Frequency modulated continuous wave radar system with interference mitigation

Abstract

A method (600) for dithering a radar frame includes determining at least one of a chirp period Tc of a radar chirp in the radar frame (615) and a chirp slope S of the radar chirp in the radar frame (625). In response to determining the chirp period Tc, a maximum chirp dither Δc(max) is determined (620), and for a radar frame N, a random chirp dither Δc(N) between negative Δc(max) and positive Δc(max) is determined (640). In response to determining the chirp slope S, a maximum slope dither Ψ(max) is determined (630), and for the radar frame N, a random slope dither Ψ(N) between negative Ψ(max) and positive Ψ(max) is determined (645). A radar sensor circuit generates the radar chirp in the radar frame N based on at least one of (1) the chirp period Tc and the random chirp dither Δc(N) and (2) the chirp slope S and the random slope dither Ψ(N) (650).

Description

Technical Field Background Technology

[0001] Many driver assistance systems implement Frequency Modulated Continuous Wave (FMCW) radar systems to assist with collision warning, blind spot warning, lane change assist, parking assist, and rear collision warning. The basic transmitted signal of FMCW radar is a frequency ramp, often referred to as a "chirp." A chirp is a signal whose frequency varies linearly over time. For example, a millimeter-wave radar system can transmit a chirp with a bandwidth of 4 GHz, starting at 77 GHz and increasing linearly to 81 GHz. The transmitted chirp reflects off one or more objects, and the reflected signal is received at one or more receiver antennas. FMCW radar systems transmit a series of these equidistant chirs in units called frames. The reflected signals are down-converted, digitized, and then processed to obtain the range, speed, and angle of arrival of objects ahead of the radar system.

[0002] With the increasing prevalence of radar systems in automobiles, manufacturing, and other sectors, the possibility of interference between radar systems has also increased. One technique to reduce or mitigate radar interference is to jitter the chirp timing within a frame compared to chirp timing across radar frames. However, intra-frame chirp jitter can increase the noise floor of the radar system and reduce the sensitivity to detect weak targets. Summary of the Invention

[0003] An apparatus includes one or more processors and one or more non-transitory computer-readable media storing machine instructions. The machine instructions, when executed by the one or more processors, cause the one or more processors to determine at least one of a chirp period Tc and a chirp slope S of a radar chirp in a radar frame. In response to determining the chirp period Tc, the processor determines a maximum chirp jitter Δc(max), and for a radar frame N, determines a random chirp jitter Δc(N) between a negative Δc(max) and a positive Δc(max). In response to determining the chirp slope S, the processor determines a maximum slope jitter Ψ(max), and for a radar frame N, determines a random slope jitter Ψ(N) between a negative Ψ(max) and a positive Ψ(max). The processor then causes the radar sensor circuitry to generate a radar chirp in radar frame N based on at least one of (1) the chirp period Tc and the random chirp jitter Δc(N), and (2) the chirp slope S and the random slope jitter Ψ(N). In some embodiments, the device further includes radar sensor circuitry.

[0004] In some implementations, the chirp period Tc of the radar chirp is determined based on the threshold unambiguous velocity, and the maximum chirp jitter Δc(max) is based on a threshold deviation from the threshold unambiguous velocity. In some implementations, the chirp slope S is based on the frequency range of the radar chirp, the threshold range resolution, and the chirp period Tc, and the maximum slope jitter Ψ(max) is based on a threshold deviation from the threshold range resolution.

[0005] In some embodiments, the non-transitory computer-readable medium further includes machine instructions that cause a processor to determine the period TF and the maximum frame jitter ΔF(max) of a radar frame. For a radar frame N, the processor determines a random frame jitter ΔF(N) between a negative ΔF(max) and a positive ΔF(max), and further generates the radar frame N based on the period TF and the random frame jitter ΔF(N). In some embodiments, the period TF of the radar frame is based on the update rate, and the maximum frame jitter ΔF(max) is based on a threshold deviation from the update rate.

[0006] In some embodiments, the non-transitory computer-readable medium further includes machine instructions that cause a processor to determine the subsequent radar frame jitter ΔF(N+1) between the negative ΔF(max) and positive ΔF(max) of the subsequent radar frame N+1. The processor causes radar sensor circuitry to generate the subsequent radar frame N+1 based on the period TF and the subsequent random frame jitter ΔF(N+1). In some embodiments, the subsequent random frame jitter ΔF(N+1) is not equal to the random frame jitter ΔF(N).

[0007] In some embodiments, the non-transitory computer-readable medium further includes machine instructions that cause one or more processors to determine at least one of a subsequent random chirp jitter Δc(N+1) between negative Δc(max) and positive Δc(max) and a subsequent random slope jitter Ψ(N) between negative Ψ(max) and positive Ψ(max). The processor causes radar sensor circuitry to generate a radar chirp in the subsequent radar frame N+1 based on at least one of (1) the chirp period Tc and the subsequent random chirp jitter Δc(N+1) and (2) the chirp slope S and the subsequent random slope jitter Ψ(N+1). In some embodiments, the subsequent random chirp jitter Δc(N+1) is not equal to the random chirp jitter Δc(N), and the subsequent random slope jitter Ψ(N+1) is not equal to the random slope jitter Ψ(N). Attached Figure Description

[0008] For a detailed description of the various examples, reference will now be made to the accompanying drawings, in which:

[0009] Figure 1 A block diagram of an example radar system is shown.

