Single carrier frequency coherent pulse radar target speed characteristic modulation method based on intermittent sampling and forwarding

Abstract

The invention provides a single-carrier-frequency coherent pulse radar target speed characteristic modulation method based on intermittent sampling and forwarding. The method comprises the following steps: step 1, intercepting radar transmitting signals and estimating parameters; 2, determining an ISRJ (Intermittent Sampling and Forwarding Interference) control signal parameter according to a preset interference effect; step 3, periodically sampling and forwarding radar emission signals; and 4, generating a speed false target. The invention innovatively provides a single-carrier-frequency coherent pulse radar target speed deception jamming method based on intermittent sampling and forwarding, and the application of the intermittent sampling and forwarding technology in the aspect of radar speed measurement jamming is expanded. Compared with frequency shift forwarding interference and other forwarding type speed measurement interference methods based on the DRFM technology, the single carrier frequency coherent pulse radar target speed deception interference method based on intermittent sampling forwarding provided by the invention directly performs forwarding operation after sampling, and has lower signal processing time delay and better realizability. Compared with the traditional passive interference, the method has obvious advantages in the aspect of interference energy.

Description

Technical Field

[0001] A method for modulating the target velocity characteristics of a single-carrier frequency coherent pulse radar based on intermittent sampling and forwarding belongs to the technical field of radar active jamming. Specifically, it relates to the field of speed measurement jamming of single-carrier frequency coherent pulse radars. Further, by quickly sampling and forwarding the received radar signals, the radar speed measurement processing results are severely distorted, thereby confusing and deceiving the single-carrier frequency coherent pulse radar system.

Background Art

[0002] Coherent radars using techniques such as coherent integration can obtain extremely high signal coherent processing gains by utilizing the coherence of their waveforms within or between pulses, and are one of the most widely used radar systems today. As one of the most representative narrowband coherent radars, single-carrier frequency coherent pulse radars are widely used in important aspects such as ground moving target surveillance and short-range fire control systems. To effectively reduce the exposure risk of high-value combat targets during maneuvers, developing interference techniques for single-carrier frequency coherent pulse radars has great theoretical value and practical prospects.

[0003] The emergence of coherent radars has significantly suppressed the interference effectiveness of traditional blocking interference methods such as noise interference. If one wants to effectively interfere with coherent radars using blocking interference, it is necessary to greatly increase the transmitting power of the jammer, which is obviously not advisable. Thus, it forces the interfering party to adopt coherent interference techniques for countermeasures. The core of coherent interference techniques is to utilize the coherent characteristics of radar signals, and by generating interference signals highly correlated with the radar transmitted signals, the interference signals also obtain high coherent processing gains, thereby achieving a suppression or deception interference effect on coherent radars. Coherent interference can be achieved through two means: one is to perform high-precision parameter estimation on the intercepted radar signals, and the jammer generates an interference signal highly coherent with it based on the estimated parameters. This requires the interfering party to predict the other party's radar system in advance and obtain the in-pulse characteristics of the signals in real time, which is difficult; the other is to sample the radar signals without distortion and then forward them, also known as repeater jamming, which has been widely applied due to its simple principle and engineering implementation. With the emergence of advanced electronic devices such as high-speed broadband ADCs and DACs, especially the gradual maturity of Digital Radio Frequency Memory (DRFM) technology, it provides strong technical support for the engineering implementation of repeater jamming. Currently, many research works have confirmed that DRFM technology can be used for deceptive jamming of coherent pulse train signals, such as frequency shift jamming, pulse skipping jamming, etc.

