Frequency Division Multiple Access in Vehicle Radar Systems

Abstract

A method for implementing frequency division multiple access (FDMA) in a radar system for a vehicle includes simultaneously transmitting a chirp signal from each of a plurality of transmit elements of the radar system. The chirp signal transmitted by each of the plurality of transmit elements linearly increases or decreases in frequency within a frequency range over a duration, and the chirp signals transmitted by adjacent ones of the plurality of transmit elements partially overlap in frequency range. The method also includes processing reflections received based on the chirp signals transmitted by the plurality of transmit elements being reflected by one or more objects, and controlling operation of the vehicle based on locating the one or more objects.

Description

Technical Field

[0001] The subject disclosure relates to frequency division multiple access (FDMA) in a radar system for a vehicle. Background Art

[0002] Vehicles (e.g., cars, trucks, construction equipment, agricultural equipment, automated factory equipment) increasingly include sensors to obtain information about the vehicle and its surroundings. For example, this information facilitates semi-autonomous and autonomous operation of the vehicle. Exemplary sensors include cameras, light detection and ranging (lidar) systems, and radio detection and ranging (radar) systems. In radar systems with multiple transmitters and multiple receivers (referred to as multiple-input, multiple-output (MIMO) radar systems), different schemes are employed to help resolve reflections generated by different transmitters. Time division multiple access (TDMA) and code division multiple access (CDMA) schemes have known disadvantages. Therefore, it is desirable to provide a vehicle radar system that employs frequency division multiple access (FDMA). Summary of the Invention

[0003] In one exemplary embodiment, a method for implementing frequency division multiple access (FDMA) in a radar system for a vehicle includes simultaneously transmitting a chirp signal from each of a plurality of transmit elements of the radar system. The chirp signal transmitted by each of the plurality of transmit elements linearly increases or decreases in frequency within a frequency range over a duration, and the chirp signals transmitted by adjacent ones of the plurality of transmit elements partially overlap in frequency range. The method also includes processing reflections received based on the chirp signals transmitted by the plurality of transmit elements being reflected by one or more objects, and controlling operation of the vehicle based on locating the one or more objects.

[0004] In addition to one or more features described herein, the chirp signal transmitted by each of the plurality of transmitting elements has the same slope.

[0005] In addition to one or more features described herein, a start point of a frequency range of the chirp signal transmitted by each of the plurality of transmit elements differs from a start point of a frequency range of the chirp signal transmitted by every other of the plurality of transmit elements by a different frequency offset multiple.

[0006] In addition to one or more features described herein, the frequency offset is B and is given by:

[0007] in

[0008] s is the speed of light, R max is the maximum detectable range of the radar system, and α is the slope.

[0009] In addition to one or more features described herein, the method further includes multiplying the reflections by a reference signal to obtain a frequency difference result, the reference signal being one of the chirp signals transmitted by one of the plurality of transmit elements, and the frequency difference result separating reflection components corresponding to each chirp transmitted by the plurality of transmit elements into different frequency ranges.

[0010] In addition to one or more features described herein, the frequency difference result associated with each of the plurality of transmit elements includes a component that is frequency shifted by D from the frequency difference result associated with each other of the plurality of transmit elements.

[0011] In addition to one or more features described herein, the method further includes performing a range fast Fourier transform on the frequency difference results.

[0012] In addition to one or more features described herein, the method also includes identifying a range bin associated with a distance hypothesis corresponding to each component.

[0013] In addition to one or more features described herein, the method further includes compensating for phase variations based on a library of distances identified corresponding to each component to obtain a vector z representing the absolute distance of the reflection. The number of elements of vector z is the number of components.

[0014] In addition to one or more features described herein, the method also includes performing beamforming using a range-independent beamforming matrix and applying a detection threshold to locate one or more objects.

[0015] In another exemplary embodiment, a vehicle having a radar system implementing frequency division multiple access (FDMA) includes a plurality of transmitting elements of the radar system. Each of the plurality of transmitting elements simultaneously transmits a chirp signal. The chirp signal transmitted by each of the plurality of transmitting elements linearly increases or decreases in frequency within a frequency range over a duration, and the frequency ranges of the chirp signals transmitted by adjacent ones of the plurality of transmitting elements partially overlap. The vehicle also includes a controller that processes reflections received by a receiving element of the radar system based on reflections of the chirp signals transmitted by the plurality of transmitting elements from one or more objects, and controls operation of the vehicle based on locating the one or more objects.

