A Low-Cost Continuous L-Band Phase Shifter/Attenuator for Low Power Applications

A simple continuous phase shifter and attenuator module for L-band applications is presented. The phase shift and the attenuation can be continuously varied over 360°and 20 dB, respectively. The phase shifter is a hybrid unit, consisting of a 180° discrete PIN diode phase shifter and a novel 180° continuous varactor diode phase shifter. Both phase shlfters are optimized for small frequency variations, which are less than 10° over a 7% bandwidth (1.5 to 1.7 GHz) at all phase shifts. The attenuator is a 3 dB hybrid, loaded by two tuned PIN-diodes. The interaction between phase shift and attenuation is negligible at the center frequency (1.6 GHz). The insertion loss for the complete module is about ¿2 dB at the center frequency, the return loss is less than ¿15 dB, and the maximum input level is about 10 mW.