[0004] Interrupted-Sampling Repeater Jamming (ISRJ) technology is a new type of repeater jamming technology based on DRFM technology, which was first proposed by Wang Xuesong et al. from the National University of Defense Technology in 2006. The proposal of ISRJ is to solve the two major problems of high-speed sampling and isolation degree between transmitting and receiving antennas faced by repeater jammers when dealing with large time-bandwidth radar signals such as linear frequency modulation signals. Its core idea is to sample and forward a small segment of radar signal with high fidelity, then continuously sample the next small segment of radar pulse signal and forward it. Such short-time sampling and short-time forwarding are carried out quickly and alternately until the end of the entire radar pulse signal. Since its proposal, ISRJ has developed for more than a decade. Researchers have greatly enriched the interference patterns of ISRJ by diversely modulating the sampled signals before forwarding or adopting different forwarding strategies.

[0005] In recent years, Xu Letao, Feng Dejun et al. from the National University of Defense Technology have systematically and deeply carried out research on the interrupted-sampling repeater jamming of broadband radar systems. They have respectively studied the characteristics of radar signals after sampling, the one-dimensional ranging deception jamming method for broadband radars based on ISRJ, and the ISAR imaging deception jamming method based on ISRJ, and achieved rich research results. Considering that the periodic "sampling-forwarding" process of ISRJ can essentially disrupt the phase coherence between radar emission pulses regularly and greatly disturb the spectral structure of the real target echo signal. On the other hand, the velocity measurement result of a single-carrier coherent pulse radar is very sensitive to the spectral structure of the radar echo. Therefore, this characteristic can be applied to the target velocity deception jamming of a single-carrier coherent pulse radar, making it difficult to perceive the motion of the real target and further improving the survival ability of high-value combat maneuvering targets.

Summary of the Invention

[0006] The present invention aims to enrich the theoretical system of the action mechanism of ISRJ in more characteristic dimensions and fill the gap in the research on the interference effect of ISRJ on single-frequency coherent pulse radars. It proposes a method for modulating the target velocity characteristics of a single-carrier coherent pulse radar based on interrupted-sampling forwarding. Its core idea is to use DRFM technology to perform high-speed periodic sampling-forwarding on the radar echo. After the echo signal is processed by coherent accumulation, multiple false targets with different false velocities appear in the radar velocity measurement result. By adjusting the parameters of the jammer, the velocity, quantity, and energy intensity of the false targets can be controlled. To achieve the above-mentioned velocity deception jamming effect, this method is implemented through the following steps:

[0007] Step 1: Interception and parameter estimation of the radar transmission signal

[0008] Use the electronic reconnaissance device integrated in the interference system to intercept the radar transmission signal, locate the azimuth of the opponent's radar, and estimate the basic parameters of the signal waveform from it, including: carrier frequency f c, signal wavelength λ, pulse width T p , pulse repetition frequency f r .

[0009] Step 2: Determine the ISRJ control signal parameters according to the preset interference effect

[0010] In the intermittent sampling and forwarding interference, the process of completing single sampling and single forwarding of the intercepted radar signal within a sampling-forwarding cycle (hereinafter referred to as "sampling cycle") can be equivalent to applying a pulsed ISRJ control signal to the original radar signal, that is, the pulse width is τ and the period is T s of (the corresponding frequency is its reciprocal f s ) pulsed control signal p(t). Without considering velocity ambiguity, the velocity spectrum V of the deceptive false target generated by the present invention can be represented by , where δ(·) is the impulse function, v represents the velocity value, v0 is the velocity value of the real target, and a n is the energy intensity of the nth harmonic spectral line of the ISDJ control signal spectrum, which can be represented by a n = a n = τf s Sa(nτf s π)exp(-jnτf s π), k i is the energy intensity of the ith spectral line of the original signal comb spectrum (determined by the radar signal pulse width T p and pulse repetition frequency f r ). In summary, the energy intensity of the false target with velocity value is a n k i , that is, the velocity value of the false target, the situation of the number and energy intensity of the deceptive false target are jointly determined by the ISRJ control signal parameters (pulse width τ, frequency f s ) and the radar transmission signal parameters (pulse width T p , wavelength λ, pulse repetition frequency f r ). According to the different requirements of wartime strategies, first set the expected interference effect to be achieved, such as equally spaced false target interference, scattered false target interference, class suppression multi-false target interference, single main false target interference, etc., and then combine the previously intercepted target radar waveform parameters to further determine the parameters of the ISRJ control signal: ① Equally spaced false target interference: Determine the ISRJ control signal frequency f r according to the magnitude of the pulse repetition frequency f s so that the false target velocity is equally spaced; ② Scattered false target interference: Determine the ISRJ control signal frequency f r according to the magnitude of the pulse repetition frequency f s so that the false target velocity Scattered distribution; ③ Type suppression multi-false target interference: according to the pulse repetition frequency f r The size of the ISRJ control signal frequency f s , making the false target speed As close to each other as possible, on this basis, control the ISRJ control signal pulse width τ, slow down a n Energy attenuation caused by; ④ Single main false target interference: control the ISRJ control signal pulse width τ, strengthen a n The energy attenuation caused by this makes the energy intensity of the false target a n k i When n>1, it decays rapidly to a very low level. On this basis, according to the pulse repetition frequency f r The size of the ISRJ control signal frequency f s , control the main false target speed to