[0016] In addition to one or more features described herein, the chirp signal transmitted by each of the plurality of transmitting elements has the same slope.

[0017] In addition to one or more features described herein, a start point of a frequency range of the chirp signal transmitted by each of the plurality of transmit elements differs from a start point of a frequency range of the chirp signal transmitted by every other of the plurality of transmit elements by a different frequency offset multiple.

[0018] In addition to one or more features described herein, the frequency offset is B and is given by:

[0019] in

[0020] s is the speed of light, R max is the maximum detectable range of the radar system, and α is the slope.

[0021] In addition to one or more features described herein, the controller multiplies the reflections by a reference signal to obtain a frequency difference result, wherein the reference signal is one of the chirp signals transmitted by one of the plurality of transmit elements, and the frequency difference result separates components of the reflections corresponding to each chirp transmitted by the plurality of transmit elements into different frequency ranges.

[0022] In addition to one or more features described herein, the frequency difference result associated with each of the plurality of transmit elements includes a component that is frequency shifted by d from the frequency difference result associated with each other of the plurality of transmit elements.

[0023] In addition to one or more features described herein, the controller performs a range fast Fourier transform on the frequency difference results.

[0024] In addition to one or more features described herein, the controller identifies a distance library associated with a distance hypothesis corresponding to each component.

[0025] In addition to one or more features described herein, the controller compensates for phase variations based on a library of distances corresponding to each component identification to obtain a vector z representing an absolute range of the reflection, the number of elements of vector z being the number of components.

[0026] In addition to one or more features described herein, the controller performs beamforming using a range-independent beamforming matrix and applies a detection threshold to locate one or more objects.

[0027] The above features and advantages and other features and advantages of the present disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Additional features, advantages and details appear by way of example only in the following detailed description, which refers to the accompanying drawings, in which:

[0029] Figure 1 is a block diagram of a vehicle having a radar system employing frequency division multiple access (FDMA);

[0030] Figure 2is a flow chart of a method of a radar system employing FDMA according to one or more embodiments; and

[0031] Figure 3 Detailed description is a process flow of a method for detecting an object using a radar system employing FDMA according to one or more embodiments. DETAILED DESCRIPTION

[0032] The following description is merely exemplary in nature and is in no way intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0033] As mentioned earlier, a radar system is one of the sensors that can be used to obtain information about a vehicle and its environment. A MIMO radar system requires some mechanism to separate the reflections generated by the transmissions from each of the multiple transmitters. Typically, each transmission is a linear frequency modulated continuous wave (LFMCW) signal whose frequency increases or decreases linearly over a period of time. This LFMCW signal is called a chirp. Time division multiple access schemes require a time delay between the chirps transmitted by each transmitter and cannot benefit from the increased transmission power generated by simultaneous transmissions. CDMA requires each transmitter to transmit a different code sequence (i.e., a differently coded chirp), which results in Doppler ambiguity (i.e., ambiguity in the radial velocity of the detected object).

[0034] Existing FDMA methods also have disadvantages. In existing FDMA schemes, the frequency band is divided between transmitters so that chirps transmitted by different transmitters do not use the same frequency within their chirp cycles. Therefore, the available bandwidth for each chirp is limited by the number of transmitters. This is discussed below as the first problem with existing FDMA methods. Also in existing FDMA schemes, the range correlation of the angle estimate, as further detailed, leads to inefficient processing of received reflections. This is discussed below as the second problem with existing FDMA methods. Embodiments of the systems and methods detailed herein relate to a radar system for a vehicle that employs FDMA with frequency shifting and with reflection processing to address the problems of existing methods.

[0035] According to an exemplary embodiment, Figure 1 is a block diagram of a vehicle 100 having a radar system 110 employing FDMA. Figure 1 The exemplary vehicle 100 shown is automobile 101. Vehicle 100 includes a MIMO radar system 110 having transmit elements 105a through 105n (generally referred to as 105) and receive elements 115a through 115m (generally referred to as 115). According to various embodiments, a subset of transmit elements 105 and receive elements 115 may be used, based on the number of transmit channels being less than the number of transmit elements 105 and the number of receive channels being less than the number of receive elements 115.

