Electronic switchable bandpass filter using PIN diodes for wireless low cost system-on-a-package applications

Abstract

A reconfigurable band-pass filter for wireless applications has been designed and demonstrated. The topology has been designed on Duroid, a low cost organic substrate intended for system-on-a-package (SOP) applications. The design achieves discrete bandwidth tuning by direct manipulation of its geometry and implements PIN diodes as switching elements. The filter was designed with a centre frequency of 5.8 GHz and a passband tunablity ratio of 2:1. Several tests such as one-tone power handling and two-tone intermodulation measurements were conducted to investigate the filter's response to different power signal levels as well as the level of signal distortion. The filter produced third-order intermodulation intercept points (IIP3s) greater than 46 dBm around the centre frequency for tones separated by 1 MHz. The resulting circuit presented here does not produce significant distortion and it is capable of handling signals with power levels greater than 2 W. The two distinct bandwidths produced by the filter were 10.12% with an insertion loss of 3.95 dB and 5.43% with an insertion loss of 4.73 dB. The physical size of the fabricated filter layout including the realisation of bias circuitry is comparable to the size of a conventional filter.