A Broadband Active Quasi Circulator for UHF and L Band Applications

This letter presents a compact, broadband three-port MMIC-based quasi circulator for UHF and L bands. As a motivation and application, the use of this circuit in a network analyzer is presented. The circuit is designed using differential amplifier and lossy broadband combiner to obtain effective phase cancellation for high directivity. The designed quasi circulator has return losses at all ports better than 10 dB and reverse isolation above 30 dB in the frequency range from 0.2 to 2.5 GHz. The quasi circulator has directivity of 15 to 52 dB and load dynamic range of 10 to 49 dB, over the 0.2 to 1.7 GHz band. The proposed circuit thus can be used in portable network analyzers and other applications designed for the UHF and L bands.