UC Santa Barbara

The increasing data consumption due to the development in smart devices demands broadband, high-data-rate communication links both in the user end-point and backhaul links. Backhaul communication links over fiber can further be developed using optical technologies. Millimeter-wave wireless technologies can provide high data rates for both end-users and in base-stations. Millimeter-waves provide wide unlicensed and unallocated frequency bands, creating an opportunity for broadband wireless communications. At these frequencies the signal propagation range is limited and attenuation is high; but signal strength can be recovered in part by using phased arrays. In addition, short wavelengths at these frequencies allow one to place a massive number of antennas within even a small aperture, which can provide a massive number of simultaneous independent beams (multi-input multi-output: MIMO). MIMO can provide large increases in the overall system data rate.

In the first part of the dissertation, two optical phase-locked loops (OPLLs) are demonstrated. These consume 1.3 and 1.8 W of power respectively and have larger than 15 GHz locking ranges. These OPLLs were then integrated with a magnesium fluoride (MgF2) microresonator-based optical frequency comb in order to show two chip-scale optical frequency synthesizers (OFSs). This comb has a 50-dB span of 25 nm (~3 THz) around 1550 nm with a 25.7 GHz repetition rate. The optical synthesizers consume 2 and 1.7 W of power within a 10 cm^3 volume respectively. The first generation OFS achieves a tuning resolution better than 100 Hz within 5 Hz accuracy, and can switch >5 nm in wavelength in less than 200 ns by jumping over 28 comb lines.

In the second part of the dissertation, a broadband transceiver using 22 nm fully-depleted silicon on insulator (FD-SOI) complimentary-metal-oxide-semiconductor (CMOS) technology is demonstrated. The work includes transistor characterization and design of the circuit building blocks. The transmit and receive channels have more than 10 GHz 3-dB bandwidth, sufficient to support more than 10 GBaud data transmission rate. The thesis then reports transmission experiments using an earlier design generation of 140 GHz MIMO transceivers, which was fabricated in 45 nm SOI CMOS. In transmission experiments over 20 cm propagation distance in air, open eye diagrams were observed even at symbol rates as high as 8 GBaud using a 145.8 GHz carrier frequency.

We report low-cost, yet efficient printed circuit board (PCB) based off-chip antenna arrays, and IC-antenna transitions at D-Band. These are the first such reported designs working above 140 GHz. An 8-element single-row, series-fed patch antenna array shows 14 dB gain with 7 GHz bandwidth (S21). It has 9-degree E-plane and 65-degree H-plane 3-dB beamwidths. Measurement results align well with the simulations, except that the antenna resonant frequency is 4 GHz higher than design and the gain is 1-1.5 dB lower. A wirebonding transition between the transceiver ICs and antenna arrays are designed. Its performance is evaluated using 3D full electromagnetic simulations in Ansys HFSS. The transition loss is low, only about 1.8 dB, with a 10 GHz bandwidth in simulations. These simulations align well with the measurements from packaged transceivers.

Finally, a fully-packaged 4-channel MIMO receiver and a fully-packaged 2-channel transmitter are demonstrated. In wireless data transmission experiments over a 25 cm propagation distance, a single-channel transceiver using these boards shows open eye patterns up to 5 GBaud data rate using a 146.7 GHz carrier frequency. The bit-error-rate (BER) is measured at less than 10^-3 up to 2.5 GBaud data rate using the same data transmission experiment. The modules designed in this dissertation are the first fully integrated phased array ICs working above 140 GHz to the best of the author's knowledge. These modules can support multi-beam communications for the next generation of wireless communications with a massive number of beams, each providing 1-10 Gb/s, approaching 1-10 Tb/s overall data rate.