Device for processing radar signals

Abstract

An apparatus for processing a radar signal configured to receive a radar signal comprising a radar frame of a plurality of chirps comprising at least a first group transmitted at a first pulse repetition interval and a second group transmitted at a second pulse repetition interval, wherein the groups are separated by a group separation time interval between a final chirp in the first group and a first chirp in the second group, the group separation time interval being different from one or both of the first pulse repetition interval and the second pulse repetition interval; a modified received radar frame is generated by at least: a first extrapolation based on temporal locations of the chirps in the first group of received radar frames to generate at least one extrapolated chirp in the modified received radar frame; processing is performed based on the modified received radar frame.

Description

Technical Field

[0001] The present disclosure relates to an apparatus for processing frequency modulated continuous wave (FMCW) radar signals. Specifically, the present disclosure relates to a system configured to transmit radar frames and receive radar frames reflected from one or more targets. The present disclosure also relates to an associated method. Background Art

[0002] FMCW radars are commonly used in automotive applications. One of the more challenging issues affecting automotive radar systems is real-time velocity disambiguation in the context of time-division multiplexing (TDM) radars (e.g., TDM-MIMO). These challenges also apply to other types of multiplexed radars. Summary of the Invention

[0003] According to a first aspect of the present disclosure, a device for processing a frequency modulated continuous wave (FMCW) radar signal is provided, the device being configured to:

[0004] receiving a radar signal comprising a radar frame reflected from one or more targets, wherein the radar frame comprises a plurality of chirps, the plurality of chirps comprising at least two groups of chirps, the at least two groups of chirps comprising a first group transmitted with a first pulse repetition interval between the chirps therein and a second group transmitted with a second pulse repetition interval between the chirps therein, wherein the first group and the second group are separated by a group separation time interval between a final chirp in the first group and a first chirp in the second group, the group separation time interval being different from one or both of the first pulse repetition interval and the second pulse repetition interval;

[0005] Generate a modified received radar frame by at least:

[0006] a first extrapolation based on the temporal positions of the chirps in the first group of the received radar frames to produce at least one extrapolated chirp in the modified received radar frame;

[0007] Processing is performed based on the modified received radar frame to determine a property of the one or more targets.

[0008] In one or more examples, the first pulse repetition interval is the same as the second pulse repetition interval.

[0009] In one or more embodiments, the at least one extrapolated chirp generated by the first extrapolation is extrapolated to a time later in the received radar frame and between two chirps of the second group in the received radar frame.

[0010] In one or more embodiments, the first extrapolation is configured to generate a plurality of extrapolated chirps that are extrapolated such that the plurality of extrapolated chirps are interleaved with the chirps of the second group in the modified received radar frame.

[0011] In one or more embodiments, said generating of said modified received radar frame further comprises:

[0012] A second extrapolation is performed based on the temporal positions of the chirps in the second group of the received radar frames to produce at least one extrapolated chirp in the modified received radar frame.

[0013] In one or more embodiments, the at least one extrapolated chirp generated by the second extrapolation is extrapolated to a time between two chirps of the first group in the modified received radar frame.

[0014] In one or more embodiments, the second extrapolation is configured to generate a plurality of extrapolated chirps that are extrapolated such that the plurality of extrapolated chirps are interleaved with the chirps of the first group in the modified received radar frame.

[0015] In one or more embodiments, the generating of the extrapolated chirp is configured to generate the modified received radar frame having a pulse repetition interval that is less than the first pulse repetition interval and less than the second pulse repetition interval.

[0016] In one or more embodiments, the extrapolation comprises linear extrapolation.

[0017] In one or more embodiments, the apparatus is configured to perform the extrapolation based on Burg's algorithm for autoregressive parameter estimation.

[0018] In one or more embodiments, the generation of the modified received radar frame further includes the device being configured to:

[0019] extracting the chirp corresponding to the first group from the received radar frame to generate a first received radar frame;

[0020] extracting the chirp corresponding to the second group from the received radar frame to generate a second received radar frame;

[0021] generating the modified first received radar frame by performing the first extrapolation based on the temporal positions of the chirps in the first group of the first received radar frame to produce at least one extrapolated chirp at a later time in the modified first received radar frame;

[0022] generating the modified second received radar frame by performing a second extrapolation based on the temporal positions of the chirps in the second group of the second received radar frame to produce at least one extrapolated chirp at an earlier time in the modified second received radar frame;

[0023] generating a Fast Fourier Transform (FFT) of the modified first received radar frame;

[0024] generating an FFT of the modified second received radar frame; and

[0025] The modified received radar frame includes a sum of the FFT of the modified first received radar frame and the FFT of the modified second received radar frame.

