Research On Generation Technology Of Linear Chirp Signal Based On Microwave Photons

As an important device for target detection and distance measurement,radar is not only widely used in the military field,but also plays an important role in national economic and social development.With the expansion of radar application fields,people have higher and higher requirements for radar performance.Linear chirp signal is a common waveform of radar system,which has the characteristics of large timebandwidth product(TBWP),which can improve the resolution and detection range of radar system at the same time.In current radar systems,linear frequency modulation(LFM)signals are usually generated in the electrical domain.But due to the bottleneck in the electronic domain,they have narrow signal bandwidth and limited TBWP.It is difficult to adapt to the application of high frequency and large bandwidth waveform required by radar.In order to improve the resolution and detection range of radar systems,the generation and processing of microwave and millimeter-wave signals based on microwave photonics has many advantages,and it is expected to generate linear chirp signals with higher frequency,wider bandwidth and lower phase noise.Based on this,this paper studies the generation of linear chirp signals by microwave photonics technology,and proposes several different formats of multi-band chirp signal generation schemes.The specific work is as follows:(1)Based on DPol-DPMZM,a multi-band dual-chirp signal scheme with flexible and adjustable center frequency is proposed.Optical sidebands of different orders are generated by changing the amplitude and phase of the DPMZM1 driving signal and parameters such as bias voltage.The lightwave generated by DPMZM1 and the optical frequency comb generated by DPMZM2 are orthogonally combined and recombined,and then the optical heterodyne beat frequency is carried out by a balanced detector to generate a multi-band double chirp signal with a flexible and adjustable center frequency.The simulation results show that four groups of double-chirp chirp signals with different center frequencies can be generated by adjusting the bias voltage.The generated multi-band doublechirp signal can cover the X-W band at the same time,and can be dynamically tuned,which can improve the detection flexibility of the radar system.(2)A multi-band double-chirp signal scheme based on cascaded MZMs is proposed.By setting the relationship between the frequency of the RF driving signal driving MZM1 and the carrier frequency and bandwidth of the frequency band chirp signal driving MZM2,the starting point of the upper chirp signal and the end point of the lower chirp signal can be exactly equal,so as to obtain a large bandwidth Multi-band dual chirp signal.The simulation generates a four-band double-chirp signal,and its center frequency-bandwidth is 10GHz-4GHz,30GHz-4GHz,50GHz4GHz and 70GHz-4GHz,and the chirp rate of the double-chirp signal in each band is the driving chirp signal.The generated multi-band doublechirp signal with large TBWP can improve the speed resolution and detection range of the radar system.(3)A scheme based on DP-DPMZM to generate dual-band chirp signal with adjustable sign and anti-amplitude fading is proposed.By adjusting the bias voltage of DPMZM1 to change the relative phases of the upper and lower branches of DPMZM1,the chirp sign of the chirp signal generated by the beat frequency of the photodetector can be switched between positive,negative and double.By setting the bias voltage of the sub-MZM reasonably,the carrier-suppressed single-sideband modulation can be realized,which can effectively suppress the single-frequency interference in the generated chirp signal band,and can effectively avoid the amplitude fading caused by the dispersion in the optical fiber transmission.The simulation results show that positive chirp,negative chirp and double chirp signals can be generated at 10GHz and 30GHz by adjusting the bias voltage on the DPMZM1 main modulator.