MIMO simultaneous transmission method based on phase shifter random coding, MIMO radar

Abstract

The present application relates to a MIMO simultaneous transmission method and a MIMO radar based on phase shifter random coding. The method comprises: the first transmission link transmits a first chirp signal through a first random code phase shift, and the second transmission link transmits a second chirp signal through a second random code phase shift, wherein the first chirp signal and the second chirp signal are transmitted simultaneously; the receiving link receives the mixed echo signal of the first chirp signal and the second chirp signal, and after performing a distance-dimensional fast Fourier transform operation on the mixed echo signal, the mixed echo signal is compensated by a compensation code and then subjected to a speed-dimensional fast Fourier transform operation to separate the echo signal of the first chirp signal and the echo signal of the second chirp signal. A high-performance radar is realized in all aspects, including angle resolution and accuracy, distance resolution, speed unambiguous range, and detection signal-to-noise ratio gain.

Description

Technical Field

[0001] The present application relates to the field of automotive electronic technology, and more specifically, to a MIMO simultaneous transmission method based on phase shifter random coding and a MIMO radar. Background Art

[0002] In recent years, with the increasing integration of RF chips and the increasingly higher requirements for the angular resolution performance of millimeter-wave radars in autonomous driving applications, the number of transceiver channels in radar antenna arrays has increased. The increase in the number of channels has improved the radar's angular resolution, angular accuracy, signal-to-noise ratio and other indicators on the one hand, but it has also greatly increased the complexity of system design on the other.

[0003] Due to the size limitation of vehicle-mounted radar, MIMO technology is generally used to form virtual channels. The aperture of the antenna array composed of virtual channels is larger than the actual physical antenna array aperture, which can improve the angular resolution. Due to the power consumption and cost limitations, millimeter wave radars all transmit continuous waves. Under the continuous wave system, the design of conventional simultaneous MIMO solutions is often impossible to implement or encounter problems such as excessive computation and severe performance degradation that cannot be engineered due to reasons such as shared VCO for transmission. Summary of the invention

[0004] In order to overcome the above problems in the prior art, the present application provides a MIMO simultaneous transmission method based on phase shifter random coding and a MIMO radar.

[0005] A MIMO simultaneous transmission method based on phase shifter random coding is applied to a MIMO radar provided with a first transmission link, a second transmission link, and at least one receiving link, the method comprising:

[0006] The first transmission link transmits a first chirp signal by phase shifting using a first random code, and the second transmission link transmits a second chirp signal by phase shifting using a second random code, wherein the first chirp signal and the second chirp signal are transmitted simultaneously;

[0007] The receiving link receives the mixed echo signals of the first chirp signal and the second chirp signal, performs a distance-dimensional fast Fourier transform operation on the mixed echo signal, performs a compensation code compensation on the mixed echo signal, and then performs a speed-dimensional fast Fourier transform operation to separate the echo signal of the first chirp signal and the echo signal of the second chirp signal.

[0008] Optionally, the first random code is obtained through a PM code encoder, and each of the first chirp signals is encoded with a random initial phase through the first random code.

[0009] Optionally, the second random code is obtained through a PM code encoder, and each of the second chirp signals is encoded with a random initial phase through the second random code.

[0010] Optionally, the first random code and the second random code are orthogonal pseudo-random codes, wherein: Wherein, a(n) is the first random code, and b(n) is the second random code.

[0011] Optionally, after performing a distance-dimensional fast Fourier transform operation on the mixed echo signal, the signal along the velocity direction is: Wherein, S1 is the data of any channel of the receiving link.

[0012] Optionally, performing a speed-dimensional fast Fourier transform operation on the mixed frequency echo signal after performing compensation code compensation, including:

[0013] Calculate a first compensation code and a second compensation code according to the first random code and the second random code;

[0014] Any channel data S1 is compensated with the first compensation code and the second compensation code respectively, and then a speed-dimensional fast Fourier operation is performed.