[0026] In one or more embodiments, the device is configured to:

[0027] Transmission of the radar frame having properties of the first pulse repetition interval, the second pulse repetition interval, and the group separation time interval is provided.

[0028] In one or more embodiments, the first pulse repetition interval and the second pulse repetition interval each comprise the product of the number of groups N and the base time interval T; and the group separation time interval between any two temporally adjacent groups comprises NT plus or minus T.

[0029] In one or more embodiments, one or both of the following are present:

[0030] performing the first extrapolation and any further extrapolations; and

[0031] selecting the group separation time interval and the first pulse repetition time interval and the second pulse repetition time interval;

[0032] Such that the extrapolated chirp does not overlap with the chirp of the received radar frame in time.

[0033] In one or more embodiments, the properties of the one or more targets determined based on the modified received radar frame include one or more of: a range to the one or more targets; a direction towards the one or more targets; and a speed of the one or more targets.

[0034] According to a second aspect of the present disclosure, a method for processing a frequency modulated continuous wave (FMCW) radar signal is provided. The device is configured to:

[0035] receiving a radar signal comprising a radar frame reflected from one or more targets, wherein the radar frame comprises a plurality of chirps, the plurality of chirps comprising at least two groups of chirps, the at least two groups of chirps comprising a first group transmitted with a first pulse repetition interval between the chirps therein and a second group transmitted with a second pulse repetition interval between the chirps therein, wherein the first group and the second group are separated by a group separation time interval between a final chirp in the first group and a first chirp in the second group, the group separation time interval being different from one or both of the first pulse repetition interval and the second pulse repetition interval;

[0036] The modified received radar frame is generated by the following operations:

[0037] a first extrapolation based on the temporal positions of the chirps in the first group of the received radar frames to produce at least one extrapolated chirp in the modified received radar frame; and

[0038] Processing is performed based on the modified received radar frame to determine a property of the one or more targets.

[0039] In one or more examples, the first extrapolation is configured to generate a plurality of extrapolated chirps that are extrapolated such that the plurality of extrapolated chirps are at least partially interleaved with the second group of chirps in the modified received radar frame.

[0040] In one or more examples, the generating of the modified received radar frame further includes:

[0041] A second extrapolation is performed based on the temporal positions of the chirps in the second group of the received radar frames to produce a plurality of extrapolated chirps in the modified received radar frame.

[0042] In one or more examples, the plurality of extrapolated chirps generated by the second extrapolation are extrapolated such that the plurality of extrapolated chirps are at least partially interleaved with the first group of chirps in the modified received radar frame.

[0043] In one or more instances, one or both of the following are present:

[0044] performing the first extrapolation and the second extrapolation; and

[0045] selecting the group separation time interval and the first pulse repetition time interval and the second pulse repetition time interval;

[0046] The extrapolated chirp is made to not overlap with the chirp of the received radar frame in time.

[0047] While the present disclosure is susceptible of various modifications and alternative forms, the features of the present disclosure have been illustrated by way of example in the drawings and will be described in detail. However, it should be understood that other embodiments besides the specific embodiments described are possible. All modifications, equivalents, and alternative embodiments falling within the spirit and scope of the appended claims are also encompassed.

[0048] The above discussion is not intended to represent every example embodiment or every implementation within the scope of the current or future claim sets. The following figures and detailed description further illustrate various example embodiments. The various example embodiments can be more fully understood by considering the following detailed description in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] One or more embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0050] Figure 1 An example embodiment showing a block diagram including devices within a radar system;

[0051] Figure 2 shows a first example embodiment of a radar frame and the generation of a modified received radar frame that has been reflected from one or more objects;

[0052] Figure 3 A second example embodiment of a radar frame and the generation of a modified received radar frame that has been reflected from one or more objects is shown;

[0053] Figure 4 A third example embodiment of a radar frame and the generation of a modified received radar frame that has been reflected from one or more objects is shown;

[0054] Figure 5 A fourth example embodiment of a radar frame and the generation of a modified received radar frame that has been reflected from one or more objects is shown;

[0055] Figure 6 A comparison of example plots of range bins versus Doppler bins is shown for a received radar frame and a modified received radar frame. DETAILED DESCRIPTION

[0056] This document discloses an embodiment of a device that provides real-time velocity deambiguation in the context of TDM-MIMO radar, but is also applicable to other types of division multiplexing. As is familiar to those skilled in the art, for a given wavelength, the maximum unambiguous velocity that can be determined from a radar signal depends on the pulse repetition interval (PRI).