[0010] Figure 2A The waveform of a frame of a chirp-free signal without jitter is shown, based on an example.

[0011] Figure 2B shows Figure 2A An example representation of the distance Fast Fourier Transform (FFT) of the unjittered chirped signal in the frame shown.

[0012] Figure 2C shows Figure 2A The waveform of the Doppler FFT of the unjittered chirped signal in the frame shown.

[0013] Figure 3A The waveform of the intra-frame jitter chirp signal is shown based on the example.

[0014] Figure 3B It shows Figure 3A An example representation of the distance Fast Fourier Transform (FFT) of the intra-frame jitter chirp signal in the frame shown.

[0015] Figure 3C Showing Figure 3A The Doppler FFT waveform of the intra-frame jitter chirp signal in the frame shown.

[0016] Figure 4A The waveform of the inter-frame jitter chirp signal is shown based on the example.

[0017] Figure 4B The waveform of the jitter frame of the chirp signal is shown according to the example.

[0018] Figure 4C The waveforms of chirped signals with different slopes are shown, based on the example.

[0019] Figure 4D It shows that according to Figure 4A , Figure 4B and Figure 4C The example shown is a waveform of a jittered frame with an inter-frame jitter chirp signal having different slopes.

[0020] Figure 5 A graph showing the cumulative distribution function of the number of cells in each distance chamber affected by the interference signal is presented.

[0021] Figure 6 An example process for jittering radar frames is shown in flowchart form, based on the example.

[0022] The same reference numerals are used in the accompanying drawings for the same or similar (in terms of function and / or structure) features. Detailed Implementation

[0023] The disclosed radar system implements inter-frame chirp jitter to mitigate interference from other radar systems. Inter-frame chirp jitter reduces the number of cells affected by interference signals in each particular range cell, unlike intra-frame jitter which introduces phase noise into the Doppler Fast Fourier Transform. Alternatively, the radar system may implement jitter over the period from the beginning of one radar frame to the beginning of another. Further, alternatively, the radar system may implement slope jitter to adjust the slope of the radar chirp from one radar frame to another.

[0024] Figure 1 A block diagram of an example radar system 100 is shown. The radar system 100 can be used in vehicles, such as driver assistance systems in automobiles. In this example, the radar system 100 includes radar sensor circuitry 160, a central processing unit (CPU) 110, a display 140, and a storage device 150. The radar sensor circuitry 160 includes a transmitter 170 that drives an antenna array 175 of one or more transmitter (TX) antennas. A receiver 185 receives signals from an antenna array 180 of one or more receiver (RX) antennas. A baseband processor 190 amplifies and filters the received signals reflected from objects in the path of the transmitted chirped signal. In this example radar system 100, the transmitter 170 operates in the 77 GHz region and generates a frequency-modulated continuous wave (FMCW) signal. The FMCW signal is frequency-modulated to form a series of chirps using a local oscillator (LO) 165. In the example radar system 100, the TX antenna array 175 and the RX antenna array 180 are fixed. In other examples, the antenna array can be configured to transmit and receive across a certain area, such as through mechanical movement.

[0025] FMCW radar, also known as continuous wave frequency modulation (CWFM) radar, is capable of determining distance, velocity, and angle of arrival (AAC). In an FMCW system, a transmitted chirped signal of a known stable frequency continuous wave is modulated, with the frequency varying over a fixed time interval. The received reflections are then mixed with the transmitted chirped signal to generate a received beat signal, which, after signal processing, provides the distance, velocity, and AAC of the target object. The frequency difference between the received reflections and the transmitted chirped signal increases with delay and is therefore proportional to the distance.

[0026] The phase difference between received reflections across a continuous chirp allows for the calculation of the target object's velocity. The phase difference between received reflections at the first receiver antenna and those at the second receiver antenna allows for the calculation of the target object's angle of arrival. Therefore, with an FMCW radar system, the distance between the target object and the radar system, the target object's relative velocity, and the target object's relative angle can be calculated.

[0027] During normal operation, linear frequency chirps are transmitted and reflected signals are received. The receiver and transmitter are arranged as a coherent system such that the received reflected signal is directly down-converted to baseband in receiver 185 using a copy of the transmitted signal from LO 165. The baseband signal is then filtered and amplified by baseband processor 190 through a filter and a variable gain amplifier. After converting the baseband signal to the digital domain, time-domain to frequency-domain transformations, such as Fast Fourier Transform (FFT), can be applied, and other signal processing can be performed to determine the distance, velocity, and angle of arrival between the target object and radar system 100. For example, the down-converted and digitized received signal corresponding to each chirp is first transformed using an FFT (called the range FFT). The range FFT produces a series of range bins, where the value of each range bin represents the signal strength of the reflected target at the corresponding distance. Doppler FFT is then performed on all chirs across a frame for each range bin to estimate the velocity of the reflected target.

