Continuous Broadband GaAs and GaN MMIC Phase Shifters

We describe the design of two broadband monolithic microwave integrated circuit (MMIC) loaded-line reflective phase shifters and their performance over the 6–12-GHz band. Lange couplers with transistor-loaded transmission-line reactive loads provide variable phase shift through reverse-bias control. A GaAs phase shifter with four diode-connected transistors in each of the two reactive loads is designed with discrete inductors to provide an increasing phase shift with frequency. A GaN reflective phase shifter uses 14 transistors in each reactive load with a goal of increasing the phase shift across the band. Measurements show continuous phase shift from 40° to 70° with less than 6-dB insertion loss over the 6–10-GHz band and from 60° to 165° with less than 8-dB insertion loss across the 8–12-GHz band for the GaAs and GaN MMICs, respectively. The power performance of the MMICs is compared in terms of large-signal
$S$
-parameters, harmonics, and IP3. The GaN phase shifter exhibits similar level of harmonic generation like the GaAs device at a 20-dB higher input power.