[0057] Among other things, there are four main challenges in reducing PRI:

[0058] a) constructing a voltage-controlled oscillator (VCO) / phase-locked loop (PLL) capable of providing very short chirp for a given bandwidth,

[0059] b) Construct a VCO / PLL with extremely fast recovery rate (hysteresis),

[0060] c) providing a processor powerful enough to process the signal and provide interference mitigation and range determination Fast Fourier Transform between two consecutive chirps, and

[0061] d) Providing an analog-to-digital (ADC) converter with a sampling rate high enough to achieve the desired upper range determination.

[0062] The described example embodiments transmit radar frames divided into spaced-apart subframes or groups, with a predetermined separation between the constituent chirps of each subframe or group. It has been discovered that extrapolation techniques can be applied to received radar signals to interleave real and extrapolated samples, thereby reducing the PRI. A lower PRI allows for a larger maximum unambiguous velocity determination for a target from the radar signal.

[0063] Example Figure 1 A block diagram of the devices within a typical radar system 100 is shown. The radar system 100 in this example is of the Time Division Multiplexing Multiple Input Multiple Output (TDM-MIMO) type. This example is also of the FMCW type. However, the present disclosure is not limited to TDM-MIMO radar systems.

[0064] Radar system 100 includes one or more transmitter arrangements 101 for transmitting radar signals. The radar signals may be formed from a plurality of radar frames, each at a different frequency. A radar frame comprises a plurality of time-spaced chirps. Radar system 100 includes one or more receiver arrangements 102 for receiving the transmitted radar signals that have been reflected from one or more targets in the environment. Thus, each receiver arrangement may receive radar frames at a different frequency and provide the radar frames to device 103 for processing. Device 103 schematically illustrates a series of processing steps that illustrate processing of an embodiment and will be described later.

[0065] In general, transmitter arrangement 101 can receive a signal 104 from a device 103, causing transmitter arrangement 101 to transmit a radar signal that may include one or more radar frames. In general, transmitter arrangement 101 includes a VCO or PLL 105 that can be controlled to generate a radar frame comprising a plurality of chirps with a specific pulse repetition interval between chirps. A coupler / splitter 106 is configured to provide a portion 107 of the signal comprising the generated radar frame to the remainder of transmitter arrangement 101 and to provide a portion 108 of the signal comprising the generated radar frame to receiver arrangement 102. An amplifier 110 is configured to amplify portion 107, and a phase shifter 111 applies a phase shift to the amplified signal. An antenna 112 provides for transmission of the radar signal into the environment, enabling the radar signal to be reflected from one or more targets that may be present.

[0066] Receiver arrangement 102 may include an antenna 113 to receive transmitted radar signals, specifically radar frames reflected from one or more targets in the environment. Amplifier 114 amplifies the signal. Mixer 115 of receiving portion 108 also downconverts the radar signal. Bandpass filter 116 or another type of filter filters the signal. Analog-to-digital converter 117 digitizes the signal and provides it to device 103 for processing. Thus, device 103 may be configured to receive (e.g., digital) signals representing transmitted reflected radar frames.

[0067] It will be appreciated that the transmitter arrangement 101 and the receiver arrangement 102 may take other forms and may contain additional or alternative components.

[0068] In general, device 103 is configured to process a frequency modulated continuous wave (FMCW) radar signal, which may be received from receiver arrangement 101 at input 118. In some examples, device 103 may be provided separately from receiver arrangement 101 and / or transmitter arrangement 102. Thus, the functionality of device 103 may be provided and configured to be coupled with receiver arrangement 101 and / or transmitter arrangement 102. In the present example, device 103 includes functionality for generating a radar frame for the transmitter arrangement using signal 104, but the transmitter arrangement is a separate component. However, in some examples, device 103 may not provide signal 104 for generating a radar frame, and this task may be performed by a separate device (not shown). In such examples, the device may be informed of the form of the radar frame.

[0069] The device 103 may be configured to pre-process raw data received from one or more receiver arrangements at step 120. Range compression may be performed at step 121. Steps 122-125 may comprise advantageous steps performed by the device of the present disclosure and will be described in more detail below.

[0070] Constant false alarm rate (CFAR) detection may optionally be performed at step 126. MIMO array construction may be performed at step 127. Direction of arrival estimation may be performed at step 128. Step 128 may include velocity determination.

[0071] It should be understood that in other embodiments, steps 122 - 125 may be performed at different times, or may be distributed among other processing steps in a different manner.

