Monolithic Integration of Self-Biased ${C}$ -Band Circulator on SiC Substrate for GaN MMIC Applications

We have designed and fabricated the first self-biased circulator operating in
${C}$
-band and monolithically integrated it with Qorvo’s GaN MMIC technology by embedding a FeNi-based magnetic nanowire composite (MNC) in a
$100~\mu \text{m}$
thick SiC substrate. This integrated microstrip circulator shows a circulation frequency centered at 5.7 GHz, with an insertion loss of 2.7 dB and isolation of 14 dB. The circulator also demonstrated power handling of 9.6 W with continuous wave and at least 40 W under pulsed conditions. This letter points a path in integrating miniaturized circulators into full-duplex GaN T/R MMICs with stringent form factor limits.