Radar speed measurement method and radar system

Abstract

A radar velocity measurement method includes the following steps: (A) obtaining a previous velocity and a previous azimuth angle of a target object based on a plurality of previously transmitted signals and a plurality of previously echo signals; (B) for each transmitting antenna, obtaining a phase compensation corresponding to the corresponding transmitting antenna based on the previous azimuth angle, the distance between the transmitting antenna and a reference transmitting antenna, and the wavelength of the current transmitted signal of the transmitting antenna; (C) for each transmitting antenna, obtaining a Doppler frequency compensation corresponding to the corresponding transmitting antenna based on the previous velocity, the wavelength of the current transmitted signal of the transmitting antenna, and a transmission time; and (D) obtaining a current distance, a current velocity, and a current azimuth angle of a target object based on the phase compensation, the Doppler frequency compensation, the current transmitted signals, and the current echo signals.

Description

Technical Field

[0001] This invention relates to a speed measurement method, and more particularly to a radar speed measurement method and radar system that measures speed by means of radar wave frequency reflection. Prior Technology

[0002] Multiple-input multiple-output (MIMO) radar transmits a signal through an array antenna. After being reflected by the target, the received echo signal has a time difference with the transmitted signal. The target distance can be calculated through this time difference. In addition, by using the Doppler principle to analyze the frequency difference between the transmitted signal and the echo signal, the speed of the target relative to the radar can be accurately measured.

[0003] To enable the receiver to distinguish echo signals from different transmitting antennas, MIMO radar often employs time-division MIMO (TDM-MIMO) transmission, where each transmitting antenna transmits signals sequentially. However, because the transmission times are not synchronized, for moving targets, the echoes from each antenna will contain additional phase differences caused by the target's motion. When the moving target's speed is high, the phase change caused by the transmission time difference between the transmitting antennas may exceed 2π. This results in velocity ambiguity in the velocity estimation results. Summary of the Invention

[0004] Therefore, the objective of this invention is to provide a radar speed measurement method that solves the speed ambiguity problem.

[0005] Therefore, the radar speed measurement method of the present invention is applicable to detecting the speed of a target object and is implemented by a radar system. The radar system includes multiple transmitting antennas for transmitting multiple transmitted signals, a receiving antenna for receiving multiple echo signals corresponding to the corresponding transmitted signals, and a processing unit that connects the transmitting antennas and the receiving antenna. The method includes the following steps:

[0006] (A) The processing unit obtains a previous velocity and a previous azimuth angle of the target object based on a plurality of previously transmitted signals and a plurality of previously echo signals, wherein the plurality of previously transmitted signals are transmitted signals emitted by the transmitting antennas at a plurality of previous time points in a previous time interval, and the plurality of previously echo signals are echo signals received by the receiving antenna corresponding to the plurality of previously transmitted signals;

[0007] (B) For each transmitting antenna, the arithmetic unit obtains a phase compensation for the corresponding transmitting antenna based on the previous azimuth angle, the distance between the transmitting antenna and a reference transmitting antenna, and the wavelength of the current transmitted signal of the transmitting antenna, wherein the reference transmitting antenna is the transmitting antenna that has the earliest transmitted signal among the transmitting antennas;

[0008] (C) For each transmitting antenna, the processing unit obtains a Doppler frequency compensation corresponding to that transmitting antenna based on the previous velocity, the wavelength of the current transmitted signal of the transmitting antenna, and the transmission time of the transmitting antenna; and

[0009] (D) The arithmetic unit obtains the current velocity and a current azimuth angle of one of the targets based on the phase compensation, the Doppler frequency compensation, the current transmitted signals and the current echo signals, wherein the current transmitted signals are the transmitted signals emitted by the transmitting antennas at multiple current time points in the current time interval of the previous time interval, and the current echo signals are the echo signals received by the receiving antenna corresponding to the current transmitted signals.

[0010] Another objective of this invention is to provide a radar system that solves the speed ambiguity problem.

[0011] Therefore, the radar system of the present invention includes multiple transmitting antennas, one receiving antenna, and a computing unit.

[0012] Each transmitting antenna transmits a signal, and the receiving antenna is used to receive multiple echo signals corresponding to the same transmitted signal.

[0013] The arithmetic unit is electrically connected to the transmitting antenna and the receiving antenna, and performs the radar speed measurement method described above.

