This project will research innovative approaches to develop methods and fabrication techniques to enable practical access to the millimeter wave spectrum. This is important for handling future cellular data traffic, expected to grow at a rate of 40-70% annually. As existing cellular bands are already crowded, it is necessary to explore other bands, and more specifically millimeter-wave (mm-wave) frequencies. Critical issues for practical millimeter wave transceivers on handhelds are power and bandwidth handling. With this in mind, the goal of this research is to explore power-reduced and hardware-reduced transceivers to realize several concurrent high gain beams for multiple-input multiple-output (MIMO) communications and to concurrently overcome propagation losses for cellular connectivity. Achieving these goals is expected to have transformative impact on all aspects of wireless communications. Concurrently, the large available bandwidth at millimeter wave frequencies will enable secure wireless communications systems for large data rate transfers. This research is also in line with the National Broadband Plan aimed at providing every American with affordable access to robust broadband services. Moreover, this project will train students in emerging wireless technologies. Specifically, a variety of outreach activities are planned to attract undergraduates and underrepresented students in engineering, including high school students through summer camps and wireless connectivity projects relating to 1) medical sensors, 2) short distance communication applications and 3) energy harvesting using ambient RF signals. Examples of societal impact include the realization of reliable high bandwidth handhelds and secure wireless communications systems for large data rate transfers.Several innovations are proposed to enable practical use of the yet unharnessed capacity of the mm-wave spectrum. Among them are: 1) Novel ultra-wideband arrays that incorporate balanced feeds. 2) Hybrid frequency and code division multiplexing for secure high data rate communications to cover an unprecedented 10GHz bandwidth. 3) A beamformer architecture that combines all antenna array signals into a single analog-to-digital (ADC)/digital-to-analog (DAC) converter without loss of signal path identity. This is done by introducing a novel on-site code division multiplexing technique. It is noted that reduction of ADCs and DACs by a factor of 10 or more implies proportional reduction in power usage and back-end circuitry. 4) Hybrid integration of the phased array with complementary metal-oxide semiconductor (CMOS) and/or III-V transceiver and associated digital beamforming processor. Antenna arrays will be fabricated on low temperature co-fired ceramic (LTCC) substrates and be vertically integrated to ensure the highest possible gain and compactness. 5) Indoor/Outdoor measurements of the aforementioned integrated mm-wave system to characterize the impact of line-of-sight (LOS) versus non-LOS links, range, angle of arrival distributions, pathloss/shadowing, and delay spreads. Such outdoor measurements have yet to be performed at mm-waves using beamforming arrays.
