QPSK调制与解调，低通滤波器采用了时域和频域两种实现方式，截止频率fc = 200hz,采样频率fs= 1000hz,欢迎下载参考！-QPSK modulation and demodulation, using a low-pass filter with a time domain and frequency domain implemented way, the cutoff frequency fc = 200hz, the sampling frequency fs = 1000hz