说明：  本程序是关于卫星上下变频的简单的实现算法，首先产生双边带调制信号，与收本振混频后，通过低通滤波器完成下变频。再与发本振混频，通过高通滤波器后完成上变频
(This program is a simple algorithm on the satellite and down-conversion, the first double-sideband modulation signal generated, after the close of the oscillator mixer, low-pass filter complete the conversion. Again and send the local oscillator mixer, followed by the completion of the high-pass filter frequency)