A fast-moving target detection method for frequency-division MIMO radar

Abstract

The present invention discloses a method for detecting fast-moving targets using a frequency-division MIMO radar, relating to the field of radar technology. The method comprises: performing frequency mixing and matched filtering decomposition processing on an acquired echo signal, transforming it into the frequency domain for pulse compression, correcting the linear range offset and velocity ambiguity index of the pulse compression frequency domain signal, and using a first corrected frequency domain signal to obtain an estimated target velocity ambiguity index and an estimated radial velocity of the moving target; compensating the pulse compression frequency domain signal, and then correcting it using baseline transformation and the estimated target velocity ambiguity index to obtain a second corrected frequency domain signal. Using the second corrected frequency domain signal, an enhanced angle estimate of the moving target is obtained in the transmit-receive domain. By correcting the linear range offset and velocity ambiguity index, the present invention corrects the coupling term, thereby accurately detecting the angle and velocity parameters of the moving target.

Description

Technical Field

[0001] The present invention belongs to the field of radar technology, and in particular relates to a method for detecting fast-moving targets using a frequency-division MIMO radar. Background Art

[0002] When dealing with Doppler ambiguity for high-speed moving targets, pulse Doppler radar (PD) faces a trade-off between range ambiguity and Doppler ambiguity. Specifically, to avoid range ambiguity, a low pulse repetition frequency (PRF) is required, while to achieve unambiguous velocity measurement, a high PRF is required. Range ambiguity is typically more difficult to handle, so a low PRF is often chosen, which results in Doppler ambiguity.

[0003] In recent years, a new array structure called frequency diversity array (FDA) has attracted widespread research interest. By applying a small frequency offset to the transmitting array elements, a transmit beam pattern related to range, angle, and time is formed. However, the transmit beam pattern of the coherent FDA exhibits an "S" shape and contains multiple peaks, which leads to ambiguity in the range-angle pair, thereby affecting the accuracy of target positioning. In addition, the change of the beam pattern over time poses complex processing challenges. Therefore, by combining MIMO technology and transmitting orthogonal waveforms and then separating these waveforms after matched filtering, degrees of freedom (DOF) can be achieved in the range domain. In this context, FDA-MIMO radar has been widely used in fields such as suppressing mainlobe deceptive interference, unambiguous parameter estimation, range ambiguity clutter suppression, and high-resolution synthetic aperture radar (SAR) imaging due to its flexible signal processing capabilities.

[0004] Frequency diversity arrays address range ambiguity by introducing small frequency offsets between array elements. However, for high-speed targets, Doppler ambiguity can occur, causing the power spectrum in the transmitted spatial frequency domain to become spread out, impacting target detection and positioning performance. Frequency offsets within the echo signal introduce varying degrees of coupling between parameters such as angle and velocity, making direct estimation of these parameters from the echo signal challenging. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a method for detecting fast moving targets using a frequency division MIMO radar. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0006] The present invention provides a method for detecting fast-moving targets using a frequency-division MIMO radar, comprising:

[0007] Step 1: Use the receiving array element of the frequency division MIMO radar to obtain the echo signal;

[0008] Step 2: After performing frequency mixing and matched filtering decomposition processing on the echo signal, a matched filtering output signal is obtained;

[0009] Step 3: transforming the matched filter output signal into the frequency domain and performing pulse compression to obtain a corresponding pulse compression frequency domain signal, and correcting the linear range offset and velocity ambiguity index of the pulse compression frequency domain signal to obtain a first corrected frequency domain signal;

[0010] Step 4: transforming the first corrected frequency domain signal into the time domain to obtain a corresponding corrected time domain signal, obtaining an estimated target velocity ambiguity index based on the corrected time domain signal, and obtaining an estimated radial velocity of the moving target based on the estimated target velocity ambiguity index;

[0011] Step 5: compensating the pulse compression frequency domain signal to obtain a compensation signal, and correcting the coupling term of the compensation signal using baseline transformation and the estimated target velocity ambiguity index to obtain a second corrected frequency domain signal;

