051] At block 625, the processing unit estimates the carrier phase offset in the received signal. As discussed herein, the carrier phase offset can be estimated using least squares or a spectrum-based technique applied to the phase difference between signal pairs. In some embodiments, estimates of the carrier phase offset from multiple snapshots can be combined to increase the robustness of the estimates. The carrier phase offsets estimated for different sets of snapshots should be consistent with each other; for example, after accounting for variance introduced by factors such as estimator noise, the estimated carrier phase offsets should be substantially equal.

[0052] At block 630, the processing unit applies a filter to the estimated carrier phase offset to remove inconsistent values ​​of the carrier phase offset. In some embodiments, the estimated carrier phase offset is averaged, a majority vote is performed, or other methods are used to filter the carrier phase offset. Changing the estimated carrier phase offset can exclude snapshots containing multiple objects that would otherwise corrupt the overall estimate of the carrier phase offset.

[0053] At block 635, the processing unit corrects the final set of carrier phase offset estimates. In some embodiments, carrier phase offset correction is performed using information generated during the calibration snapshot at block 615.

[0054] At box 640, the processing unit performs direction of arrival estimation. Direction of arrival estimation can be used to expand the detection list by including the object's angle information.

[0055] Figure 7 A piecewise linear model 700 for the phase in a snapshot of a dual-base array according to some embodiments is shown. The piecewise linear model 700 is used to estimate, for example... Figure 1 The coherent distributed radar system 100 shown and Figure 2 The diagram shows the carrier phase offset in the corresponding system of two radar sensors in a coherent distributed radar system, specifically part 200. This can be used as... Figure 6 A portion of block 625 shown in the diagram performs a least-squares method to estimate the carrier phase offset.

[0056] In the illustrated embodiment, the bistatic virtual array is centered and then mirrored, such that the modified bistatic virtual array includes a portion 702 representing the (unmirrored) phase response on the right side of the bistatic virtual array and a portion 704 representing the phase response on the left side of the bistatic virtual array that has been mirrored to the right. The phase is expanded to remove the ambiguity of an integer number of 2π radians that may be introduced when extracting the phase from the phasor. The phase in portion 702 is represented as... And the phase in part of 704 is represented as The piecewise linear model 700 includes two linear phase relationships: and The parameters a1, b1, a2, and b2 are estimated using a least-squares model. In some embodiments, the carrier phase offset is estimated by estimating b1-b2. The phase values ​​are extracted from section 702. Following a linear relationship with a1 and b1, and the phase value extracted from part 704. It follows a linear relationship with a2 and b2. Phase value. Follow the phase value The same linear relationship, but they are shifted by -13a1. Phase value They also have similar characteristics, relative to It has shifted by -13a2.

[0057] Least squares models use cost functions or error functions. This minimizes the squared error between the observed values ​​and the linear model. In the illustrated embodiment, the error function is:

[0058]

[0059] The error function is differentiated relative to each parameter in the linear model, and the resulting function is set to zero to define the extrema of the error function.

[0060] The partial derivative with respect to a1 is:

[0061]

[0062] The partial derivative with respect to a2 is:

[0063]

[0064] The partial derivative with respect to b1 is:

[0065]

[0066] The partial derivative with respect to b2 is:

[0067]

[0068] The partial derivatives are equal to zero, and the phase response is shifted to the right side of the equation to generate a least-squares solution as a matrix-vector problem. In the illustrated embodiment, the matrix-vector problem to be solved is:

[0069]

[0070] in and and These are matrices of length all 1s and all 0s, respectively. The inverse of the matrix multiplied by the parameter is given by the following formula:

[0071]

[0072] As discussed above, the carrier phase offset estimate only requires determining the difference between b1 and b2. In the illustrated embodiment, this difference is given by the following formula:

[0073]

[0074] in

[0075]

[0076] in

[0077] Then, the estimated carrier phase offset is given by a weighted sum of the following phase differences:

[0078]

[0079] Replacing the piecewise linear model, we get:

[0080]

[0081] in (in That is, they are located at the position of the folded array.

