A Dual-Gate FET Constant Phase Variable Power Amplifier

A 1-Watt X-band variable power amplifier is described which employs an 1800 µm GaAs dual-gate FET. Small-signal models of the device are presented and used to design for minimum insertion phase change over the gain control range. The amplifier has a power-added efficiency of 25 percent and its insertion phase varies less than 15 degrees over a 15 dB gain control range.