[0015] Optionally, the first random code and the second random code are optimized according to a cost function to obtain a first supplementary code and a second supplementary code; the cost function formula is:

[0016]

[0017] Among them, w 1 and w 2 is the weighted adjustment coefficient, and w 1 +w 2 =1.

[0018] Optionally, the first compensation code and the second compensation code are respectively compensated for any channel data S1, and then a speed-dimensional fast Fourier operation is performed to separate the first chirp signal and the second chirp signal. The specific formula is as follows:

[0019] S ch1 =fft(S 1 *a)…(4),

[0020] S ch2 =fft(S 1 *b)…(5);

[0021] Among them, S ch1 is the first chirp signal, S ch2 is the second chirp signal, a is the first compensation code, and b is the second supplementary code.

[0022] In addition, the present application also provides a MIMO radar, including the above-mentioned MIMO simultaneous transmission method based on phase shifter random coding, and also including a first phase shifter, a second phase shifter, a waveform generator, a fast Fourier transform module, a first transmission link, at least one second transmission link, and at least one receiving link;

[0023] The waveform generator is connected to the first transmission link and the second transmission link, and the continuous wave generated by the waveform generator transmits the first chirp signal and the second chirp signal through the first transmission link and the second transmission link respectively;

[0024] The first transmission link is connected to the first phase shifter, and the first transmission link transmits the first chirp signal through the first phase shifter with a first random code phase shift; the second transmission link is connected to the second phase shifter, and the second transmission link transmits the second chirp signal through the second phase shifter with a second random code phase shift;

[0025] The receiving link is connected to the fast Fourier transform module, and the receiving link receives the mixed echo signals of the first chirp signal and the second chirp signal, and after performing a distance-dimensional fast Fourier transform operation on the mixed echo signal, performs a compensation code compensation on the mixed echo signal and then performs a speed-dimensional fast Fourier transform operation to separate the echo signal of the first chirp signal and the echo signal of the second chirp signal.

[0026] Optionally, the MIMO radar has two-transmit and four-receive antennas.

[0027] Compared with the prior art, the beneficial effects of the present application are: the present application solves the coupling problem of speed and angle measurement results caused by the existing time-sharing MIMO scheme, and can be used as a scalable high-performance radar basic framework technology, on this basis in cascade and ultra-high-resolution radars to achieve all-round high-performance radars such as angle resolution and accuracy, distance resolution, speed unambiguous range, and detection signal-to-noise ratio gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of a MIMO simultaneous transmission method based on phase shifter random coding according to an embodiment of the present application.

[0029] Figure 2 This is a schematic diagram of a first transmission signal and a second transmission signal according to an embodiment of the present application.

[0030] Figure 3 This is a flowchart of the algorithm optimization of the cost function of an embodiment of the present application.

[0031] Figure 4 Schematic diagram of a two-transmit four-receive MIMO radar according to an embodiment of the present application. DETAILED DESCRIPTION

[0032] The present application is further described below in conjunction with specific implementation methods.

[0033] The same or similar numbers in the drawings of the embodiments of the present application correspond to the same or similar parts; in the description of the present application, it should be understood that if the terms "upper", "lower", "left", "right", "top", "bottom", "inside", "outside", etc. indicate the orientation or position relationship, it is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent.

[0034] In addition, if there are terms such as "first" and "second", they are only used for descriptive purposes, mainly to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components, and cannot be understood as indicating or implying relative importance.