[0012] Step 6: Obtain an enhanced angle estimate of the moving target in the transmit-receive domain based on the second corrected frequency domain signal.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The invention discloses a method for detecting fast-moving targets using a frequency-division MIMO radar. The method comprises the following steps: obtaining an echo signal by using a receiving array element of a frequency-division MIMO radar; performing frequency mixing and matched filtering decomposition processing on the echo signal to obtain a matched filtering output signal; transforming the matched filtering output signal into the frequency domain and performing pulse compression to obtain a corresponding pulse compression frequency domain signal; correcting a linear range offset and a speed ambiguity index of the pulse compression frequency domain signal to obtain a first corrected frequency domain signal; transforming the first corrected frequency domain signal into the time domain to obtain a corresponding corrected time domain signal; obtaining an estimated target speed ambiguity index based on the corrected time domain signal; and obtaining an estimated radial speed of the moving target based on the estimated target speed ambiguity index; compensating the pulse compression frequency domain signal to obtain a compensated signal; correcting a coupling term of the compensated signal by using a baseline transformation and the estimated target speed ambiguity index to obtain a second corrected frequency domain signal; and obtaining an enhanced angle estimation of the moving target in a transmitting-receiving domain based on the second corrected frequency domain signal. The present invention addresses the problem that the frequency offset in the echo signal introduces different degrees of coupling between the angle and velocity parameters. By correcting the linear range offset and the velocity ambiguity index, the coupling term is corrected, and the angle and velocity parameters of the moving target can be accurately detected.

[0015] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following preferred embodiments are specifically cited and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 1 is a schematic diagram of a method for detecting fast-moving targets using a frequency-division MIMO radar, provided by an embodiment of the present invention;

[0017] Figure 2 is the estimation result of the target speed fuzzy index provided by the embodiment of the present invention;

[0018] Figure 3 is the result of enhanced angle estimation of a moving target provided by an embodiment of the present invention;

[0019] Figure 4 This is a comparison diagram of focusing results before and after beamforming provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following is a detailed description of a frequency division MIMO radar fast moving target detection method proposed according to the present invention in conjunction with the accompanying drawings and specific embodiments.

[0021] The aforementioned and other technical contents, features, and effects of the present invention are clearly presented in the following detailed description of the specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a deeper and more specific understanding of the technical means and effects adopted by the present invention to achieve the intended purpose can be obtained. However, the accompanying drawings are provided for reference and illustration purposes only and are not intended to limit the technical solutions of the present invention.

[0022] The embodiment of the present invention provides a method for detecting fast moving targets by frequency division MIMO radar. Figure 1 , Figure 1 FIG is a schematic diagram of a method for detecting fast moving targets using a frequency division MIMO radar according to an embodiment of the present invention. Figure 1 As shown, the frequency division MIMO radar fast moving target detection method of this embodiment includes:

[0023] Step 1: Use the receiving array element of the frequency division MIMO radar to obtain the echo signal.

[0024] In this embodiment, the frequency division MIMO radar includes M transmitting array elements and N receiving array elements, and both the transmitting and receiving array elements are uniform linear arrays (ULA), wherein the spacing between the transmitting array elements is d T , the receiving array element spacing is dR Frequency division MIMO radar is based on MIMO radar, but adds a frequency offset Δf between the transmitting array elements. That is, there is a frequency offset between the transmitting carrier frequencies of the M transmitting array elements. Taking the transmitting carrier frequency of the first transmitting array element as the reference, the transmitting carrier frequency of the mth transmitting array element is:

[0025] f m =f0+Δf m ,m=1,2,...,M;

[0026] Where f0 is the carrier frequency of the first transmitting element; Δf m =(m-1)Δf represents the frequency offset associated with the mth transmitting array element. Then, the vector form of the transmitting carrier frequency of the M transmitting array elements can be expressed as f=[f1,f2,…,f M ] T ∈C M , the vector form of the frequency offset of M transmitting array elements can be expressed as Δf=[Δf1,Δf2,…,Δf M ] T ∈C M .