[0011] Step 3: Periodic sampling - forwarding radar transmission signal

[0012] According to the ISRJ control signal parameters determined in step 2: pulse width τ and frequency f s , configure the ISRJ jammer in a sampling period T s The sampling time width τ and sampling frequency f s (corresponding to the above ISRJ control signal parameters one by one, represented by the same symbols), the jammer configures the radar transmit signal with a frequency of f according to the above parameters. s The signal is sampled periodically. In each sampling period, the sampled signal slice with a duration of τ is reduced to the intermediate frequency. After completing the signal processing processes such as low-pass filtering, A / D conversion, storage, and D / A conversion in DRFM, it is immediately forwarded through the mixer at the ISRJ transmitting end. In order to make the interference signal energy generated by the jammer significantly greater than the radar echo energy of the real target, it is necessary to rely on a high-power transmitting antenna to align with the radar wave direction for forwarding radiation.

[0013] Step 4: Generation of speed false target

[0014] The interference signal j(t) generated by ISRJ enters the single-carrier coherent pulse radar system and is mixed with the local oscillator signal s in the mixer at the front end of the radar receiver. o (t) = exp(-j2πf c t) is multiplied to obtain the intermediate frequency signal, and the interfered baseband signal j after baseband filtering base (t) After further coherent accumulation processing, the false target interference result preset by step 2 will be displayed, that is, the speed measurement deception interference effect of the method proposed in the present invention is achieved.

[0015] The beneficial effects of the present invention are:

[0016] First, an innovative method for spoofing the target velocity of a single-carrier coherent pulse radar based on intermittent sampling and forwarding is proposed, expanding the application of intermittent sampling and forwarding technology in radar velocity measurement interference.

[0017] Second, compared with other forwarding-type velocity measurement interference methods based on DRFM technology, the method for spoofing the target velocity of a single-carrier coherent pulse radar based on intermittent sampling and forwarding proposed in the present invention directly performs a forwarding operation after sampling, having a lower signal processing delay and better feasibility. Compared with traditional passive interference, it has a significant advantage in terms of interference energy.

[0018] Third, by deeply combining the spectral characteristics of the single-carrier coherent pulse signal emitted by the radar itself, a mapping analysis model between the jammer parameters and the interference effect is established, enabling users to simply change the duty cycle D and pulse width τ of the ISRJ pulsed control signal to generate flexible and rich interference effects such as equally spaced false target interference, scattered false target interference, quasi-suppression multi-false target interference, single main false target interference, etc., realizing flexible control of the false target velocity, quantity, and energy intensity.

Description of the Drawings

[0019] Figure 1 It is a flow chart of the radar target velocity spoofing interference method.

[0020] Figure 2 It is a schematic diagram of intermittent sampling and forwarding interference.

