Recursive cubic canceller based on moving target display

Abstract

The invention discloses a recursive cubic canceller based on moving target display, which is characterized in that after a radar system receives a target echo, a radio frequency end transmits a signal to a signal processor, and the signal processor performs AD acquisition, filtering extraction, channel correction and beam forming processing on the signal; the method comprises the following steps of: firstly, performing FFT (Fast Fourier Transform) processing on the target information, and filtering static or low-speed clutters such as ground clutters through a moving target indication MTI (Moving Target Indication) canceller, finally, detecting the target information through constant false alarm detection processing, and extracting the target information through a DSP (Digital Signal Processor) end, and the canceller is a non-recursive canceller which can be divided into a primary canceller, a secondary canceller and a multi-time canceller. The defects of a low-order canceller and a high-order canceller are made up by increasing the recursion times of the cancellers, and simulation verification is carried out under various coefficient conditions. A simulation result shows that the recursive cubic canceller can obtain better passband flatness, and the signal-to-noise ratio of a to-be-detected signal is remarkably improved.

Description

Technical Field

[0001] The invention relates to the field of communications, and in particular to a recursive cubic canceller based on moving target display. Background Art

[0002] The main components of the phased array include array antenna, TR components, beam control components, power supply components, etc. Compared with traditional radar front-end systems, it has the characteristics of agile beam pointing, high system stability, and strong anti-interference ability. It is widely used in seekers, fighter radars, satellite remote sensing, etc.

[0003] Most of the existing phased array front ends are narrowband systems with relatively simple functions. At the same time, there are also problems such as low scalability and high maintenance and update costs. Compared with narrowband phased arrays, broadband phased arrays have the characteristics of multi-purpose and strong imaging capabilities. They have great advantages in the fields of bush penetration, hidden target detection, and high-resolution imaging. Compared with narrowband phased arrays, using only phase shifters to achieve beam pointing in broadband phased arrays will seriously affect the instantaneous bandwidth. Under large-angle and large-bandwidth scanning, it is directly manifested as the inconsistency of beam pointing with frequency, that is, "beam squint"; in addition, for large-angle scanning of large-aperture phased arrays, the radar pulse envelope will be separated in the time domain after pulse compression, which is the so-called "aperture transit time". Summary of the invention

[0004] The object of the present invention is to provide a recursive cubic canceller based on moving target display, which makes up for the deficiencies of low-order cancellers and high-order cancellers by increasing the number of recursions of the canceller.

[0005] To achieve the above object, the present invention provides the following technical solution: a recursive cubic canceller based on moving target display, after the radar system receives the target echo, the RF end transmits the signal to the signal processor, the signal processor performs AD acquisition, filtering extraction, channel correction, and beam synthesis processing on the signal, and then performs FFT processing on the signal and filters out static or low-speed clutter such as ground clutter through the moving target indication MTI canceller, and finally detects the target information through the constant false alarm detection process, and completes the target information extraction through the DSP end, characterized in that the canceller

[0006] The canceller is a non-recursive canceller and can be divided into a primary canceller, a secondary canceller and a multiple canceller. The primary canceller includes a delay unit and an adder, x is the time domain input sequence, n represents the sequence length, H is the frequency domain representation of the filter, z represents the z-transform, and z to the power of -1 refers to a delay unit, and its cancellation formula and its system function are:

[0007] y(n)=x(n)-x(n-1)

[0008] H(z)=1-z-1

[0009] The secondary canceller consists of two primary cancellers in cascade.

[0010] The quadratic canceller system function is:

[0011] H(z)=1-Kz -1 +z -2

[0012] A canceller with a feedback loop is called a recursive canceller. The advantage of a recursive canceller is that the frequency response of the filter can be designed through the feedback loop. Adding a feedback branch to a primary canceller is a recursive primary canceller.

[0013] Assume that the input and output are x(n) and y(n) respectively, and the intermediate variable is w(n), then the difference equation is:

[0014] y(n)=w(n)-w(n-1)

[0015] w(n)=x(n)+k1w(n-1)

[0016] After Z transformation of the above difference equation:

[0017] Y(z)=W(z)-W(z)z -1

[0018] W(z)=X(z)+K1W(z)z -1

[0019] From this we can get the system function:

[0020]

[0021] Similarly, the system function of the recursive quadratic canceller can be obtained:

[0022]

[0023] Similarly, for the recursive cubic canceller, coefficient K1 is the feedforward coefficient, and coefficients K2, K3, and K4 are feedback coefficients. The system function of the recursive cubic canceller is:

[0024]

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The shortcomings of low-order and high-order cancellers are compensated by increasing the number of recursions of the canceller, and simulation verification is performed under various coefficient conditions. The simulation results show that the recursive cubic canceller can obtain better passband flatness and significantly improve the signal-to-noise ratio of the signal to be detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a structural diagram of the primary canceller of the present invention;