[0036] In the exemplary embodiment shown, transmit elements 105a through 105n transmit transmit signals 205a through 205n, respectively (generally referred to as 205), and receive elements 115a through 115m receive reflections 215a through 215m, respectively (generally referred to as 215). In the exemplary scenario, each reflection (e.g., reflection 215a) is generated by some energy of transmit signals 205a through 205n reflecting off an object 140 in the field of view of radar system 110. For example, object 140 may be another vehicle, a pedestrian, a sign, or a building.

[0037] An exemplary transmit signal 205 is shown. Time is shown on the t-axis, and frequency is shown on the f-axis. As shown, the exemplary LFMCW signal (i.e., a chirp) has a frequency that increases linearly over time T from an initial frequency f1 to a final frequency f2. Therefore, the slope α of the chirp is (f2-f1) / T. A given reflection 215 at a given receiving element 115 is the sum of the reflected energy generated by all emitted transmit signals 205a to 205n. The vehicle 100 may include other sensors 130 (e.g., cameras, lidar systems). The number and relative arrangement of transmit and receive elements 105, 115, as well as the number and location of other sensors 130, are not limited by the exemplary illustration.

[0038] The vehicle 100 includes a controller 120 that acquires information from the radar system 110 and one or more other sensors 130. The controller 120 can control or communicate with a controller of the vehicle 100 that operates semi-autonomously or autonomously based on the information acquired by the controller 120. Processing of the reflections received by the receiving element 115 can be performed by a controller of the radar system 110, the controller 120, or a combination of both. The controller of the radar system 110 and the controller 120 can include processing circuitry that can include application-specific integrated circuits (ASICs), electronic circuitry, processors (shared, dedicated, or grouped), and memory that executes one or more software or firmware programs, combinational logic circuitry, and / or other suitable components that provide the described functionality.

[0039] Figure 2 FIG. 1 is a process flow of a method 200 for operating a radar system 110 employing FDMA according to one or more embodiments. Figure 1 The method 200 includes, at block 210, determining a frequency offset B between the transmitted signals 205. The offset B is given by:

[0040]

[0041] In Equation 1, Rmax is the maximum detectable range, and s is the speed of light. (2 / s)R maxThe term α is the round-trip time from the transmit element 105 of the radar system 110 to the object 140 and back to the radar system 110, specifically to the receive element 115. Multiplying this term by the chirp slope α, which is the same for all transmit signals 205, provides the maximum frequency shift that the transmitted chirp pulse may experience. By selecting the offset B based on this maximum frequency shift, it is ensured that the frequency shift experienced by a given transmit signal 205 (of a given transmit element 105) over all detectable ranges is in a frequency band that does not overlap with the frequency band of another transmit signal 205 (of another transmit element 105).

[0042] That is, adjacent transmit elements 105 can transmit transmit signals 205 that are offset in frequency by B from one another. At block 220, transmitting multiple transmit signals 205 refers to transmitting signals from the transmit elements 105 simultaneously. For illustrative purposes, transmit signals 205-1, 205-2, and 205-3 transmitted from three exemplary transmit elements 105 are shown as having different patterns, as shown in diagram 201. Frequency ranges fr1, fr2, and fr3, respectively, spanned by each of the transmit signals 205-1, 205-2, and 205-3 are shown.

[0043] As shown, the starting frequency of each transmit signal 205 differs from the starting frequencies of the previous and next transmit signals 205 by a frequency offset B. Thus, transmit signal 205-1 has a starting frequency of fc, transmit signal 205-2 has a starting frequency of fc+B, and transmit signal 205-3 has a starting frequency of fc+2B. Significantly, as indicated by frequency ranges fr1, fr2, and fr3, the offset B ensures that there is overlap between adjacent frequency ranges fr1, fr2, and fr3. As a result, the bandwidth of each transmit signal 205 is not limited to one-third of the total bandwidth (in the exemplary case of three transmit elements 105). Instead, each of the three exemplary transmit signals 205-1, 205-2, and 205-3 has a respective frequency range fr1, fr2, or fr3 that spans more than one-third of the total frequency range. This solves the first problem mentioned with existing FDMA schemes.

