UC San Diego

In the quest to increase channel bandwidths in wireless communication systems, two important trends are to move towards wider continuous bands at mm-wave frequencies and to aggregate smaller bands at cellular frequencies. In this dissertation a few of the challenges and possible circuit and DSP solutions for efficient high data rate communication using these techniques are described. First, an issue relating to cellular uplink carrier aggregation is discussed and a DSP based solution developed. Second, the design of a broad band CMOS PA for mm-wave applications is presented. Third, the design of an mm-wave predistortion system and its use to predistort an array of mm-wave CMOS SOI PAs is described. In the near term, cellular carriers plan on employing carrier aggregation to increase data rates. This can lead to significant receiver desensitization for a number of LTE band combinations, because of the cross-modulation products created by the nonlinearity of RF front-end components. To mitigate this effect, an all-digital cancellation algorithm is proposed in this thesis that canceled the cross-modulation product and improved the signal-to-interference-plus-noise ratio (SINR) and error-vector-magnitude (EVM) of the desired received signal by up to 20 dB. In the second part of the dissertation, the possibility of using mm-wave CMOS PAs for wideband communication is described. The design of CMOS stacked-FET PAs with an emphasis on appropriate complex impedances between the transistors is presented. The stacking of multiple FETs enables the use of higher supply voltages, which in turn allows higher output power and a broader bandwidth output matching network. A 4-stack amplifier design that achieves a saturated output power greater than 21 dBm while achieving a maximum power-added- efficiency (PAE) greater than 20% from 38 GHz to 47 GHz is reported. Finally, the thesis describes predistortion of an array of stacked-FET PAs after spatial power combining. Predistortion improved the signal quality to a high level, which allowed the use of complex modulation schemes, which in turn allows high data rates in a spectrally efficient manner. After predistortion a 100-MHz wide, 1024-QAM signal was demodulated with an EVM of 1.3%, which corresponds to a data rate of 1 Gb/s