A HBT-based quasi-circulator with wideband equalization technique

An innovative wideband equalization technique for use in a quasi-circulator is presented. The technique utilizes both gain and phase equalization, which provides wideband frequency operation with good return loss and isolation between ports. The circulator is realized by configuring three heterojunction bipolar transistors together with an equalizing phase shifter. Both theoretical analyses and experimental validations are performed. Experimental results show that it can operate over the frequency range 0.8-2.2 GHz. Copyright © 2011 Wiley Periodicals, Inc.