[0028] CPU 110 includes one or more CPU cores, a digital signal processor, an application-specific integrated circuit (ASIC), etc. The term "CPU" (singular) is used herein to refer to one or more CPU cores and broadly describes a central processing unit, digital signal processor, ASIC, etc. CPU 110 includes a chirp controller 120 that receives a data stream from the receiver antenna array 180 via an analog-to-digital converter (ADC) 130 and performs chirp generation and transmitter control via a digital-to-analog converter (DAC) 125. A variable voltage tuning control signal from the DAC 125 is used to control LO 165. CPU 110 also includes a signal processor 115 capable of performing signal processing for determining speed, angle of arrival, target object, and distance between the radar system 100, etc.

[0029] Signal processor 115 can provide determined values ​​to display 140 and / or communicate with other systems via network interface 135. Network 135 may include various combinations of, for example, local area network (LAN), wide area network (WAN), Internet, and / or other known or later developed wired or wireless communication mechanisms. Storage device 150 can be used to store instructions and data received from antenna 180 or signal processor 115. Storage device 150 may be any suitable storage medium, such as static random access memory (SRAM).

[0030] Figure 2AThe waveform of an unjittered chirped signal 205 according to an example is shown. A frame 200 with a period TF comprises a number M unjittered chirped signals 205 transmitted at equal intervals based on the chirp period Tc. A jamming radar system may have jamming chirped signals 210A-M similar to the unjittered chirped signals 205A-M, for example, because the jamming radar systems are from the same manufacturer. For the unjittered chirped signals, each jamming chirped signal 210 has the same delay τ0 relative to each corresponding unjittered chirped signal 205.

[0031] Figure 2B shows the relationship between... Figure 2A Example representation 230 shows the range FFT performed on the received signal corresponding to the transmitted un-jittered chirped signals 205A-M. An FFT is performed on the received data corresponding to each chirped signal 205, resolving the received radar reflections to range bins. In addition to reflections from the transmitted chirped signals 205A-M, the received signals also include interfering chirped signals 210A-M. Because interfering signals 210A-M have the same delay τ0 relative to the corresponding un-jittered chirped signals 205A-M, interfering signals 210 appear as objects at a particular range bin 240. Any genuine radar reflections at the particular range bin 240, with power lower than that of interfering signals 210, are masked. Figure 2C shows the range FFT performed on the received data corresponding to each chirped signal 205A-M. Figure 2A The waveform 250 of the Doppler FFT performed on the range bins of chirp 205 in frame 200, excluding range bin 240. This particular range bin does not include the interference signal 210. An FFT is performed on the range bins of the un-jittered chirps 205A-N across frames 200, which resolves the radar reflection to a velocity bin. Because there is no timing jitter, there is no phase distortion across chirps 205A-M, and therefore both strong target 260 and weak target 270 are visible in the Doppler FFT.

[0032] Figure 3A The waveform of an intra-frame jitter chirp signal 305 according to an example is shown. A frame 300 with a period TF includes a number M jitter chirp signals 305 transmitted at different intervals. For example, in a first interval between the start of a first chirp signal 305A and the start of a second chirp signal 305B, the chirp period Tc and the first chirp jitter Δc (1) are added together. In a second interval between the start of a second chirp signal 305B and the start of a third chirp signal 305C, the chirp period Tc and the second chirp jitter Δc (2) are added together. Each chirp signal 305 in frame 300 may be associated with a unique chirp jitter Δc, and another frame of the chirp signal may have the same or different chirp jitter as frame 300. In some embodiments, the duration of the chirp jitter Δc may be 5% to 10% of the chirp period Tc. Each radar system randomly and independently selects the chirp jitter Δc.

[0033] The jamming radar system may have jamming chirp signals 310A-N similar to the intra-frame jitter chirp signals 305A-M, for example, because the jamming radar systems are from the same manufacturer. The chirp jitter Δc of the jamming chirp signals 310A-M differs from that of the chirp signals 305A-M because the radar system and the jamming radar system independently select the corresponding chirp jitter Δc. Therefore, with respect to the intra-frame jitter chirp signals, each jamming chirp signal 310 has a unique delay τ relative to the corresponding intra-frame jitter chirp signal 305. For example, the jamming chirp signal 310A has a first delay τ1 relative to the intra-frame jitter chirp signal 305A, while the jamming chirp signal 310B has a second delay τ2 relative to the intra-frame jitter chirp signal 305B. As another example, the interfering chirp signal 310M is delayed by τ(M) before the intra-frame jitter chirp signal 305M.

[0034] Figure 3B Showing the like Figure 3A Example representation 330 of the range FFT performed on the received signal corresponding to the transmitted intra-frame jitter chirp signals 305A-M. An FFT is performed on the received data corresponding to each chirp signal 305, resolving the received radar reflections into range bins. In addition to reflections from the transmitted chirp signals 305A-M, the received signal also includes interfering chirp signals 310A-M. Because the interfering signals 310A-M have a different delay τ relative to the corresponding chirp signals 305A-M, the interfering signals 310A-M appear as objects in different range bins 340A-M, rather than the same range bin 240 as shown in Figure 2B. Therefore, with... Figure 2A Compared to the unjittered chirped signal 205 shown, the maximum number of cells per range chamber affected by the interference signal 310 is reduced. Techniques for detecting and repairing affected cells are more effective for the reduced number of affected cells per range chamber.

