High-Power X-Band 5-b GaN Phase Shifter With Monolithic Integrated E/D HEMTs Control Logic

A high-power X-band GaN-based 5-b digital phase shifter with control logic circuit on-chip is demonstrated for the first time, which is implemented with monolithic integrated GaN E/D HEMTs fabrication process. Gate trench etching togetherwith Al2O3 as gate dielectric is used to form the gate of the E-mode GaN HEMTs. Switched filter and high-pass/low-pass topology are used to design the 11.25 degrees/22.5 degrees and 45 degrees/90 degrees/180 degrees phase shifters, respectively. A novel three stages control logic circuit is described and characterized. The fabricated 5-b phase shifter demonstrates an rms phase error less than 4.5 degrees, an rms amplitude error less than 0.6 dB, an insertion loss less than 11 dB, and an input-output return loss better than -10 dB across 8.5-11.5 GHz for all 32 states. In addition, the phase shifter exhibits a typical P-1 dB input power of 34.8 dBm in the continuous wave power handling capability measurement at 9 GHz.