DESIGN OF SWITCHED FILTER BANK AND TUNABLE MICROSTRIP BAND PASS FILTER

Abstract

This work proposes a switched filter bank at UHF band to avoid harmonics which generated after power amplifier in transmitter and also proposes microstrip tunable bandpass filter which can be used as pre selector in receiver and it also can be used in various applications like Radar, Satellite communication, jamming. The operating frequency of switched filter bank is from 30 – 512 MHz, SPDT switches are used to both side of chebyshev low pass filter, which having insertion loss of 0.0436 dB, VSWR is 1.065 and out of band rejection is 70 dB. Integrating filter and switch components into a single module abolishes the necessity for circuit transitions, resulting in optimal matching, Improved insertion loss, flatness, VSWR, and overall device performance are the end result. Since all the components are integrated in to a single module, Switched Filter banks are compact and save a considerable amount of board space. This work also proposes tunable microstrip band pass filter using BST varactor, which have tuning range from 900 – 1275 MHz, insertion loss in 2.6 – 3.2 dB return loss is better than 10 dB, switching speed is 60 micro-seconds, IP3 point is 50 dBm, average RF power up to 5W, single control voltage from 7 – 24 V, absolute bandwidth is 64 – 72 MHz. Dimension of tunable microstrip band pass filter is 40 mm X 25 mm.