MIMO radar waveform orthogonal performance improvement method

Abstract

The invention discloses an MIMO radar waveform orthogonal performance improvement method, which comprises the following steps of: after an MIMO radar antenna receives echo signals, performing down-conversion and digital-to-analog conversion on the echo signals of each receiving array element, and converting analog signals into digital signals; performing matched filtering on the digital signal of each receiving array element through different matched filters, and storing output data of the matched filters; subtracting output data of other matched filters in the nth receiving array element from output data of the mth matched filter in the nth receiving array element to obtain a first result; and according to the first result and a correlation coefficient between orthogonal waveforms output by different transmitting array elements, calculating to obtain improved data of output data of the mth matched filter in the nth receiving array element, thereby completing improvement of radar waveform orthogonal performance. According to the invention, the orthogonal performance of the waveform is improved on the premise of not changing the phase information of the signal.

Description

Technical Field

[0001] The present invention relates to the field of radar signal processing technology, and more specifically, to a method for improving the orthogonality performance of MIMO radar waveforms. Background Art

[0002] With the continuous development of electronic information technology, the target characteristics and detection environment faced by radars have become increasingly complex, which has brought greater challenges to the target detection performance of radars. The traditional phased array radar system is relatively simple, forming a narrow beam in the transmitting airspace, with strong directivity, and can obtain a signal power gain proportional to the square of the number of array elements in the normal direction, which is widely used in various radar equipment. However, phased array radars also have disadvantages. They are easily intercepted by enemy radars; the beam of phased array radars is a narrow beam. When detecting targets, the phased array needs to illuminate the space at different angles separately, and cannot detect the entire airspace at the same time; in addition, phased array radars can usually only use the airspace freedom of the receiving end, and the limitation of the size of the radar antenna array makes it difficult for phased array radars to increase the airspace freedom to improve target detection capabilities.

[0003] Multiple-input multiple-output (MIMO) radar uses multiple antennas at both the transmitting and receiving ends. MIMO radars are mainly divided into two types: distributed MIMO radars and centralized MIMO radars. Here, we mainly discuss centralized orthogonal MIMO radars. The array distribution of centralized MIMO radars is basically the same as that of traditional radars. Using waveform diversity technology, the signal waveforms between each transmitting array element or transmitting channel of the radar are mutually orthogonal. At the receiving end, each waveform signal is extracted separately through a matching filter or other filter, so that the spatial freedom of the transmitting end can be obtained. Therefore, the spatial freedom of MIMO radar during signal processing is much higher than that of phased array radar, and higher target detection performance can be obtained. At the same time, since MIMO radars transmit orthogonal waveforms and the radar's transmission pattern is omnidirectional, MIMO radars can detect the entire airspace at the same time.

[0004] In summary, orthogonal waveforms are a necessary condition for the normal operation of centralized orthogonal MIMO radars. However, in practice, completely orthogonal waveforms do not exist, so improving the orthogonal performance of waveforms is an important research direction for orthogonal MIMO radars. Waveform performance is usually reflected in several aspects, such as autocorrelation main-sidelobe ratio, orthogonality, and range resolution. Among them, the range resolution is determined by the main lobe width output after matched filtering. The narrower the main lobe, the better the range resolution; the autocorrelation main-sidelobe ratio refers to the ratio of the main lobe to the sidelobe peak after the signal passes through the matched filter. A high main-sidelobe ratio can avoid the problem of weak target masking; orthogonality refers to the cross-correlation amplitude between different transmitted signals. The orthogonal performance of the waveform will directly affect the signal separation effect at the receiving end, thereby affecting the performance of the MIMO radar.

[0005] In order to improve the orthogonal performance of MIMO radar, many researchers at home and abroad have studied the design of MIMO radar orthogonal waveforms. There are four main forms of orthogonal MIMO radar waveforms, namely code division addressing, time division addressing, frequency division addressing and Doppler division addressing. Based on these four waveform forms, many MIMO radar orthogonal waveform design methods have been proposed, but none of them can achieve complete orthogonality.

[0006] In summary, since the current MIMO radar waveform is a non-orthogonal waveform, and the non-orthogonal waveform will have a certain impact on the performance of the orthogonal MIMO radar, a method for improving the orthogonal performance of the waveform is needed. Summary of the invention

[0007] The present invention provides a method for improving the orthogonality performance of MIMO radar waveforms in order to improve the orthogonality performance of existing MIMO radar waveforms and thereby reduce the influence of non-orthogonal waveforms on the target detection performance of MIMO radars.

