Development of an analog phase shifter for particle accelerator control circuits

This paper presents the design and development of a voltage controlled analog 0-360° variable phase shifter at 1.3 GHz using RF vector addition method. The input RF signal is split into four signals having phases 0, 90°, 180°, 270° using a 3-dB rat-race coupler and 2 branch line couplers. Each of these signals is next passed through a voltage controlled FET based attenuator and the four signals are then combined to get the phase shifted RF output signal. A novel circuit has been developed to supply control voltages to the attenuators to get the full monotonic phase shift range of 0-360°. The circuit has been designed, simulated and optimized and fabricated on microstrip. Suitable layout has enabled the realization of the component in a very small size. This component is useful in control circuits for particle accelerators.