[0035] In such Figure 1-2In the illustrated embodiment, the present application provides a MIMO simultaneous transmission method based on phase shifter random coding, which is applied to a MIMO radar provided with a first transmission link, a second transmission link, and at least one receiving link. The method includes: the first transmission link transmits a first chirp signal through a first random code phase shift, and the second transmission link transmits a second chirp signal through a second random code phase shift, wherein the first chirp signal and the second chirp signal are transmitted simultaneously; the receiving link receives a mixed echo signal of the first chirp signal and the second chirp signal, and after performing a distance-dimensional fast Fourier transform operation on the mixed echo signal, the compensation code is compensated for the mixed echo signal and then a speed-dimensional fast Fourier transform operation is performed to separate the echo signal of the first chirp signal and the echo signal of the second chirp signal. In this embodiment, the present application encodes a random initial phase for each first chirp signal and each second chirp signal through a phase shifter at the transmitting end, respectively, with a first random code and a second random code; and at the receiving end, a matched filtering operation is performed according to the compensation code, and an orthogonal matched filter group is formed in combination with the FFT operation, thereby separating the signals of different transmissions. Among them, the compensation code corresponds to the first random code and the second random code. The simultaneous MIMO algorithm scheme based on the random coding of the 0-pi phase shifter can solve the coupling problem of the speed and angle measurement results caused by the existing time-sharing MIMO scheme, and can be used as an expandable high-performance radar basic framework technology, and on this basis, the cascade and ultra-high-resolution radar can realize the high-performance radar in all aspects such as angle resolution and accuracy, distance resolution, speed unambiguous range, and detection signal-to-noise ratio gain. The present application utilizes the 0° and 180° resolution of the binary phase shifter in the existing hardware to correspond to 1 and -1, and at the same time utilizes the existing results of the PM encoder, and designs the orthogonal random coding that meets the requirements through the genetic algorithm to control the switching of the phase shifter, and combines it with the FFT operation to overcome the problem that the traditional simultaneous MIMO orthogonal matching filter has a large amount of computation or requires parallel physical channels. This application has robust performance, is easy to implement, and does not require additional requirements for hardware and computing power. This application uses a simultaneous transmission MIMO solution to solve all of the above problems, including providing a radar basic solution that can comprehensively improve performance. The next generation of high-performance radars also needs to be developed on this basis, such as: ultra-large bandwidth high-resolution radars, large bandwidth requires a long chrip cycle, thereby reducing the speed unambiguous range; cascade radar, multiple transmissions, such as 6 / 8 / 12, etc., using TDM, the speed unambiguous range will be very low, only a few meters per second; complex cluster target recognition and other functions, eliminate the influence of speed on angle, so that clustering is not interfered with; fundamentally solve the low-frequency envelope problem, and improve detection and measurement performance at close range.

[0036] In some embodiments, the first random code is obtained by a PM code encoder, and each first chirp signal is encoded with a random initial phase by the first random code. The second random code is obtained by a PM code encoder, and each second chirp signal is encoded with a random initial phase by the second random code. The first random code and the second random code are orthogonal pseudo-random codes, wherein: Among them, a(n) is the first random code, and b(n) is the second random code. In this embodiment, a=[1 1 -1 -1 1…], b=[1 -111 -1 …]; taking two-transmit and four-receive MIMO as an example, two groups of 0-1 random codes are designed for two-way transmission, and each channel configures the phase shifter according to its own coding, and sets the initial phase for each chrip pulse. When the code is 0, the phase shifter is configured to 0°, which is equivalent to multiplying by 1, and when the code is 1, the phase shifter is configured to 180°, which is equivalent to multiplying by -1. After performing a one-dimensional FFT on each chrip of the received signal, all chrips are combined into a two-dimensional matrix structure. Due to the phase modulation between different chrips, it is equivalent to modulating the signal in the chrip slow time dimension with a group of random signals composed of 1 / -1. Because different random signals are designed according to orthogonal random codes, the received signal can be compensated for the corresponding pseudo-random code in the slow time dimension and then FFT operation is performed, and the signal corresponding to another group of random codes can be filtered out by using the orthogonality, which is equivalent to constructing an orthogonal filter group. The second-dimensional FFT result after the random code corresponding to the slow time dimension compensation corresponds to the signal of the transmission channel, and the distinction of the simultaneously transmitted signals is completed at this time, that is, the simultaneous MIMO is completed. PM pseudo-random code is a simple to use orthogonal pseudo-random code that can easily generate a specific number of orthogonal code groups, because it is strictly orthogonal only under a constant envelope, and the matched filter group constructed by the FFT operation is a sinusoidal signal envelope. Therefore, in order to obtain a strictly orthogonal code group under a sinusoidal envelope, the optimization process of PM simplified random coding can be used, that is, the initial random code is selected from the PM code group, rather than directly setting a completely random initial code.