[0014] The advantage of this invention is that by calculating the phase compensation corresponding to the corresponding transmitting antenna and performing phase difference compensation by the computing unit, the speed ambiguity problem can be avoided. Simple Explanation of the Diagram

[0015] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: Figure 1 is a block diagram illustrating a radar system implementing an embodiment of the radar velocity measurement method of the present invention; Figure 2 is a flowchart illustrating an embodiment of the radar speed measurement method of the present invention; Figure 3 is a flowchart illustrating how a processing unit obtains a target's previous distance, previous velocity, and previous azimuth angle; and Figure 4 is a flowchart illustrating how the computing unit obtains the target object's current distance, current velocity, and current azimuth angle. Implementation

[0016] Before the invention is described in detail, it should be noted that similar elements are represented by the same numbers in the following description.

[0017] Referring to Figure 1, an embodiment of the radar speed measurement method of the present invention is applicable to detecting the speed of a target object and is implemented by a radar system. The radar system includes multiple transmitting antennas 11 for transmitting multiple transmitted signals, a receiving antenna 12 (which may also be multiple antennas 12) for receiving multiple echo signals corresponding to the same transmitted signals, and a processing unit 13 that connects the transmitting antennas 11 and the receiving antennas 12. In this embodiment, the radar system is, for example, a multi-input multi-output (MIMO) radar based on frequency modulated continuous waveform (FMCW) signals. Since each receiving antenna 12 operates similarly, the following description will only use a single receiving antenna 12.

[0018] Referring to Figures 1 and 2, the following will illustrate the operational details of each component in the radar system through an embodiment of the radar speed measurement method of the present invention.

[0019] In step 21, the processing unit 13 obtains a previous distance, a previous velocity, and a previous azimuth angle of the target object based on a plurality of previously transmitted signals and a plurality of previously echo signals. The previously transmitted signals are those transmitted by the transmitting antennas 11 at a plurality of previous time points within a previous time interval, and the previously echo signals are the echo signals received by the receiving antenna 12 corresponding to the previously transmitted signals.

[0020] It is worth mentioning that step 21 includes the following sub-steps.

[0021] In sub-step 211, the arithmetic unit 13 mixes the previously transmitted signals and the previously echoed signals to generate a plurality of previously beat frequency signals.

[0022] In sub-step 212, the arithmetic unit 13 performs analog-to-digital conversion on the previous beat frequency signals to obtain a plurality of previous digital signals.

[0023] In sub-step 213, the arithmetic unit 13 performs a distance-fast Fourier transform based on the preceding digital signals to obtain a spectrum of preceding distance information.

[0024] In sub-step 214, the operation unit 13 performs a Doppler-Fast Fourier transform based on the previous distance information spectrum to obtain a previous velocity information spectrum.

[0025] In sub-step 215, the processing unit 13 uses a target detection algorithm to obtain the previous distance and previous speed of the target object based on the previous speed information spectrum. In this embodiment, the target detection algorithm is the Constant False Alarm Rate (CFAR) algorithm. In this embodiment, the processing unit 13 obtains not only the previous speed of the target object but also its previous distance; however, in other embodiments, the processing unit 13 may only obtain the previous speed of the target object.

[0026] In sub-step 216, the computation unit 13 uses an angle estimation algorithm to obtain the previous azimuth angle of the target object. In this embodiment, the angle estimation algorithm is, for example, a multi-signal classification (MUSIC) algorithm.

[0027] In step 22, for each transmitting antenna 11, the arithmetic unit 13 calculates the previous azimuth angle. The distance between the transmitting antenna 11 and a reference transmitting antenna 11 The wavelength of the current transmitted signal of the transmitting antenna 11 Using the following formula (1), the phase compensation of a pair of transmitting antennas 11 can be obtained. The reference transmitting antenna 11 is the transmitting antenna 11 that was the first to transmit a signal among the transmitting antennas 11. …(1)

[0028] To further explain, in one embodiment, in a radar system with 12 transmitting antennas 11 arranged in a straight line in one direction, the first transmitting antenna 11 is the rightmost transmitting antenna 11, the twelfth transmitting antenna 11 is the leftmost transmitting antenna 11, and if the spacing between the antennas is d, when the actual phase of the first transmitting antenna 11 towards a target is... At that time, the phase of the second transmitting antenna 11 with respect to the same target is... The phase of the third transmitting antenna 11 towards the same target Similarly, in order to avoid the discrepancies caused by the phase difference of each antenna, it is necessary to compensate the phase of the second to twelfth transmitting antennas 11 so that they are close to or the same as the phase of the first transmitting antenna 11.

