Research On Microwave Instantaneous Frequency Measurement Based On SBS Effec

The traditional instantaneous frequency measurement(IFM)technology of electronics is limited by the analog to digital conversion rate and instantaneous bandwidth of electronic devices,so it is difficult to adapt to the rapidly changing measurement environment.However,with the development of microwave photonics and relevant optical devices,IFM methods based on microwave photonics have attracted the attention of researchers,and a variety of scattering based on dispersion,four-wave mixing and stimulated Brillouin scattering(SBS)were proposed.Due to the inherent narrow linewidth and low threshold of SBS,microwave IFM systems based on the SBS effect have improved in terms of measurement range and measurement error.This paper mainly studies the broadband adjustable microwave IFM scheme based on SBS effect and the multi-frequency channelized microwave IFM scheme.Firstly,a broadband tunable IFM system is designed based on the SBS effect of the highly nonlinear fiber in which the carrier suppressed single sideband modulated signal of the Brillouin frequency shift acts as pump light.The amplitude comparison function(ACF)is constructed by the power radio of the two paths in the system.The frequency measurement range and measurement accuracy can be tuned by changing the frequency difference of the two phase modulation signals.The tunable frequency measurement ranges of 2～5 GHz,2～10 GHz,2～15 GHz,2～20 GHz,and 2～24 GHz are realized,and the corresponding measurement accuracies are 3.64 d B/GHz,2.17 d B/GHz,1.87d B/GHz,1.22 d B/GHz,and 0.77 d B/GHz,respectively.Then,in order to improve the measurement range,a wideband IFM system is proposed and analyzed.Based on the SBS effect,the phase modulation to intensity modulation conversion is implemented,and the microwave frequency can be measured by detecting the change of the output power.The theoretical analysis shows that the frequency measurement range can be extended to 4f_b by adjusting the two sweeping signals of the phase modulators with a difference of 2f_b.The IFM system is setup using the VPI transmission maker and the performances are simulated and analyzed.The simulation results show that the measurement range is 0.5～45.96 GHz with the maximum measurement error is less than 9.9 MHz.Finally,a channeled multi-frequency measurement scheme is proposed by SBS effect and optical frequency comb.The channel is divided by the wavelength division multiplexer to realize the mapping of frequency to space.By detecting the change of the output signal power of the corresponding channel,the multi-frequency measurement within 0.1～25 GHz is realized,and the measurement error is less than13.5 MHz.