[0044] At block 230, receiving reflections 215 refers to each receiving element 115 receiving reflections 215 resulting from all simultaneously transmitted transmit signals 205. That is, the reflections 215 received at each receiving element 115 are the sum of the energy from all transmit signals 205 reflected by a given object 140 toward the receiving element 115. If the transmit signal 205 encounters more than one object 140, the reflections 215 received at each receiving element 115 are the sum of the reflected energy from all objects 140 toward the receiving element 115.

[0045] A reflection 215 received at a given receiving element 115 is Figure 2 205 - 3 . As shown, reflection 215 includes three components C1, C2, and C3, which correspond to the reflected energy of three transmit signals 205-1, 205-2, and 205-3, respectively, as indicated by their patterns and labels. A reference transmit signal Tref is also shown. As part of the processing at blocks 220, 230, or 240, reference transmit signal Tref is selected as one of transmit signals 205. In the exemplary case, reference transmit signal Tref is transmit signal 205-3. As shown in diagram 202, reflection 215 is received at a time delay td after the transmission of transmit signal 205. As also indicated in diagram 202, components C1, C2, and C3, corresponding to the contributions from each of transmit signals 205-1, 205-2, and 205-3 to reflection 215, overlap in frequency. These overlaps are resolved at block 240.

[0046] At block 240, multiplying each reflection 215 by the reference transmit signal Tref facilitates separating the components C1, C2, and C3 of the reflection 215 into separate frequency bins F1, F2, and F3, which in the exemplary case correspond to each transmit signal 205-1, 205-2, and 205-3. Figure 2 The result of multiplying an exemplary reflection 215 (shown in FIG. 202 ) by an exemplary reference transmit signal Tref (i.e., transmit signal 205-3 in this example) is shown. The result of the multiplication is the difference between the frequency of the reference transmit signal Tref and the frequency of each of the components C1, C2, and C3 of the reflection 215 at a certain time (e.g., td).

[0047] In diagram 203, the "x" pattern on the reference transmit signal Tref (in diagram 202) is overlaid on the pattern of each component C1, C2, and C3 of reflection 215 (in diagram 202), identifying the multiplication results FD1, FD2, and FD3. The frequency segments F1, F2, and F3 corresponding to the multiplication results are also labeled. These frequency segments F1, F2, and F3 are discussed further. As shown in diagram 203, component C3 of reflection 215, which has a frequency closest to the frequency of the reference transmit signal Tref (as shown in diagram 202), has the lowest frequency difference FD3 in diagram 203. On the other hand, component C1 of reflection 215, which has a frequency farthest from the frequency of the reference transmit signal Tref (as shown in diagram 202), has the highest frequency difference FD1 in diagram 203.

[0048] As shown in diagram 203, each of frequency bins F1, F2, and F3 spans a frequency range corresponding to a frequency shift D. Furthermore, each component of the multiplication result is separated from adjacent components of the multiplication result by a frequency shift D. The frequency shift D is proportional to the shift B between the transmitted signals 205. That is, the frequency bins F1, F2, and F3 are a function of the corresponding frequency shifts 0, B, and 2B, and therefore a function of the distance to the object 140 that reflected the transmitted signal 205.

[0049] For example, multiplying component C3 (in diagram 202) by the reference transmit signal Tref results in a constant frequency of FD3 (as shown in diagram 203). This constant frequency is proportional to the distance to the object 140. That is, the constant frequency within frequency segment F3 is obtained by using the distance to the object 140 instead of R. max The result of Equation 1 is obtained. Multiplying component C2 (in diagram 202) by the reference transmit signal Tref also results in a constant frequency of FD2 (as shown in diagram 203). This constant frequency is also proportional to the distance of object 140. However, this final constant frequency ("final frequency") within frequency segment F2 is obtained by using a constant frequency in addition to the distance to object 140 (R object ) instead of R max The result of Equation 1 is obtained by adding the frequency shift B. That is, Equation 1 is modified as follows:

[0050]

[0051] Similarly, Equation 1 is modified by multiplying C1 (as shown in diagram 202) with the reference transmit signal Tref, resulting in a constant frequency of FD1 (as shown in diagram 203) within frequency segment F1, and by adding 2B as the relevant offset instead of B as shown in Equation 2.