[0021] Figure 3(a) is a time-domain waveform diagram of the ISRJ control signal.

[0022] Figure 3(b) is a frequency spectrum diagram of the ISRJ control signal.

[0023] Figure 4(a) is a comparison diagram of the time-domain situation of the signal before and after being interfered by ISRJ.

[0024] Figure 4(b) is a comparison diagram of the frequency-domain situation of the signal before and after being interfered by ISRJ.

[0025] Figure 5 It is the signal processing flow of a typical single-carrier coherent pulse radar.

[0026] Figure 6 It is the radar velocity measurement result without ISRJ interference.

[0027] Figure 7(a) is the false target velocity and quantity situation when the sampling frequency f s = 0.12f r and the duty cycle D = 0.4.

[0028] Figure 7(b) is the sampling frequency fs = 0.125f r and the false target speed and quantity conditions when the duty cycle D = 0.4.

[0029] Figure 7(c) shows the sampling frequency f s = 0.2f r and the false target speed and quantity conditions when the duty cycle D = 0.4.

[0030] Figure 7(d) shows the sampling frequency f s = 0.5f r and the false target speed and quantity conditions when the duty cycle D = 0.4.

[0031] Figure 8(a) shows the sampling frequency f s = 1.125f r and the false target energy intensity conditions when the duty cycle D = 0.4.

[0032] Figure 8(b) shows the sampling frequency f s = 3.125f r and the false target energy intensity conditions when the duty cycle D = 0.4.

[0033] Figure 8(c) shows the sampling frequency f s = 5.125f r and the false target energy intensity conditions when the duty cycle D = 0.4.

[0034] Figure 9(a) shows the sampling frequency f s = 1f r when the ISRJ interference fails.

[0035] Figure 9(b) shows the sampling frequency f s = 2f r when the ISRJ interference fails.

[0036] Figure 9(c) shows the sampling frequency f s = 3f r when the ISRJ interference fails.

[0037] Figure 10(a) shows the sampling frequency f s = 0.12f r and the false target energy intensity conditions when the duty cycle D = 0.5.

[0038] Figure 10(b) shows the sampling frequency f s = 0.12f r and the false target energy intensity conditions when the duty cycle D = 0.2.

[0039] Figure 10(c) shows the sampling frequency f s = 0.12f rAnd the false target energy intensity when the duty cycle D = 0.05.

Specific Embodiment

[0040] To better understand the method of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] The applicable object of the present invention is a fully coherent radar using a single carrier frequency pulse system. Taking an X-band radar system as an example, the signal emitted by the radar to be jammed is a single carrier frequency coherent pulse train with a center frequency of 10 GHz (in the following examples, it is assumed that the radar does not use frequency hopping technology), a signal wavelength λ of 3 cm, a pulse repetition frequency f r of 100 kHz, and a pulse width T p of 4 μs. The radar accumulates 128 pulses in one coherent accumulation, and the velocity resolution is 11.7 m / s. It is assumed that the radial velocity of the real target relative to the radar is 230 m / s, and the ISRJ jammer is assembled on the real target and moves along with it.

[0042] The present invention relates to the following specific steps, and the specific process is as Figure 1 shown.

[0043] Step 1: Interception and parameter estimation of the radar emission signal

[0044] In the actual application process, it is necessary for the electronic reconnaissance system to work in real time and feedback the waveform parameters of the radar emission signal. The ISRJ jammer makes judgments, processes, and responses based on the intercepted information to continuously achieve the preset jamming effect. The basic parameters of the radar emission signal are obtained by using the electronic reconnaissance system, including the carrier frequency f c = 10 GHz, the signal wavelength λ = 3 cm, the pulse width T p = 4 μs, and the pulse repetition frequency f r = 100 kHz.

