Collaborative Research: EARS: Broadband Mobile Wireless Access Using mm-Waves Bands Beyond 100 GHz

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The importance of wireless communication on the quality of our lives and on our economy cannot be overstated. While network operators and researchers have done a tremendous job to improve the capacity of existing networks, there is a strong need to explore new options to support the exponentially growing wireless Internet traffic. This research will investigate a completely new spectrum in the mm-wave band that could enable Gigabit links for mobile users, allowing network operators to expand capacity in a graceful manner. Up to now, mm-wave communication has been mostly limited to either point-to-point links or to short-range communication for fixed terminals. Using mm-wave radios for mobile communication requires a complete rethinking and co-design of the circuits, antennas, packages, and systems and protocols. This research will explore the design of mm-wave circuits and systems at 120 GHz, enabling large arrays of radios to communicate with very high data rates ( 10 Gbps) over relatively long ranges (hundreds of meters). Compared to research below 100 GHz, this area is relatively unexplored, with only about a dozen demonstrations of working transceivers. The research team will investigate system and circuit architectures to support beam forming, beam nulling, multi-user MIMO (multiple-input multiple-output), allowing efficient spectrum re-use through spatial filtering and interference rejection. Novel circuit design concepts will be prototyped in 28 nm CMOS (Complementary Metal-Oxide Silicon) technology along with GaN (Gallium Nitride) transistors for high power transmission. Today's mm-wave transmitters are extremely inefficient when the waveform has a high peak to average ratio (2% average efficiency), whereas the proposed transmitter architectures will increase both the output power and efficiency by an order of magnitude. The range of mm-wave systems realized in CMOS, particularly without the use of lens, will also be increased from a few meters to hundreds of meters. This research will enable the exploitation of completely untapped spectrum for 5G cellular and beyond applications.The technical objective of the proposed collaborative research project is to focus on circuit and system level realization of a hardware platform that can enable the study of optimal beam forming and beam nulling (interference cancellation), while allowing practical measurements to be carried out on the propagation characteristics of indoor and outdoor channels above 100 GHz. Specifically, the PI, co-PI and a team of researchers will design and implement key building blocks for the transceiver to enable measurement and characterization of communication above 100 GHz. This project involves four main thrust areas to be investigated. The first thrust area will focus on transmitter circuit design and integration challenges and explore technology limits for silicon-based power amplifiers for MIMO applications in CMOS, especially above 100 GHz. The second thrust will provide insight regarding the integration of GaN transistors with CMOS to allow for high-density logic for digital signal processing and waveform shaping, and high breakdown voltage GaN devices for power generation. The third thrust will focus on antenna and system architectures to support beam forming with special attention to solving problems regarding LO (local oscillator) generation and distribution and finding the optimal configuration to minimize power consumption in a large array. The final thrust area will focus on investigating system level integration challenges from the sub-modules developed in the other thrust areas to produce a 120GHz transceiver.