[0027] Assuming that a linear frequency modulation (LFM) signal is used as the transmitted signal, the baseband waveform transmitted by the mth transmitting array element can be expressed as:

[0028]

[0029] in, is the waveform representation of the linear frequency modulation signal LFM, t is the fast time variable, Indicates T p As the pulse duration, is the frequency modulation slope, and B is the signal bandwidth.

[0030] When a moving target in the far field is located at angle θ, range R, and enters the radar at radial velocity V, considering the case of two-way propagation, the first transmitting array element is selected as the reference. Therefore, the echo signal of the kth pulse received by the nth receiving array element is expressed as:

[0031]

[0032] Where s n (t,t k ) is the echo signal of the kth pulse received by the nth receiving element, t is the fast time variable, t k is the slow time variable, M is the number of transmitting array elements, ξ t is the complex echo amplitude, R m,n (t k) is the round-trip distance between the mth transmitting element and the nth receiving element, c is the speed of light, j is the imaginary unit, and f m is the transmitting carrier frequency of the mth transmitting array element.

[0033] In this embodiment, ξ t The complex echo amplitude considering the transmission amplitude-phase, target scattering and propagation effects is expressed as Among them, P t , G t , G r ,λ0,δ t They represent the target's peak transmission power, component transmission gain, component receiving gain, signal wavelength, and radar cross section (RCS) coefficient respectively. m,n (t k )=2R-2Vt k -(m-1)d T sinθ-(n-1)d R sinθ, where t k =kT r represents the slow time variable; T r is the pulse repetition time (PRT).

[0034] Step 2: After mixing and matched filtering the echo signal, a matched filter output signal is obtained.

[0035] In an optional embodiment, step 2 includes:

[0036] Step 2.1: Perform frequency mixing on the echo signal to obtain a mixed echo signal.

[0037] Step 2.2: Decompose the mixed echo signal using a matched filter to obtain M independent matched filter output signals, where M is the number of transmitting array elements.

[0038] In this embodiment, after the echo signal is multiplied by exp{-j2πf0t} for mixing, the mixed echo signal is decomposed by a matched filter to obtain M independent matched filter output signals, where the mth matched filter output signal is expressed as:

[0039]

[0040] in, is the pulse compression coefficient after the mth matched filter is modulated, which can simultaneously complete the pulse compression and waveform separation of the signal. ss [Δt,(m'-m)Δf] is the correlation function between different emission waveforms, expressed as:

[0041] χ ss[Δt,(m'-m)Δf]=Asinc[((m'-m)Δf+μΔt)(T p -|Δt|)];

[0042] Where A is the amplitude of the correlation function, expressed as m' represents a matched filter different from m.

[0043] Since the cross-correlation between different frequency-divided waveforms is small, the output signal after the mth matched filter can be approximated as:

[0044]

[0045] Step 3: Transform the matched filter output signal into the frequency domain and perform pulse compression to obtain the corresponding pulse compression frequency domain signal. Correct the linear range offset and velocity ambiguity index of the pulse compression frequency domain signal to obtain the first corrected frequency domain signal.

[0046] In an optional embodiment, step 3 includes:

[0047] Step 3.1: Transform the matched filter output signal into the frequency domain to obtain the corresponding frequency domain signal.

[0048] In this embodiment, the frequency domain signal obtained by transforming the matched filtering output signal into the frequency domain can be expressed as:

[0049]

[0050] Where, f r is the frequency variable corresponding to the fast time variable, is the intermediate parameter, c is the speed of light, j is the imaginary unit, θ is the angle of the moving target, B is the signal bandwidth, v0 is the main velocity of the moving target, and l0 is the target velocity ambiguity index.

[0051] Step 3.2: According to the fixed phase principle, pulse compression is performed on the frequency domain signal to obtain a pulse compressed frequency domain signal.

[0052] In this embodiment, according to the fixed phase principle, the frequency domain signal is pulse compressed to obtain a pulse compressed frequency domain signal, which can be expressed as:

[0053]

[0054] Where V is the radial velocity of the moving target.

