A Calibrated Phase and Amplitude Control System for a 1.9 GHz Phased-Array Transmitter Element

A system is proposed to allow the phase and amplitude of a signal to be accurately set and regulated over process and power supply variations. It uses a variable gain amplifier (VGA) in conjunction with the phase shifter to compensate for the variable losses of the phase shifter and simultaneously provide a means of adjusting the amplitude of the signal. The system has been fabricated in a 0.18 ¿m CMOS process, and operates at 1.9 GHz. The phase can be set with 5 bits of control over a 240° range and the amplitude can be varied over a 20 dB range. The feedback loops reduce the variation in |S21| across the phase control range from 12.1 to 0.4 dB. For a changing power supply voltage the feedback loops reduce the maximum phase deviation from 28° to 7° , and across different test chips the maximum standard deviation over the phase control range is reduced from 12° to 3°.