A constant position LFM radar group target synthesis method

Abstract

The application provides a position constant LFM radar group target synthesis method, and is characterized by the following steps: step one, mixing the LFM radar signal with a time delayed signal, processing the frequency difference to obtain an intermittent sampling frequency f s , forming an intermittent sampling control signal p(t|f s ); step two, mixing the LFM radar signal with a time delayed signal, processing the frequency difference to obtain a frequency shift frequency Δf, forming a bidirectional frequency shift control signal v(t|Δf); step three, sequentially processing the LFM radar signal by intermittent sampling and bidirectional frequency shift control to obtain a group target simulation signal. The application solves the problem of position jump in the group target synthesis method of fixed intermittent sampling frequency intermittent sampling processing or fixed frequency shift frequency frequency shift control processing. The group target synthesized by the application has an expanded distance coverage range, which is beneficial to synthesizing a group target with a wider distance coverage range. Meanwhile, the position constant group target synthesis method is relatively simple to implement.

Description

[Technical Field]

[0001] This invention proposes a group target synthesis method for frequency-modulated slope-agile linear frequency (LFM) radar, which relates to the field of LFM radar signal processing, specifically to frequency-modulated slope-agile LFM radar signal simulation and processing technology, and particularly to a position-constant group target synthesis method for frequency-modulated slope-agile LFM radar. [Background Technology]

[0002] Electromagnetic environment simulation is crucial for performance testing of electronic information equipment such as radar. Traditional methods for swarm target simulation mainly include delay methods, intermittent sampling methods, and frequency shifting methods. For advanced LFM radars such as those with frequency modulation slope agility, traditional swarm target simulation techniques suffer from problems such as high system resource consumption and abrupt changes in swarm target positions. How to conveniently and quickly synthesize swarm targets with constant positions for effective accumulation is one of the challenges in the field of electromagnetic environment simulation technology for advanced radars such as those with frequency modulation slope agility. [Summary of the Invention]

[0003] The technical problem to be solved by this invention is: to propose a position-constant LFM radar group target synthesis method under the condition of frequency modulation slope agility;

[0004] The technical solution adopted in this invention is as follows:

[0005] The first step is to mix the LFM radar signal with its own time-delay signal and calculate the frequency difference to obtain the intermittent sampling frequency f. s This generates an intermittent sampling control signal p(t|f) s ).

[0006] The LFM radar signal is denoted as u(t), and delayed by Δτ1 to obtain the time-delayed signal u(t-Δτ1). u(t) and u(t-Δτ1) are mixed to obtain the signal Δu1(t), and the frequency difference of the Δu1(t) signal is calculated. This frequency difference is used as the intermittent sampling frequency f. s This generates an intermittent sampling control signal p(t|f) s ).

[0007] The second step involves mixing the LFM radar signal with its own time delay signal and calculating the frequency difference to obtain the frequency shift frequency Δf, thus forming a two-way frequency shift control signal v(t|Δf).

[0008] The LFM radar signal is delayed by Δτ2 to obtain the time-delayed signal u(t-Δτ2); u(t) and u(t-Δτ2) are mixed to obtain the signal Δu2(t), and the frequency difference of the Δu2(t) signal is obtained. This frequency difference is used as the frequency shifting frequency Δf, thereby forming the two-way frequency shifting control signal v(t|Δf).

[0009] The third step involves sequentially performing intermittent sampling and two-way frequency shift control processing on the LFM radar signal to obtain a simulated group target signal.

[0010] The intermittent sampling control signal p(t|f) s The two-way frequency shift control signal v(t|Δf) is multiplied with the LFM radar signal u(t) to complete the intermittent sampling processing and two-way frequency shift control processing in sequence, thereby obtaining the simulated target group signal u. S (t).

[0011] The advantages of this invention are:

[0012] First, it solves the problem of target position jumps when the LFM radar signal frequency modulation slope is agile, which is a problem in group target synthesis methods such as intermittent sampling processing with fixed intermittent sampling frequency or frequency shift control processing with fixed frequency shift frequency.

[0013] Second, compared with traditional group target synthesis methods such as intermittent sampling processing or frequency shift control, the group targets synthesized by this invention have an expanded range in the range direction, which is beneficial for synthesizing group targets with a wider range of range coverage.