[0055] From the above formula, we can see that the linear distance traveled is determined by the variable f r and slow time variable t kThis is caused by coupling and becomes more obvious when fast-moving targets are detected.

[0056] For fast-moving targets, velocity ambiguity is very likely to occur due to the limited radar pulse repetition frequency (PRF). In this case, the radial velocity of the moving target can be written as:

[0057] V=v0+l0V u ;

[0058] Among them, v0 represents the main velocity of the moving target, l0V u Indicates the fuzzy speed of the moving target, l0 is the target speed fuzzy index, V u is the maximum unambiguous speed, expressed as

[0059] Substituting the expression of the radial velocity of the moving target into the pulse compression frequency domain signal, we can obtain:

[0060]

[0061] From the above formula, we can see that the variable f r and slow time variable t k The coupling term between them is related to the main velocity v0 of the moving target and the target velocity ambiguity index l0. In addition, due to the frequency difference between the transmitting array elements, t k and Δf m There is a coupling term between them, which causes the echoes output by different matched filters to be incoherent.

[0062] Step 3.3: Use baseline transformation to correct the first channel data of the pulse compression frequency domain signal to eliminate the linear range offset caused by the main velocity of the moving target, and obtain the first channel data after linear range offset correction.

[0063] Since baseline transformation (KT) has excellent performance in low signal-to-noise ratio environments, in this embodiment, baseline transformation is used to eliminate the influence of linear range migration. The original baseline transformation can be expressed as:

[0064]

[0065] Among them, τ k Represents the new slow time variable.

[0066] Taking into account the incoherence between different matched filter output signals, the original baseline transformation is applied to the first channel data of the pulse compression frequency domain signal to correct it. The obtained first channel data after linear range offset correction can be expressed as:

[0067]

[0068] At this time, the linear range deviation caused by the main velocity v0 of the moving target is corrected.

[0069] Step 3.4: Based on the first channel data corrected for the linear range offset, all velocity ambiguity indices are iteratively corrected to obtain a first corrected frequency domain signal.

[0070] In this embodiment, the first corrected frequency domain signal obtained by iteratively correcting all possible velocity ambiguity indices can be expressed as:

[0071]

[0072] Step 4: transform the first corrected frequency domain signal into the time domain to obtain a corresponding corrected time domain signal, obtain an estimated target velocity ambiguity index based on the corrected time domain signal, and obtain an estimated radial velocity of the moving target based on the estimated target velocity ambiguity index.

[0073] In an optional embodiment, step 4 includes:

[0074] Step 4.1: Perform time domain transformation on the first corrected frequency domain signal using range IFFT (Inverse Fast Fourier Transform) and azimuth FFT (Fast Fourier Transform) to obtain a corrected time domain signal.

[0075] In this embodiment, the modified time domain signal obtained by performing time domain transformation on the first modified frequency domain signal using range IFFT and azimuth FFT can be expressed as:

[0076]

[0077] Among them, A d is the compression gain of the slow time variable, f d is τ k The corresponding Doppler frequency variable.

[0078] In this embodiment, the corrected time domain signal can be used to focus on the moving target in the range time and azimuth Doppler domains.

[0079] Step 4.2: Focus the moving target in the range, time and azimuth Doppler domains based on the corrected time domain signal. Get the estimated target velocity ambiguity index, where f d is τ k The corresponding Doppler frequency variable, τ k is the new slow time variable, f0 is the transmitting carrier frequency of the first transmitting array element, v0 is the main velocity of the moving target, and c is the speed of light.

[0080] In this embodiment, the velocity ambiguity index is matched by using the modified time domain signal to focus the target on At this time, the estimated target speed ambiguity index can be obtained It can be expressed as:

[0081]

[0082] in, represents the fast Fourier transform along slow time, represents the inverse fast Fourier transform along the frequency range.

[0083] Step 4.3: Calculate the estimated radial velocity of the moving target based on the estimated target velocity ambiguity index.