[0045] Step 2: Determine the parameters of the ISRJ control signal according to the preset jamming effect

[0046] Figure 2 The intermittent sampling signal shown can be equivalent to a pulsed ISRJ control signal p(t) with a pulse width of τ and a period of T s . The reciprocal of T s is f s , that is, the ISRJ sampling frequency. The time domain p(t) and frequency spectrum P(f) of the ISRJ control signal are shown in Figures 3(a) and 3(b) respectively. p(t) and P(f) can be expressed by formulas (1) and (2):

[0047]

[0048]

[0049] where \(t\) represents the time variable. When then otherwise \(g\) represents the \(g\)-th cycle of the ISRJ control signal in the time domain, \(j\) is the imaginary unit, and \(f\) represents the frequency variable. It shows that the spectrum \(P(f)\) of the ISRJ control signal is a comb spectrum with a sinc function as the envelope. The parameters \(\tau\) and \(f\) of the control signal s correspond to the single-sampling duration and sampling period of the ISRJ jammer respectively. By flexibly controlling the above two important parameters of the jammer, rich preset jamming effects can be achieved. Conversely, according to the preset jamming effects, the jammer can reverse-deduce the parameters of the ISRJ jammer, and this process will be completed in this step.

[0050] Step 3: Periodically sample and forward the radar transmitted signal

[0051] According to the ISRJ control signal parameters determined in Step 2, the jammer continuously and periodically samples and forwards the single-carrier coherent pulse signal transmitted by the radar in real time. Different from other pulse signals using complex intra-pulse modulation techniques, the intra-pulse of the coherent pulse train is a single-frequency signal with a frequency equal to the carrier frequency. The coherent pulse signal of \(M\) pulses transmitted by the radar can be expressed as:

[0052]

[0053] In the formula, is the constant initial phase of the radar transmitted signal, \(f\) c is the radar carrier frequency, and \(u(t)\) is the rectangular pulse train envelope

[0054]

[0055] In the formula, represents the convolution operation. After calculation, the spectrum of the coherent pulse train signal is a comb spectrum with a sinc function as the envelope, and its expression is:

[0056]

[0057] From the perspective of the time domain, the sampling and forwarding process of the intermittent sampling and repeater jamming can be equivalent to applying a pulsed ISRJ control signal p(t) to the original radar signal. That is, the transmitted jamming signal is the product of the real target echo s(t) and the ISRJ control signal p(t), as shown in Fig. 4(a). The time-domain multiplication operation corresponds to the frequency-domain convolution operation. The spectral structure of the jamming signal is the convolution result of the radar transmitted signal spectrum S(f) and the control signal spectrum P(f). Therefore, from the perspective of the frequency domain, this process is equivalent to causing the original echo to generate a harmonic expansion that obeys the sinc attenuation distribution, as shown in Fig. 4(b). Assuming that the time-domain model of the jamming signal transmitted by the ISRJ is j(t) and the spectrum is J(f), the above process can be expressed by the following formula:

[0058] j(t) = s(t)·p(t) (6)

[0059]

[0060] where a n = τf s Sa(nτf s π)exp(-jnτf s π). It must be pointed out that the jammer uses a high-power transmitting device, and the forwarding power of this jamming signal will be much stronger than the power of the real target echo s(t). Therefore, in the discussion of this invention, the influence of the real target echo on the radar speed measurement result is ignored.

[0061] Step 4: Generation of speed false targets

[0062] According to Figure 5 the signal processing flow of the typical single-carrier frequency coherent pulse radar shown, the jamming signal j(t) transmitted by the ISRJ will successively pass through a single-sideband filter, a clutter suppression filter, a moving target indicator (MTI filter), a Doppler filter bank (MTD processing), and a CFAR detection processing, so as to obtain the final speed measurement jamming result. Figure 6 is the real target speed measurement simulation result without ISRJ jamming. At this time, it conforms to the set real target speed of 230 m / s.