[0082] The above discussion implies the extraction of phase information y from it. i Bibase snapshot ( , (This can be transformed into a folded snapshot) The phase of a folded snapshot should have a linear phase response. The symmetry of bistatic arrays means that least-squares fitting techniques can be applied to folded arrays. In this case, the least-squares problem can be formulated as:

[0083]

[0084] in and It is an all-1 vector of length 8. Therefore, the estimated value of the carrier phase offset is:

[0085]

[0086] Therefore, some embodiments of carrier phase offset estimation include:

[0087] ● Extracting phase information from bistatic snapshots

[0088] ●Expanding the phase makes the phase Exhibits approximately piecewise linear behavior

[0089] ● Estimate carrier phase offset as phase weighted sum

[0090] ● Determine weights based on the positions of elements in the folded bistatic array and apply the least squares fitting method.

[0091] ● In embodiments where the bistatic array is symmetrical, the carrier phase offset is the phase difference. weighted sum

[0092] You can also calculate the slope To derive arrival and / or departure direction information from the snapshot. First slope. Indicates a relationship The direction of arrival from the first radar sensor. Due to the second slope It is obtained through a mirrored antenna element, so its direction of arrival angle is the same as that of the second radar sensor. The relationship is Given. First angle. It is also the departure direction angle of the second radar sensor, and the second angle It is the departure direction angle of the first radar sensor. In the case of a single bounce reflection, And for distant objects, These characteristics can be used as a coarse distinguisher between single-bounce and multiple-bounce reflections. The first angle is analyzed relative to the detected bistatic distance R. Second angle This allows for more accurate indications. For example, given a first angle, a second angle, and a baseline, the detected bistatic distance R should be:

[0093]

[0094] First corner Second angle A good estimate should be available using the above expression. This expression also shows that, for the limiting case… The object should be at infinity, that is, the bistatic response with the same departure and arrival directions is true for very distant objects.

[0095] Figure 8 A method 800 for estimating the carrier phase offset between two radar sensors in a coherent distributed radar system using the least squares method, according to some embodiments, is illustrated. Method 800 in... Figure 1 The coherent distributed radar system 100 shown Figure 2 In some embodiments of part 200 of the coherent distributed radar system shown, and in Figure 6 The method 600 shown is implemented in block 625.

[0096] At box 805, the bistatic virtual array is centered and then folded, such that elements on the left side of the bistatic virtual array are mirrored to the right side of the bistatic virtual array. An example of folding a bistatic virtual array is shown in... Figure 7 As shown in the image.

[0097] At box 810, phase unrolling is performed to remove the ambiguity of an integer number of 2π radians that may be introduced when extracting the phase from the phasor.

[0098] At box 815, least squares estimation is used to estimate the parameters of the linear model representing the phase response in a bistatic virtual array, as discussed in this paper.

[0099] At box 820, the carrier phase offset is estimated based on the linear model parameters generated using the least squares estimation technique.

[0100] In some embodiments, at block 825, the arrival and departure directions at radar sensors in a coherent distributed radar system are estimated, as discussed herein.

[0101] Figure 9 A method 900 is illustrated, according to some embodiments, for estimating the carrier phase offset between two radar sensors in a coherent distributed radar system using spectrum-based techniques applied to the phase difference between signal pairs. Method 900 in... Figure 1 The coherent distributed radar system 100 shown Figure 2 In some embodiments of part 200 of the coherent distributed radar system shown, and in Figure 6 The method 600 shown is implemented in block 625. In the illustrated embodiment, the bistatic array representing the antenna elements in the two radar sensors is symmetrical, and the bistatic snapshots are filtered such that they comprise a single object.

[0102] At box 905, the bistatic array of the virtual antenna element associated with the radar sensor is centered such that the middle of the array ends at position 0, as discussed herein. In some embodiments, the centered bistatic array may also be shifted by one or more integer displacements.