[0072] Now refer to Figure 1 and 2 Example embodiments are described. Figure 2 1 shows a radar frame transmitted by transmitter arrangement 101. Radar frame 200 will be modified by its interactions with the environment and reflections. However, for the purposes of describing this embodiment, radar frame 200 can also be considered to represent at least the content received by receiver arrangement 102 that has been reflected from one or more targets. Example embodiments provide for advantageous processing of radar frames having a particular form. Thus, as mentioned above, device 103 can generate a radar frame and process its reflections from one or more targets, or, in other examples, can receive information indicative of a radar frame transmitted by a different device, enabling advantageous processing.

[0073] In summary, a device is configured to receive radar signal 118 representing a reflected radar frame 200. The transmitted radar frame 200 includes a plurality of chirps 201-206. In this example, the plurality of chirps of the radar frame are arranged into two groups, including a first group 201-203 and a second group 204-206. For ease of explanation, each group is shown with three chirps, but more chirps may be present. In other examples, two or more, or three or more, groups of chirps may be provided in a radar frame. The chirps of one group may have the same form (i.e., frequency variation over time) or may differ relative to the chirps of another group and / or within a group. However, the chirps of the first group 201-203 are transmitted with a first pulse repetition interval 207 between the chirps. In this example, the chirps 204-206 of the second group are also transmitted with a first pulse repetition interval 207 between the chirps therein (although in other examples, the PRI can be different). The first group 201-203 and the second group 204-206 are separated by a group separation time interval 208 between the final chirp 203 in the first group 201-203 and the first chirp 204 in the second group 204-206, which is different from the first pulse repetition interval 207. In one or more examples, the group separation time interval 208 differs from the first pulse repetition interval 207 by one chirp duration 209 or at least one chirp duration 209.

[0074] In some examples, the group separation time interval 208 is greater than the first pulse repetition interval 207 by at least one chirp duration 209. In some examples, the group separation time interval 208 is less than the first pulse repetition interval 207 by at least one chirp duration.

[0075] In this example, the first pulse repetition interval 207 comprises 2 T. The group separation time interval 208 comprises 3 T. Thus, in this example, the first pulse repetition interval 207 comprises twice the base time interval T, while the group separation time interval 208 is larger, e.g., larger by at least one base time interval T, and in some examples comprises an odd integer multiple of the base time interval T.

[0076] In other examples, the first pulse repetition interval 207 comprises NT, where N is the number of chirp groups and T is a predetermined base time interval. The group separation time interval 208 differs from the first pulse repetition interval 207 by at least one chirp duration.

[0077] In another example, the first pulse repetition interval 207 includes 2T to 4T.

[0078] Device 103 is configured to generate modified received radar frame 210 based on received radar frame 200 by performing the following steps: Device 103 may include a processor and memory or other processing circuitry for performing the generation of modified received radar frame 210 .

[0079] Device 103 is configured to perform first extrapolation 211 based on the temporal positions of chirps 201 - 203 in the first group of received radar frames to generate at least one extrapolated chirp 212 at a later time in modified received radar frame 210 .

[0080] First extrapolation 211 may include determining time intervals between the first group of chirps 201 - 203 and, by linear extrapolation, determining a time at which at least one extrapolated chirp 212 would be received if the at least one extrapolated chirp 212 were transmitted in radar frame 200 .

[0081] Group separation time interval 208 and first pulse repetition interval 207 are determined such that one or more extrapolated chirps 212 do not temporally overlap with plurality of chirps 201 - 206 in modified received radar frame 210 .

[0082] Device 103 is configured to perform processing based on the modified received radar frame 210 to determine properties of one or more targets. The properties that can be determined can be those that are conventionally determined by processing FMCW radar frames and are familiar to those skilled in the art. For example, determining the presence or amount of one or more targets, determining the range to one or more targets, determining the direction to one or more targets, and / or determining the velocity of one or more targets.

[0083] Example Figure 3 Another example of generating a modified received radar frame 302 is shown. In this example, modified received radar frame 302 is generated by first extrapolation 311 (result shown as 300) and second extrapolation 312 (result shown as 301) to form final modified received radar frame 302. However, it should be understood that in other embodiments, the modified received radar frame may include a frame shown as 300 or 301 where only a portion of the extrapolation is performed.

[0084] In example (partially) modified received radar frame 300, first extrapolation 311 is again based on the temporal positions of chirps 201-203 in the first group of received radar frame 200. In this example, first extrapolation is configured to produce a plurality of extrapolated chirps 212, 213, 214, each at a different, later time in modified received radar frame 210.