[0028] Figure 2 It is a secondary canceller of the present invention;

[0029] Figure 3 The comparison of the frequency domain characteristics of the primary canceller, the secondary canceller and the tertiary canceller of the present invention is shown in the figure;

[0030] Figure 4 A recursive primary canceller of the present invention;

[0031] Figure 5 A recursive quadratic canceller according to the present invention;

[0032] Figure 6 A recursive cubic canceller of the present invention;

[0033] Figure 7 A comparison diagram of simulation results of different cancellers of the present invention;

[0034] Figure 8 : is the frequency response curve of the recursive cubic canceller under different parameters of the present invention;

[0035] Fig. 9 It is the distance dimension FFT result of the present invention;

[0036] Fig.10 is the processing result of the primary canceller of the present invention;

[0037] Fig.11 is the processing result of the third canceller of the present invention;

[0038] Fig.12 The processing result of the recursive three-time canceller of the present invention;

[0039] Fig.13 A three-dimensional graph is processed by the recursive cubic canceller of the present invention. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] like Figure 1As shown, the present invention provides a recursive cubic canceller based on moving target display. After the radar system receives the target echo, the radio frequency end transmits the signal to the signal processor, and the signal processor performs AD acquisition, filtering extraction, channel correction, and beam synthesis processing on the signal, and then performs FFT processing on the signal and filters out static or low-speed clutter such as ground clutter through the moving target indication MTI canceller. Finally, the target information is detected through the constant false alarm detection process, and the target information is extracted through the DSP end.

[0042] The canceller is a non-recursive canceller and can be divided into a primary canceller, a secondary canceller and a multiple canceller. The primary canceller is also called a double pulse canceller, which has a simple structure and is easy to implement. It is mainly composed of a delay unit and an adder. x is the time domain input sequence, n represents the sequence length, H is the frequency domain representation of the filter, z represents the z transformation, and z to the power of -1 refers to a delay unit. Its cancellation formula and its system function are:

[0043] y(n)=x(n)-x(n-1)

[0044] H(z)=1-z -1

[0045] The structure diagram of the primary canceller is as follows: Figure 1 As shown:

[0046] The secondary canceller is also called a three-pulse canceller. It is composed of two primary cancellers in cascade. It is usually used to solve the problem of limited noise suppression capability of the primary canceller. Its structure is shown in the figure below. Figure 2 As shown:

[0047] The quadratic canceller system function is:

[0048] H(z)=1-Kz -1 +z -2

[0049] Comparison of frequency domain characteristics of primary canceller, secondary canceller, and tertiary canceller Figure 3 As shown:

[0050] A canceller with a feedback loop is called a recursive canceller. The advantage of a recursive canceller is that the frequency response of the filter can be designed through the feedback loop. Adding a feedback branch to a primary canceller is a recursive primary canceller. Its structure is shown in the figure below. Figure 4 As shown:

[0051] Assume that the input and output are x(n) and y(n) respectively, and the intermediate variable is w(n), then the difference equation is:

[0052] y(n)=w(n)-w(n-1)

[0053] w(n)=x(n)+k1w(n-1)

[0054] After Z transformation of the above difference equation:

[0055] Y(z)=W(z)-W(z)z -1

[0056] W(z)=X(z)+K1W(z)z -1

[0057] From this we can get the system function:

[0058]

[0059] Similarly, the system function and structure diagram of the recursive quadratic canceller can be obtained. The structure diagram of the recursive quadratic canceller is as follows: Figure 5 As shown:

[0060]

[0061] Similarly, for the recursive cubic canceller, coefficient K1 is the feedforward coefficient, and coefficients K2, K3, and K4 are feedback coefficients. The system function of the recursive cubic canceller is:

[0062]

[0063] The structure diagram of the recursive cubic canceller is as follows: Figure 6 As shown,

[0064] In this comparative simulation, the primary, triple, recursive primary, and recursive triple cancellers are compared and analyzed. The K1 in the recursive primary canceller is 0.25. The coefficients in the recursive triple canceller are [0.99, 0.70, -0.24, 0.6]. Figure 7 shown.

[0065] It can be seen from the simulation comparison result diagram that the passband width of the primary canceller is large, but the passband flatness and stopband are small, and it cannot fully filter out the clutter with spectrum broadening in typical scenarios; the passband width of the recursive primary canceller is larger, but the passband flatness and stopband are small, and it cannot fully filter out the clutter with spectrum broadening in typical scenarios; although the cubic canceller can filter out clutter in typical scenarios, its passband flatness and passband width performance are poor; the recursive cubic canceller has the best passband flatness and passband width performance, and its performance is better than other cancellers.