[0035] Figure 3C Showing the results from Figure 3AThe waveform 350 of the Doppler FFT performed on the distance FFT of chirp 305 in frame 300 is shown. This distance bin does not include the interference signal 310. Due to the different chirp timings of chirp 305 across frame 300, phase noise and the corresponding noise floor 370 are introduced into the Doppler FFT. The magnitude of the noise floor 370 relative to the peak value of the strong target 360 corresponds to the amount of chirp jitter. For example, more chirp jitter corresponds to a higher noise floor 370, while less chirp jitter corresponds to a lower noise floor 370. Although the strong target is clearly visible in Doppler FFT 360, the weak target 270 shown in waveform 250 of the Doppler FFT used for chirp 205 has a power lower than the noise floor 370 and is occluded in the Doppler FFT of the intra-frame jitter chirp 305. Therefore, although intra-frame jitter chirp 305 reduces the maximum number of cells affected by interference in each range cell, intra-frame jitter introduces a background noise in the Doppler FFT that is present in all range cells, regardless of whether interference is present in a particular range cell, and this background noise is not present in the un-jitter chirp 205.

[0036] Figure 4A The waveform 400 of an inter-frame jitter chirp signal according to an example is shown. In the first frame N with a period TF, inter-frame jitter chirp signals 405A-M are transmitted at fixed intervals based on the chirp period Tc and the first chirp jitter Δc(N). Consider the interfering chirp signal 415, which also has inter-frame jitter chirp signals transmitted at fixed intervals based on the same chirp period Tc and different chirp jitter Δd(N). The difference δ(N) between the chirp jitter Δc(N) and Δd(N) causes the delay τ relative to the corresponding inter-frame jitter chirp signal 405 to vary across frame N. For example, the interfering chirp signal 415A has an initial delay τ(N) relative to the corresponding chirp signal 405A, the interfering chirp signal 415B has a second delay τ(N) plus δ(N) relative to the corresponding chirp signal 405B, and the interfering chirp signal 415C has a third delay τ(N) plus twice δ(N) relative to the corresponding chirp signal 405C. Here, δ(N) represents the difference in chirp jitter between the chirp signal 405 and the interfering chirp signal 415 (i.e., δ(N) = Δd(N) - Δc(N)), and can be positive or negative.

[0037] In subsequent frames N+1 with the same period TF, inter-frame chirped signals 410A-M are transmitted at fixed intervals based on the chirped period Tc and the second chirped jitter Δc(N+1). For interfering chirped signals 420 with different chirped jitter Δd(N+1), the difference δ(N+1) between the chirped jitter Δc(N+1) and Δd(N+1) causes the delay τ relative to the corresponding inter-frame jittered chirped signal 410 to vary across frames N+1. For example, interfering chirped signal 420A has an initial delay τ(N+1) relative to the corresponding chirped signal 410A, interfering chirped signal 420B has a second delay τ(N+1) plus δ(N+1) relative to the corresponding chirped signal 410B, and interfering chirped signal 420C has a third delay τ(N+1) plus twice δ(N+1). The initial delay τ(N+1) of frame N+1 can be the same as or different from the initial delay τ(N) of frame N.

[0038] The chirp jitter Δc is fixed within the chirp within a frame, but varies across frames. Similar to... Figure 3A The delay variations between the intra-frame jitter chirp signal 305, the inter-frame jitter chirp signal 405 and the interfering chirp signal 415, and between the inter-frame jitter chirp signal 410 and the interfering chirp signal 420, as shown, cause the interfering signals 415 and 420 to appear as objects in different range bins, rather than objects in the same range bin. The inter-chirp delay Tc+Δc(N) between sequential chirp signals 405 in frame N and the inter-chirp delay Tc+Δc(N+1) between sequential chirp signals 410 in frame N+1 are constant within each frame, and therefore there is no phase distortion across chirps 405A-M and across chirps 410A-M, similar to... Figure 2A The unjittered chirp signal 205 is shown.

[0039] Figure 4B Waveform 425 of a jittered frame of a chirped signal according to an example is shown. In the first frame N, chirped signals 430A-M are transmitted at fixed intervals based on the chirped period Tc, and the period TF of frame N is jittered with frame jitter ΔF(N), such that the time length from the beginning of frame N to the beginning of frame N+1 is TF+ΔF(N). In the second frame N+1, chirped signals 435A-M are transmitted at the same fixed intervals based on the chirped period Tc as in the first frame N, but the period TF of frame N+1 is jittered with the second frame jitter ΔF(N+1), so that the time length from the beginning of frame N+1 to the beginning of frame N+2 is TF+ΔF(N+1). Frame jitter does not affect the number or duration of chirps in each frame. Because chirped signals 430 and 435 are transmitted at fixed intervals across frames N and N+1, no phase noise or background noise is introduced into the Doppler FFT. Frame jitter is often used in combination with inter-frame chirp jitter.

[0040] Figure 4CThe waveform 450 of a chirped signal with a jitter slope is shown according to an example. In the first frame N with a period TF, slope-jittered chirps 455A-M are transmitted at fixed intervals based on the chirp period Tc and have a slope S plus a first slope jitter Ψ(N). For the interfering chirped signal 465, the first slope jitter Ψ(N) causes the delay τ relative to the corresponding slope-jittered chirped signal 455 to vary based on frequency. For example, the interfering chirped signal 465A has a steeper slope than the slope-jittered chirped signal 455A, and the delay τ is larger at lower frequencies than at higher frequencies.