[0063] Assume that the radar receiver adopts zero-IF processing technology. Due to the function of the single-sideband filter, the spectral range of interest for both the attacker and the defender is limited to its passband, that is, the effective speed measurement interval B = [-f r / 2, +f r / 2]. Approximating each spectral line of the comb spectrum of the single-carrier frequency coherent pulse signal as an impulse function, the echo amplitude spectrum of the coherent pulse train can be expressed as:

[0064]

[0065] where \(i\) is the spectral line number of the original signal's comb spectrum, and \(k\) i is the energy intensity of the \(i\)-th spectral line of the original signal's comb spectrum, and \(f\) d is the Doppler frequency shift corresponding to the true target. Then, the spectrum of the interfered baseband signal \(j\) base (t) is:

[0066]

[0067] Equation (9) illustrates the principle of generating velocity false targets by ISRJ: When affected by ISRJ, each spectral line of the original signal is weighted by \(a\) n as the amplitude, and extends along the positive and negative directions of the frequency axis by \(nf\) s . The spectral lines falling within the range \(B\) are extracted by the single-sideband filter and the Doppler filter. This shows that ISRJ essentially generates velocity false targets in the frequency domain using the spectral line energy of the original pulse signal itself. From the above analysis, it is easy to know that the sampling frequency \(f\) s determines which spectral lines can fall into the passband of the single-sideband filter after extension, and the weighting coefficient \(a\) n determines the attenuation degree of these spectral lines after \(n\) times of extension. In addition, from the expression of \(a\) n , it can be seen that it is uniquely determined by the duty cycle \(D = \tau f\) s of the control signal, that is, the interference effect of ISRJ is mainly affected by these two factors: the sampling frequency \(f\) s and the duty cycle \(D\) of the control signal. Set the sampling frequency as \(f\) s = \(lf\) r , and \(F\) is the set of effective false target frequency points. Then:

[0068]

[0069] where \(Z\) represents the set of integers, and the velocity measurement results corresponding to the frequency points still satisfy the linear mapping relationship between the Doppler frequency shift and the velocity

[0070] When the duty cycle of the ISRJ control signal is fixed at \(D = 0.4\), the values of \(l\) of the sampling frequency are set to \(0.12\), \(0.125\), \(0.2\), and \(0.5\) respectively. The velocity measurement interference results obtained by simulation are shown in Figures 7(a)-(d) in turn. It can be concluded that compared with the chaotic distribution of the velocity false targets in Figure 7(a), the velocity false targets generated at the latter three sampling frequencies all satisfy the characteristics of equally spaced distribution, and are distributed at the 8, 5, and 2 equal division points corresponding to \(B\) in turn.

[0071] When the duty cycle of the ISRJ control signal is fixed at D = 0.4, the l values of the sampling frequency are set to 1.125, 3.125, and 5.125 respectively. The velocity measurement interference results obtained by simulation are shown in Figures 8(a)-(c) in sequence. Combining with Figure 7(b), it can be concluded that when the fractional part of the l value of the sampling frequency remains unchanged, the velocity distribution position of the false target does not change, while the energy intensity of the false target will decrease with the increase of the integer part of the l value of the sampling frequency. In fact, the fundamental reason for this phenomenon lies in that the spectral line amplitude k i obeys a sinc-shaped envelope.

[0072] When the duty cycle of the ISRJ control signal is fixed at D = 0.4, the l values of the sampling frequency are set to 1, 2, and 3 respectively. The velocity measurement interference results obtained by simulation are shown in Figures 9(a)-(c) in sequence. Under these three settings of the sampling frequency, the velocity measurement results of the radar are the same as those Figure 6 shown without interference, indicating that the ISRJ interference fails at this time. It can be seen from formula (10) that when the l value of the sampling frequency is exactly an integer, there is only one false target frequency point, and it exactly coincides with the real target, that is, the simulation results are consistent with the theory.

