Non-Reciprocal MMIC-Based Dual-Band Bandpass Filters

A new class of an RF front-end component that exhibits the co-designed function of a dual-band bandpass filter and an RF isolator is presented. The proposed non-reciprocal dual-band bandpass filter (NDBPF) is based on two multiresonant cells and one non-reciprocal resonant stage. By cascading them in series, a dual-band transfer function-shaped by four poles (two for each passband) and six transmission zeros-is created in the forward direction and full RF signal cancellation is obtained in the reverse one. For proof-of-concept demonstration purposes, a NDBPF prototype was designed at X-band and manufactured with a commercially-available MMIC GaAs process. It exhibited two bands with the following RF measured characteristics: center frequencies: 8.33 GHz and 10.17 GHz, 3-dB fractional bandwidth: 6.4% and 3.6%, maximum gain: 6.38 dB and 0.3 dB, and isolation >36.7 dB and 19.5 dB at respectively the lower and upper band.