[0085] In this example, at least one extrapolated chirp generated by first extrapolation 311 is extrapolated to the time between two chirps of the second group in the received radar frame. Thus, extrapolated chirp 213 is between chirps 204 and 205. Similarly, extrapolated chirp 214 is between chirps 205 and 206.

[0086] Furthermore, in this example, first extrapolation 311 is configured to generate a plurality of extrapolated chirps 212, 213, 214 that are extrapolated such that extrapolated chirps 212, 213, 214 are interleaved with chirps 204-206 of the second group in the (partially) modified received radar frame 300. Furthermore, in this or other examples, at least one extrapolated chirp 212 may be extrapolated to a time that is (directly) temporally adjacent to first chirp 204 of the second group 204-206.

[0087] The generation of modified received radar frame 301 includes a second extrapolation 312 based on the temporal positions of the chirps in second group 204-206 of received radar frames to generate at least one extrapolated chirp 215, 216, 217 at an earlier time in (part of) modified received radar frame 301. In this example, multiple extrapolated chirps 215, 216, 217 are generated, each at a different earlier time.

[0088] In this example, at least one of the extrapolated chirps 215, 216, and 217 generated by the second extrapolation 312 is extrapolated to a time between two chirps of the first group 201-203 in the received radar frame. Thus, the extrapolated chirp 215 is between chirps 201 and 202. Similarly, the extrapolated chirp 216 is between chirps 202 and 203.

[0089] Moreover, in this example, second extrapolation 312 is configured to generate a plurality of extrapolated chirps 215, 216, 217 that are extrapolated such that extrapolated chirps 215, 216, 217 are interleaved with the chirps 201-203 of the first group in modified received radar frame 301. Furthermore, in this or other examples, at least one extrapolated chirp 217 can be extrapolated to a time that is (directly) temporally adjacent to the final chirp 203 of the first group 201-203.

[0090] Finally, a modified received radar frame 302 is generated based on a combination of the result of the first extrapolation 311 and the result of the second extrapolation 312 .

[0091] Modified received radar frame 302 has a pulse repetition interval 303 that is less than the first pulse repetition interval 2T of the base time interval T. At least a velocity determination of one or more targets may be performed on one or more such generated modified received radar frames 302. It has been discovered that the reduced pulse repetition interval 303 "T," generated by interpolating actual chirps from different groups, results in a more efficient unambiguous velocity determination of one or more targets.

[0092] Thus, in summary, radar frame 200 is generated using chirps of at least two groups having at least a first pulse repetition interval and a group separation time interval 208, and based on extrapolation of chirps of at least a subset of the groups, at least a portion of a modified received radar frame 302 generated by the extrapolation has a pulse repetition interval that is less than the first pulse repetition interval. Furthermore, the extrapolation and / or group separation time interval 208 and first pulse repetition interval 207 are selected so that the extrapolated chirps do not temporally overlap with chirps of received radar frame 200.

[0093] Figure 4 Another embodiment is shown that includes separating the first group from the second group in the received radar frame and performing a first extrapolation and a second extrapolation on the separated parts before reassembling the parts. In this example, a fast Fourier transform is applied before reassembling the parts.

[0094] Therefore, reference Figure 4 , the device 100 may be configured to:

[0095] extracting chirps 201-203 corresponding to a first group from received radar frame 200 to generate a first received radar frame;

[0096] extracting chirps 204-206 corresponding to a second group from received radar frame 200 to generate a second received radar frame;

[0097] generating the modified first received radar frame 401 by performing the first extrapolation based on the temporal positions of the chirps in the first group of first received radar frame 401 to generate a plurality of extrapolated chirps 412-415 at a later time in the modified first received radar frame; and

[0098] Modified second received radar frame 402 is generated by performing a second extrapolation based on the temporal positions of the chirps in the second group of second received radar frame 402 to produce a plurality of extrapolated chirps 416 - 418 at an earlier time in modified second received radar frame 402 .

[0099] Device 103 is configured to determine an FFT of modified first received radar frame 401. Furthermore, device 103 is configured to determine an FFT of modified second received radar frame 402.

[0100] Thus, in this example, modified received radar frame 420 includes the sum of the FFT of the modified first received radar frame and the FFT of the modified second received radar frame.

[0101] Returning now to steps 122-125 shown in apparatus 103, the steps include performing a first extrapolation at step 122, although many other extrapolations, such as a second extrapolation, may be performed to achieve interleaved, modified received radar frames (also referred to as "Doppler samples"). This may be performed for each frequency at which radar system 100 operates.

[0102] Step 123 represents computing the FFT of the first / second / etc. modified received radar frame for each group individually.

[0103] Step 124 represents constructing a modified received radar frame 420 , or “Doppler profile,” by summing the FFT results for each group determined in step 123 .