[0052] For clarity, the frequency ranges fr1, fr2, and fr3 (shown in diagram 201) spanned by each of the transmit signals 205-1, 205-2, and 205-3, respectively, do overlap (as shown in diagram 201). However, the frequency segments F1, F2, and F3 (shown in diagram 203), resulting from multiplying each of the received components C1, C2, and C3 of the reflection 215 (shown in diagram 202) by the reference transmit signal Tref, do not overlap. This is a result of the frequency offset B between adjacent frequency ranges in the frequency ranges fr1, fr2, and fr3. As previously discussed, by selecting the offset B based on the maximum possible frequency shift (as discussed with reference to Equation 1), it is ensured that the frequency shift experienced by a given transmit signal 205 (which spans the frequency range fr1, fr2, or fr3) across all detectable ranges is within a frequency band (F1, F2, or F3) that does not overlap with the frequency band associated with another transmit signal 205.

[0053] The multiplication (i.e., frequency subtraction) at block 240 helps focus on the frequency difference at a given time (e.g., td) rather than on the overlapping frequency range of the C1, C2, and C3 components shown in diagram 202 of reflection 215. Because the transmitted signal 205 that resulted in the components C1, C2, and C3 of reflection 215 are separated by a frequency shift B, the frequency differences shown in diagram 203 are consequently separated by a frequency shift D, which is proportional to frequency shift B. Frequency shift D is explained further.

[0054] As shown in diagram 202, if the time delay td increases, the frequency difference between the reference transmit signal Tref and each of the C1, C2, and C3 components of the reflection 215 at a given time (e.g., td) will also increase. The time delay td is a function of the distance to the reflecting object 140 (e.g., as the distance to the object 140 increases, the time delay td for the transmit signal 205 to reach the object 140 and return as the reflection 215 also increases). That is, for example, the maximum time delay td corresponds to the maximum detectable range Rmax.

[0055] Thus, when the reflecting object 140 is at the maximum detectable range Rmax, and accordingly, the time delay td is at a maximum, the difference (at block 240) between the frequency of the reference transmit signal Tref and the frequency of each of the C1, C2, and C3 components of the reflection 215 will be at a maximum. This maximum frequency difference corresponds to a frequency shift D, which, like the offset B, is proportional to the maximum detectable range Rmax. As shown in diagram 203, the fact that the frequency difference result at block 240 is separated by the frequency shift D, and the fact that each of the frequency bins F1, F2, and F3 are separated rather than overlapping, facilitates efficient processing of the multiplication results, as shown in reference to FIG. Figure 3 These efficiencies address the second issue noted with existing FDMA approaches.

[0056] In reference Figure 3 Before discussing the processing of the results of block 240, a typical detection process is outlined for illustrative purposes. Typically, two Fast Fourier Transforms (FFTs) are performed. The first is along range, and the second is along Doppler, which corresponds to radial velocity. More specifically, a first (range) Fast Fourier Transform is performed on each transmitted signal 205 (i.e., chirp) to implement a range-matched filtering process. A second (Doppler) FFT is performed on each range bin of the first FFT results for all simultaneously transmitted signals 205 to implement a Doppler-matched filtering process. Following the FFTs, a range-Doppler map is obtained for each combination of transmitting element 105 and receiving element 115. Each range-Doppler map indicates a set of range bins, a set of Doppler bins, and the intensity associated with each range bin and Doppler bin combination. A beamforming process is performed on the range-Doppler map to identify and locate (i.e., obtain a direction of arrival (DOA)) each detected object 140.

