Photon-assisted radar frequency shift interference and intermittent sampling forwarding interference integrated signal generation method

Abstract

The invention discloses a photon-assisted radar frequency shift interference and intermittent sampling forwarding interference integrated signal generation method, and relates to the technical field of microwave photon and radar countermeasure. The method is shown in a figure 1 in the specification and is realized based on a laser device (LD), an arbitrary waveform generator (AWG), a dual-drive Mach-Zehnder modulator (DDMZM), an intensity modulator (IM) and a photoelectric detector (PD). According to the method, by adjusting the period of sawtooth waves, the duty ratio of rectangular pulse signals and the sampling period, generation of interference signals integrating various frequency shift interferences and intermittent sampling and forwarding interferences can be achieved. According to the invention, two simple modulators are adopted, and complex bias voltage and polarization state control is not needed; a digital radio frequency memory is not adopted, analog-to-digital and digital-to-analog conversion is not needed, the real-time performance is good, and parameter tuning is flexible; an electric domain frequency dependent device is not adopted, interference signals with the broadband of more than 1 GHz and the wave band of more than Ku can be generated, and the device is suitable for an electronic countermeasure system with the broadband of more than 1 GHz and the wave band of more than Ku in the future.

Description

Technical Field

[0001] The present invention relates to the fields of microwave photon technology and radar countermeasure technology, and mainly relates to a method for generating integrated signals of radar frequency shift interference and intermittent sampling and forwarding interference by utilizing microwave photon technology. Background Art

[0002] In modern warfare, radar is a key device for obtaining important military intelligence such as enemy military equipment and battlefield dynamics, and is also the "eyes" of all high-tech weapons and equipment. Radar jamming technology is based on effective reconnaissance and uses a variety of electronic jamming methods to make the enemy's radar detection ineffective and missile strikes out of control, helping our army gain the initiative on the battlefield.

[0003] Linear frequency modulation (LFM) pulse compression radar can not only solve the contradiction between radar detection range and range resolution, but also has the ability to resist non-coherent interference and coherent processing gain, so it is widely used. In electronic countermeasure systems, radar jamming technology is an effective means of self-protection. Therefore, the research on jamming technology for LFM pulse compression radar has become the focus of academic and industrial circles.

[0004] Radar jamming technology can be divided into two categories: suppression jamming and deception jamming. Suppression jamming mainly uses noise to cover the target's echo signal to prevent the radar from detecting target information. The main purpose of deception jamming is to provide false target information to the enemy radar, causing the radar to produce serious false alarms and unable to correctly track the real target. Compared with deception jamming, suppression jamming requires higher transmission power of the jammer and has poor jamming effect on coherent radar. Deception jamming can produce multiple false targets and has a good jamming effect on coherent radar. It is currently a commonly used jamming technology.

[0005] In the traditional electrical domain, commonly used interference methods include frequency shift interference (FSJ), intermittent sampling and forwarding interference (ISRJ), comb spectrum modulation interference, cosine phase modulation interference, etc., which are usually implemented based on digital radio frequency memory (DRFM). DRFM is used to sample, store, reconstruct and retransmit radar signals to generate a variety of interference signals. However, due to the sampling rate limitation of the analog-to-digital converter in DRFM, the instantaneous operating bandwidth of mature DRFM is less than 1 GHz, and the operating frequency is lower than the Ku band, which cannot meet the needs of future electronic countermeasure systems with bands above Ku and bandwidths above 1 GHz.

[0006] Microwave photonic technology uses optical devices to process microwave signals in the optical domain. It has the advantages of large working bandwidth, high frequency band, small electromagnetic interference and low transmission loss. Generating radar jamming signals through microwave photonic technology can overcome the electronic bottleneck of traditional radar jamming technology and improve the performance of electronic countermeasure systems. Summary of the invention

[0007] In order to realize the generation of deception jamming signals with a broadband above 1 GHz and a band above Ku, the present invention proposes a method for generating integrated signals of photon-assisted radar frequency shift jamming and intermittent sampling and forwarding jamming. The method is based on a dual-drive Mach-Zehnder modulator DDMZM cascaded intensity modulator IM, and by adjusting the period of the sawtooth wave loaded on the DDMZM, the duty cycle and sampling period of the rectangular pulse signal loaded on the IM, a variety of FSJ and ISRJ integrated jamming signals can be generated.