[0029] In step 23, for each transmitting antenna 11, the processing unit 13 calculates the speed based on the previous velocity. The wavelength of the current transmitted signal of the transmitting antenna 11 The chirp duration time of the transmitting antenna 11. Using the following formula (2), the Doppler frequency compensation of the corresponding transmitting antenna 11 can be obtained. It is worth noting that the Doppler frequency compensation of each transmitting antenna 11 is based on the speed generated by the calculation when receiving the signal. The calculation unit 13 calculates the Doppler frequency compensation of each transmitting antenna 11 once using formula (2). …(2)

[0030] In step 24, the arithmetic unit 13 obtains the current distance, current speed and current azimuth angle of the target object based on the phase compensation, the Doppler frequency compensation, the current transmitted signal and the current echo signal, wherein the current transmitted signal is the transmitted signal emitted by the transmitting antenna 11 at multiple current time points in the current time interval that is later than the previous time interval, and the current echo signal is the echo signal received by the receiving antenna 12 corresponding to the current transmitted signal.

[0031] It is worth mentioning that step 24 includes the following sub-steps.

[0032] In sub-step 241, the arithmetic unit 13 mixes the current transmitted signals and the current echo signals to generate multiple current beat frequency signals.

[0033] In sub-step 242, the arithmetic unit 13 compensates the current beat frequency signals according to the phase compensation and the Doppler frequency compensation to obtain multiple compensated current beat frequency signals.

[0034] In sub-step 243, the arithmetic unit 13 performs analog-to-digital conversion on the compensated current beat frequency signals to obtain multiple current digital signals.

[0035] In sub-step 244, the arithmetic unit 13 performs a distance-fast Fourier transform based on the current digital signals to obtain a current distance information spectrum.

[0036] In sub-step 245, the operation unit 13 performs a Doppler-Fast Fourier transform based on the current distance information spectrum to obtain a current velocity information spectrum.

[0037] In sub-step 246, the computing unit 13 uses the target detection algorithm to obtain the current distance and current speed of the target object based on the current speed information spectrum. In this embodiment, the computing unit 13 obtains not only the current speed of the target object but also its current distance. However, in other embodiments, the computing unit 13 may only obtain the current speed of the target object.

[0038] In sub-step 247, the operation unit 13 uses the angle estimation algorithm to obtain the current azimuth angle of the target object.

[0039] In step 25, the arithmetic unit 13 repeats steps 22-24. In the next execution of step 22, the current azimuth angle is taken as the previous azimuth angle, and the current transmission signal is the transmission signal transmitted by the transmitting antenna 11 at the next time point in the next time interval of the current time interval. In the next execution of step 23, the current speed is taken as the previous speed, and the current transmission signal is the transmission signal transmitted by the transmitting antenna 11 at the next time point in the next time interval. In the next execution of step 24, the current transmission signals are the transmission signals transmitted by the transmitting antenna 11 at the next time point in the next time interval, and the current echo signals are the echo signals received by the receiving antenna 12 corresponding to the transmission signals transmitted in the next time interval. It is worth noting that if a more accurate estimate of the target's distance, speed, and azimuth is required, steps 22 to 24 can be repeated multiple times. However, in other implementations, steps 22 to 24 may not be repeated.

[0040] In summary, the radar speed measurement method of the present invention, by calculating the corresponding phase compensation for the transmitting antenna 11 by the computing unit 13 and performing phase difference compensation, can avoid the speed ambiguity problem and improve the accuracy of radar speed measurement, thus effectively achieving the purpose of the present invention.

[0041] However, the above description is merely an embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any simple equivalent changes and modifications made in accordance with the scope of the patent application and the contents of the patent specification of the present invention shall still fall within the scope of the patent of the present invention.