[0041] In subsequent frames N+1 with the same period TF, slope jitter chirps 460A-N are transmitted at fixed intervals based on the chirp period Tc and have a slope S plus a second slope jitter Ψ(N+1). For interfering chirp signal 470, the second slope jitter Ψ(N+1) causes the delay τ relative to the corresponding slope jitter chirp signal 460 to vary based on frequency. For example, interfering chirp signal 470A has a steeper slope than slope jitter chirp signal 460A, and the delay τ is larger at lower frequencies than at higher frequencies.

[0042] During each chirp, the varying delays between the slope jitter chirp signal 455 and the interfering chirp signal 465, and between the slope jitter chirp signal 460 and the interfering chirp signal 470, cause the interfering signals 465 and 470 to propagate across different range bins, rather than the same range bin. The inter-chirp delay Tc between consecutive chirp signals is constant within each frame with respect to the slope S+Ψ(N) of chirp signals 455 and 460; therefore, there is no phase corruption across chirp 455A-M and across chirp 460A-M. The Doppler-FFT for chirp 455 in frame N and chirp 460 in frame N+1 does not display an image. Figure 3C The background noise shown is like the background noise of 370.

[0043] In respectively Figure 4A , Figure 4B and Figure 4C The inter-frame jitter, frame jitter, and slope jitter techniques described herein can be used in combination with one or more other techniques to further reduce the number of cells in each range cell affected by interfering chirped signals, and to further reduce the amount of phase noise introduced into the Doppler FFT and the corresponding noise floor. Figure 4D It shows that according to Figure 4A , 4B The waveform 475 of the jittered frame of the chirped signal with different slopes of inter-frame jitter in the embodiment shown in 4C.

[0044] In the first frame N, the inter-frame and slope-jittered chirped signal 480A-M is transmitted at fixed intervals based on the chirped period Tc and the first chirped jitter Δc(N), and has a slope S plus a first slope jitter Ψ(N). The period TF of frame N is jittered with frame jitter ΔF(N). For the interfering chirped signal 490, the first chirped jitter Δc(N) and the first slope jitter Ψ(N) cause the delay τ relative to the corresponding inter-frame and slope-jittered chirped signal 480 to vary across the corresponding chirped signal 480, and increases across frame N.

[0045] For example, interfering chirp signal 490A has an initial delay τ(N; low) relative to the low frequency of the corresponding chirp signal 480A, and an initial delay τ(N; high) relative to the high frequency of the corresponding chirp signal 480A. Interfering chirp signal 490B has a second delay τ(N; low) plus Δ(N) relative to the low frequency of the corresponding chirp signal 480B, and a second delay τ(N; high) plus δ(N) relative to the high frequency of the corresponding chirp signal 480B. Interfering chirp signal 490C has a third delay τ(N; low) plus twice δ(N) relative to the low frequency of the corresponding chirp signal 480C, and a third delay τ(N; high) plus twice δ(N) relative to the high frequency of the corresponding chirp signal 480C.

[0046] In the second frame N+1, the inter-frame, slope-jittered chirped signal 485A-N is transmitted at fixed intervals based on the chirped period Tc and the second chirped jitter Δc(N+1), and has a slope S plus a second slope jitter Ψ(N+1). The period TF of frame N+1 is jittered with the second frame jitter ΔF(N+1). For the interfering chirped signal 495, the second time jitter Δc(N+1) and the second slope jitter Ψ(N+1) cause the delay τ relative to the corresponding inter-frame, slope-jittered chirped signal 485 to vary across the corresponding chirped signal 485 and increase across frame N+1.

[0047] For example, interfering chirp signal 495A has an initial delay τ(N+1; low) relative to the low frequency of the corresponding chirp signal 485A, and an initial delay τ(N+1; high) relative to the high frequency of the corresponding chirp signal 485A. Interfering chirp signal 495B has a second delay τ(N+1; low) plus δ(N+1) relative to the low frequency of the corresponding chirp signal 485B, and a second delay τ(N+1; high) plus δ(N+1) relative to the high frequency of the corresponding chirp signal 485B. Interfering chirp signal 495C has a third delay τ(N+1; low) plus twice δ(N+1) relative to the low frequency of the corresponding chirp signal 485C, and a third delay τ(N+1; high) plus twice δ(N+1) relative to the high frequency of the corresponding chirp signal 485C.

[0048] The combination of inter-frame and slope jitter causes the delay between interfering signals 490 and 495 and their corresponding chirped signals 480 and 485 to vary across a single chirp and across frames N and N+1. Therefore, interfering signals 490 and 495 appear as objects in different range bins, rather than in the same range bin, and... Figure 4A The interference signals 415 and 420 shown are... Figure 4B The interference signals 440 and 445 shown are as follows Figure 4C Compared to interference signals 465 and 470, fewer cells are affected in either range chamber. Techniques for detecting and repairing affected cells are more effective with a reduced number of affected cells.