[0073] When the l value of the sampling frequency is fixed at 0.12, the duty cycle D of the ISRJ control signal is set to 0.5, 0.2, and 0.05 respectively. The velocity measurement interference results obtained by simulation are shown in Figures 10(a)-(c) in sequence. As the duty cycle D decreases, due to the main lobe width of the amplitude weighting factor a n continuously increasing, more and more spectral lines enter the passband range of the single-sideband filter with a smaller attenuation, thus forming more and more effective velocity false targets. When the duty cycle decreases to 0.05, a large number of false target spectral lines almost completely cover the effective velocity measurement range, forming a multi-false target interference effect similar to the suppression type.

[0074] It is not difficult to see from the simulation experiment results that the velocity, quantity, and energy intensity of the radar velocity false targets generated by the ISRJ jammer are controlled by the jammer parameters f s and D. By presetting appropriate jammer parameters, diverse velocity false target deception interference effects can be achieved on the single-carrier frequency coherent pulse radar, which is consistent with the theoretical analysis and also proves the effectiveness of the method proposed in the present invention.

Claims

1. A single-carrier frequency coherent pulse radar target velocity feature modulation method based on intermittent sampling and forwarding, characterized in that: include: Step 1: interception and parameter estimation of radar transmission signals; Utilize the electronic reconnaissance device integrated in the jamming system to intercept the radar transmission signal, locate the direction of the enemy radar, and estimate the basic parameters of the signal waveform; Step 2: Determine the intermittent sampling and forwarding interference ISRJ control signal parameters according to the preset interference effect; Intermittent sampling and forwarding interference is a process in which a single sampling and single forwarding of the intercepted radar signal is completed within a sampling-forwarding cycle, referred to as the sampling cycle. This process is equivalent to applying a pulsed ISRJ control signal to the original radar signal. Without considering the velocity ambiguity, the velocity spectrum V of the deceptive false target is generated by It is represented by, where δ(·) is the impulse function, v represents the velocity value, v0 is the velocity value of the real target, and a n is the nth harmonic line energy intensity of the ISDJ control signal spectrum, which is given by a n =τf s Sa(nτf s π)exp(-jnτf s π) represents, k i is the energy intensity of the i-th spectral line of the original signal comb spectrum; Step 3: Periodic sampling-forwarding radar transmission signal; According to the ISRJ control signal parameters, the ISRJ jammer is configured to perform a sampling cycle T s The sampling pulse width τ and sampling frequency f s The jammer modulates the radar transmission signal with a frequency of f s The sampling is performed periodically. In each sampling period, the sampled signal slice with a duration of τ is reduced to the intermediate frequency and then the signal processing flow of low-pass filtering, A / D conversion, storage, and D / A conversion is completed in DRFM in sequence. Then, it is immediately forwarded through the mixer at the ISRJ transmitter for up-conversion. Step 4: Generation of speed false target; The interference signal j(t) generated by ISRJ enters the single-carrier coherent pulse radar system and is mixed with the local oscillator signal s in the mixer at the front end of the radar receiver. o (t) = exp(-j2πf c t) is multiplied to obtain the intermediate frequency signal, and the interfered baseband signal j after baseband filtering base (t) After further coherent accumulation processing, the preset false target interference result will be displayed, that is, the speed measurement deception interference effect will be achieved.

2. According to the method of claim 1, the single-carrier frequency coherent pulse radar target speed characteristic modulation method based on intermittent sampling and forwarding is characterized in that: In step 2, the velocity value is The false target energy intensity is a n k i That is, the speed value of the false target is the speed, number and energy intensity of the deceptive false target, which are jointly determined by the ISRJ control signal parameters and the radar transmission signal parameters.

