A simple wide-band frequency independent quadrature phase shifter

Quadrature phase sensitive detectors (QPSD) are a very important part of phase measuring systems, such as communication receivers. These types of devices are able to measure phase angles between two periodic signals very accurately even in the presence of noise. In the QPSD system, there is a specific block that produces a 90/spl deg/ phase shift for a sinusoidal input signal. Current design approaches are based on either a simple differentiator or integrator but they have some disadvantages such as frequency dependency. In this paper, the authors present a new design scheme for a simple, low cost quadrature phase shifter (QPS). This new design scheme exploits the current controlled gain of operational transconductance amplifiers which yields a relatively simple QPS design. The theoretical derivation and characterization of the new design scheme are provided. In addition, we present simulation and experimental results.