INVESTIGATIONS OF FOUR-PORT CIRCULATOR UTILIZING CYLINDRICAL FERRITE COUPLED LINE JUNCTION

In this paper the numerical and experimental investiga- tions of four-port circulator utilizing longitudinally magnetized cylin- drical ferrite coupled lines (CFCL) section are presented for the flrst time. In comparison to earlier models the proposed structure of cir- culator utilizes multilayer magic-T junction cascaded with cylindri- cal ferrite section of …=4 Faraday angle. The advantage of utilization of cylindrical section over the planar one is the possibility to design shorter ferrite junctions ensuring lower insertion losses. Moreover, the multilayer magic T-junction allows to improve performance of the pro- posed circulator by omitting the bandwidth limitation which exists in commonly used hybrid couplers with air-bridges. In the analysis of CFCL junction the full wave hybrid approach combining flnite difier- ence frequency domain method with method of moments and mode matching technique is applied. The planar feeding structures of circu- lator are designed with the use of commercial software. The simulated results of the entire circulator are compared with the measurement results of the fabricated prototype and a good agreement is achieved.