Monolithically Integrated Self-Biased Circulator for mmWave T/R MMIC Applications

Monolithically on-chip integrated circulator devices are demonstrated for the first time through the direct integration of polycrystalline hexaferrite magnetic material with GaN/SiC wafers. These narrow-band and broad-band self-biased (SB) circulators have an operating frequency centered at Ka-band (26.5-40 GHz) and V-band (40-75 GHz). A record SB circulator performance combining insertion loss well below 1 dB, isolation above 15 dB over a 10% fractional bandwidth and natural thermal solution on SiC substrate was achieved. Power measurements show the device is capable of handling an input power above 6 W. A full-duplex transmit/receive (T/R) MMIC, the first of its kind that is fully integrated on a semiconductor wafer, has also been demonstrated as enabled by this monolithically integrated circulator technology, showing over 100 times in size miniaturization as compared to conventional technology with promising applications in radio frequency (RF) electronics technologies for 5G and beyond.