[0014] Third, the position-constant group target synthesis method is relatively simple to implement. It only requires mixing the LFM radar signal with two time-delayed signals to calculate the frequency difference, then synthesizing the intermittent sampling control signal and the bidirectional frequency shift control signal, and then multiplying them with the LFM radar signal in sequence. [Attached Image Description]

[0015] Figure 1 This is a block diagram of the location-constant group target synthesis method.

[0016] Figure 2(a) shows the swarm targets synthesized when intermittent sampling is performed alone.

[0017] Figure 2(b) shows the synthesized swarm target when bidirectional frequency shift control is performed alone.

[0018] Figure 2(c) shows the swarm target synthesized by the method of the present invention.

[0019] Figure 3(a) shows the situation before the accumulation of target pulses synthesized by intermittent sampling processing at a fixed intermittent sampling frequency and bidirectional frequency shift control processing at a fixed frequency shift when the frequency modulation slope of the LFM radar signal changes.

[0020] Figure 3(b) shows the result of the accumulation of target pulses synthesized from intermittent sampling processing at a fixed intermittent sampling frequency and bidirectional frequency shift control processing at a fixed frequency shifting frequency when the frequency modulation slope of the LFM radar signal changes.

[0021] Figure 4(a) shows the situation before the accumulation of target pulses synthesized by the method of the present invention when the frequency modulation slope of the LFM radar signal changes.

[0022] Figure 4(b) shows the accumulation of target pulses synthesized by the method of the present invention when the frequency modulation slope of the LFM radar signal changes.

Detailed Implementation Methods

[0023] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings:

[0024] A method for synthesizing targets in a position-constant LFM radar group includes the following steps:

[0025] The first step is to mix the LFM radar signal u(t) with its own time-delayed signal Δτ1 and calculate the frequency difference to obtain the intermittent sampling frequency f. s This generates an intermittent sampling control signal p(t|f) s ).

[0026] Let the LFM radar signal u(t) be...

[0027]

[0028] Where rect(·) is a rectangular window function, and t is a time variable. The imaginary unit is , k is the LFM signal frequency modulation slope, and T represents the radar pulse duration.

[0029] Delaying u(t) by Δτ1 yields the time-delayed signal u(t-Δτ1):

[0030]

[0031] Mixing u(t) with u(t-Δτ1) yields the signal Δu1(t):

[0032]

[0033] The asterisk (*) indicates conjugate.

[0034] The signal Δu1(t) is input to the frequency discriminator to obtain the frequency difference kΔτ1. This frequency difference is used as the intermittent sampling frequency, i.e., f. s =kΔτ1, thus obtaining the intermittent sampling control signal:

[0035]

[0036] in denoted as convolution, n is an integer representing the order of the short pulse in the intermittent sampling control signal, τ is the width of the intermittent sampling pulse, and δ(·) is the impulse function.

[0037] The second step involves mixing the LFM radar signal u(t) with its own time-delayed signal Δτ2 and calculating the frequency difference to obtain the frequency shift frequency Δf, thus forming the bidirectional frequency shift control signal v(t|Δf).

[0038] Delaying u(t) by Δτ2 yields the time-delayed signal u(t-Δτ2):

[0039]

[0040] Mixing u(t) with u(t-Δτ2) yields the signal Δu2(t):

[0041]

[0042] The signal Δu2(t) is input to the frequency discriminator to obtain the frequency difference kΔτ2. This frequency difference is used as the frequency shift frequency, i.e., Δf = kΔτ2, to obtain the bidirectional frequency shift control signal.

[0043]

[0044] The third step involves sequentially performing intermittent sampling and two-way frequency shift control processing on the LFM radar signal to obtain the simulated target group signal u. S (t)

[0045] The intermittent sampling control signal p(t|f) s The two-way frequency shift control signal v(t|Δf) is multiplied with the LFM radar signal u(t) to complete the intermittent sampling processing and two-way frequency shift control processing in sequence, thereby obtaining the simulated target group signal u. S (t):

[0046] u S (t)=u(t)p(t|f s )v(t|Δf) (Formula 8)

[0047] Signal u S The amplitude y(t) of the output signal after processing by the radar matched filter is:

[0048]

[0049] in,

[0050] As can be seen from Equation 9, intermittent sampling and bidirectional frequency shifting control will produce two symmetrically distributed groups of targets on the time axis, with the peak position of the group targets appearing at:

[0051]

[0052] in, This indicates the peak position of the group target generated by positive frequency shift control. This indicates the peak position of the group target generated by negative frequency shift control.

