Amplifying single-gate mesfet phase shifters at x-band

The thesis will describe 0/180 degree digital switched-path phase shifters that exhibit insertion gains of approximately 3 dB at 9.5 GHz. The microwave switching and amplification in each phase shifter is performed with a pair of Plessey GAT4 single-gate MESFET devices. The basis for this microwave switch is a matched amplifier which when its device is pinched-off displays an insertion loss of about 17 dB down on the amplifier's peak gain of 6 dB. A characteristic feature of this switch is its large terminal mismatches when in its off state. Use has been made of these to recover part of the 3 dB division (or recombination) loss inherent in the type of switched path phase shifter used in this work. The paths that are being switched are the outputs of phase splitting networks and power dividers. A divider has been developed for use with these switches and utilises the broadband coupling properties of slotline to microstrip transitions. This phase shifter has a bandwidth of 1.4 GHz which is determined mainly by the network matching of the two devices. The phase error is less than 6 degrees in this bandwidth and phase transition times of less than 1 nS have been determined by spectrum analysis.