[0084] In this embodiment, the calculation formula for the estimated radial velocity of the moving target is:

[0085]

[0086] Where, is the estimated radial velocity of the moving target, is the estimated target velocity ambiguity index, V u is the maximum unambiguous speed.

[0087] Step 5: Compensate the pulse compression frequency domain signal to obtain a compensation signal, and use the baseline transformation and the estimated target velocity ambiguity index to correct the coupling term of the compensation signal to obtain a second corrected frequency domain signal.

[0088] In an optional embodiment, step 5 includes:

[0089] Step 5.1: Construct a speed-related compensation function and use the compensation function to compensate the pulse compression frequency domain signal to obtain a compensated signal.

[0090] Due to t k and Δf m There is incoherence caused by a coupling term, which can be compensated by applying a velocity-related compensation function to the echo signal.

[0091] In this embodiment, the compensation function of the m-th matched filter output signal of the k-th pulse is expressed as:

[0092]

[0093] Where, is the compensation function of the mth matched filter output signal of the kth pulse, is the estimated target velocity ambiguity index, t k is the slow time variable, j is the imaginary unit, is the estimated main velocity of the moving target, Δfm The frequency offset of the transmitting carrier frequency of the mth transmitting array element, c is the speed of light, f0 is the transmitting carrier frequency of the first transmitting array element, T r is the pulse repetition time.

[0094] The compensated signal obtained by compensating the pulse compression frequency domain signal using the compensation function can be expressed as:

[0095] Step 5.2: Use the baseline transformation and the estimated target velocity ambiguity index to correct the coupling term of the compensation signal to obtain a second corrected frequency domain signal.

[0096] In this embodiment, after the coupling term is corrected using the baseline transformation and the estimated target velocity ambiguity index based on the compensation signal, the obtained second corrected frequency domain signal can be expressed as:

[0097] Step 6: Based on the second corrected frequency domain signal, obtain an enhanced angle estimate of the moving target in the transmit-receive domain.

[0098] In an optional embodiment, step 6 includes:

[0099] Step 6.1: According to the second corrected frequency domain signal, obtain the MN×1 dimensional vector after the k-th pulse is superimposed.

[0100] In this embodiment, first, the second modified frequency domain signal is processed using IFFF, and Substituting the second corrected signal after IFFF processing, we get:

[0101]

[0102] in,

[0103] Secondly, the k-th pulse in the second corrected signal after IFFF processing is superimposed to obtain an MN×1-dimensional vector, which can be expressed as:

[0104]

[0105] Step 6.2: Obtain the enhanced angle estimate of the moving target in the transmit-receive domain based on the MN×1 dimensional vector. The enhanced angle estimate of the moving target is expressed as:

[0106]

[0107] Where, For the enhanced angle estimation of moving targets, w H(θ) is the transmit-receive domain weight vector, K is the number of pulses, y k is a MN×1 dimensional vector, c is the speed of light, R is the distance of the moving target, θ is the angle, τ k is the new slow time variable, and H is the conjugate transpose of the matrix.

[0108] In this embodiment, the transmit-receive domain weight vector w H (θ) is used to estimate the enhanced angle of the moving target, which can be expressed as: Where b(θ) represents the receiving steering vector, d(θ) represents the launch steering vector related to the angle.

[0109]

[0110] In an optional embodiment, the frequency division MIMO radar fast moving target detection method of this embodiment further includes: performing two-dimensional beamforming in the transmit-receive domain based on the transmit-receive domain weight vector and the MN×1 dimensional vector to improve the range resolution of the frequency division MIMO radar.

[0111] In this embodiment, two-dimensional beamforming is performed in the transmit-receive domain using the transmit-receive domain weight vector and the MN×1-dimensional vector, and bandwidth splicing is performed simultaneously. The spliced ​​signal can be expressed as:

[0112]

[0113] When the frequency offset Δf = B, the above formula can be expressed as:

[0114]

[0115] Compared with the second corrected signal after IFFF processing, it can be seen that the bandwidth of the spliced ​​signal has increased by M times, which means that the range resolution performance has increased by M times and the target detection performance has been improved.

