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Low-EVM Adaptive Millimeter-Wave Transmit and Receive Systems


Beamforming is a necessary feature of high-capacity communication links operating at millimeter-wave (mm-wave) bands. Due to the advancement of CMOS-SiGe processes, mm- wave phased arrays can be manufactured at low cost with compact sizes. Transmit arrays are capable of improving the low-output power of silicon PAs through beam directivity. However, reaching (relatively) high efficiency while maintaining high-linearity for QAM waveforms poses a design trade-off. Receive systems suffer from low signal levels and potentially high-power jammers from neighboring links that are not spatially rejected. High linearity is essential for attaining the most efficient communication for both transmit and receive systems. High directivity of the system suggests the need for adaptive beam-scanning methods that do not require skilled labor to determine the location of the transmitter and receiver. The first portion of the dissertation discusses the performance of two phased-array architectures (LO and RF scanning) in presence of jammers. Analytical equations are derived which incorporate the antenna array geometry, array circuit architecture, and channel non-linearity. Secondly, a low-EVM (error-vector- magnitude) direct-conversion I/Q modulator is presented at Q-band in 120 nm SiGe process. The effect of various circuit errors on modulation quality is analyzed. In particular, a new analysis and closed-form equations are presented for the impact of I/Q path compression, power- amplifier AM-AM and AM-PM non-linearity on the system EVM. The second version of implemented Q-band I/Q upconverter incorporates two 12-bit DACs and active mixers and is demonstrated to pre-distort a 16-QAM through an off-chip power amplifier. Finally, a novel adaptive beam-steering I /Q receiver array is proposed and demonstrated in 45 nm CMOS SOI process. The proposed architecture allows auto- steering in the direction of the incident signal and supports modulated RF signal for high-data rate communication. The technique uses combined dynamics of coupled-oscillator arrays (COA) and coupled-phased locked loops (CPLL). This is the first demonstration of self- steering mechanism in a monolithic platform

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