2.2-4.6-GHz Active Quasi-Circulator with > 24-dB Transmit Receive Isolation

摘要

An active quasi-circulator (AQC) integrated circuit is designed and fabricated in a 0.18-mu m CMOS process. The proposed design is based on a parallel combination of a common-source (CS) stage and a combined common-drain (CD) and common-gate (CG) topology. Scattering matrix of the core AQC circuit is derived considering MOSFET's secondary effects, particularly the body effect as well as output loading effects. Measurements of the quasi-circulator reveal an insertion loss of 6.8 +/- 0.5 dB between transmitter-to-antenna ports (vertical bar S-21 vertical bar) and of 7.4 +/- 0.5 dB between antenna-to-receiver ports (vertical bar S-32 vertical bar), within a frequency band of 2.2-4.6 GHz. The isolation between the transmitter and the receiver ports (vertical bar S-31 vertical bar) is better than 24 dB with a maximum value of 29.5 dB @ 3.6 GHz. The power dissipation of the proposed AQC is 40 mW and it covers an active chip area of 0.677 mm(2).