[0008] The technical solution adopted by the present invention is: the device adopted by the method includes a laser LD, an arbitrary waveform generator AWG, a direct current power supply DC, a dual-drive Mach-Zehnder modulator DDMZM, an intensity modulator IM, and a photodetector PD. The connection mode is as follows: the optical output port of the LD is connected to the optical input port of the DDMZM, the optical output port of the DDMZM is connected to the optical input port of the IM, the optical output port of the IM is connected to the optical input port of the PD, the sawtooth wave and the LFM signal generated by the AWG are respectively connected to the two radio frequency ports of the DDMZM, the rectangular pulse signal generated by the AWG is connected to the radio frequency port of the IM, the two output ports of the DC are respectively connected to the DC bias ports of the DDMZM and the IM, and the output port of the PD outputs the generated interference signal. The DDMZM is set to work at the maximum point, and the IM is set to work at the minimum point. By adjusting the period of the sawtooth wave, the frequency shift amount of the optical carrier is changed. By adjusting the duty cycle and sampling period of the rectangular pulse signal, the intermittent sampling amount of the frequency shift signal and the LFM signal is changed. After the PD performs photoelectric conversion, a variety of FSJ and ISRJ integrated interference signals are output.

[0009] The present invention comprises the following steps when working: Step 1: The light wave emitted from the laser is input into the optical input port of the DDMZM as an optical carrier. The optical carrier can be expressed as E(t) = E0 exp(j2πf c t), where E0 and f c Represent the amplitude and frequency of the optical carrier respectively. Step 2: The sawtooth wave and LFM signal generated by the arbitrary waveform generator are connected to the two RF ports of the DDMZM respectively, and the DC output of the DC power supply is input to the DC bias port of the DDMZM to control the DDMZM to work at the maximum point. The sawtooth wave expression is formula (1): Where V s , T s and T F are the amplitude, period and fall time of the sawtooth wave respectively. The expression of LFM signal is: V R (t) = V R cos(2πf0t+πkR t 2 ), where V R , f0 and k R are the amplitude, initial frequency and chirp rate of the LFM signal respectively. When the falling time of the sawtooth wave is T F When it is 0, the output signal expression of DDMZM is formula (2): in m=πV R / V π , represents the modulation index of the LFM radar signal; V π Represents the half-wave voltage of DDMZM; f s =1 / T s , represents the frequency of the sawtooth wave. Step 3: The optical signal output by DDMZM is input to the optical input port of IM, the rectangular pulse signal generated by the arbitrary waveform generator is input to the RF port of IM, and the DC output by the DC power supply is input to the DC bias port of IM to control IM to work at the minimum point. The expression of the rectangular pulse signal is formula (3): Where V p , τ and T p are the high level, pulse width and period of the rectangular pulse signal respectively. The output signal of IM can be expressed as formula (4): in Represents the phase shift introduced by the high level of the rectangular pulse signal. Step 4: The optical signal output by the IM is input to the optical input port of the photodetector for photoelectric detection. Step 5: The electrical output port of the photodetector outputs the integrated interference signal of FSJ and ISRJ, which can be expressed as formula (5):

[0010] The present invention proposes a method for generating integrated signals of photon-assisted radar frequency shift interference and intermittent sampling and forwarding interference. First, a sawtooth wave is used to modulate the phase of an optical carrier to achieve the purpose of frequency shift. Then, a rectangular pulse signal is used to intermittently sample the modulated LFM signal and the frequency-shifted light wave. Finally, after photoelectric detection, an interference signal integrating frequency shift interference and intermittent sampling and forwarding interference is obtained. By adjusting the period of the sawtooth wave, the duty cycle of the rectangular pulse signal and the sampling period, the generation of multiple integrated signals of frequency shift interference and intermittent sampling and forwarding interference can be achieved.

