A Technique for Tunable Filters with Low Insertion Loss and Narrow Bandwidth

Chang Zhou,Chen Ji,Gen Ping Wu,M Mostafa

doi:10.1051/e3sconf/20183803039

Abstract

A technique for tunable filters with low insertion loss and narrow bandwidth is proposed in the form of comb-line structure. Both resonant capacitor with pin-diodes and resonant inductance in the tunable filter were analyzed and the main source of insertion loss was obtained. A series of filters with same pin-diodes, center frequency, absolute bandwidth and low return loss was simulated. The results showed that, by changing the values of the resonant capacitor and inductance, insertion loss of the filter can be greatly restricted. This technique will allow the design of tunable LC filters with low insertion loss and narrow bandwidth.

Highlights

Tunable filter is one of the suitable solutions for intelligent RF applications satisfying multi-band or multimode standards [1]
For the value of Rpin and RL is much smaller than impedance of the resonant capacitor and inductor, IC is almost equal to IL and the value of unloaded quality factor could be concluded to be shown in (6)
The value of tap-line, the tunable filters with pin-diodes get the same the capacitors varies from 2 pf to 4 pf and the radius of values of bandwidth, return loss and center frequency. the resonant metal rib varies from 1 mm to 5 mm which the values of the insertion loss are different. keeps the center frequency of the filters at about 210 The simulation results are shown in Figure 4 and table 1

Summary

Introduction

Tunable filter is one of the suitable solutions for intelligent RF applications satisfying multi-band or multimode standards [1]. Compared to a bank of fixed filters, a tunable filter promises greater functionality, better channel selectivity, reduced size, and lower weight since the same hardware can be employed at multiple bands [2]-[5]. For tuning over an octave frequency by using pin-diodes switches or varactors, the insertion loss of the tunable filter is larger than normal fixed filters. Few research has reported the influence of values of the resonant capacitor with pin-diodes and resonant inductance on the insertions loss of the tunable filter. In this paper, both resonant capacitor with pin-diodes turned on and resonant inductance in the tunable filter were analyzed and a technique for restricting the insertion loss of tunable filters by changing the values of the resonant capacitor and inductance is reported

Theoretical Analysis Of The Resonant Circuit With PIN-DIODES

Simulation Examples

Conclusion