[0066] Comparative analysis of simulations of recursive cubic cancellers with different coefficients. In this simulation, K1, K2, K3, and K4 in coefficient 1 are [0.99, 0.8, -0.6, 0.05]; K1, K2, K3, and K4 in coefficient 2 are [1, 1.2, -0.7, 0.089]; K1, K2, K3, and K4 in coefficient 3 are [0.99, 0.70, -0.24, 0.6]; The frequency response curves of the recursive cubic canceller under different parameters are shown in Figure 2. Figure 8 As shown:

[0067] As can be seen from the figure, within the passband range, the frequency response curves of the cancellers with coefficients 1 and 2 have ripples, and the gain within the stopband range is also above -50dB; in comparison, the canceller with coefficient 3 has a large gain peak within the stopband range, but does not have the above-mentioned ripple problem.

[0068] 1. In this data simulation experiment, 100 groups of linear frequency modulation continuous wave signals are generated. In addition, three low-speed targets are set at distances of 2000m, 3000m and 4000m, respectively, and at speeds of 2m / s, 0m / s, and -2m / s, respectively. The amplitude of the target echo signal is 1. According to the above target parameters, simulated echo signals are generated, and Gaussian white noise with a signal-to-noise ratio of 10dB is added as the signal background noise to obtain simulated echo signals with Gaussian white noise added. In the next step, the signal is subjected to distance-dimensional FFT operation, and then subjected to multiple cancellation processing to obtain the required simulation experiment results. Figure 9-12 shown.

[0069] The above picture shows the simulation results, where Fig. 9 is the distance dimension FFT result, Fig.10 is the processing result of the primary canceller, Fig.11 is the processing result of the third canceller, Fig.12 is the result of the recursive cubic canceller, where the coefficient of the recursive cubic canceller is 3.

[0070] Fig.13 This is a three-dimensional image obtained after the recursive cubic canceller cancels the signal. It can be seen from the figure that the moving target can be successfully displayed.

[0071] Depend on Fig. 9 It can be seen that after the distance dimension FFT, the target distance information is successfully obtained, but it is necessary to determine whether the target is a stationary target or a moving target. Among the three targets, target 2 is a stationary target. It can be seen from the simulation result diagram that the primary, triple and recursive triple cancellers can successfully detect the moving target. However, Fig.10,11 shows that as the number of cancellations of the non-recursive canceller increases, the detection effect on target three gradually weakens. This is because the gain of the multiple canceller in-band varies greatly with the Doppler frequency, especially in the lower part of the sine square curve, where the gain is very low, which may suppress the echo of the moving target. Fig.12 It can be seen that the recursive cubic canceller has better passband flatness due to the feedback system, which can effectively improve the detection performance of the target.

[0072] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above technical means, but also include technical solutions composed of equivalent replacement of the above technical features. Matters not covered in the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A recursive cubic canceller based on moving target indication. After the radar system receives the target echo, the RF end transmits the signal to the signal processor. The signal processor performs AD acquisition, filtering extraction, channel correction, and beam synthesis processing on the signal. Then, it performs FFT processing and filters out static or low-speed clutter such as ground clutter through the moving target indication MTI canceller. Finally, the target information is detected through constant false alarm detection processing, and the target information is extracted through the DSP end. It is characterized in that: Canceller The canceller is a non-recursive canceller and can be divided into a primary canceller, a secondary canceller and a multiple canceller, wherein the primary canceller includes a delay unit and an adder, x is a time domain input sequence, n represents the sequence length, H is the frequency domain representation of the filter, z represents a z-transform, and z to the power of -1 refers to a delay unit, and its cancellation formula and its system function are: y(n)=x(n)-x(n-1) H(z)=1-z -1 The secondary canceller consists of two primary cancellers in cascade. The quadratic canceller system function is: H(z)=1-Kz -1 +z -2 A canceller with a feedback loop is called a recursive canceller. The advantage of a recursive canceller is that the frequency response of the filter can be designed through the feedback loop. Adding a feedback branch to a primary canceller is a recursive primary canceller. Assume that the input and output are x(n) and y(n) respectively, and the intermediate variable is w(n), then the difference equation is: y(n)=w(n)-w(n-1) w(n)=x(n)+k1w(n-1) After Z transformation of the above difference equation: Y(z)=W(z)-W(z)z -1 W(z)=X(z)+K1W(z)z -1 From this we can get the system function: Similarly, the system function of the recursive quadratic canceller can be obtained: Similarly, for the recursive cubic canceller, coefficient K1 is the feedforward coefficient, coefficients K2, K3 and K4 are feedback coefficients, and the system function of the recursive cubic canceller is:

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