Tunable SIW bandpass filters with PIN diodes

This paper introduces a novel tunable SIW filter implemented using PIN diode switching elements. The two-pole filter provides six states ranging from 1.55 GHz to 2.0 GHz (25% tuning). Fractional bandwidth ranges from 2.3% - 3.0% with insertion loss less than 5.4 dB and return loss greater than 14 dB over the entire tuning range. Each SIW cavity is tuned by perturbing via posts connecting or disconnecting to/from the cavity´s top metal layer. In order to separate the biasing network from the SIW filter, a three-layer PCB is fabricated using Rogers RT/duroid substrates.