[0008] In order to achieve the above-mentioned purpose of the present invention, the technical scheme adopted is as follows:

[0009] A method for improving the orthogonality performance of MIMO radar waveforms, the method comprising the following steps:

[0010] After the MIMO radar antenna receives the echo signal, it performs down-conversion and digital-to-analog conversion on the echo signal of each receiving array element to convert the analog signal into a digital signal;

[0011] The digital signal of each receiving array element is matched filtered through different matched filters, and the output data of the matched filters are stored respectively;

[0012] Subtracting output data of other matched filters in the nth receiving array element from output data of the mth matched filter in the nth receiving array element to obtain a first result;

[0013] Improved data of the output data of the mth matched filter in the nth receiving element is calculated based on the correlation coefficient between the first result and the orthogonal waveforms output by different transmitting elements, thereby improving the orthogonal performance of the radar waveform.

[0014] Preferably, assuming that the m'th waveform signal is to be extracted, the process of matched filtering is as follows:

[0015]

[0016] In the formula, y n,m' (t) represents the output data of the matched filter, x n (t) represents the received signal of the nth receiving element, h m'(t) represents the matched filter of the m′th phase-coded waveform, * represents convolution, and ξ represents the back

[0017] The power of the wave signal, s m' (t) The waveform transmitted by the m′th transmitting array element, represents the steering vector of the nth receiving array element and the m′th transmitting array element, m represents the mth orthogonal waveform, t represents the fast time, M represents the total number of orthogonal MIMO radar transmitting array elements, r m，m' represents the correlation coefficient between the mth orthogonal waveform and the m′th orthogonal waveform in 0 delay, s m (t) represents the waveform transmitted by the mth transmitting array element, Represents the steering vector of the nth receiving array element and the mth transmitting array element.

[0018] Furthermore, the calculation formula of the received signal of the nth receiving array element is as follows:

[0019]

[0020] Furthermore, the calculation formula of the matched filter of the mth phase-coded waveform is as follows:

[0021] h m (t) = s m * (-t)

[0022] in,() * Indicates conjugation; s m * (-t) indicates waveform s m The conjugate of (t) is taken and the entire signal is inverted.

[0023] Furthermore, the calculation formula of the first result is as follows:

[0024] δ n,m,m' (t) = y n,m (t)-y n,m' (t)

[0025] In the formula, y n,m (t) represents the output data of the mth matched filter in the nth receiving array element, y n,m' (t) represents the output data of the m′th matched filter in the nth receiving array element.

[0026] Furthermore, the improved data of the output data of the mth matched filter in the nth receiving element is obtained by calculating the correlation coefficient between the first result and the orthogonal waveforms output by different transmitting elements, and the calculation formula is as follows:

[0027]

[0028] In the formula, y n,m (t) indicates improved data, It means taking the real part.

[0029] Furthermore, the method further comprises:

[0030] Also to y n,m (t) is normalized as follows:

[0031]

[0032] Here, |·| is the modulus symbol.

[0033] Furthermore, the digital signal of each receiving array element is matched filtered through different matched filters, and the output data of the matched filters are stored separately, recorded as

[0034] After each element in Y is processed to obtain preliminary improved data, it is normalized and the processed data is recorded as

[0035] In the formula, Shows the data after the waveform orthogonality is improved.

[0036] A MIMO radar waveform orthogonality performance improvement system, comprising:

[0037] A processing module, configured to perform down-conversion and digital-to-analog conversion on the echo signal of each receiving array element after the MIMO radar antenna receives the echo signal, so as to convert the analog signal into a digital signal; to subtract the output data of the other matched filters in the nth receiving array element from the output data of the mth matched filter in the nth receiving array element, so as to obtain a first result; and to calculate the improved data of the output data of the mth matched filter in the nth receiving array element according to the correlation coefficient between the first result and the orthogonal waveforms output by different transmitting array elements, so as to improve the orthogonal performance of the radar waveform;

[0038] A matched filtering module, used to perform matched filtering on the digital signal of each receiving array element through different matched filters;

[0039] The storage module is used to store the output data of the matched filter respectively.

[0040] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the method described above are implemented.

[0041] The beneficial effects of the present invention are as follows:

[0042] The present invention performs matched filtering on the digital signal of each receiving array element through different matched filters. Since the signal processing of each matched filter is independent and needs to be performed separately, and each signal processing needs to use the output data of other matched filters, the method is suitable for processing at the digital signal end.

[0043] The present invention subtracts the output data of other matched filters in the nth receiving element from the output data of the mth matched filter in the nth receiving element to obtain a first result, and calculates the improved data of the output data of the mth matched filter in the nth receiving element according to the correlation coefficient, thereby improving the orthogonal performance of the waveform.

