Improved techniques for variable phase shifter design

In this paper we firstly present the design and development of a compact analog phase shifter at 1.3GHz using varactor diode based reflective load and then we present an improved technique/ method applied into phase shifter designs which mitigates the problem of large insertion loss variation with control voltage, which is very vital requirement for the phase shifter acting as an actuator or control device in RF control applications. Although many designers had earlier minimized the insertion loss variation using shunt resistors with the reflective load, but it results in significant signal loss. The improved technique herein do away with the shunt resistor while significantly mitigating the problem and resulting in significant improvement. The full circuit was modeled, simulated and optimized in ADS / Momentum and finally fabricated/ implemented on microstrip. The design methodology, simulated and measured results are presented. The phase shifter is a vital control device used in several applications, one of such application is phase feedback control of the RF cavity voltage in RF particle accelerators which is essential so that the beam sees the constant and correct phase for proper acceleration.