A circular voltage-controlled phase shifter with unlimited phase range for phase tracking loops

A circular voltage-controlled phase shifter (VCPS) is proposed to extend the range of the controlled output phase shift unlimitedly. This is made possible by configuring the system to operate in a circular way, differently from the conventional VCPS whose output phase saturates as the phase control input exceeds some value. The circular VCPS is based on a vector modulation method whose modulation signals are generated in a pseudo-sinusoidal way exploiting the current-voltage (I-V) curve of a MOS differential amplifier pair. When the circular VCPS is employed in phase tracking loops, the loop can operate in a stand-alone way thanks to its unlimited phase shifting capability.