[0049] Both the inter-chirp delay and the slope are constant within each frame. For example, in frame N, the inter-chirp delay Tc+Δc(N) and the slope S+Ψ(N) are constant, and in frame N+1, the inter-chirp delay Tc+Δc(N+1) and the slope S+Ψ(N+1) are constant. Therefore, there is no phase distortion across 480 Å in frame N or across 485 Å in frame N+1. Doppler FFTs across 480 Å or 485 Å in frame N do not display images... Figure 3C The background noise shown is like the background noise of 370.

[0050] Figure 5 Figure 500 shows the cumulative distribution function of the number of cells in each range cell affected by the jamming signal. The cumulative distribution function is an indicator of the extent to which a particular jitter technique disperses the jamming chirp signal across range cells. In this example, 256 chirped frames are transmitted in a frame period TF of approximately 6.4 milliseconds, where the chirp period Tc is approximately 25 microseconds. Twenty jamming radar systems were used to compare the cumulative distribution function 520 of an inter-frame jitter technique with ±1 microsecond jitter and the cumulative distribution function 510 of an intra-frame jitter technique with ±3.75 microsecond jitter. As indicated by reference numeral 530, the cumulative distribution function of the jitter technique described herein is... Figure 4A The cumulative distribution function 520 of the inter-frame jitter technique discussed in this paper is related to... Figure 3A The cumulative distribution function 510 of the intra-frame jitter techniques discussed is essentially the same. Although inter-frame and intra-frame jitter techniques may have essentially the same improvement in interference mitigation in range FFT, i.e., the number of units affected by the interfering signal per range cell, inter-frame jitter introduces less phase noise and a lower corresponding noise floor in Doppler FFT than intra-frame jitter.

[0051] Figure 6An example process 600 for jittering a radar frame is illustrated in flowchart form. Process 600 is executed by a processing unit using instructions stored in a non-transitory computer-readable medium such as static random access memory (SRAM). For example, process 600 may be executed by a chirp controller 120 using instructions stored in... Figure 1 The instructions in the storage device 150 shown are used for execution. Process 600 begins at step 605, where the chirp controller 120 determines the frame period TF based on the expected update rate of the radar system 100. For example, if the expected update rate of the radar system 100 is 60 frames per second, then the frame period TF is approximately 17 milliseconds (ms).

[0052] In step 610, the chirp controller 120 determines the maximum frame jitter ΔF(max) based on an acceptable deviation α(F) from the desired update rate. That is, the maximum frame jitter ΔF(max) can be set to α(F) multiplied by the frame period TF. Returning to the previous example, if a deviation α(F) of ±5% from the desired update rate is acceptable, then the maximum frame jitter ΔF(max) can be set to approximately 1 ms. In step 615, the chirp controller 120 determines the chirp period Tc based on the desired maximum unambiguous velocity vmax of the radar system 100. For example, the chirp period Tc can be expressed as:

[0053]

[0054] Where λ represents the wavelength of the chirp.

[0055] In step 620, the chirp controller 120 determines the maximum chirp jitter Δc(max) based on an acceptable deviation α(c) from the desired maximum unambiguous speed vmax. That is, the maximum chirp jitter Δc(max) can be set to α(c) multiplied by the chirp period Tc. For example, if a deviation α(c) of ±2% from the desired maximum unambiguous speed vmax is acceptable, then the maximum chirp jitter Δc(max) can be set to approximately 0.02Tc.

[0056] In step 625, the chirp controller 120 determines the chirp slope S based on the chirp frequency range, chirp period Tc, desired distance resolution, and the characteristics of LO 165. For example, the chirp slope S can be determined as:

[0057]

[0058] Here, c represents the speed of light, and Rres represents the desired distance resolution. Furthermore, the chirp slope S can be adjusted based on the characteristics of LO 165, allowing LO 165 to continuously and efficiently generate chirps with an appropriate slope S. In step 630, the chirp controller 120 determines the maximum slope jitter Ψ(max) based on the acceptable deviation α(r) from the desired distance resolution. That is, the maximum slope jitter Ψ(max) can be set to α(r) multiplied by the chirp slope S.

[0059] For each radar frame N, the chirp controller 120 performs one or more of steps 635, 640, and 645, and step 650. In step 635, the chirp controller 120 determines a random frame jitter ΔF(N) between negative ΔF(max) and positive ΔF(max). In step 640, the chirp controller 120 determines a random chirp jitter Δc(max) between negative Δc(max) and positive Δc(max). In step 645, the chirp controller 120 determines a random slope jitter Ψ(N) between negative Ψ(max) and positive Ψ(max). In step 650, the chirp controller 120 causes LO 165 in the radar sensor circuit 160 to generate a radar frame based on one or more determined frame jitter ΔF(N), chirp jitter Δc(N), and slope jitter Ψ(N).

[0060] In this description, the term "coupling" may encompass a connection, communication, or signaling path that enables the functional relationship to be consistent with this description. For example, if device A generates a signal to control device B to perform an action: (a) in a first example, device A is coupled to device B via a direct connection; or (b) in a second example, if the intervening component C does not alter the functional relationship between device A and device B, then device A is coupled to device B via the intervening component C such that the control signal generated by device B via device A is controlled by device A.

