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Phase shifter approaches for compact low-power phased array transmitters


One of the challenges in implementing phased array systems is to implement high performance phase shifters. This dissertation presents highly linear phase shifters for 2GHz wireless mobile applications and millimeter-wave phased array transmitters with active phase shifters. Different architectures of phased array systems pursue different aspects of phase shifters. In the first part of the dissertation, a low-loss, low-distortion passive variable phase shifter on Silicon-on-Glass (SOG) process will be presented. Schottky diodes in the SOG process enables very high quality factor of varactor diodes and on -chip passive inductors. A novel passive variable phase shifter with varactors and inductors presented in the dissertation has very low third-order intermodulation distortion (IMD3) and low insertion loss, which make it suitable for transmitter front-end applications in mobile devices working at CDMA bands. In the second part, two generations of integrated phased array upconverters at millimeter-wave frequencies with LO-path phase shifting will be presented. The phase-shifting is achieved by the vector summation of the I/Q LO signals in the LO path. The first version adopts a frequency doubler followed by a polyphase filter to generate the I/Q basis LO signals. The principal of the active phase shifter operation and frequency doubler are explained. The phase error due to amplitude and phase mismatch of the polyphase filter is discussed. The eight-element phased-array transmitter is implemented in a 0.18[mu] SiGe BiCMOS process in the later version. To reduce dc power consumption, a localized frequency doubling injection-locked quadrature oscillator is used to ease LO signal distribution. Measured conversion gain over frequency and IF signal is presented. Array beam scanning pattern is also presented based on the measured phase and power for each channel

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