UC Irvine

MM-wave/sub-Terahertz(THz) signal generation, radiation and detection has become increasingly attractive due to its fast-growing applications in spectroscopy, radar, biomedical and security imaging as well as high-speed wireless communication.

Silicon technology, in one hand, offering high-density signal processing capabilities due to aggressive scaling of its feature size, and on the other hand, allowing integration of mm-wave/THz antenna elements owing to their shrunk footprint at these bands, is well-suited for implementation of fully-integrated multi-antenna mm-wave/THz wireless System-on-Chips (SoC's).

Performance of such system is dominantly governed by the quality and efficiency of signal generation, transmission/reception and detection. Passive and active components as means of realizing these functionalities must be optimized for operation at these frequency range. However, excessive loss of on-chip passive components and limited gain and output power of transistors at such high frequencies demand novel passive and active structures.

Furthermore, high level of integration implies that the co-design of front-end components leads to a better end-to-end performance, thus a holistic design methodology must be employed. Radiation characteristics of the wireless signal must also be engineered to improve its transmission quality. For example, circularly polarized radiation is found to be a viable choice for many imaging and communication applications by exhibiting excellent robustness against de-polarization effects.

In this dissertation, silicon realization of on-chip waveguides, as low loss mediums for high-frequency wave propagation, is explored and implementations of low-loss cavity-backed passives are discussed. Furthermore, a silicon-integrated IMPATT diode, together with its fabrication and modeling is introduced as a solution for obtaining active behavior beyond $f_{max}$ of transistors.

Next, a high-power/efficiency mm-wave circularly-polarized cavity-backed radiator, employing a multi-port multi-function passive network as resonator, power combiner, and antenna, is introduced. Necessary conditions for robust operation of such multi-port oscillators/radiators are also derived. Fabricated in a 0.13$\mu$m SiGe BiCMOS process, the prototype chip achieves 14.2dBm EIRP, -99.3dBc/Hz phase noise at 1MHz offset, and 5.2\% DC-to-EIRP conversion efficiency which is the highest reported value among silicon-based radiators not using silicon lens or substrate processing.

Finally, a 210GHz low noise amplifier (LNA) is presented to address the detection challenges. This LNA, achieves 18dB of gain, with less than 12dB noise-figure and 3dB bandwidth of more than 15GHz, thereby showing best performance metrics among prior work. This is achieved by incorporating circuit and EM techniques enabling simultaneous optimization of stable gain-, noise- and bandwidth-performance parameters at this frequency range.