[0044] The present invention can improve the orthogonal performance of the waveform without changing the phase information of the signal itself. The present invention can be applied to various waveform signals and has no requirement on the type of waveform emitted by the radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a flowchart of the steps of the method for improving the orthogonality performance of MIMO radar waveforms described in the present invention.

[0046] Figure 2 It is a principle block diagram of the MIMO radar waveform orthogonality performance improvement system of the present invention. DETAILED DESCRIPTION

[0047] The following will describe the embodiments of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, not for limiting the scope of protection of the present invention.

[0048] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0049] Example 1

[0050] The MIMO radar involved in this embodiment uses an antenna array, and different transmitting array elements transmit mutually orthogonal waveform signals. Here, it is assumed that the transmitted waveform is a phase-coded waveform. Assume that the number of transmitting array elements of the orthogonal MIMO radar is M, the number of corresponding orthogonal waveforms is M, and the number of receiving array elements is N. Since the transmitted waveforms are known, their correlation coefficients can be calculated in advance, and the correlation coefficients of each waveform in 0 delay can be recorded for subsequent signal processing. Among them, the correlation coefficient between the mth and m'th waveforms in 0 delay is counted as r m,m' , when m=m', r m,m' is the autocorrelation coefficient. In general, the autocorrelation coefficient is 1.

[0051] like Figure 1 As shown, a method for improving the orthogonality performance of MIMO radar waveforms comprises the following steps:

[0052] After the MIMO radar antenna receives the echo signal, it performs down-conversion and digital-to-analog conversion on the echo signal of each receiving array element to convert the analog signal into a digital signal;

[0053] The digital signal of each receiving array element is matched filtered through different matched filters, and the output data of the matched filters are stored respectively;

[0054] Subtracting output data of other matched filters in the nth receiving array element from output data of the mth matched filter in the nth receiving array element to obtain a first result;

[0055] Improved data of the output data of the mth matched filter in the nth receiving element is calculated based on the correlation coefficient between the first result and the orthogonal waveforms output by different transmitting elements, thereby improving the orthogonal performance of the radar waveform.

[0056] The present invention performs matched filtering on the digital signal of each receiving array element through different matched filters. Since the signal processing of each matched filter is independent and needs to be performed separately, and each signal processing needs to use the output data of other matched filters, the method is suitable for processing at the digital signal end.

[0057] The present invention subtracts the output data of other matched filters in the nth receiving element from the output data of the mth matched filter in the nth receiving element to obtain a first result, and calculates the improved data of the output data of the mth matched filter in the nth receiving element according to the correlation coefficient, thereby improving the orthogonal performance of the waveform.

[0058] The present invention can improve the orthogonal performance of the waveform without changing the phase information of the signal itself. The present invention can be applied to various waveform signals and has no requirement on the type of waveform emitted by the radar.

[0059] In a specific embodiment, the waveform transmitted by the mth transmitting array element is denoted as s m (t), where t represents the fast time. At the receiving end, after the MIMO radar antenna receives the echo signal, the echo signal of each receiving array element is down-converted and converted to digital-to-analog, and the analog signal is converted to a digital signal. The down-conversion is to reduce the frequency, which can be achieved by a low-pass filter; the digital-to-analog conversion can be achieved directly by using a digital-to-analog conversion chip.

[0060] At this time, the received signal of the nth receiving array element can be expressed as:

[0061]

[0062] Among them, ζ is the power of the echo signal, is the phase information of the signal.

[0063] Since the transmitted waveform is a phase-coded waveform, the signal of each receiving array element must be extracted through different matched filters. The matched filter h of the mth phase-coded waveform m (t) is as follows:

[0064] h m (t) = s m * (-t)

[0065] In a specific embodiment, the digital signal of each receiving array element is matched filtered through different matched filters, and the output data of the matched filters are stored separately. Since the waveform is a non-orthogonal waveform, there are signals of other waveforms in the output of each matched filter in addition to the target signal, which we call redundant signals. After matched filtering, each waveform signal is extracted and stored separately. Therefore, the signal data dimension of each receiving array element at a certain sampling point is 1×M. At this time, the output data of the nth receiving array element after matched filtering is y n =[y n,1 ,y n,2 ,...,y n,M ], where y n,m is the output data of the mth matched filter.

[0066] Since the transmitted waveform is a phase-coded waveform, the signal of each receiving array element must be extracted through different matched filters. The matched filter h of the mth phase-coded waveform m (t) is as follows:

[0067] h m (t) = s m *(-t)

[0068] in,() * represents conjugation, s m * (-t) indicates waveform s m The conjugate of (t) is taken and the entire signal is inverted.

