| Microwave and millimeter-wave communication systems are expanding rapidly with an increased demand for lower-cost solutions. Conventional systems rely heavily on waveguide and dielectric resonator components for the high-Q passive structures, and MMIC technology for the active circuits. Planar passive components, while compatible with MMIC circuits, do have high enough performance for high-Q structures such as filters and oscillators. The problems associated with high-Q, planar elements are mainly due to the presence of the substrate. This limits the performance due to dielectric loss, radiation loss in the form of substrate modes, and ohmic loss by limiting the width of the conductor line for a given impedance. These losses limit the performance of filters by increasing insertion loss and decreasing out-of-band rejection. This thesis attempts to address these problems and reduce their effects by applying micromachining to result in low-loss, micropackaged resonators, filters, and oscillators.;The micromachining used in this work consists etching silicon to suspend microstrip lines on thin dielectric membranes. The silicon etching is then applied to shield the circuit as well. This results in transmission lines that are conductor loss limited. Several distributed transmission line resonators were fabricated using this technology and analyzed to address issues of increasing quality factor and reducing the effects of the transition from CPW-on-silicon to microstrip-on-membrane. Single resonators have been fabricated with quality factors ranging from 450--600 at 30--60 GHz. Also, micromachining was used to create integrated 3-D cavity resonators with a quality factor of 1100 at 24 GHz. A generalized filter synthesis method was developed that can be used to accurately design filters based on this technology while minimizing the amount of time intensive full-wave simulation. This method was used to design 3 and 4-pole, narrowband filters at 28 GHz with less than 1 dB insertion loss and greater than 70 dB out of band rejection. The filters were then combined to realize a planar, high-performance diplexer. The diplexer measured insertion loss was 1.4 dB and 0.9 dB with isolation of better than 35 dB and 50 dB for each channel. Micromachined resonators were also used to realize a planar, 29 GHz low-phase noise oscillator. The oscillator had a measured phase noise performance of --92 dBc/Hz at 100 kHz from the carrier and was 10 dB better than a similar oscillator fabricated without using micromachining. Micromachined interdigital bandpass filter banks and varactor loaded interdigital tunable filters were also investigated. This technology is compatible with a via-hole in silicon, silicon germanium, and gallium arsenide, and can result in low-cost systems that can be produced in high volume. |
