A Wideband Quasi-Circulator with Low NF and High P1dB Using Noise-Canceling Technique
In this paper, a wideband quasi-circulator (QC) with low noise figure (NF) and high 1-dB compression point (P1dB) is proposed. Such QC consists of a wideband 180° hybrid and a common-gate common-source (CG-CS) noise-canceling stage. The wideband 180° hybrid is introduced to achieve broadband high transmitter-receiver (TX-RX) isolation. Meanwhile, the CG-CS noise-canceling stage is utilized to reduce the RX NF and obtain the high antenna-transmitter (ANT-TX) isolation. To verify the mechanisms mentioned above, a wideband QC with an operating frequency range from 1.8 to 2.9 GHz is implemented and fabricated. The measurement exhibits the in-band TX-RX isolation of 21–32 dB. The RX insertion loss is 1.0–1.9 dB, while the minimum in-band RX NF is 3.2 dB, respectively. Besides, the TX input P1dB is higher than 24 dBm at 2.35 GHz.