[0104] Step 125 represents an execution level check, which will be described in more detail below.

[0105] It should be understood that steps 122-124 are a brief overview of the method disclosed herein. In more detail, steps 122-124 may include a device configured to perform the following operations:

[0106] 1) Provide a radar frame that transmits M groups of chirps at MT intervals within each group, where M is an even number and the group separation time interval is an odd number T between groups.

[0107] 2) Perform distance processing as will be known to those skilled in the art.

[0108] 3) For each distance partition, perform the following steps:

[0109] a. Based on Figure 4 The PRI intervals illustrated in divide the slow-time samples into groups;

[0110] b. Using extrapolation, which may include prediction techniques, to increase the length of each group (in terms of the number of chirps, including actual chirps + extrapolated chirps) so that after superposition positioning of all extrapolated groups, a full frame or nearly a full frame is obtained (i.e., slow-time samples (chirps) are evenly spaced at T)

[0111] c. Perform Doppler FFT, as in reference Figure 4 described;

[0112] 4) The device is configured to generate a range-Doppler map based on the resulting modified received radar frame for subsequent conventional processing.

[0113] The extrapolation performed in step 3 may include the Berg method, the Yule Walker Equation, or the Levinson Method to estimate an autoregressive model based on a given order. Thus, as will be understood by one skilled in the art, prediction coefficients from the AR model and the existing samples (chirps) in each group are used to extrapolate the number of chirps. A second possible method for extrapolation may be to use an adaptive filter or a neural network (RLS, LMS, etc.) as a linear predictor to predict future / past samples. Other methods are possible, and it should be understood that embodiments of the present disclosure relate to the extrapolation of chirps in the groups described herein to improve the PRI rather than to an exact method of performing extrapolation.

[0114] Before describing the degree review process, Figure 5 An embodiment is shown in which transmitted and received radar frame 500 includes four groups of chirps, namely a first group 501 , a second group 502 , a third group 503 , and a fourth group 504 .

[0115] In a first extrapolation, the first group is (only) extrapolated to a slightly later time to provide extrapolated chirps 510 , 511 , 512 .

[0116] In a second extrapolation, the second group is extrapolated to earlier and later times to provide extrapolated chirps 520 , 521 , 522 , 523 , 524 .

[0117] In a third extrapolation, the third group is extrapolated to earlier and later times to provide extrapolated chirps 530 , 531 , 532 , 533 .

[0118] In a fourth extrapolation, the fourth group is extrapolated (only) to slightly earlier to provide the extrapolated chirps 540 , 541 .

[0119] The resulting modified received radar frame is shown as 550. Thus, the number of extrapolated chirps extrapolated from a particular group can be independent of any other group. Furthermore, when generating modified received radar frame 550, the chirps of each group can be extrapolated to earlier and / or later times in received radar frame 500. Specifically, for radar frames that include three or more groups, groups located at locations both earlier and later in the radar frame where other groups exist can be extrapolated to both earlier and later times, while groups located at the beginning and end of the radar frame can be extrapolated only in one time direction.

[0120] Now refer to Figure 6 The optional level check step 125 is described.

[0121] Figure 6 A series of plots showing range binning versus Doppler binning, which will be familiar to those skilled in the art, are shown.

[0122] Plot 601 shows a plot of the FFT of the first group. Plot 602 shows a plot of the FFT of the second group. Plot 603 shows the sum of the FFT of the first group and the FFT of the second group. It can be seen that due to the slight phase error caused by the generation of the modified received radar frame, there is ambiguity represented by two regions 604 and 605 rather than a single region.

[0123] This ambiguity can be removed by simply repeatedly checking to the extent that k*FFT{G1+G2}≤FFT{G1}+FFT{G2}, as shown in plot 606, where k is a constant close to "1", and G1 is the sample representing the first group of chirps in the slow-time domain (e.g., 201-203, 212-214), and G2 is the sample representing the second group of chirps (e.g., 204-206, 215-217).

[0124] By performing this level check, it can be seen that plot 606 includes only one region 607, and the ambiguity is thus resolved. Therefore, samples where k*FFT{G1+G2}≤FFT{G1}+FFT{G2} are removed. Thus, the device can be configured to evaluate which samples representing the chirp of the radar frame meet the condition k*FFT{G1+G2}≤FFT{G1}+FFT{G2} when processing and generating a modified received radar frame, and remove these samples from the modified received radar frame.

