Low-noise receivers, micromachined antennas and low-loss transitions for millimeter-wave applications.

Abstract

This thesis investigates the integration of planar antennas with planar circuit technologies (cpw and microstrip) using standard IC fabrication techniques to achieve high performance front-end receivers at millimeter-wave frequencies. The focus is to eliminate substrate losses from surface waves which greatly limit the radiation performance and bandwidth at millimeter-wave frequencies. In the first part, millimeter-wave receivers integrated on a silicon substrate backed with a dielectric hyperhemispherical lens are described. The lens eliminates the propagation of surface modes. A 94 GHz double-slot Schottky-diode receiver is shown. A commercial Shottky-diode is placed at the center of a double-slot antenna and acts as a receiver. The LO pump signal is quasi-optically injected after being combined with the RF signal through a Martin-Pupplett diplexer. The total measured SSB conversion loss is 9.3 dB over the 86--90 GHz band. In order to avoid the drawbacks of a heavy quasi-optical diplexer, a 150 GHz subharmonic mixer where the LO is injected on-wafer using W-band probes is demonstrated. The RF signal is received by a double folded-slot antenna, which has a low impedance of 20 W at 150 GHz. In the second part, micromachining fabrication techniques are applied to microstrip antennas on silicon substrates to synthesize by removing dielectric a low dielectric constant region around the microstrip antenna, resulting in improved radiation efficiency and radiation patterns. A larger bandwidth can also be achieved. Two different approaches are investigated: first closely spaced holes are drilled around and below the microstrip patch at 13 GHz. The radiation efficiency is improved from 48% for a high er substrate antenna to 70% for the synthesized antenna. The 10-dB bandwidth is also improved from 0.8% to 8% resulting from a resonance effect in the drilled region. Second a cavity is chemically etched locally below an aperture coupled microstrip antenna at 94 GHz. The measured radiation efficiency is 58% compared to 28% for an antenna built on a full silicon substrate, while the front-to-back ratio is better than -12 dB. Also, in an array configuration, the mutual coupling between adjacent elements can be lowered to better than -20 dB, allowing the integration of this particular design in phased arrays. Finally, low-loss W-band interconnections based on electromagnetic coupling are explored. Uniplanar and vertical transitions that combine cpw and microstrip technologies show losses better than -1 dB and are very wideband, over close to the entire W-band region (70--120 GHz). These techniques are attractive approaches for low-cost, high-performance 3-dimensional monolithic millimeter-wave front-end receivers, compatible with standard IC fabrication techniques in the perspective of mass production. Applications are in personal and commercial communications, automotive radars, detection and guidance.