A Novel Multilayer Aperture-Coupled Cavity Resonator for Millimeter-Wave CMOS RFICs

A novel millimeter-wave cavity resonator, completely compatible with commercial CMOS fabrication techniques, has been designed and fabricated in a 0.25-mum CMOS process and tested. The resonator employs a capacitively loaded cavity topology effectively implemented using the CMOS multimetal-layer and via-hole structure. The CMOS capacitively loaded cavity resonator, including two coupling apertures and microstrip feed lines, occupies an area of 2 mmtimes1.4 mmtimes6.28 mum, which is much smaller than the cavity resonator designed without a capacitive load at the same resonant frequency. It resonates at 30 GHz with a corresponding insertion loss of 2 dB and unloaded quality factor of 22.2. The resonant-frequency reduction is approximately 50%, as compared to that without the capacitive load. The design and performance of a new CMOS coupling aperture, which is useful as a coupling mechanism and a vertical interconnect for highly dense millimeter-wave CMOS RF integrated circuits (RFICs) are also presented. The developed low-loss and compact CMOS cavity resonator can be used to realize various millimeter-wave on-chip passive components such as wideband bandpass filters and diplexers and is suitable for direct integration with other CMOS circuits on a single chip. It is attractive for CMOS RFIC design at millimeter-wave frequencies