[0103] At box 910, a folded bistatic snapshot is generated by combining segments of snapshots from different parts of the bistatic virtual array. Snapshots share the positions of their virtual antenna elements within the folded bistatic snapshot. In some embodiments, a folded bistatic snapshot can be represented as... ,in This is a snapshot from a bistatic virtual array, and L is half the size of the bistatic virtual array. Therefore, after folding, the elements in the folded snapshot share antenna positions; for example, y1 and y9 share position 9. For example, a difference snapshot can be generated by multiplying the complex value of the first signal by the complex conjugate of the complex value of the second signal that shares the virtual antenna position in the virtual array after folding. A folded bistatic virtual array snapshot can also be called a difference snapshot because the complex conjugate is used in the multiplication of the two individual snapshots. Therefore, the independent variable of the difference snapshot represents the difference between the phases of the signals associated with the individual snapshots.

[0104] At box 915, beamforming spectrum is generated based on difference snapshot. In some embodiments, beamforming spectra are generated by applying a Fast Fourier Transform (FFT) to the difference snapshots. Zero-insertion and zero-padding can be applied so that the input to the FFT algorithm has a length N. FFT .

[0105] At box 920, the location of the main lobe and the beamforming spectrum are identified. In some embodiments, the peak location is identified within the main lobe of the beamforming spectrum. Spectral peak or square peak Peak position This represents an estimate of the combined phase slope. , among which angle and These are the direction of arrival angles of the first and second radar sensors, respectively. For example, the index position can be an integer position associated with the grid used to calculate the beamforming spectrum. The refined maximum position can be calculated by interpolating using the maximum value at k and the values ​​at k-1 and k+1. The refined peak position... It does not have to be an integer and can contain a fractional part. The maximum value |Z| is determined when the beamforming spectrum is called Z. 2 .

[0106] At box 925, at the peak position in the main lobe, replace the beamforming spectrum with that of the Dirac delta function. The approximate beamforming spectrum is represented. In some embodiments, the amplitude is determined by interpolation. For example, in box 920.

[0107] At box 930, the array response at the center location is reconstructed. In some embodiments, the reconstruction of the array response includes extrapolating to an element m at a location using an inverse Fourier transform (e.g., inverse FFT (IFFT)):

[0108]

[0109] The carrier phase offset can then be estimated as:

[0110]

[0111] Therefore, instead of obtaining the slope and Method 900 produces an estimate of the difference between the two slopes, rather than a separate estimate. In some embodiments, the sum of the two slopes Alternatively, a second-folded bistatic array snapshot can be used to derive the slope. For example, the slope and the independent estimates that can be determined and used to generate the slope are as follows:

[0112] ● Determine the second fold bistatic snapshot This snapshot is called a sum snapshot because the phases of the two parts of the expanded snapshot are added together; that is, no complex conjugation is applied to either of the individual snapshots.

[0113] ● Use FFT, and zero-insertion and zero-filling as necessary, to determine the beamforming spectrum. This makes the input to the FFT have a length of NFFT.

[0114] ● Identify peak positions within the main lobe of the beamforming spectrum Spectral peak Peak position This represents an estimate of the combined phase slope. , among which angle and These are the direction of arrival angles of the first and second radar sensors, respectively.

[0115] ● Difference in slope and The estimated values ​​can be combined to determine separately. and and determine respectively and .

[0116] ●Single bounce reflection expectation meets the criteria And the detected bistatic distance should satisfy:

[0117]

[0118] It should be noted that not all activities or elements described in the general description above are necessary. A particular activity or part of the apparatus may be unnecessary and may perform one or more additional activities besides those described, or may include one or more additional elements besides those described. Furthermore, the order in which the activities are listed is not necessarily the order in which they are performed. And, the concepts have been described with reference to specific embodiments. However, those skilled in the art will understand that various modifications and changes can be made without departing from the scope of this disclosure as set forth in the appended claims. Therefore, the specification and drawings should be viewed in an illustrative rather than restrictive sense, and all such modifications are contemplated to be included within the scope of this disclosure.

