Design And Research Of L Band Tunable Microstrip Filter

In the today’s information society,with the increasingly complex electromagneticenvironment, interference is an increasingly serious situation, tunable filter applicationsincreasingly more and more widely. Tunable filter play the role of the latter level filter inthe transmitter, it is located between the antenna and the mixer as a part of RF-front in thereceiving system, whose role is to receive the signal from the antenna, filter theinterference spectrum, get the useful spectrum, thereby improving the signal to noise ratio.This paper discusses the1GHz~1.5GHz tunable microstrip bandpass filter design.The specific work includes: selected a compacted, superior performanced tapped comblinefilter by comparing the microstrp filter strcture, analyzes the equivalent model of the twoinput and output structure of combline filter,make a detailed study on filter’s externalcoupling and the filter internal coupling structure, combined with the electromagneticsimulation EM simulation software HFSS simulation the coupling structure,discuss on therelationship of the tapline point,the distance of the microstrip line,varactor and theparameters of filter such as insert loss,return loss,standing wave ratio,relative bandwidthetc,use the circuit simulation software ADS simulation the whole model by the co-simulation method, finally achieved the required design specifications.This paper studied the microstrip tunable filter Systematically, and simulation themicrostrip filter model, it has good value in engineering applications.