3. The method for modulating target velocity characteristics of a single-carrier frequency coherent pulse radar based on intermittent sampling and forwarding according to claim 1 or 2, characterized in that: In step 2, according to the different needs of wartime strategies, the expected jamming effect is first set, including equally spaced false target jamming, scattered false target jamming, quasi-suppression multiple false target jamming, and single main false target jamming. Then, combined with the previously intercepted target radar waveform parameters, the parameters of the ISRJ control signal are further determined: ①Equally spaced false target interference: According to the pulse repetition frequency f r The size of the ISRJ control signal frequency f s , making the false target speed Equally spaced distribution; ② Scattered false target interference: according to the pulse repetition frequency f r The size of the ISRJ control signal frequency f s , making the false target speed Scattered distribution; ③ Type of suppression multi-false target interference: according to the pulse repetition frequency f r The size of the ISRJ control signal frequency f s , making the false target speed As close to each other as possible, on this basis, control the ISRJ control signal pulse width τ, slow down a n The energy attenuation caused by ④ Single main false target interference: control the ISRJ control signal pulse width τ, strengthen a n The energy attenuation brought about by this makes the energy intensity of the false target a n k i When n>1, it decays rapidly to a very low level. On this basis, according to the pulse repetition frequency f r The size of the ISRJ control signal frequency f s , control the main false target speed to 4. The method for modulating target velocity characteristics of a single-carrier frequency coherent pulse radar based on intermittent sampling and forwarding according to claim 1 is characterized in that: In step 2, the time domain p(t) and spectrum P(f) of the ISRJ control signal are expressed by formulas (1) and (2) respectively: Among them, t represents the time variable. hour, otherwise g represents the g-th cycle of the ISRJ control signal in the time domain, j is an imaginary unit, and f represents the frequency variable. It shows that the spectrum P(f) of the ISRJ control signal is a comb spectrum with the sinc function as the envelope; the parameters τ and f of the control signal s They correspond to the single sampling duration and sampling period of the ISRJ jammer respectively.

5. The method for modulating target velocity characteristics of a single-carrier frequency coherent pulse radar based on intermittent sampling and forwarding according to claim 1 is characterized in that: In step 3, the coherent pulse signal of M pulses emitted by the radar is expressed as: In the formula, is the constant initial phase of the radar transmission signal, f c is the radar carrier frequency, u(t) is the rectangular pulse train envelope; In the formula, Represents the convolution operation; after calculation, the spectrum of the coherent pulse train signal is a comb spectrum with the sinc function as the envelope, and its expression is:

6. The method for modulating target velocity characteristics of a single-carrier frequency coherent pulse radar based on intermittent sampling and forwarding according to claim 5 is characterized in that: Assume that the time domain model of the interference signal forwarded by ISRJ is j(t) and the spectrum is J(f), then: j(t)=s(t)·p(t) (6) among them, a n =τf s Sa(nτf s π)exp(-jnτf s p).

7. The method for modulating target velocity characteristics of a single-carrier frequency coherent pulse radar based on intermittent sampling and forwarding according to claim 1 is characterized in that: In step 4, the radar receiver uses zero intermediate frequency processing. Due to the effect of the single-sideband filter, the spectrum range of interest to both the attacker and the defender is limited to its passband, that is, the effective speed measurement interval B = [-f r / 2,+f r / 2]; approximate each spectral line of the comb spectrum of the single-carrier coherent pulse signal as an impulse function, and the amplitude spectrum of the coherent pulse train echo is expressed as: Among them, i is the spectral line number of the original signal comb spectrum, k i is the energy intensity of the i-th spectral line of the original signal comb spectrum, f d is the Doppler frequency shift corresponding to the real target, then the interfered baseband signal j base The spectrum of (t) is:

8. The method for modulating target velocity characteristics of a single-carrier frequency coherent pulse radar based on intermittent sampling and forwarding according to claim 7 is characterized in that: Set the sampling frequency to f s =lf r , F is the set of effective false target frequency points, then: Among them, Z represents an integer set, and the speed measurement results corresponding to the frequency points still satisfy the linear mapping relationship between Doppler frequency shift and speed.

Images