Broadband tunable filters using high Q passive tunable ICs

Abstract

This paper presents the performance of tunable bandpass filters using high Q, wide-tuning-range passive tunable ICs. These passive tunable ICs are fabricated using ParaScan™, Paratek’s proprietary doped BST material. The tunable capacitors in these passive ICs have a tuning ratio of 4.15:1 and a Q factor over 100, from 100 MHz to 1 GHz. Two tunable filters using these passive tunable ICs were designed, fabricated, and tested. The two-pole tunable filter has a tuning range of 56% from 300 to 470 MHz, an insertion loss less than 2 dB over the entire tuning range, and an IIP3 of 52 dBm. The three-pole filter demonstrates a tuning range of 74% from 230 to 400 MHz, an insertion loss less than 2.5 dB. Control of the tunable filters is achieved through an on-board, high voltage ASIC and a microprocessor. The two-pole filter has been evaluated over temperature from −40°C to 85°C and minimal temperature drift was observed.