[0119] The benefits, other advantages, and solutions to the problems have been described above with respect to specific embodiments. However, the benefits, advantages, solutions to the problems, and any features that may cause any benefit, advantage, or solution to appear or become more apparent should not be construed as essential, necessary, or required features of any or all claims. Furthermore, the embodiments disclosed above are merely illustrative, as the disclosed subject matter can be modified and practiced in different but equivalent ways, as will be apparent to those skilled in the art who benefit from the teachings herein. No limitation is intended to be imposed on the details of the constructions or designs shown herein, other than those set forth in the appended claims. Therefore, it will be apparent that changes or modifications can be made to the embodiments disclosed above, and all such changes are considered to be within the scope of the disclosed subject matter. Therefore, the protection sought herein is as set forth in the appended claims.

Claims

1. A method, characterized in that, include: A first signal is received by a first antenna in a first radar sensor, transmitted by at least one second antenna in a second radar sensor, and reflected by at least one object; The second signal, transmitted by at least one fourth antenna in the first radar sensor and reflected by the at least one object, is received by the third antenna in the second radar sensor. Generate a snapshot including complex values ​​representing the phase responses of the first signal and the second signal; as well as The carrier phase offset between the first signal and the second signal is estimated based on the snapshot.

2. The method according to claim 1, characterized in that, The snapshot includes first information indicating the relative phase of the first signal received by the first antenna and second information indicating the relative phase of the second signal received by the third antenna.

3. The method according to claim 2, characterized in that, In addition, including: A virtual array is generated based on the snapshot, the virtual array representing the phase response of the first signal as a function of the spacing between the first antenna and the at least one second antenna, and representing the phase response of the second signal as a function of the spacing between the third antenna and the at least one fourth antenna.

4. The method according to claim 3, characterized in that, The virtual array includes multiple piecewise linear phase relationships corresponding to the positions of the at least one second antenna and the at least one fourth antenna.

5. The method according to claim 4, characterized in that, In addition, including: The slope of the plurality of piecewise linear phase relationships is determined based on the first direction of arrival of the first signal and the second direction of arrival of the second signal; The offset between the plurality of segmented linear phase relationships is determined based on the first departure direction of the first signal and the second departure direction of the second signal; as well as The carrier phase offset is estimated based on the slope and the offset.

6. A device, characterized in that, include: The first radar sensor includes multiple first antennas and at least one second antenna; The second radar sensor includes a plurality of third antennas and at least one fourth antenna, the first antenna being configured to receive a first signal transmitted by the at least one fourth antenna and reflected by at least one object, and the third antennas being configured to receive a second signal transmitted by the at least one second antenna and reflected by the at least one object; as well as At least one processing unit is configured to generate a snapshot including complex values ​​representing the phase responses of the first signal and the second signal, and to estimate the carrier phase offset between the first signal and the second signal based on the snapshot.

7. The device according to claim 6, characterized in that, The snapshot includes first information indicating the relative phase of the first signal received by the first antenna, and second information indicating the relative phase of the second signal received by the third antenna.

8. The device according to claim 7, characterized in that, The processing unit is configured to generate a virtual array based on the snapshot, the virtual array representing the phase response of the first signal as a function of the spacing between the first antenna and the at least one fourth antenna, and representing the phase response of the second signal as a function of the spacing between the third antenna and the at least one second antenna.

9. A device, characterized in that, include: A plurality of radar sensors, wherein each of the plurality of radar sensors includes a plurality of receiving antennas and at least one transmitting antenna, wherein the receiving antenna in a first subgroup of the radar sensors is configured to receive a first signal transmitted by the transmitting antenna in a second subgroup of the radar sensors and reflected by at least one object, and the receiving antenna in the second subgroup of the radar sensors is configured to receive a second signal transmitted by the at least one transmitting antenna in the first subgroup of the radar sensors and reflected by at least one object; as well as At least one processing unit is configured to generate a snapshot including complex values ​​representing the phase responses of the first signal and the second signal, and to estimate the carrier phase offset between the first signal and the second signal based on the snapshot.

10. The device according to claim 9, characterized in that, The at least one processing unit is configured to estimate the carrier phase offset based on the offset between a piecewise linear phase relationship in the phase responses of the first signal and the second signal, the piecewise linear phase relationship corresponding to at least one position of the at least one transmit antenna.

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