[0061] A device “configured” to perform a task or function may be configured by the manufacturer at manufacturing time (e.g., programmed and / or hardwired) to perform that function, and / or may be configured (or reconfigurable) by the user after manufacturing to perform that function and / or other additional or alternative functions. Configuration can be achieved through firmware and / or software programming of the device, through the construction and / or layout of the device’s hardware components and interconnects, or a combination thereof. As used herein, the terms “terminal,” “node,” “interconnect,” “pin,” and “lead” are used interchangeably. Unless specifically stated otherwise, these terms are generally used to refer to interconnects or terminations between device elements, circuit elements, integrated circuits, devices, or other electronic or semiconductor components.

[0062] A circuit or device described herein as including certain components may alternatively be adapted to be coupled to those components to form the described circuit system or device. For example, a structure described as including one or more semiconductor elements (such as transistors), one or more passive elements (such as resistors, capacitors, and / or inductors), and / or one or more sources (such as voltage and / or current sources) may alternatively include only semiconductor elements within a single physical device (e.g., a semiconductor die and / or integrated circuit (IC) package), and may be adapted to be coupled to at least some of the passive elements and / or sources during or after manufacturing (e.g., by an end user and / or a third party) to form the described structure.

[0063] The circuits described herein can be reconfigured to include additional or different components to provide functionality at least partially similar to that available before the component replacement. Unless otherwise stated, "about," "approximately," or "substantially" preceding a value means + / - 10% of the stated value. Modifications may be made to the described examples, and other examples may be possible within the scope of the claims.

[0064] Modifications may be made to the described embodiments, and other embodiments are possible within the scope of the claims.

Claims

1. A non-transitory computer-readable storage device for storing machine instructions, said machine instructions causing the one or more processors, when executed by said processors: Determine the chirp period Tc of the radar chirp in the radar frame; Determine the maximum chirp jitter Δc(max); Determine the chirp slope S of the radar chirp in the radar frame; Determine the maximum slope jitter Ψ(max); For radar frame N, determine at least one of the following: The random chirping fluctuation Δc(N) between negative Δc(max) and positive Δc(max), and The random slope jitter Ψ(N) between negative Ψ(max) and positive Ψ(max); and The radar sensor circuit generates the radar chirp in the radar frame N based on at least one of the chirp period Tc, the chirp slope S, the random chirp jitter Δc(N), and the random slope jitter Ψ(N).

2. The storage device of claim 1, wherein the machine instruction that causes the radar sensor circuit to generate the radar chirp in the radar frame N causes the one or more processors to cause the radar sensor circuit to transmit a plurality of radar chirps having the chirp slope S plus the random slope jitter Ψ(N).

3. The storage device of claim 1, wherein the machine instruction that causes the radar sensor circuit to generate the radar chirp in the radar frame N causes the one or more processors to cause the radar sensor circuit to transmit a plurality of radar chirps at intervals equal to the chirp period Tc plus the random chirp jitter Δc(N).

4. The storage device of claim 1, further comprising machine instructions that, when executed by the one or more processors, cause the one or more processors to: Determine the period TF of the radar frame; Determine the maximum frame jitter ΔF(max); For the radar frame N, determine the random frame jitter ΔF(N) between negative ΔF(max) and positive ΔF(max); and The radar sensor circuit further generates the radar frame N based on the period TF and the random frame jitter ΔF(N).

5. The storage device of claim 4, wherein the period TF of the radar frame is based on the update rate, and the maximum frame jitter ΔF(max) is based on a threshold deviation from the update rate.

6. The storage device of claim 4, wherein the machine instruction that causes the radar sensor circuit to generate the radar chirp in the radar frame N causes the one or more processors to cause the radar sensor circuit to transmit a plurality of radar chirps during the period TF plus the random frame jitter ΔF(N).

7. The storage device of claim 4, further comprising machine instructions that, when executed by the one or more processors, cause the one or more processors to: For subsequent radar frames N+1, determine the subsequent random frame jitter ΔF(N+1) between negative ΔF(max) and positive ΔF(max); and The radar sensor circuit further generates a radar chirp in the subsequent radar frame N+1 based on the period TF and the subsequent random frame jitter ΔF(N+1).

8. The storage device according to claim 7, wherein the subsequent random frame jitter ΔF(N+1) is not equal to the random frame jitter ΔF(N).

9. The storage device of claim 1, further comprising machine instructions that, when executed by the one or more processors, cause the one or more processors to: For subsequent radar frame N+1, determine at least one of the following: The subsequent random chirping jitter Δc(N+1) between negative Δc(max) and positive Δc(max); The subsequent random slope jitter Ψ(N+1) between negative Ψ(max) and positive Ψ(max); and The radar sensor circuit generates a radar chirp in the subsequent radar frame N+1 based on at least one of the chirp period Tc, the chirp slope S, the subsequent random chirp jitter Δc(N+1), and the subsequent random slope jitter Ψ(N+1).

10. The storage device of claim 9, wherein the subsequent random chirp jitter Δc(N+1) is not equal to the random chirp jitter Δc(N).

11. The storage device of claim 9, wherein the subsequent random slope jitter Ψ(N+1) is not equal to the random slope jitter Ψ(N).

12. The storage device of claim 1, wherein the chirp period Tc of the radar chirp is based on a threshold unambiguous velocity, and the maximum chirp jitter Δc(max) is based on a threshold deviation from the threshold unambiguous velocity.