[0053] The possible distribution range Δt of the group of targets is:

[0054]

[0055] Where N represents the maximum order of a target among a group of targets that can be detected by radar.

[0056] Formula 10 shows that when the LFM radar signal frequency modulation slope k changes, with fixed delays Δτ1 and Δτ2, the intermittent sampling frequency f... s =kΔτ1 and the frequency shift frequency Δf =kΔτ2 are adaptively adjusted with the frequency modulation slope k, so the peak position of the group target remains constant. Similarly, as can be seen from Equation 11, compared with the individual intermittent sampling processing and frequency shift control processing, the group target distribution range synthesized by the method of this invention can be wider, bringing more degrees of freedom for practical applications.

[0057] like Figure 1 The diagram shows the implementation block diagram of the position-constant group target synthesis method. Assume the LFM signal pulse length is 100µs, and the frequency modulation slopes corresponding to three adjacent LFM signal pulses are k = 3 × 10⁻⁶. 11 Hz / s, 2×10 11 Hz / s and 1×10 11 Hz / s.

[0058] Figures 2(a) to 2(c) are comparison diagrams of swarm targets synthesized by different methods. Figure 2(a) shows the swarm targets synthesized using different methods. s Figure 2(b) shows the group targets synthesized when Δf = 0.56MHz and intermittent sampling is performed alone; Figure 2(c) shows the group targets synthesized when Δf = 2.78MHz and bidirectional frequency shift control is performed alone; s When Δ = 0.56 MHz and Δf = 2.78 MHz, the group targets synthesized by the method of the present invention are as follows. Comparing Figures 2(a) to 2(c), it can be seen that the group targets synthesized by the method of the present invention are symmetrically distributed along the time axis, and the range of group targets synthesized by the method is wider than that synthesized by individual intermittent sampling processing or frequency shift control processing methods.

[0059] Figures 3(a) and 3(b) show the corresponding frequency modulation slope k = 3 × 10 11 Hz / s, 2×10 11 Hz / s and 1×10 11 At Hz / s, a fixed intermittent sampling frequency f sA group of targets was synthesized by intermittent sampling processing at 0.5 MHz and bidirectional frequency shift control processing at a fixed frequency shift Δf = 3 MHz. Figure 3(a) shows the group of targets before pulse accumulation, and Figure 3(b) shows the group of targets after pulse accumulation. As can be seen from Figure 3(a), because the intermittent sampling frequency and frequency shift frequency are fixed, the synthesized group of targets undergoes positional jumps between the three pulses where the frequency modulation slope changes; as can be seen from Figure 3(b), it is difficult for the group of targets to form effective accumulation.

[0060] Figures 4(a) and 4(b) show the corresponding frequency modulation slope k = 3 × 10 11 Hz / s, 2×10 11 Hz / s and 1×10 11 At Hz / s, the group targets synthesized by the method of this invention. Δτ1 = 1.85µs, Δτ2 = 1.67µs are set, so that the intermittent sampling frequency and frequency shift modulation amount automatically change with the frequency modulation slope; wherein, in the first group target synthesis pulse signal, f s =0.56MHz, Δf=0.5MHz, in the second group target synthesized pulse signal f s =0.37MHz, Δf=0.33MHz, in the third group target synthesized pulse signal f s =0.19MHz, Δf=0.17MHz; As can be seen from Figure 4(a), since the intermittent sampling frequency and frequency shift frequency adaptively change with the frequency modulation slope, the group target maintains a constant position when the frequency modulation slope changes; Comparing Figure 3(b) and Figure 4(b), it can be found that the group target synthesized by the method of the present invention can form an effective accumulation.