[0069] Preferably, assuming that the m'th waveform signal is to be extracted, the process of matched filtering is as follows:

[0070]

[0071] In the formula, y n,m' (t) represents the output data of the matched filter, x n (t) represents the received signal of the nth receiving element, h m' (t) represents the matched filter of the m′th phase-coded waveform, * represents convolution, ξ represents the power of the echo signal, and s m' (t) The waveform transmitted by the m′th transmitting array element, represents the steering vector of the nth receiving element and the m′th transmitting element, m represents the mth orthogonal waveform, t represents the fast time, M represents the total number of orthogonal MIMO radar transmitting array elements, r m，m' represents the correlation coefficient between the mth orthogonal waveform and the m′th orthogonal waveform in 0 delay, s m (t) represents the waveform transmitted by the mth transmitting array element, Represents the steering vector of the nth receiving array element and the mth transmitting array element.

[0072] According to the above formula, in addition to the target signal, there is also a small amount of honor signal in the output of the matched filter. The power of the redundant signal is determined by the correlation coefficient r m,m' The output result of each receiving element after the received signal passes through the matched filter is stored and recorded as

[0073] In a specific embodiment, the output data of the mth matched filter in the nth receiving array element is subtracted from the output data of other matched filters in the nth receiving array element to obtain a first result; wherein the calculation formula of the first result is as follows:

[0074] δ n,m,m' (t) = y n,m (t)-y n,m' (t)

[0075] In the formula, y n,m (t) represents the output data of the mth matched filter in the nth receiving array element, y n,m'(t) represents the output data of the m′th matched filter in the nth receiving array element.

[0076] This completes the signal preprocessing, and we call the first result difference data.

[0077] In a specific embodiment, the improved data of the output data of the mth matched filter in the nth receiving element is calculated based on the correlation coefficient between the first result and the orthogonal waveforms output by different transmitting elements, and the calculation formula is as follows:

[0078]

[0079] In the formula, y n,m (t) indicates improved data, It means taking the real part.

[0080] The output data of the mth matched filter in this embodiment is added with the difference data, which improves the orthogonal performance of the signal. Through the above processing, the redundant signal component in the output data of the mth matched filter can be greatly reduced without changing the phase of the signal itself, thereby improving the orthogonal performance of the waveform.

[0081] The above formula can finally get the improved data y of the output data of the mth matched filter in the nth receiving array element: n,m (t), y n,m The component ratio of the redundant signal in (t) is y n,m (t) is greatly reduced.

[0082] Finally, each y n,m (t) normalization is also required, and the method further comprises:

[0083] Also to y n,m (t) is normalized as follows:

[0084]

[0085] Here, |·| is the modulus symbol.

[0086] In this embodiment, each element in Y needs to be processed through the above steps (after obtaining the preliminary improved data, normalization is performed), and the processed data is recorded as In the formula, Shows the data after the waveform orthogonality is improved.

[0087] In this way, signal processing of all data is completed, thereby improving the orthogonality performance of all array element signals.

[0088] Example 2

[0089] Based on the MIMO radar waveform orthogonality performance improvement method described in Example 1, this embodiment further provides a MIMO radar waveform orthogonality performance improvement system, including:

[0090] include:

[0091] A processing module, configured to perform down-conversion and digital-to-analog conversion on the echo signal of each receiving array element after the MIMO radar antenna receives the echo signal, so as to convert the analog signal into a digital signal; to subtract the output data of the other matched filters in the nth receiving array element from the output data of the mth matched filter in the nth receiving array element, so as to obtain a first result; and to calculate the improved data of the output data of the mth matched filter in the nth receiving array element according to the correlation coefficient between the first result and the orthogonal waveforms output by different transmitting array elements, so as to improve the orthogonal performance of the radar waveform;

[0092] A matched filtering module, used to perform matched filtering on the digital signal of each receiving array element through different matched filters;

[0093] The storage module is used to store the output data of the matched filter respectively.

[0094] Example 3

[0095] This embodiment also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for improving the orthogonality performance of MIMO radar waveforms as described in Example 1 are implemented.

[0096] Among them, the memory and the processor are connected in a bus manner, and the bus may include any number of interconnected buses and bridges, and the bus connects various circuits of one or more processors and memories together. The bus can also connect various other circuits such as peripherals, voltage regulators, and power management circuits, which are well known in the art and are therefore not further described herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be one element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices on a transmission medium. The data processed by the processor is transmitted on a wireless medium via an antenna, and further, the antenna also receives data and transmits the data to the processor.

