Design Of Adjustable Microvave Optical Delay Line

The true delay of wideband microwave signal is widely applied,in the system of phased array radar,such as phase matching,EW spectrum analysis and electronic warfare jamming signal generation,we can see the figure of microwave delay line.By delaying radar signal,we can verify the ranging function of radar in radar test,and we can carry out distance jamming by delaying the early warning radar signal.The traditional microwave signal processing technology is difficult to meet the demand of wide-band radio frequency signal without distortion and large real delay.This paper combines the advantages of ultra wideband,low loss and anti-interference with microwave photon technology,and designs and implements a tunable microwave optical delay line.The performance index of microwave optical delay line using IMDD link is calculated,including gain,noise figure and three order spurious free dynamic range.The signal distortion due to electro-optic modulation and power fading due to fiber dispersion are analyzed.The device level design of electro-optical and optical conversion module of microwave optical delay link is designed,and a digitalized adjustable delay system is designed.Finally,a prototype of digitally tunable microwave optical delay line which is mainly for radar testing is completed.The prototype delay line using RS232 or Ethernet control,test results show that the delay frequency range of 10 MHz-18GHz,the switching time is less than 2ms,the maximum delay time delay 98us,step 4.9us,delay accuracy is better than 5ns,10GHz signal excitation,a gain of-39dB,noise figure 56dB,SFDR 100dB(1 Hz).Compared with the same type of delay line,it has the advantages of high degree of digitalization,high delay precision and small adjustment granularity,performance can meet the radar and electronic countermeasure under the background of different needs,and has made some achievements in practical testing system in radar.