[0125] In implementation, the device is configured to apply the techniques described herein to each equally divided range line or range partition. As will be appreciated, if a range-Doppler map is available, then the equally divided range line or range partition can be a horizontal line containing all Doppler partitions at that particular distance. In one or more examples, the techniques described herein may be selectively applied.

[0126] In one or more examples, the extrapolation can be based on an autoregressive (AR) parameter estimation technique, where the AR prediction coefficients are the same for all groups 201, 202, 501, 502, 503, 504, meaning they can be calculated only once or averaged for all groups to achieve more robust performance. This also applies to multiple RXs and TXs, meaning that for a 3TX-4RX TDM MIMO radar, only one set of coefficients is needed for all channels.

[0127] In one or more examples, the level check step 125 may replace the CFAR step 126 .

[0128] The extrapolation described herein can take various forms. In one or more examples, the extrapolation performed is linear extrapolation. In one or more other examples, the extrapolation is based on a Berg algorithm for autoregressive parameter estimation.

[0129] Berg algorithm

[0130]

[0131] Where x is the input signal to the algorithm, where p is the order or pole number describing the autoregressive model, N is the number of samples in x, Ak is the prediction coefficient, and the vectors f0, b0, f k and b k is the intermediate result in the algorithm, μ k is the prediction step size.

[0132] The Berg algorithm for AR parameter estimation allows extrapolation of the input signal, which helps increase spectral resolution. Since it is most popular for minimizing forward and backward prediction errors, the Berg algorithm can be viewed as constrained least squares minimization.

[0133] The assumption for this algorithm is that the process is generally stationary, so that the coefficients of the backward prediction error are the same as the coefficients of the optimal forward prediction error, but conjugate and reversed in time. Thus, the forward linear prediction error fe(n) is defined for p≤n≤N-1, where ap0 is defined as unity, apk is the AR coefficient at order p, and xn is the data sample.

[0134]

[0135] The backward linear prediction error is also defined for p≤n≤N-1 and is defined as:

[0136]

[0137] The asterisk indicates the complex conjugate operation. To estimate the AR model coefficients, each apk coefficient must satisfy the Levinson recursion:

[0138]

[0139] where i = [1, k] and μ is the constraint coefficient.

[0140] This constraint ensures that the filter is stable, which means that all poles are located inside the unit circle. Berg changed the way μ is calculated by minimizing the sum of fe(n) and be(n).

[0141] The pseudocode snapshot above shows that μ is updated for each k. This is possible based on the following: the forward linear prediction equation is written in a recursive way based on Levinson recursion and the backward linear prediction equation

[0142] After updating μ, the AR model parameter apk is updated in the last line. The Burg algorithm shows computational complexity, requiring 3Np-p2-N+3p complex multiplications, 3Np-p2-2N-p complex additions, and p real divisions. Furthermore, 3N+p+2 complex values need to be stored.

[0143] Unless a specific order is explicitly stated, the instructions and / or flowchart steps in the above figures may be executed in any order. In addition, those skilled in the art will recognize that although an example instruction set / method has been discussed, the materials in this specification may be combined in various ways to produce other examples and should be understood within the context provided in this detailed description.

[0144] In some example embodiments, the instruction sets / method steps described above are implemented as functions and software instructions embodied as executable instruction sets that are implemented on a computer or machine programmed with and controlled by the executable instructions. Such instructions are loaded for execution on a processor (e.g., one or more CPUs). The term processor includes a microprocessor, a microcontroller, a processor module or subsystem (including one or more microprocessors or microcontrollers), or other control or computing devices. A processor may refer to a single component or a plurality of components.

[0145] In other examples, the instruction sets / methods described herein and the data and instructions associated therewith are stored in corresponding storage devices, which are implemented as one or more non-transient machine or computer readable or computer usable storage media. Such one or more computer readable or computer usable storage media are considered part of an article (or product). An article or product may refer to any manufactured single component or multiple components. As defined herein, non-transient machine or computer usable media does not include signals, but such media is capable of receiving and processing information from signals and / or other transient media.

[0146] Example embodiments of the materials discussed in this specification may be implemented in whole or in part via network, computer, or data-based devices and / or services. These may include the cloud, the Internet, an intranet, a mobile device, a desktop, a processor, a lookup table, a microcontroller, a consumer device, infrastructure, or other enabling devices and services. As may be used herein and in the claims, the following non-exclusive definitions are provided.

[0147] In one example, one or more instructions or steps discussed herein are automated. The terms "automated" or "automatic" (and similar variations thereof) mean the controlled operation of equipment, systems, and / or processes using computers and / or mechanical / electrical means without the need for human intervention, observation, effort, and / or decision-making.