Claims

1. A method for synthesizing target groups using a position-constant LFM radar, characterized in that: The steps are as follows: Step 1: Mix the LFM radar signal with its own time-delay signal and calculate the frequency difference to obtain the intermittent sampling frequency f. s This generates an intermittent sampling control signal p(t|f) s ); The LFM radar signal is denoted as u(t), and delayed by Δτ1 to obtain the time-delayed signal u(t-Δτ1). u(t) and u(t-Δτ1) are mixed to obtain the signal Δu1(t), and the frequency difference of the Δu1(t) signal is calculated. This frequency difference is used as the intermittent sampling frequency f. s This generates an intermittent sampling control signal p(t|f) s ); Step 2: Mix the LFM radar signal with its own time delay signal and calculate the frequency difference to obtain the frequency shift frequency Δf, forming a two-way frequency shift control signal v(t|Δf); The LFM radar signal is delayed by Δτ2 to obtain the time-delayed signal u(t-Δτ2); u(t) and u(t-Δτ2) are mixed to obtain the signal Δu2(t), and the frequency difference of the Δu2(t) signal is calculated. This frequency difference is used as the frequency shifting frequency Δf, thereby forming the two-way frequency shifting control signal v(t|Δf). Step 3: The LFM radar signal is subjected to intermittent sampling and two-way frequency shift control processing in sequence to obtain the simulated signal of the group target; The intermittent sampling control signal p(t|f) s The two-way frequency shift control signal v(t|Δf) is multiplied with the LFM radar signal u(t) to complete the intermittent sampling processing and two-way frequency shift control processing in sequence, thereby obtaining the simulated target group signal u. S (t).

2. The method for synthesizing target groups using a position-constant LFM radar according to claim 1, characterized in that: In step one, let the LFM radar signal u(t) be: Where rect(·) is a rectangular window function, and t is a time variable. The imaginary unit is , k is the LFM signal frequency modulation slope, and T represents the radar pulse duration.

3. A position-constant LFM radar swarm target synthesis method according to claim 1 or 2, characterized in that: In step one, u(t) is delayed by Δτ1 to obtain the time-delayed signal u(t-Δτ1): Mixing u(t) with u(t-Δτ1) yields the signal Δu1(t): The asterisk (*) indicates conjugate.

4. The method for synthesizing target groups in a position-constant LFM radar system according to claim 3, characterized in that: In step one, the signal Δu1(t) is input to the frequency discriminator to obtain the frequency difference kΔτ1, and this frequency difference is used as the intermittent sampling frequency, i.e., f. s =kΔτ1, thus obtaining the intermittent sampling control signal: in denoted as convolution, n is an integer representing the order of the short pulse in the intermittent sampling control signal, τ is the width of the intermittent sampling pulse, and δ(·) is the impulse function.

5. The method for synthesizing target groups in a position-constant LFM radar system according to claim 1, characterized in that: In step two, u(t) is delayed by Δτ2 to obtain the time-delayed signal u(t-Δτ2): Mixing u(t) with u(t-Δτ2) yields the signal Δu2(t): Where k is the LFM signal frequency modulation slope, and T represents the radar pulse duration.

6. The method for synthesizing target groups in a position-constant LFM radar according to claim 5, characterized in that: In step two, the signal Δu2(t) is input to the frequency discriminator to obtain the frequency difference kΔτ2. This frequency difference is used as the frequency shift frequency, i.e., Δf = kΔτ2, to obtain the bidirectional frequency shift control signal.

7. The method for synthesizing target groups using a position-constant LFM radar according to claim 1, characterized in that: In step three, the intermittent sampling control signal p(t|f) is used. s The two-way frequency shift control signal v(t|Δf) is multiplied with the LFM radar signal u(t) to complete the intermittent sampling processing and two-way frequency shift control processing in sequence, thereby obtaining the simulated target group signal u. S (t): u S (t)=u(t)p(t|f s v(t|Δf)(Formula 8).

8. A position-constant LFM radar swarm target synthesis method according to claim 1 or 7, characterized in that: In step three, signal u S The amplitude y(t) of the output signal after processing by the radar matched filter is: Among them, a n =τf s Sa(nπτf s ), T represents the duration of the radar pulse, and τ is the width of the intermittent sampling pulse.

9. A method for synthesizing target groups in a position-constant LFM radar system according to claim 8, characterized in that: In step three, intermittent sampling and bidirectional frequency shifting control will generate two symmetrically distributed groups of targets on the time axis. The peak position of the group targets appears at: in, This indicates the peak position of the group target generated by positive frequency shift control. This indicates the peak position of the target group generated by negative frequency shift control, and k is the frequency modulation slope of the LFM signal.

10. A method for synthesizing target groups in a position-constant LFM radar system according to claim 9, characterized in that: In step three, the range Δt of the group target distribution is: Where N represents the maximum order of the target among the group of targets detected by the radar; when the frequency modulation slope k of the LFM radar signal changes, with fixed delays Δτ1 and Δτ2, the intermittent sampling frequency f s =kΔτ1 and the frequency shift frequency Δf =kΔτ2 are adaptively adjusted with the frequency modulation slope k, so the peak position of the group target remains constant.

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