[0037] In some embodiments, after performing a range-dimensional fast Fourier transform operation on the mixed echo signal, the signal along the velocity direction is: Among them, S1 is the data of any channel of the receiving link.

[0038] After the compensation code is applied to the mixed echo signal, a speed-dimensional fast Fourier transform operation is performed, including:

[0039] Calculate a first compensation code and a second compensation code according to the first random code and the second random code;

[0040] Any channel data S1 is compensated with the first compensation code and the second compensation code respectively, and then a speed-dimensional fast Fourier operation is performed.

[0041] Optionally, the first random code and the second random code are optimized according to a cost function to obtain a first supplementary code and a second supplementary code; the cost function formula is:

[0042]

[0043] Among them, w 1 and w 2 is the weighted adjustment coefficient, and w 1 +w 2 =1.

[0044] Optionally, the first compensation code and the second compensation code are respectively compensated for any channel data S1, and then a speed-dimensional fast Fourier operation is performed to separate the first chirp signal and the second chirp signal. The specific formula is as follows:

[0045] S ch1 =fft(S 1 *a)…(4),

[0046] S ch2 =fft(S 1 *b)…(5);

[0047] Among them, S ch1 is the first chirp signal, S ch2 is the second chirp signal, a is the first compensation code, and b is the second supplementary code.

[0048] In this embodiment, the original time domain data obtained by 2 transmitters and 4 receivers simultaneously is the data of 4 channels S1-S4. After performing one-dimensional FFT in the distance direction, the data is multiplied by the a and b code words respectively when performing two-dimensional FFT to obtain the data of ch1-ch4 corresponding to Tx1 and ch5-ch8 corresponding to Tx2. Taking S1 data and single target full cycle sampling as an example, the signal in the velocity direction after the one-dimensional FFT is

[0049]

[0050] Compensate S1 to encode a and b, and then perform the second-dimensional FFT to separate the two parts to obtain the data of the corresponding transmission channel.

[0051] S ch1 =fft(S 1 *a)…(4)

[0052] S ch2 =fft(S 1 *b)…(5)

[0053] Genetic algorithm optimization of coding: Orthogonal binary codes a and b are orthogonal only under a constant envelope and are close to orthogonal under a trigonometric function envelope. The cost function of the ideal optimization is

[0054]

[0055] Considering the actual situation and optimization efficiency, we can choose to make the first equation not completely zero, so the actual cost function is set to

[0056]

[0057] w 1 and w 2 is the weighted adjustment coefficient, satisfying w 1 +w 2 = 1. In actual optimization, the ready-made PM code can be selected as the initial value. The present application can perform continuous iterative optimization according to the cost function. The specific algorithm can be found in Figure 3 .

