A survey of active quasi-circulators

Abstract

With the development of multi-band wireless communication and the increasing data transmission rate, the circulator as an antenna interface must be able to work in multiple frequency bands and provides large bandwidth. It presents a high challenge to the design of circulators, especially the active quasi-circulators. In this survey, we review the representative active quasi-circulators and summarize three different techniques and the corresponding structures to show an incremental improvement of the isolation and bandwidth of the active quasi-circulators. In addition, we also compare the performance of several state-of-art active circulators, and analyze their advantages and disadvantages. Finally, we conclude the future trend of the active quasi-circulators.

Active quasi circulator: Comprehensive review and performance comparison

“…In Figure 2, difference between active 3‐way and active‐quasi circulator is shown 13 . From the illustration, it can be observed that an active‐quasi circulator has similar operation principle compared to the conventional three‐way circulator.…”

“…In Figure 2, difference between active 3-way and active-quasi circulator is shown. 13 From the illustration, it can be observed that an active-quasi circulator has similar operation principle compared to the conventional three-way circulator. However, quasi-circulator does not allow signal transmission from port 3 (receiver) to port 1 (transmitter), due to which the S parameter S 13 = 0.…”

“…In the case of quasi-circulators, the insertion losses are denoted by the S 21 and S 32 parameters, as shown in Figure 2. 13 Lowering the insertion loss is beneficial for the active quasi-circulator, as it enhances the transmitter's transmission efficiency, decreases power usage, and reduces receiver noise. Reduction in insertion loss can be achieved by incorporating PA and buffers in the output signal pathway.…”

“…According to a study conducted in Reference 13, active circulators using Monolithic Microwave Integrated Circuits (MMIC) offer better solutions for integrated system‐on‐a‐chip (SOC) applications. They offer the benefit of increased bandwidth and high‐frequency operation at a similar level of insertion loss compared to conventional systems.…”

“…In contrast, ferrite circulators typically have limited bandwidth with comparatively higher insertion loss, especially at high frequencies. For instance, a conventional ferrite material‐based circulator functioning at W‐band typically possesses 1 W diminishing power handling, ˜2.1‐dB insertion loss and ˜2% bandwidth (BW) 13 . Thus, to ensure high‐frequency operation, MMIC active circulators capable of SoC implementation exhibit significant promise to assure reliable performance over a wide application range.…”