A $W$ -Band Micromachined 3-D Cavity-Backed Patch Antenna Array With Integrated Diode Detector

A 2 × 2 array of W-band air-dielectric cavity-backed patch antennas is presented. The array and its components are fabricated using a sequential surface micromachining technique known as the Polystrata process. Each antenna has a simulated 4.1% 10-dB return-loss bandwidth of about 94.5 GHz, a radiation efficiency of 95%, and a gain of 8.3 dB at broadside with a 76° 3-dB beamwidth. The simulated gain of the entire array is 13 dB. To facilitate system integration and measurement, several methods of interface are explored, including ground-signal-ground probing, direct transition to WR-10 waveguide, and hybridly integrated detector diodes. A measured return loss of 32 dB at 94 GHz with a 10-dB bandwidth of 3.25 GHz is measured for a single antenna, and 18 dB with a 10-dB bandwidth of 4.6 GHz is measured for an array. Measured E- and H-plane 3-dB beamwidths of 25° are reported. Antenna pattern measurements show good correlation with simulated results. The measured broadside gain for the antenna array is 13.5 dB at 94 GHz.