Design and implementation of the quadrature waveform generator
Shengqian Ma · Journal of Northwest Normal University · 2006
The design and implementation of quadrature waveform generator are described based on the AT89C52,phase-locked loop(PLL) and switched-capacitor filter(SCF).The square wave is generated by single-chip micro-controller.It is shifted 90 degree by a digital circuit.In order to obtain quadrature sinusoidal waves,the dual-channel square waves are filtered by two 8-order Butterworth lowpass SCF MAX295.The clock of MAX295 comes from PLL.For suppressed the affect of the sampling clock,the second order continue time filters are used.It covers frequency range 0.1~20 kHz.The errors of frequency and phase are less than 1%.