C-Band Attenuator/Phase Shifter Unit

Abstract

A C band attenuator/phase shifter unit has been designed. The unit has an attenuation range of 0-40 dB and can control the phase in 45° steps between 0-360°. The bandwidth is approximatly 18% with a center frequency of 5.5 GHz. The unit consists of an attenuator and 3 bit PIN diode phase shifter. The attenuator is of the absorptive type and uses phase optimized PIN diode modules. The unwanted phase variation as a function of attenuation is minimized to ±15° in the entire frequency range. Each phase shifter bit is of the hybrid coupler reflective type and uses broadside coupled transmission lines as matching networks as well as DC isolation. The matching networks are designed to give optimized phase vs frequency response.