Design of compact broadband phase shifter with constant loss variation

Two types of compact broadband phase shifter MMICs (monolithic microwave integrated circuits) with constant insertion loss variations are presented. Both phase shifters are reflection-type phase shifters using a Lange coupler as a 3-dB coupler and LC resonance terminations. The first type phase shifter uses a single diode with reverse biasing as a varactor and adopts a miniaturized Lange coupler to maximize compactness and to minimize parasitic loss. The second type adopts back-to-back connected diodes with reverse biasing as a varactor for wider tunable phase range and parallel resistors for constant insertion loss variation. For both types, MMIC's are fabricated in GaAs 0.15-μm low noise pHEMT (p-high electron mobility transition) process and required indcutances are implemented by microstrip lines. The implemented MMIC phase shifter of the first type shows the measured relative phase shift range of 80 and measured insertion loss of 2.1 ± 0.2 dB at 20 GHz. The measured relative phase shift range of 72 ± 9 and the measured insertion loss variation of ±0.2 dB are obtained from 15 to 25 GHz. Similarly, the second type phase shifter shows the measured relative phase shift range of 104 and measured insertion loss of 2.4 ± 0.1 dB at 21 GHz. Also, the broadband characteristic of the second type is verified by the measured relative phase shift range of 96 ± 8 with the constant insertion loss variation of ±0.2 dB from 17 to 25 GHz.