在信号处理中，信号发射时，信号通过载波，调制，以电磁波的形式发射出来

在接收端，射频信号通过天线接收，超外差式等方式进行处理，变频到中频

然后通过数字技术对中频信号进行处理，此时的中频信号采样率很高，多达几十兆赫

而要解调出来的信号很小，此时就要经过滤波来得到我们需要的信号

如果直接设计滤波器，阶数会非常庞大，软件，硬件设备都承受不了

因此，一般常用的技术是进行下变频处理，其主要技术就是通过抽取滤波进行下变频

常用的滤波器就是CIC抽取, 希望可以帮助一些坛友解决基本的问题。

-In signal processing, signal emission, signal through the carrier, in the form of electromagnetic wave modulation, launched

In the receiver, rf signals through the antenna, specialized superheterodyne type means such as processing, the frequency conversion to intermediate frequency

Then through digital technology of intermediate frequency signal processing, at this time of intermediate frequency signal sampling rate is very high, as many as several decades MHZ

But the signal demodulation out is very small, at this time would be passing filter to get what we need signal

If design directly filter, order number be colossal, software, hardware equipment all suffer

Therefore, the technology is usually used for down-transducer processing, its main technical is by extracting filtering down-transducer

Commonly used filter is CIC extraction, the hope can help some friends solve basic problems of the altar.