Broadband Active Circulator for Mobile Radio Applications

Abstract

Circulator is part of antenna system both receiving and transmitting signals through the single antenna. It also called duplexers for the mobile radio applications. The conventional circulators have more insertion loss and narrow bandwidth. This project introduces two active circulators which formed by the Wilkinson power divider/combiner and low noise amplifiers only. They are transmitting/receiving devices that suitable for the front-end with a sufficient isolation, noise figure and power handling. i.Broadband Active 3-Port Circulator It is non-reciprocal and signal transmission from one port to the adjacent port in one direction only. The broadband performance is 1 to 2.8 GHz by employing three power divider/combiner and Field-Effect Transistor (FET) together. The unilateral characteristic of the design make the good isolation and no oscillation. And it has less insertion loss. ii.Broadband Active 3-Port Quasi-Circulator It uses power divider/combiner and the in-phase and out-of-phase unilateral amplifiers. It is symmetric for the phase cancellation method on the port 1 to port 3 to make the good isolation and the bandwidth is about 1.3 to 2.6 GHz. This active circulator is compatible with the future software defined radio.