[0058] In some embodiments, the present application also provides a MIMO radar, including the above-mentioned MIMO simultaneous transmission method based on phase shifter random coding, and also including a first phase shifter, a second phase shifter, a waveform generator, a fast Fourier transform module, a first transmission link, at least one second transmission link, and at least one receiving link; the waveform generator is connected to the first transmission link and the second transmission link, and the continuous wave generated by the waveform generator transmits a first chirp signal and a second chirp signal through the first transmission link and the second transmission link respectively; the first transmission link is connected to the first phase shifter, and the first transmission link The link transmits the first chirp signal with a first random code phase shift through a first phase shifter; the second transmission link is connected to the second phase shifter, and the second transmission link transmits the second chirp signal with a second random code phase shift through the second phase shifter; the receiving link is connected to the fast Fourier transform module, the receiving link receives the mixed echo signal of the first chirp signal and the second chirp signal, and after performing a distance-dimensional fast Fourier transform operation on the mixed echo signal, the mixed echo signal is compensated by a compensation code and then a speed-dimensional fast Fourier transform operation is performed to separate the echo signal of the first chirp signal and the echo signal of the second chirp signal. In this embodiment, see Figure 4, MIMO radar can be two transmitting and four receiving antennas. This solution avoids the problem of complex orthogonal waveform design and multiple physical parallel matched filter channels constructed at the receiving end of the conventional simultaneous MIMO solution. The transmitting end only randomly flips the phase shifter in each chrip cycle, and the receiving end directly uses the original FFT unit operation. This application is easy to implement and compatible with existing hardware without requiring additional hardware. At the same time, the amount of calculation is greatly reduced with the help of the FFT operation unit, and no additional processing operation is required for the back-end software. It is highly robust and scalable, suitable for different numbers of transmitting and receiving channels, and can be used as a basic framework technology for the comprehensive high-performance improvement of vehicle-mounted millimeter-wave radar. The principle of this application is to use the 0° and 180° flipping of the binary phase shifter to randomly phase encode different transmission signals, perform pseudo-code compensation on the mixed signal at the receiving end according to the corresponding transmission channel, and form an orthogonal matching filter group with the help of FFT operation, so as to achieve the separation of two signals transmitted simultaneously in one receiving channel. Taking two-transmit four-receive MIMO as an example, two groups of 0-1 random codes are designed for two-way transmission, each channel configures the phase shifter according to its own code, and sets the initial phase for each chrip pulse. When the code is 0, the phase shifter is configured to 0°, which is equivalent to multiplying by 1. When the code is 1, the phase shifter is configured to 180°, which is equivalent to multiplying by -1. After performing a one-dimensional FFT on each chrip of the received signal, all chrips are combined into a two-dimensional matrix structure. Due to the phase modulation between different chrips, it is equivalent to modulating the signal with a set of random signals composed of 1 / -1 in the chrip slow time dimension. Because different random signals are designed according to orthogonal random codes, the received signal is compensated for the corresponding pseudo-random code in the slow time dimension and then FFT operation is performed. The orthogonality can be used to filter out the signal corresponding to another set of random codes, which is equivalent to constructing an orthogonal filter group. The second-dimensional FFT result after compensating for the corresponding random code in the slow time dimension corresponds to the signal of the transmitting channel. At this time, the distinction between simultaneously transmitted signals is completed, that is, simultaneous MIMO is completed. The simultaneous MIMO algorithm solution based on 0-pi phase shifter random coding proposed in the present invention can solve the coupling problem of speed and angle measurement results caused by the existing time-sharing MIMO solution, and can be used as a scalable high-performance radar basic framework technology, and can realize high-performance radar in all aspects such as angle resolution and accuracy, distance resolution, speed unambiguous range, and detection signal-to-noise ratio gain on this basis in cascade and ultra-high resolution radars. This application uses the 0° and 180° resolution of the binary phase shifter in the existing hardware to correspond to 1 and -1, and uses the existing results of the PM encoder to design an orthogonal random coding that meets the requirements through a genetic algorithm to control the switching of the phase shifter, and combines it with the FFT operation to overcome the problem that the traditional simultaneous MIMO orthogonal matching filter has a large amount of computation or requires parallel physical channels. This solution has robust performance, is easy to implement, and does not require additional requirements for hardware and computation.