13. The storage device of claim 1, wherein the chirp slope S is based on the frequency range of the radar chirp in the radar frame, the threshold distance resolution, and the chirp period Tc, and wherein the maximum slope jitter Ψ(max) is based on a threshold deviation from the threshold distance resolution.

14. An apparatus for jittering radar frames, comprising: One or more processors; as well as One or more non-transitory computer-readable media storing machine instructions that, when executed by the one or more processors, cause the one or more processors to: Determine at least one of the chirp period Tc of the radar chirp in the radar frame and the chirp slope S of the radar chirp in the radar frame; In response to determining the chirp period Tc: Determine the maximum chirp jitter Δc(max); For radar frame N, determine the random chirp jitter Δc(N) between negative Δc(max) and positive Δc(max); In response to determining the chirp slope S: Determine the maximum slope jitter Ψ(max); as well as For the radar frame N, determine the random slope jitter Ψ(N) between negative Ψ(max) and positive Ψ(max); as well as The radar sensor circuit generates a radar chirp in the radar frame N based on at least one of (1) the chirp period Tc and the random chirp jitter Δc(N) and (2) the chirp slope S and the random slope jitter Ψ(N).

15. The apparatus of claim 14, wherein the one or more non-transitory computer-readable media further comprises machine instructions that, when executed by the one or more processors, cause the one or more processors to: Determine the period TF of the radar frame; Determine the maximum frame jitter ΔF(max); and For the radar frame N, a random frame jitter ΔF(N) between negative ΔF(max) and positive ΔF(max) is determined, wherein the machine instruction that causes the radar sensor circuit to generate the radar chirp in the radar frame N causes the one or more processors to cause the radar sensor circuit to generate the radar chirp in the radar frame N based on the period TF and the random frame jitter ΔF(N).

16. The apparatus of claim 15, wherein the one or more non-transitory computer-readable media further comprises machine instructions that, when executed by the one or more processors, cause the one or more processors to: For subsequent radar frames N+1, determine the subsequent random frame jitter ΔF(N+1) between negative ΔF(max) and positive ΔF(max); and The radar sensor circuit generates a radar chirp in the subsequent radar frame N+1 based on the period TF and the subsequent random frame jitter ΔF(N+1).

17. The device of claim 16, wherein the subsequent random frame jitter ΔF(N+1) is not equal to the random frame jitter ΔF(N).

18. The apparatus of claim 14, wherein the one or more non-transitory computer-readable media further comprises machine instructions that, when executed by the one or more processors, cause the one or more processors to: For subsequent radar frames N+1, determine at least one of the following: the subsequent random chirp jitter Δc(N+1) between negative Δc(max) and positive Δc(max) and the subsequent random slope jitter Ψ(N+1) between negative Ψ(max) and positive Ψ(max); and The radar sensor circuit generates a radar chirp in the subsequent radar frame N+1 based on at least one of the chirp period Tc and the subsequent random chirp jitter Δc(N+1) and the chirp slope S and the subsequent random slope jitter Ψ(N+1).

19. The apparatus according to claim 18, wherein: The subsequent random chirping jitter Δc(N+1) is not equal to the random chirping jitter Δc(N); and The subsequent random slope jitter Ψ(N+1) is not equal to the random slope jitter Ψ(N).

20. The device of claim 14, further comprising the radar sensor circuit.

21. A method for jittering radar frames, comprising: Determine at least one of the chirp period Tc of the radar chirp in the radar frame and the chirp slope S of the radar chirp in the radar frame; In response to determining the chirp period Tc: Determine the maximum chirp jitter Δc(max); For radar frame N, determine the random chirp jitter Δc(N) between negative Δc(max) and positive Δc(max); In response to determining the chirp slope S: Determine the maximum slope jitter Ψ(max); as well as For the radar frame N, determine the random slope jitter Ψ(N) between negative Ψ(max) and positive Ψ(max); as well as The radar sensor circuit generates a radar chirp in the radar frame N based on at least one of (1) the chirp period Tc and the random chirp jitter Δc(N) and (2) the chirp slope S and the random slope jitter Ψ(N).

22. The method of claim 21, wherein the chirp period Tc of the radar chirp is based on a threshold unambiguous velocity associated with the radar sensor circuit, and wherein the maximum chirp jitter Δc(max) is based on a threshold deviation from the threshold unambiguous velocity.

23. The method of claim 21, further comprising: Determine the period TF of the radar frame; Determine the maximum frame jitter ΔF(max); as well as For the radar frame N, determining the random frame jitter ΔF(N) between negative ΔF(max) and positive ΔF(max), wherein causing the radar sensor circuit to generate the radar chirp in the radar frame N includes causing the radar sensor circuit to generate the radar chirp in the radar frame N based on the period TF and the random frame jitter ΔF(N).

24. The method of claim 23, wherein the period TF of the radar frame is based on an update rate associated with the radar sensor circuit, and wherein the maximum frame jitter ΔF(max) is based on a threshold deviation from the update rate.

25. The method of claim 21, wherein the chirp slope S is based on the frequency range of radar chirps in the radar frame, the threshold distance resolution, and the chirp period Tc, and wherein the maximum slope jitter Ψ(max) is based on a threshold deviation from the threshold distance resolution.

Images