[0042] 11: Transmitting Antenna 12: Receiving antenna 13: Computational Unit Steps 21-25 211~216: Sub-steps 241~247: Sub-steps

Claims

1. A radar speed measurement method, applicable to detecting the speed of a target object, and implemented by a radar system, the radar system comprising a plurality of transmitting antennas for transmitting a plurality of transmitting signals, a receiving antenna for receiving a plurality of echo signals corresponding to the corresponding transmitting signals, and a processing unit for signal connection between the transmitting antennas and the receiving antenna, and comprising the following steps: (A) the processing unit obtains a previous speed and a previous azimuth angle of the target object based on a plurality of previous transmitting signals and a plurality of previous echo signals, wherein the previous transmitting signals are transmitting signals emitted by the transmitting antennas at a plurality of previous time points in a previous time interval, and the previous echo signals are echo signals received by the receiving antenna corresponding to the corresponding previous transmitting signals; (B) for each transmitting antenna, the processing unit obtains a phase compensation corresponding to the transmitting antenna based on the previous azimuth angle, the distance between the transmitting antenna and a reference transmitting antenna, and the wavelength of the current transmitting signal of the transmitting antenna, wherein the reference transmitting antenna is the transmitting antenna among the transmitting antennas that has the earliest transmitting signal; (C) For each transmitting antenna, the arithmetic unit obtains a Doppler frequency compensation corresponding to the transmitting antenna based on the previous velocity, the wavelength of the current transmitted signal of the transmitting antenna, and the transmission time of the transmitting antenna; and (D) The arithmetic unit obtains a current velocity and a current azimuth angle of the target based on the phase compensation, the Doppler frequency compensation, the current transmitted signals, and the current echo signals, wherein the current transmitted signals are the transmitted signals emitted by the transmitting antennas at multiple current time points in a current time interval that is later than the previous time interval, and the current echo signals are the echo signals received by the receiving antenna corresponding to the current transmitted signals.

2. The radar speed measurement method as described in claim 1, wherein, Step (A) includes the following sub-steps: (A-1) The processing unit mixes the previously transmitted signals and the previously echoed signals to generate a plurality of previously transmitted beat signals; (A-2) The processing unit performs analog-to-digital conversion on the previously transmitted beat signals to obtain a plurality of previously transmitted digital signals; (A-3) The processing unit performs a range-fast Fourier transform on the previously transmitted digital signals to obtain a previously transmitted range information spectrum; (A-4) The processing unit performs a Doppler-fast Fourier transform on the previously transmitted range information spectrum to obtain a previously transmitted velocity information spectrum; (A-5) The processing unit uses a target detection algorithm to obtain the previously transmitted velocity of the target object based on the previously transmitted velocity information spectrum; and (A-6) The processing unit uses an angle estimation algorithm to obtain the previously transmitted azimuth angle of the target object.

3. The radar speed measurement method as described in claim 1, wherein, Step (D) includes the following sub-steps: (D-1) The processing unit mixes the current transmitted signals and the current echo signals to generate multiple current beat frequency signals; (D-2) The processing unit compensates the current beat frequency signals according to the phase compensation and the Doppler frequency compensation to obtain multiple compensated current beat frequency signals; (D-3) The processing unit performs analog-to-digital conversion on the compensated current beat frequency signals to obtain multiple current digital signals; (D-4) The processing unit performs a range-fast Fourier transform on the current digital signals to obtain a current range information spectrum; (D-5) The processing unit performs a Doppler-fast Fourier transform on the current range information spectrum to obtain a current velocity information spectrum; (D-6) The processing unit uses a target detection algorithm to obtain the current velocity of the target object based on the current velocity information spectrum; and (D-7) The processing unit uses an angle estimation algorithm to obtain the current azimuth angle of the target object.

4. The radar speed measurement method as described in claim 1, further comprising the following steps after step (D): (E) The arithmetic unit repeatedly executes steps (B) to (D), wherein in the next executed step (B), the current azimuth angle is taken as the previous azimuth angle, the current transmitted signal is the transmitted signal transmitted by the transmitting antenna at the next time point corresponding to the next time interval in the next time interval, in the next executed step (C), the current speed is taken as the previous speed, the current transmitted signal is the transmitted signal transmitted by the transmitting antenna at the next time point corresponding to the next time interval, in the next executed step (D), the current transmitted signals are the transmitted signals transmitted by the transmitting antenna at the next time point corresponding to the next time interval, and the current echo signals are the echo signals received by the receiving antenna corresponding to the transmitted signals transmitted in the next time interval.

5. A radar system comprising: a plurality of transmitting antennas, each transmitting antenna transmitting a transmitted signal; a receiving antenna for receiving a plurality of echo signals corresponding to the equal transmitted signals; and a processing unit signal-connected to the transmitting antennas and the receiving antenna, and for executing the radar speed measurement method of any one of claims 1 to 4.

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