The Research Of Frequency Measurement Based On Microwave Photonic

In modern electronic warfare,frequency measurement is an important technology.Only by detecting the electromagnetic radiation information of the other party can the information of the enemy be investigated,captured,interfered and confronted.Through the frequency measurement system,we can quickly locate the frequency band of unknown signals,help to identify the type and number of enemy electronic equipment and other important information,obtain reasonable attacks or countermeasures.Due to the existence of electronic bottlenecks,the performance of traditional electronic frequency measurement mechanism has been in place for a long time,and it has been difficult to meet the targets of future wars.By using the new microwave photonics research and microwave photonics technology to process the signal in microwave system,a microwave signal processing system with low loss,small size,light weight,low power consumption,wide bandwidth and strong anti-electromagnetic interference can be realized.This paper mainly studies the frequency measurement technology based on microwave photonics.According to the principle of frequency-power mapping frequency measurement scheme,two microwave photon frequency measurement schemes are proposed.The measurement range and accuracy of different schemes are studied.The feasibility of the scheme is verified by simulation using Matlab and Optisystem software.The main work and innovations of this paper are as follows:(1)The principle of two traditional electronic microwave signal frequency measurement systems is analyzed.Based on the orthogonal frequency measurement scheme,a microwave photonics frequency measurement scheme using both intensity modulation and phase modulation is proposed.In this scheme,a one-to-one correspondence between frequency information and amplitude comparison function(ACF)of microwave signal is established by using single mode dispersion fiber,and the frequency measurement of microwave signal is completed.The simulation and result analysis of the scheme are carried out.Through the study of the characteristics of ACF function and the comparison of branch microwave power,it is concluded that the scheme can achieve a frequency measurement range of 0-15 GHz and a frequency measurement accuracy of ±0.3 GHz.In addition,under the condition of setting the initial parameters,the effects of three parameters,namely,fiber length,fiber dispersion coefficient and optical carrier wavelength,on ACF function and frequency measurement results are simulated and studied concretely,and relevant conclusions are drawn.(2)An improved microwave photon frequency measurement scheme using phase modulation is proposed,which is based on the principle that the dispersion effect of single mode optical fibers can cause microwave power attenuation.Four single mode dispersion fibers are used in the improved scheme,and three different ACF functions are generated by optimizing the length of the fibers.As a reference,the original scheme is simplified to two single mode dispersion fibers.Firstly,the reference scheme is simulated and analyzed.It is concluded that the error of frequency measurement is ±0.3GHz in the range of 5-17 GHz microwave frequency.Then the proposed improvement scheme is verified by simulation,and the measurement error is ±0.2 GHz in the range of 3-24 GHz.The improved scheme not only enlarges the effective range of frequency measurement and improves the accuracy of frequency measurement,but also solves the problem of low accuracy of frequency measurement in low frequency band(< 8GHz).