Active quasi circulator: Comprehensive review and performance comparison

Designing circulator as an antenna interface device becomes a daunting task, particularly active-quasi circulator. This article focuses on demonstrating the basic operation principle, design methods, technical parameters, and performance metrics of active quasi-circulator. In addition, the study provides an analogy of the circuits and structures proposed by the researchers to enhance certain performance metrics. Active signal cancellation and passive signal cancellation are identified as the major design approaches. Tunable, wideband, and wideband-tunable are the major types of circulators found in existing literature. Moreover, this article provides a performance comparison of the active-quasi circulators available in existing literature. Several active quasi-circulators were able to operate in high frequencies such as 60 GHz with acceptable isolation levels. On the other hand, several designs have over 30 dB isolation, which is a highly desired parameter. At last, the future design challenges associated with active-quasi circulators have been discussed to provide insight into future research.