We also researched the frequency structure of ddc and interchanged the filter multiphase heft and taking out - operation using the theory of equivalent counterchange in multisampling system 从理论上研究了数字下变频的频谱结构，利用多采样率系统中结构的等效变换原理，将滤波器多相分量与抽取操作进行互换。
Architecture of ddc based on its principle and structure is proposed by this dissertation , and then the principles of each module in ddc as well as some algorithm used in these modules are illustrated 本论文首先基于数字下变频的原理和结构,提出了本设计中的ddc构架,然后对其中各部分的原理和涉及到的算法作说明。
Data after ad sampling and digital down converter transfer to computer through pci bus interface , while base - band signal processing may choose cots dsp board or general high - performance pc in term of the need Ad采样、数字下变频后的数据通过pci接口传入计算机，基带处理可视需要选用多种商用dsp处理板，或选用高性能pc机。
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 chapter 3 , analyzing the feasibility of if digital receiver , simulate the ad sampling , ddc and am / fm signal ' s software demodulation by system simulation software - systemview 本文在第三章对中频数字接收机方案的可行性作了分析，并通过系统仿真工具systemview对a d ，数字下变频( ddc )及am 、 fm等调制信号的软件解调作了仿真。
It is expected to be designed based on the software radio technology in order to define the function of the hardware by the software , which can greatly improve the facility and the reliability of the systems 于是基于软件无线电技术的宽带中频数字接收机的研究正逐渐成为现代雷达系统设计的重要组成部分。数字下变频是其中的一个关键技术。
The main contents of this thesis include : ( 1 ) analyze the consistency between the traditional receiver and digital receiver in detail . the theory and the excellence of the digital down converter are also analyzed 本文的主要内容如下： （ 1 ）详细分析了传统接收机与数字接收机的等效性，分析了采用高速数据采集后数字下变频的原理和优点。
The paper designed the pn analyzer with using receiver circuit with optimized twice down - convert and highly efficient process arithmetic and comprehensive design and particularly harmonious system . in the system the 该文研制的pn分析仪pnscanner采用了很优化的二次下变频接收机电路以及效率很高的基带处理算法,严谨周到的设计和独特的协调机制。
It is very difficult to realize digital rf , but we can realize digital if . digital if mainly include : digital up convert ( duc ^ digital down convert ( ddc ) , a / tk d / a and number control oscillator ( nco ) 目前实现射频数字化还有一定的困难，但可以实现中频部分数字化。数字中频处理主要包括数字上变频、数字下变频、 a d与d a的处理以及数控振荡器等。
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。