[0116] The present invention's method for detecting fast-moving targets using frequency-division MIMO radar addresses the problem of varying degrees of coupling between angle and velocity parameters introduced by frequency offsets within echo signals. By correcting the linear range offset and velocity ambiguity index, the coupling term is corrected, enabling accurate detection of the angle and velocity parameters of moving targets. Through beamforming (bandwidth splicing), range resolution performance is increased by a factor of M, allowing precise derivation of target position parameters.

[0117] Furthermore, the effect of the fast-moving target detection method of the frequency division MIMO radar of this embodiment is described through simulation experiments.

[0118] Basic parameters: Consider a fast-moving target with a signal-to-noise ratio of -30 dB before matched filtering. The target's actual range, radial velocity, and angle are 3.6 km, 1604 m / s, and 30°, respectively. The main velocity is 104 m / s, and the target velocity ambiguity index is 2.

[0119] Apply KT to the output signal corresponding to the first channel of the matched filter to obtain the estimated target velocity ambiguity index, as Figure 2 As shown, Figure 2 This is the estimation result of the target speed fuzzy index provided by the embodiment of the present invention. It can be seen from the figure that the estimated target speed fuzzy index is consistent with the real target speed fuzzy index, which illustrates the effectiveness of the method of the present invention.

[0120] Enhanced angle estimation for moving targets. Combining both transmit and receive array degrees of freedom results in lower side lobes and more accurate estimates. Figure 3 , Figure 3 is the result of the enhanced angle estimation of the moving target provided by the embodiment of the present invention, such as Figure 3 As shown, the enhanced angle estimation of the moving target is consistent with the true target angle, which illustrates the effectiveness of the method of the present invention.

[0121] Beamforming is performed based on the parameter estimation results, and the focusing results before and after beamforming are compared. Figure 4 As shown, Figure 4 This figure compares the focusing results before and after beamforming, as provided by an embodiment of the present invention. This numerical comparison reveals a 30dB increase in target amplitude. Compared to the single-channel accumulation results, beamforming not only increases the target amplitude but also achieves wide-bandwidth synthesis.

[0122] It should be noted that, in this document, relational terms such as first and second are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not explicitly listed. Without further limitation, an element defined by the phrase "comprising a..." does not preclude the presence of additional identical elements in the article or device comprising the element. Terms such as "connected" or "connected" are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. References to orientations or positional relationships, such as "upper," "lower," "left," and "right," are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate description and simplify the description of the present invention. They do not indicate or imply that the device or element referred to must have, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present invention.

[0123] The above is a further detailed description of the present invention in conjunction with specific preferred embodiments, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for detecting fast-moving targets using a frequency-division MIMO radar, characterized in that: include: Step 1: Use the receiving array element of the frequency division MIMO radar to obtain the echo signal; Step 2: After performing frequency mixing and matched filtering decomposition processing on the echo signal, a matched filtering output signal is obtained; Step 3: Converting the matched filter output signal to the frequency domain and performing pulse compression to obtain a corresponding pulse compression frequency domain signal; correcting the linear range offset and velocity ambiguity index of the pulse compression frequency domain signal to obtain a first corrected frequency domain signal; the linear range offset is caused by the main velocity of the moving target; Step 4: transforming the first corrected frequency domain signal into the time domain to obtain a corresponding corrected time domain signal, obtaining an estimated target velocity ambiguity index based on the corrected time domain signal, and obtaining an estimated radial velocity of the moving target based on the estimated target velocity ambiguity index; Step 5: Construct a compensation function related to speed, use the compensation function to compensate the pulse compression frequency domain signal to obtain a compensation signal, use the baseline transformation and the estimated target speed ambiguity index to correct the coupling term of the compensation signal to obtain a second corrected frequency domain signal; wherein, The first pulse The compensation function of the matched filter output signal is expressed as: ； Where, For the The first pulse The compensation function of the matched filter output signal, is the estimated target velocity ambiguity index, is the slow time variable, is the imaginary unit, is the estimated main velocity of the moving target, No. The frequency offset of the transmitting carrier frequency of each transmitting array element, is the speed of light, is the transmitting carrier frequency of the first transmitting array element, is the pulse repetition time; Step 6: Obtain an enhanced angle estimate of the moving target in the transmit-receive domain based on the second corrected frequency domain signal.

