By analysis of the intermediate frequency signals which through eight antennae and receiver channels , eight channels radio spatial spectrum direction finding system can reach the purpose of finding radio direction 八通道无线电空间谱测向系统通过分析经过八路天线和接收机通道以后的中频信号达到确定无线电信号方向的目的。
Digital down converter ( ddc ) converts digitized if data into filtered baseband data which can be processed by a standard dsp microprocessor . ddc is a core part of a software defined radio ( sdr ) system 数字下变频( ddc : digitaldownconvert )是将中频信号数字下变频至零中频且使信号速率降至适宜通用dsp器件处理速率的技术。
In this thesis , aimed at the above - mentioned two - side problems , based on analyzing the theory of lfmcw radar ranging deeply , we implement the work of intermediate frequency signal processing 本论文针对上述两方面的问题,在深入分析lfmcw雷达测距理论基础上,在工程上完成了一部8mm毫米波线性调频连续波测距雷达的中频信号处理工作。
But it is not feasible to realize the ideal sdr by directly placing the ad converter close to the antenna . converting the broadband rf signal to the if signal which can be digital is the key to realize the sdr 由于直接将a / d变换置于天线端的理想软件无线电解决方案目前还不可行,将宽带的射频信号转换为可数字化的中频信号是软件无线电得以实现的关键。
Only by digital down converter , the data processing work which used to be handled by hardware can be done by software . this paper discusses the realization of digital down converter in detail , the main content is listed as following : 1 经过数字下变频处理,中频信号被下变频至软件可以处理的零中频,是实现用软件来完成原来需要硬件完成的工作的关键。
In this paper , variant metering methods are taken in terms of the different features of the analog signal and the digital signal . the rf signal is attenuated and down converted to intermediate frequency and then transmitted to the digital circuit 本课题针对模拟和数字电视信号的不同特点采用了不同的测量方法，在对射频信号进行衰减和下变频处理后的中频信号经过模数转换后，进入数字电路处理。
By the tuner , the dvb - t signal received has been converted to the if signal , and then demodulated by the cofdm demodulation chip . in the end , the usb controller sends the ts ( transport stream ) to the pc where it is decoded by the software 接收到的dvb - t信号经调谐器进行下变频处理后输出中频信号,再进行cofdm (编码正交频分复用)解调,得到的ts码流信号通过usb控制器送入pc机中进行软件解码播放。
As the spread spectrum and despread of digitalization are handled on the digital baseband , it is very important to convert medium frequency signal in analogue to digital baseband signal , and the downconverter functions to convert analogue medium frequency to analogue baseband signal , and to digital baseband signal through a / d transformation and decimation filter 所以把模拟的中频信号变为数字基带信号的下变频器就显得非常重要。在这里下变频器的作用是将由前一级接收而来的模拟中频信号变为模拟的基带信号，再经过a / d转换和抽取滤波成为数字的基带信号。
In the end , implementation of if digital receiver unit of tdrss user transponder by the method of fpga and dsp cooperation design are completed successfully , which leads to good ds - ss if receiver design for the signal whose carrier frequency is 3mhz , pseudorandom code rate is 3mchips / s , data rate is 10kbps , frequency offset is no more 1khz , and modulation mode is bpsk 最后，完成了该中频数字接收机设计，并对其进行调试和测试。测试结果表明，该接收机能对载频为3mhz ，频偏不大于1khz ，伪随机码速率为3mchips / s ，信息码速率为10kbps ， bpsk调制的直接序列扩频中频信号进行接收，基本满足设计要求。
On the basis of the theory of software radio , this paper discusses how to design and develop a realtime digital signal processing system in graphic programming language on a universal hardware workbench of digital signal processing aiming at satellitic intermediate frequency signal 本文论述了基于软件无线电思想，在一个通用的数字信号处理硬件平台上，针对卫星中频信号，用美国国家仪器公司提供的开发虚拟仪器的labview平台研制开发了一个实时的数字信号处理系统。