[0148] It should be understood that any components referred to as being coupled may be coupled or connected directly or indirectly. In the case of an indirect coupling, additional components may be disposed between the two components referred to as being coupled.

[0149] In this specification, example embodiments have been presented based on a selected set of details. However, those skilled in the art will appreciate that many other example embodiments can be practiced that include different selected sets of these details. It is intended that the appended claims cover all possible example embodiments.

Claims

1. A device for processing frequency modulated continuous wave (FMCW) radar signals, characterized in that: The device is configured to: receiving a radar signal comprising a radar frame reflected from one or more targets, wherein the radar frame comprises a plurality of chirps, the plurality of chirps comprising at least two groups of chirps, the at least two groups of chirps comprising a first group transmitted with a first pulse repetition interval between the chirps therein and a second group transmitted with a second pulse repetition interval between the chirps therein, wherein the first group and the second group are separated by a group separation time interval between a final chirp in the first group and a first chirp in the second group, the group separation time interval being different from one or both of the first pulse repetition interval and the second pulse repetition interval; Generate a modified received radar frame by at least: a first extrapolation based on the temporal positions of the chirps in the first group of the received radar frames to produce at least one extrapolated chirp in the modified received radar frame; Processing is performed based on the modified received radar frame to determine a property of the one or more targets.

2. The device according to claim 1, characterized in that The at least one extrapolated chirp generated by the first extrapolation is extrapolated to a time later in the received radar frame and between two chirps of the second group in the received radar frame.

3. The device according to claim 1, characterized in that The first extrapolation is configured to generate a plurality of extrapolated chirps that are extrapolated such that the plurality of extrapolated chirps are interleaved with the second group of chirps in the modified received radar frame.

4. The device according to claim 1 or claim 2, characterized in that The generating of the modified received radar frame additionally comprises: A second extrapolation is performed based on the temporal positions of the chirps in the second group of the received radar frames to produce at least one extrapolated chirp in the modified received radar frame.

5. The device according to claim 4, characterized in that The at least one extrapolated chirp generated by the second extrapolation is extrapolated to a time between two chirps of the first group in the modified received radar frame.

6. Apparatus according to any preceding claim, characterised in that The generation of the modified received radar frame additionally includes the apparatus being configured to: extracting the chirp corresponding to the first group from the received radar frame to generate a first received radar frame; extracting the chirp corresponding to the second group from the received radar frame to generate a second received radar frame; generating the modified first received radar frame by performing the first extrapolation based on the temporal positions of the chirps in the first group of the first received radar frame to produce at least one extrapolated chirp at a later time in the modified first received radar frame; generating the modified second received radar frame by performing a second extrapolation based on the temporal positions of the chirps in the second group of the second received radar frame to produce at least one extrapolated chirp at an earlier time in the modified second received radar frame; generating a Fast Fourier Transform (FFT) of the modified first received radar frame; generating an FFT of the modified second received radar frame; and The modified received radar frame includes a sum of the FFT of the modified first received radar frame and the FFT of the modified second received radar frame.

7. Apparatus according to any preceding claim, characterised in that The device is configured to: Transmission of the radar frame having properties of the first pulse repetition interval, the second pulse repetition interval, and the group separation time interval is provided.

8. The device according to claim 7, characterized in that The first pulse repetition interval and the second pulse repetition interval each comprise the product of the number of groups N and a base time interval T; and the group separation time interval between any two temporally adjacent groups comprises NT plus or minus the base time interval T.

9. The device according to claim 7, characterized in that One or both of the following exist: performing the first extrapolation and any further extrapolations; and selecting the group separation time interval and the first pulse repetition time interval and the second pulse repetition time interval; Such that the extrapolated chirp does not overlap with the chirp of the received radar frame in time.

10. A method for processing frequency modulated continuous wave (FMCW) radar signals, characterized in that: The device is configured to: receiving a radar signal comprising a radar frame reflected from one or more targets, wherein the radar frame comprises a plurality of chirps, the plurality of chirps comprising at least two groups of chirps, the at least two groups of chirps comprising a first group transmitted with a first pulse repetition interval between the chirps therein and a second group transmitted with a second pulse repetition interval between the chirps therein, wherein the first group and the second group are separated by a group separation time interval between a final chirp in the first group and a first chirp in the second group, the group separation time interval being different from one or both of the first pulse repetition interval and the second pulse repetition interval; The modified received radar frame is generated by the following operations: a first extrapolation based on the temporal positions of the chirps in the first group of the received radar frames to produce at least one extrapolated chirp in the modified received radar frame; as well as Processing is performed based on the modified received radar frame to determine a property of the one or more targets.

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