[0059] Obviously, the above embodiments of the present application are merely examples for clearly illustrating the present application, and are not intended to limit the implementation methods of the present application. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A MIMO simultaneous transmission method based on phase shifter random coding, characterized in that: Applied to a MIMO radar provided with a first transmission link, a second transmission link, and at least one receiving link, the method comprises: The first transmission link transmits a first chirp signal by phase shifting using a first random code, and the second transmission link transmits a second chirp signal by phase shifting using a second random code, wherein the first chirp signal and the second chirp signal are transmitted simultaneously; The receiving link receives the mixed echo signal of the first chirp signal and the second chirp signal, performs a distance-dimensional fast Fourier transform operation on the mixed echo signal, performs a compensation code compensation on the mixed echo signal, and then performs a speed-dimensional fast Fourier transform operation to separate the echo signal of the first chirp signal and the echo signal of the second chirp signal; The method of performing a speed-dimensional fast Fourier transform operation after performing compensation code compensation on the mixed frequency echo signal includes: Calculate a first compensation code and a second compensation code according to the first random code and the second random code by optimizing the cost function; The speed dimension data of any channel in the receiving link is compensated with a first compensation code and a second compensation code respectively, and then a speed dimension fast Fourier operation is performed.

2. The MIMO simultaneous transmission method based on phase shifter random coding according to claim 1, characterized in that: The first random code is obtained through a PM code encoder, and each of the first chirp signals is encoded with a random initial phase through the first random code.

3. The MIMO simultaneous transmission method based on phase shifter random coding according to claim 1, characterized in that: The second random code is obtained by a PM code encoder, and each of the second chirp signals is encoded with a random initial phase by the second random code.

4. The MIMO simultaneous transmission method based on phase shifter random coding according to claim 1, characterized in that: The first random code and the second random code are orthogonal pseudo-random codes, wherein: …(1), where is the first random code, is the second random code.

5. The MIMO simultaneous transmission method based on phase shifter random coding according to claim 1, characterized in that: After performing a distance-dimensional fast Fourier transform operation on the mixed echo signal, the signal along the velocity direction is: …(2), where S1 is the data of any channel of the receiving link.

6. The MIMO simultaneous transmission method based on phase shifter random coding according to claim 5, characterized in that: The first random code and the second random code are optimized according to a cost function to obtain a first supplementary code and a second supplementary code; the cost function formula is: …(3); in, and is the weighted adjustment coefficient, and .

7. The MIMO simultaneous transmission method based on phase shifter random coding according to claim 5, characterized in that: The first compensation code and the second compensation code are respectively compensated for any channel data S1, and then a speed-dimensional fast Fourier operation is performed to separate the first chirp signal and the second chirp signal. The specific formula is as follows: …(4)， …(5)； in, is the first chirp signal, is the second chirp signal, a is the first compensation code, and b is the second supplementary code.

8. A MIMO radar, characterized in that: The MIMO simultaneous transmission method based on phase shifter random coding according to any one of claims 1 to 7 further comprises a first phase shifter, a second phase shifter, a waveform generator, a fast Fourier transform module, a first transmission link, at least one second transmission link, and at least one receiving link; The waveform generator is connected to the first transmission link and the second transmission link, and the continuous wave generated by the waveform generator transmits the first chirp signal and the second chirp signal through the first transmission link and the second transmission link respectively; The first transmission link is connected to the first phase shifter, and the first transmission link transmits the first chirp signal with a first random code phase shift through the first phase shifter; The second transmission link is connected to the second phase shifter, and the second transmission link transmits the second chirp signal with a second random code phase shift through the second phase shifter; The receiving link is connected to the fast Fourier transform module, and the receiving link receives the mixed echo signals of the first chirp signal and the second chirp signal, and after performing a distance-dimensional fast Fourier transform operation on the mixed echo signal, a compensation code is performed on the mixed echo signal and then a speed-dimensional fast Fourier transform operation is performed to separate the echo signal of the first chirp signal and the echo signal of the second chirp signal.

9. A MIMO radar according to claim 8, characterized in that: The MIMO radar has two transmitting and four receiving antennas.

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