[0057] Figure 3 FIG. 3 is a process flow diagram of a method 300 for detecting an object 140 using a radar system 110 employing FDMA according to one or more embodiments. Figure 2 For purposes of explanation, assume again three exemplary transmitted signals 205 having overlapping frequency ranges fr1, fr2, and fr3 (shown in diagram 201). As shown, the results at block 240 (frequency differences FD1, FD2, FD3 in the exemplary case) are input to the process of method 300. At block 310, a range FFT is performed on each transmitted signal 205. The results are shown as 315, indicating that the range FFT results RF3, RF2, and RF1 do not overlap. As shown, frequency f is shown along one axis and amplitude A is shown along the other axis. Each range FFT result RF3, RF2, and RF1 includes two exemplary range hypotheses, as shown. A range hypothesis refers to a peak in amplitude A exceeding a defined threshold. Range FFT result RF3 includes hypotheses h31, h32; range FFT result RF2 includes hypotheses h21, h22; and range FFT result RF1 includes hypotheses h11, h12).

[0058] At block 320, for the respective range hypotheses h31, h21, and h11, a range library associated with each transmitting element 105 is extracted. The distance R to the range hypothesis h31 is shown. The distance to each subsequent range hypothesis is a multiple of the frequency shift D from the distance R. The frequency shift D is proportional to the offset B and is a function of the distance (i.e., corresponds to R). max ). Thus, the distances corresponding to hypotheses h31, h21, and h11 (i.e., x(R), x(R+D), x(R+2D)) are offset by D (like frequency differences FD3, FD2, and FD1 in diagram 203). The phase shift φ (from transmit signal 205) indicated by the reflection 215 associated with each transmit signal 205 is a function of the arrival azimuth θ to the object 140 that caused the reflection 215. In the absence of FDMA (i.e., when the central wavelength λ of each transmit signal 205 is the same), the difference in phase shift φ indicated by the reflection 215 associated with each transmit signal 205 depends only on the DOA and not additionally on the distance. That is, there is no range-dependent term in the beamforming process (at block 340). However, FDMA results in a different beamforming matrix being required for each range. This significantly increases processing complexity relative to non-FDMA systems.

[0059] According to one or more embodiments, as discussed, inefficiencies that may be caused by FDMA are addressed. Specifically, compensating for phase variations (at block 330) based on a range library facilitates using the same beamforming matrix regardless of reflections 215 caused by the transmitted signal 205. Figure 3 , phase shifts φ3, φ2, and φ1 associated with each of transmit signals 205-3, 205-2, and 205-1 are shown. Wavelengths λ3, λ2, and λ1 correspond to the center frequencies of each of the exemplary transmit signals 205-3, 205-2, and 205-1. The positions of the exemplary three transmit elements 105 corresponding to transmit signals 205-3, 205-2, and 205-1 are x3, x2, and x1. An optional Doppler FFT may follow the range FFT performed at block 320.

[0060] At block 330, compensating for phase variations based on the range bins utilizes a known relationship between the range bins that relates to the frequency shift B between the transmitted signals 205. The reflection 215, represented below as vector z, compensates for the range dependency. Specifically,

[0061]

[0062] As a result, a beamforming process is performed at block 340, using the same beamforming matrix A for each element of the vector z. Specifically, the beamforming matrix A consists of as many vectors (a(θ) as there are hypotheses of arrival azimuth angles θ. i ). Therefore, for p hypotheses, A is given by:

[0063] A=[a(θ0),a(θ1),…,a(θ p )] [Equation 4]

[0064] Each vector a(θ i ) is the angle θ when the distance correlation is eliminated i The array response is given by:

[0065]

[0066] Although for the exemplary case of three transmit signals 205, each vector a(θ i ) are shown with three elements, but each vector a(θ i ) will depend on the number of transmit signals 205 and, accordingly, on the number of elements of vector z. The beamforming process involves multiplying vector z with the Hermitian transpose of the beamforming matrix A (denoted by H), as shown in Equation 6.

[0067] y=A H z [Equation 6]

[0068] As part of the beamforming process at block 340, peak detection is performed at each range to identify and locate the object 140. That is, each value of the vector y corresponds to one of the hypotheses for the arrival azimuth angle θ. Thus, each y value that exceeds the defined detection threshold is determined based on its corresponding θ. i The value indicates the location of the object 140. As previously described, the controller 120 can use this location information to control aspects of the operation of the vehicle 100.

[0069] Although the above disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present invention. Additionally, many modifications may be made to adapt particular circumstances or materials to the teachings of the present disclosure without departing from the essential scope of the present disclosure. Therefore, it is intended that the present disclosure is not limited to the particular embodiments disclosed, but rather encompasses all embodiments falling within its scope.