[0097] This embodiment further provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the method for improving the orthogonality performance of MIMO radar waveforms as described in Example 1 are implemented.

[0098] That is, those skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including several instructions to enable a device (which can be a single-chip microcomputer, chip, etc.) or a processor to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0099] Obviously, the above embodiments of the present invention are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for improving the orthogonality performance of MIMO radar waveforms, characterized in that: The method comprises the following steps: After the MIMO radar antenna receives the echo signal, it performs down-conversion and digital-to-analog conversion on the echo signal of each receiving array element to convert the analog signal into a digital signal; The digital signal of each receiving array element is matched filtered through different matched filters, and the output data of the matched filters are stored respectively; Subtracting output data of other matched filters in the nth receiving array element from output data of the mth matched filter in the nth receiving array element to obtain a first result; Improved data of the output data of the mth matched filter in the nth receiving element is calculated based on the correlation coefficient between the first result and the orthogonal waveforms output by different transmitting elements, thereby improving the orthogonal performance of the radar waveform.

2. The method for improving MIMO radar waveform orthogonality performance according to claim 1, characterized in that: Assuming that the m'th waveform signal is to be extracted, the process of matched filtering is as follows: In the formula, y n,m' (t) represents the output data of the matched filter, x n (t) represents the received signal of the nth receiving element, h m' (t) represents the matched filter of the m′th phase-coded waveform, * represents convolution, ξ represents the power of the echo signal, and s m' (t) The waveform transmitted by the m′th transmitting array element, represents the steering vector of the nth receiving array element and the m′th transmitting array element, m represents the mth orthogonal waveform, t represents the fast time, M represents the total number of orthogonal MIMO radar transmitting array elements, r m，m' represents the correlation coefficient between the mth orthogonal waveform and the m′th orthogonal waveform in 0 delay, s m (t) represents the waveform transmitted by the mth transmitting array element, represents the steering vector of the nth receiving array element and the mth transmitting array element.

3. The method for improving MIMO radar waveform orthogonality performance according to claim 2, characterized in that: The calculation formula of the received signal of the nth receiving array element is as follows:

4. The method for improving MIMO radar waveform orthogonality performance according to claim 2, characterized in that: The calculation formula for the matched filter of the mth phase-coded waveform is as follows: h m (t)=s m * (-t) in,(·) * Indicates conjugation; s m * (-t) indicates waveform s m The conjugate of (t) is taken and the entire signal is inverted.

5. The method for improving MIMO radar waveform orthogonality performance according to claim 1, characterized in that: The calculation formula of the first result is as follows: δ n,m,m' (t)=y n,m (t)-y n,m' (t) In the formula, y n,m (t) represents the output data of the mth matched filter in the nth receiving array element, y n,m' (t) represents the output data of the m′th matched filter in the nth receiving array element.

6. The method for improving MIMO radar waveform orthogonality performance according to claim 5, characterized in that: The improved data of the output data of the mth matched filter in the nth receiving element is obtained by calculating the correlation coefficient between the first result and the orthogonal waveforms output by different transmitting elements, and the calculation formula is as follows: In the formula, y n,m (t) indicates improved data, It means taking the real part.

7. The method for improving MIMO radar waveform orthogonality performance according to claim 6, characterized in that: The method further comprises: Also to y n,m (t) is normalized as follows: Here, |·| is the modulus symbol.

8. The method for improving MIMO radar waveform orthogonality performance according to claim 7, characterized in that: The digital signal of each receiving array element is matched filtered through different matched filters, and the output data of the matched filters are stored separately, recorded as After each element in Y is processed to obtain preliminary improved data, it is normalized and the processed data is recorded as In the formula, Represents the data after the orthogonality of the waveforms has been improved.

9. A MIMO radar waveform orthogonality performance improvement system, characterized by: include: A processing module, configured to perform down-conversion and digital-to-analog conversion on the echo signal of each receiving array element after the MIMO radar antenna receives the echo signal, so as to convert the analog signal into a digital signal; to subtract the output data of the other matched filters in the nth receiving array element from the output data of the mth matched filter in the nth receiving array element, so as to obtain a first result; and to calculate the improved data of the output data of the mth matched filter in the nth receiving array element according to the correlation coefficient between the first result and the orthogonal waveforms output by different transmitting array elements, so as to improve the orthogonal performance of the radar waveform; A matched filtering module, used to perform matched filtering on the digital signal of each receiving array element through different matched filters; The storage module is used to store the output data of the matched filter respectively.

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

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