Research On High-frequency Lfm Signal Generation Technology Based On Microwave Photonics

In the design of radar systems,performance parameters such as carrier frequency range,distance resolution and velocity resolution have become important indicators of radar performance.How to generate high quality high-frequency microwave signals has become an urgent problem to be solved.Since single carrier frequency pulsed signals cannot have the performance characteristics of large time width and large bandwidth at the same time,Linear Frequency Modulated(LFM)signals with pulse compression performance are widely used in radar systems.However,the LFM signal generated by the traditional electric domain method is difficult to meet the requirements of high frequency and large time-bandwidth product(TBWP)of radar system due to the limitation of electronic devices.To solve this problem,microwave photonics techniques are introduced to improve the performance parameters of LFM signals.In this paper,three high-frequency LFM signal generation schemes are proposed using microwave optical frequency doubling and phase modulation techniques.The primary focus of this research and the key innovations can be summarized as follows:1.An eight-frequency microwave signal generation scheme based on a Dual-Polarization Mach-Zehnder Modulator(DPol-MZM)and a Polarizer(Pol)cascade and a sixteen-frequency microwave signal generation scheme based on two Dual-Parallel Mach-Zehnder Modulators(DPWZM)are proposed.Mach-Zehnder Modulator(DPMZM).The feasibility of the proposed scheme is verified by using a sine wave signal and an LFM signal as the driving signals of the proposed scheme,and the simulation output is further explored to be affected by non-ideal factors.The simulation results show that the octave system generates an LFM signal with a center frequency of 40 GHz and a bandwidth of 8 GHz with a TBWP of 800,and the optical sideband rejection ratio(OSSR)of this scheme is 34.05 dB,the Ra-dio spurious sideband rejection ratio(OSSR)is 34.05 dB,and the optical sideband rejection ratio(OSSR)is 34.05 dB.The OSSR and FRSSR of the proposed scheme are 40.68 dB and 33.95 dB.Compared with the existing schemes,the proposed scheme can generate a variety of microwave signals according to the radar requirements,and none of them needs to be filtered in the optical domain,and the reconfigurability is better.2.To address the problem that the generated signal is greatly affected by the performance parameters of the driving signal source in the above frequency doubling scheme,an LFM signal generation scheme with high frequency doubling and large TBWP based on cascaded two DPMZM and cyclic secondary phase modulation loop is proposed in combination with the external electro-optical phase modulation technique.The simulation results show that the scheme can generate LFM signals with center frequency of 160 GHz,bandwidth of 32 GHz,and TBWP of 327.68.The TBWP of the generated LFM signal can be increased to 1272.05,966.04 and 13653.34 by processing the driving signal of the phase modulator(PM)in the cyclic secondary phase modulation loop.In addition,the generated LFM signals have independently tuned and non-interfering time width and bandwidth,and the detection performance of the radar system can be further improved.