For digital mobile phone services in Canada, Mexico and the United States, Personal Communications Service (PCS) is one of the most popular standards, and its downlink frequency band is centered at 1.96GHz with 60MHz bandwidth. This research presents a microcontroller AT89c5131 configured active analog phase shifter at 1.96GHz with phase-shifting range of 90°. The phase shifter can be applied in cellular base station downlink circuits, and the concept could be extended to radar and smart antenna applications.;The vector addition phase shifter has the following advantages: using microcontroller (MCU) increases the flexibility of control circuits and provides possibility to extend the phase shifter to a phased array antennas system smoothly; applying algorithm to compensate the amplifier's gain-versus-control-voltage non-linear characteristics results in continuous phase shifting with a small RMS phase error of 1.3°; constant gain (|S21|>1) increases transmission power efficiency.
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