2. The method for detecting fast-moving targets using frequency-division MIMO radar according to claim 1, wherein: The frequency division MIMO radar includes transmit elements and receiving array elements, the There is a frequency offset between the transmitting carrier frequencies of the transmitting array elements; Among them, The receiving element receives the The echo signal of a pulse is expressed as: ； Where, For the The receiving element receives the The echo signal of a pulse, is the fast time variable, is the slow time variable, is the number of transmitting array elements, is the complex echo amplitude, For the The transmitting element and the The round-trip distance between the receiving elements of the signal transmission and reception, is the speed of light, is the imaginary unit, For the The transmitting carrier frequency of the transmitting array element, It is the waveform representation of the linear frequency modulation signal LFM.

3. The method for detecting fast-moving targets using frequency-division MIMO radar according to claim 1, wherein: The step 2 includes: Step 2.1: performing frequency mixing processing on the echo signal to obtain a mixed echo signal; Step 2.2: Decompose the mixed echo signal using a matched filter to obtain An independent matched filter output signal, is the number of transmitting array elements.

4. The method for detecting fast-moving targets using frequency-division MIMO radar according to claim 1, wherein: The step 3 includes: Step 3.1: transforming the matched filter output signal into the frequency domain to obtain a corresponding frequency domain signal; Step 3.2: performing pulse compression on the frequency domain signal according to the fixed phase principle to obtain the pulse compressed frequency domain signal; Step 3.3: Correcting the first channel data of the pulse compression frequency domain signal using a baseline transformation to eliminate the linear range offset caused by the main velocity of the moving target, thereby obtaining the first channel data after the linear range offset correction; Step 3.4: According to the first channel data after the linear range offset correction, all velocity fuzzy exponents are iteratively corrected to obtain the first corrected frequency domain signal.

5. The method for detecting fast-moving targets using frequency-division MIMO radar according to claim 1, wherein: The step 4 comprises: Step 4.1: Performing a time domain transform on the first corrected frequency domain signal using a range IFFT and an azimuth FFT to obtain the corrected time domain signal; Step 4.2: Focus the moving target in the range, time and azimuth Doppler domains based on the modified time domain signal. , obtain the estimated target speed ambiguity index, where, for The corresponding Doppler frequency variable, is the new slow time variable, is the transmitting carrier frequency of the first transmitting array element, is the main velocity of the moving target, is the speed of light; Step 4.3: Calculate the estimated radial velocity of the moving target according to the estimated target velocity ambiguity index.

6. The method for detecting fast-moving targets using frequency-division MIMO radar according to claim 5, wherein: The calculation formula of the estimated radial velocity of the moving target is: ； Where, is the estimated radial velocity of the moving target, is the estimated target velocity ambiguity index, is the maximum unambiguous speed.

7. The method for detecting fast-moving targets using frequency-division MIMO radar according to claim 1, wherein: The step 6 comprises: Step 6.1: According to the second modified frequency domain signal, obtain the After the pulse superposition dimensional vector; Step 6.2: According to the The enhanced angle estimation of the moving target is obtained by the dimensional vector in the transmit-receive domain. The enhanced angle estimation of the moving target is expressed as: ； Where, For enhanced angle estimation of moving targets, is the transmit-receive domain weight vector, is the number of pulses, for dimensional vector, is the speed of light, is the distance of the moving target, is the angle, is the new slow time variable, is the conjugate transpose of the matrix.

8. The method for detecting fast-moving targets using frequency-division MIMO radar according to claim 7, wherein: The method further comprises: according to the transmit-receive domain weight vector and the dimensional vector, and performs two-dimensional beamforming in the transmit-receive domain to improve the range resolution of the frequency division MIMO radar.

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