正交信号发生器的设计与实现

描述了基于AT89C52单片机、锁相环和开关电容滤波器的正交信号发生器的设计和实现方法.单片机产生方波,通过数字接口实现相位差为90°的方波,再通过两个8阶BUTTERWORTH低通开关电容滤波器MAX295对双路方波进行滤波,从而产生正交的正弦波.MAX295的时钟由锁相环倍频产生.采用连续时间滤波器抑制采样时钟的影响.频率覆盖范围0.1~20 kHz.频率和相位误差小于1%.

Design and implementation of the quadrature waveform generator

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%.