A continuously tunable 95?138 MHz bandpass resonator with 40 dBm IIP3

This paper reports on the design of a frequency-tunable lumped-element bandpass resonator with wide tuning range (1.45:1) and high third-order input intercept point (IIP3 > 40 dBm). The filter tuning is realized by means of a continuously variable capacitance that is formed by a hybrid combination of a back-to-back varactor pair-operated in the high DC bias region-and a switched network of static capacitors. An experimental prototype was designed, built and measured for proof-of-concept demonstration purposes. It exhibited a tunable frequency between 95 and 138 MHz (1.45:1) and insertion loss between 1.83 and 2.25 dB. Within this frequency range, the in-band IIP3 was measured above 40 dBm.