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

Abstract

An active quasi-circulator (AQC) integrated circuit is designed and fabricated in a 0.18-[Formula: see text]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 [Formula: see text] dB between transmitter-to-antenna ports ([Formula: see text]) and of [Formula: see text] dB between antenna-to-receiver ports ([Formula: see text]), within a frequency band of 2.2–4.6 GHz. The isolation between the transmitter and the receiver ports ([Formula: see text]) is better than 24 dB with a maximum value of 29.5[Formula: see text]dB @ 3.6[Formula: see text]GHz. The power dissipation of the proposed AQC is 40[Formula: see text]mW and it covers an active chip area of 0.677[Formula: see text]mm2.

Active quasi circulator: Comprehensive review and performance comparison

“…Active circulators can be categorized into two major types: quasi‐circulator and conventional three‐way circulator 25 . By analyzing the existing literature in References 11,26–68, theory and operation principle of active‐quasi circulator is presented in the following sub‐sections.…”

“…In upcoming wireless communication systems, it is essential for the quasi‐circulator to support multiple frequency bands. In existing literature, 11,26–68 three distinct types of circulators are observed: tunable, wideband, and dual. Each of the active‐quasi circulator types have several benefits and drawbacks.…”