[0011] The beneficial effects of the present invention are as follows: the present invention adopts two simple modulators, namely DDMZM and IM, so that the structure is simple and complex bias adjustment and polarization state control are not required; no digital radio frequency memory is adopted, analog-to-digital conversion and digital-to-analog conversion are not required, the real-time performance is good and the parameter tuning is flexible; no electrical domain frequency-dependent devices are adopted, and interference signals with a broadband of more than 1 GHz and a band of more than Ku can be generated, and the present invention is suitable for future electronic countermeasure systems with a broadband of more than 1 GHz and a band of more than Ku. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The schematic diagram of the integrated signal generation method of photon-assisted radar frequency shift jamming and intermittent sampling and forwarding jamming of the present invention is shown. Figure 2 This is the interference signal of FSJ and ISRJ integration generated when the sawtooth wave frequency is 3MHz, the rectangular pulse signal frequency is 2MHz and the duty cycle is 50%; Figure 2 (a) is the electrical spectrum of the signal; Figure 2 (b) is the waveform diagram of the signal; Figure 2 (c) is the time-frequency diagram of the signal; Figure 2 (d) is the time domain diagram of the signal after pulse compression. Figure 3 This is the interference signal of FSJ and ISRJ integration generated when the sawtooth wave frequency is 3MHz, the rectangular pulse signal frequency is 2MHz and the duty cycle is 20%; Figure 3 (a) is the electrical spectrum of the signal; Figure 3 (b) is the waveform diagram of the signal; Figure 3 (c) is the time-frequency diagram of the signal; Figure 3 (d) is the time domain diagram of the signal after pulse compression. Figure 4 This is the interference signal of FSJ and ISRJ integration generated when the sawtooth wave frequency is 5MHz, the rectangular pulse signal frequency is 2MHz and the duty cycle is 50%; Figure 4 (a) is the electrical spectrum of the signal; Figure 4 (b) is the waveform diagram of the signal; Figure 4 (c) is the time-frequency diagram of the signal; Figure 4 (d) is the time domain diagram of the signal after pulse compression. Figure 5 This is the interference signal of FSJ and ISRJ integration generated when the sawtooth wave frequency is 5MHz, the rectangular pulse signal frequency is 4MHz and the duty cycle is 50%; Figure 5 (a) is the electrical spectrum of the signal; Figure 5 (b) is the waveform diagram of the signal; Figure 5 (c) is the time-frequency diagram of the signal; Figure 5 (d) is the time domain diagram of the signal after pulse compression. Figure 6 This is the simulation result for synthetic aperture radar imaging; Figure 6 (a) is the imaging effect without interference; Figure 6 (b) is the interference imaging effect of FSJ and ISRJ integration generated when the sawtooth wave frequency is 3MHz, the rectangular pulse signal frequency is 1MHz and the duty cycle is 25%. DETAILED DESCRIPTION

[0013] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0014] As shown in the attached figure of the instruction manual Figure 1 As shown, in this example, the devices used include a laser LD, an arbitrary waveform generator AWG, a DC power supply DC, a dual-drive Mach-Zehnder modulator DDMZM, an intensity modulator IM, and a photodetector PD. The arbitrary waveform generator is used to generate a linear frequency modulation signal, a sawtooth wave, and a rectangular pulse signal; the DC power supply is used to generate a DC voltage to control the DDMZM to work at the maximum point and the IM to work at the minimum point.

