Wideband Directional Coupler For Radar Analog Signal Processing

With electromagnetic wave as the carrier,radar can screen all environmental factors to detect enemy aircraft,early warning aircraft and other air targets.In the real world,especially in advanced modern warfare,how to accurately find non-cooperative targets in complex,covert and remote situations is crucial.When high-power radar detects non-cooperative air targets,the large pulse signals in the air will produce great interference suppression.How to eliminate the interference suppression of the large pulse signals has always been a technical difficulty.One of the solutions is to use the time domain cancellation of radar analog signals.Directional coupler is a key component in time domain radar analog signal system which can eliminate interference suppression of large pulse signal.The directional coupler used for time domain radar analog signal processing requires small size,large bandwidth and easy integration.Directional coupler is a power distribution device,which can sample,detect and isolate signals.It requires high accuracy and reliability.Research on high performance directional couplers and improving the directivity of directional couplers are the focus of this field.The main task of this paper is to design a wide-band directional coupler for radar analog signal interference suppression.In this paper,two miniaturized microstrip directional couplers with high directivity are designed based on single-section microstrip coupled transmission lines and multi-section symmetric microstrip coupled transmission lines and combined with microstrip line matching network.The work of this paper mainly covers the following aspects:1.Introduced the development process,development trend,working mechanism and technical indicators of directional couplers,and explained in detail the network analysis,directional analysis,Matlab application and several typical directional couplers.2.Summarized the theoretical analysis and comprehensive methods of five commonly used coupling transmission lines,and gave the corresponding Matlab programming.3.The high directional directional coupler based on broadband multi-node parallel microstrip line is studied.As an example,based on the multi-section symmetric microstrip coupling line,a multi-section directional coupler with 25 d B coupling degree and better directivity than the 6-14 ghz coupler with 30 d B is designed.4.A broadband high-directional microstrip line directional coupler based on matching network is studied.As an example,based on single microstrip coupling transmission line and combined with microstrip line matching circuit,a miniaturized microstrip directional coupler with 2.2ghz coupling degree of 17 d B and better directivity than 30 d B is designed.