Instantaneous Microwave Frequency Measurement Based On Frequency-amplitude Mapping

Photonics assisted instantaneous microwave frequency measurement technology is a technology that has been widely concerned and researched.This technology is often used in modern electronic countermeasures,high resolution signal detection and other scenes.This technology is to measure the microwave frequency of ultrahigh frequency and above rapidly and accurately in the scene,so as to obtain the initiative of information.It is based on microwave photonics.The principle is to modulate the microwave signal to the optical domain,process the microwave signal with optical method to form parameter mapping,and then obtain the microwave frequency.This technology fully integrates the advantages of microwave communication and optical communication technology,and has better development potential than the traditional electronic frequency measurement technology.The system based on this technology has the advantages of unlimited component bandwidth,anti-electromagnetic interference,small volume,good reconfigurability,etc.,which can break through the"electronic bottleneck"of the traditional electronic frequency measurement system.This paper mainly studies the photonics assisted instantaneous microwave frequency measurement technology based on frequency-amplitude mapping.In order to improve the frequency measurement accuracy and expand the frequency measurement range,two frequency measurement schemes are proposed according to the different detection power.According to the different schemes,the principle derivation,analysis of the influence of relevant parameters on the frequency measurement range and accuracy,error analysis,etc.are carried out.The feasibility of the scheme is verified by MATLAB and optisystem software.The main achievements of this paper are as follows:（1）The instantaneous frequency measurement technology based on frequency microwave power mapping is studied.An improved frequency measurement scheme based on polarization modulation,dispersion effect and with tunable characteristics is introduced.In this system,single-mode fiber is used as dispersion element to construct two branch power attenuation and two branch microwave power ratio is used to establish amplitude comparison function（ACF）to achieve a one-to-one correspondence between frequency and microwave power.The influences of wavelengthλ₀,fiber length L,polarization angleα,bias angleφon the frequency measurement range and accuracy of the system is analyzed,and the tunable measurement with high accuracy in four frequency bands is realized by adjustingαorφ.The circulator structure of the system can ameliorate the influence of polarization mode dispersion existing in the original system,and verify that it has a better effect on the accuracy.Theoretically,when the length of the optical fiber is 5km,the system can realize the tunable frequency measurement of four frequency bands within 0～26.3GHz by adjustingαorφ,and the error can be controlled within±0.25GHz.（2）The instantaneous frequency measurement technology based on frequency optical power mapping is studied.A frequency measurement scheme of dual polarization Mach Zehnder modulator（Dpol-MZM）based on interference principle is proposed.In this system,Dpol-MZM and polarization beam splitter are used to construct an optical filter structure with orthogonal power output response.Then,the ACF function is established by the optical power ratio of the two signals,and the one-to-one correspondence between the frequency to be measured and the optical power to be measured is realized.The influence of the only adjustable parameter in the ACF function of the scheme,time delayτ,on the system frequency measurement range and frequency measurement accuracy is analyzed.Theoretical derivation verifies that the system can achieve different measurement ranges and frequency measurement accuracy by adjusting the time delayτ.The simulation results show that whenτis set to 12.5ps,the frequency measurement system has a high-precision frequency measurement capability of 0～40GHz.The system can obtain results with an error of less than±0.030GHz in this relatively wide frequency measurement range.