[0015] Reference Figure 1-6 In this example, the specific implementation steps of the method are as follows: Step 1: The laser generates a continuous light wave with an operating wavelength of 1550.1 nm and a power of 14 dBm, and the continuous light wave is input as an optical carrier into the optical input port of the dual-drive Mach-Zehnder modulator DDMZM. Step 2: Use an arbitrary waveform generator to generate an LFM radar signal with a center frequency of 12 GHz, a bandwidth of 500 MHz, and a duration of 10 μs, and input the LFM radar signal to an RF port of the DDMZM; use an arbitrary waveform generator to generate a sawtooth wave with a frequency of 3 MHz and input it to another RF port of the DDMZM; use an arbitrary waveform generator to generate a rectangular pulse signal with a frequency of 2 MHz and a duty cycle of 50% and input it to the RF port of the IM; the DC output of the DC power supply is input to the DC bias port of the DDMZM to control the DDMZM to work at the maximum point; the DC output of the DC power supply is input to the DC bias port of the IM to control the IM to work at the minimum point. Step 3: Input the output signal of IM into PD for photoelectric detection, and PD outputs the generated interference signal. Step 4: Use a spectrum analyzer to observe the electrical spectrum of the generated interference signal; use an oscilloscope to observe the waveform of the generated interference signal; use MATLAB software to analyze the time-frequency diagram of the generated interference signal and the time domain diagram after pulse compression. Step 5: In order to generate interference signals with different intermittent sampling duty cycles and explore the influence of the duty cycle of the rectangular pulse signal on the generated interference signal, adjust the duty cycle of the rectangular pulse signal in step 2 to 20%, and repeat steps 2 to 4. Step 6: In order to generate interference signals with different frequency shift amounts and explore the effect of the sawtooth wave frequency on the generated interference signal, adjust the sawtooth wave frequency in step 2 to 5 MHz and repeat steps 2 to 4. Step 7: In order to generate interference signals with different intermittent sampling frequencies and explore the influence of the frequency of the rectangular pulse signal on the generated interference signal, the frequency of the rectangular pulse signal in step 2 is adjusted to 4 MHz, and steps 2 to 4 are repeated. Step 8: In order to explore the interference effect of the generated interference signal on synthetic aperture radar imaging, the sawtooth wave frequency is set to 3MHz, the rectangular pulse signal frequency is set to 1MHz and the duty cycle is set to 25% to generate an integrated interference signal of FSJ and ISRJ, and the imaging interference effect is analyzed using the software MATLAB.

[0016] In summary, the present invention realizes a signal generation method for integrated photon-assisted radar frequency shift jamming and intermittent sampling forwarding jamming. The method adopts two simple modulators, namely DDMZM and IM, so that the structure is simple and no complicated bias adjustment and polarization state control are required; no digital radio frequency memory is adopted, and no analog-to-digital conversion and digital-to-analog conversion are required, so the real-time performance is good and the parameter tuning is flexible; no electrical domain frequency-dependent devices are adopted, and interference signals with broadband above 1 GHz and band above Ku can be generated, which is suitable for future electronic countermeasure systems with broadband above 1 GHz and band above Ku.

[0017] In conclusion, the above-mentioned embodiments are only examples of the present invention and are not intended to limit the protection scope of the present invention. It should be noted that, for those skilled in the art, several equivalent deformations and substitutions can be made based on the content disclosed in the present invention, and the optical wavelength, optical power, signal power, frequency, frequency range of broadband signals, and bandwidth of broadband signals can all be changed. These equivalent deformations and substitutions and adjustments to the frequency range should also be considered as the protection scope of the present invention.

Claims

1. A method for generating integrated signal of photon-assisted radar frequency shift jamming and intermittent sampling forwarding jamming, which is based on a laser LD, an arbitrary waveform generator AWG, a direct current power supply DC, a dual-drive Mach-Zehnder modulator DDMZM, an intensity modulator IM, and a photodetector PD, and is characterized by: The continuous optical carrier output by the laser is input into the DDMZM, the linear frequency modulation LFM radar signal and the sawtooth wave generated by the AWG are respectively input into the two RF ports of the DDMZM, the DC bias point of the DDMZM is set to the maximum point, the optical signal output by the DDMZM is input into the IM, the rectangular pulse signal generated by the AWG is input into the RF port of the IM, the DC bias point of the IM is set to the minimum point, the optical signal output by the IM is input into the PD for photoelectric detection, and the output port of the PD outputs the interference signal integrating the frequency shift interference FSJ and the intermittent sampling forwarding interference ISRJ.

2. According to claim 1, a method for generating integrated signal of photon-assisted radar frequency shift jamming and intermittent sampling and forwarding jamming, characterized in that: By adjusting the period of the sawtooth wave, the duty cycle of the rectangular pulse signal and the sampling period, the generation of multiple FSJ and ISRJ integrated interference signals can be achieved.

Images