On-chip GaAs-based dual-band bandpass filters/isolators (DBPFIs)

MMIC co-designed RF components exhibiting the collocated RF signal processing actions of a dual-band bandpass filter and an RF isolator (DBPFI) are presented. They are based on in-parallel cascaded bandpass filters/isolators that operate at two different frequencies and two multi-resonant cells that are added in the RF input and RF output to increase the selectivity and the out-of-band isolation of the DBPFI through six added transmission zeros. For proof-of-concept demonstration purposes, a DBPFI prototype was designed and manufactured using a commercially available GaAs MMIC process. It exhibited the following RF-measured characteristics: center frequencies: 8.14 GHz and 10.8 GHz, 3-dB fractional bandwidth (FBW): 11.1% and 16.4%, |S₂₁|: −3.7 dB and −8.8 dB, isolation >36.6 dB and 16.5 dB, IP_1dB: 11.8 dBm and 12.8 dBm, IIP₃: 18.2 dBm and 16.5 dBm, and OIP₃: 14.2 dBm and 6.7 dBm, respectively, at the lower and the upper band.