Claims

1. A method for implementing frequency division multiple access in a radar system of a vehicle, the method comprising: transmitting a chirp signal simultaneously from each of a plurality of transmitting elements of the radar system, the chirp signal transmitted by each of the plurality of transmitting elements linearly increasing or decreasing in frequency over a frequency range within a duration, and the frequency ranges of the chirp signals transmitted by adjacent ones of the plurality of transmitting elements partially overlapping; as well as processing reflections received based on chirp signals transmitted by the plurality of transmitting elements and reflected by one or more objects; multiplying the reflections by a reference signal to obtain a frequency difference result, wherein the reference signal is one of the chirp signals transmitted by one of the plurality of transmitting elements, and the frequency difference result separates components of the reflections corresponding to each chirp transmitted by the plurality of transmitting elements into different frequency ranges; and Operation of the vehicle is controlled based on locating the one or more objects.

2. The method according to claim 1, wherein The chirp signal transmitted by each of the plurality of transmitting elements has the same slope.

3. The method according to claim 2, wherein: A start point of a frequency range of the chirp signal transmitted by each of the plurality of transmitting elements differs from a start point of a frequency range of the chirp signal transmitted by every other of the plurality of transmitting elements by a different frequency offset multiple.

4. The method according to claim 3, wherein: The frequency offset is B and is given by: in s is the speed of light, R max is the maximum detectable range of the radar system, and α is the slope.

5. The method of claim 1 , wherein the frequency difference result associated with each of the plurality of transmit elements comprises a component that is frequency shifted D apart from the frequency difference result associated with each other of the plurality of transmit elements, and the method further comprises performing a range fast Fourier transform on the frequency difference results, identifying a range bin associated with a range hypothesis corresponding to each component, compensating for phase variations based on the range bin identified corresponding to each component to obtain a vector z representing an absolute range of the reflection, wherein the number of elements of vector z is the number of components, performing beamforming using a range-independent beamforming matrix, and applying a detection threshold to locate the one or more objects.

6. A vehicle having a radar system implementing frequency division multiple access, the vehicle comprising: a plurality of transmitting elements of a radar system, each of the plurality of transmitting elements being configured to simultaneously transmit a chirp signal, the chirp signal transmitted by each of the plurality of transmitting elements linearly increasing or decreasing in frequency over a frequency range within a duration, and the frequency ranges of the chirp signals transmitted by adjacent ones of the plurality of transmitting elements partially overlapping; as well as a controller configured to process reflections received by a receiving element of the radar system based on reflections of chirp signals transmitted by the plurality of transmitting elements by one or more objects, multiply the reflections by a reference signal to obtain a frequency difference result, wherein the reference signal is one of the chirp signals transmitted by one of the plurality of transmitting elements, and the frequency difference result separates components corresponding to the reflections of each chirp transmitted by the plurality of transmitting elements into different frequency ranges, and control operation of the vehicle based on locating the one or more objects.

7. The vehicle according to claim 6, wherein: The chirp signal transmitted by each of the plurality of transmitting elements has the same slope.

8. The vehicle according to claim 7, wherein: A start point of a frequency range of the chirp signal transmitted by each of the plurality of transmitting elements differs from a start point of a frequency range of the chirp signal transmitted by every other of the plurality of transmitting elements by a different frequency offset multiple.

9. The vehicle according to claim 8, wherein: The frequency offset is B and is given by: in s is the speed of light, R max is the maximum detectable range of the radar system, and α is the slope.

10. The vehicle according to claim 6, wherein The frequency difference result associated with each of the plurality of transmit elements includes a component that is frequency shifted D apart from the frequency difference result associated with each other of the plurality of transmit elements, the controller being configured to perform a range fast Fourier transform on the frequency difference results to identify a range bin associated with a range hypothesis corresponding to each component, and to compensate for phase variations based on the range bin identified corresponding to each component to obtain a vector z representing an absolute range of the reflection, wherein the number of elements of the vector z is the number of components, and the controller being configured to perform beamforming using a range-independent beamforming matrix and apply a detection threshold to locate one or more objects.

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