Design and Implementation of Self-tracking 90 Degrees Phase Shift Circuit

Abstract

Based on the linear phase shift of Bessel filter and the frequency doubling function of phase-locked loop, the new structure of 90 degrees phase shift circuit is proposed. The input signal is amplified and shaped into digital signal, and the clock of switched capacitor filter MAX296 is generated by the phase-locked loop. It can control the ratio between clock and input signal frequency of the filter. So when sinusoidal signal is as input of the filter, in a wide frequency range of from 20Hz to 1kHz, the 90 degrees phase shift can be achieved at the output of the filter. The working principle of the system is described, and the design circuit and experimental results are given.