FM 解调及AFC算法的VHDL设计实现

根据遥测中频PCM/FM信号的解调原理,介绍了FM解调及自动频率控制(AFC)设计的理论架构和实现方法,通过理论分析、公式推导和Matlab仿真等手段证明了方法的正确性,在此基础上完成VHDL程序设计,最后进行了仿真测试和实验验证.仿真结果和实验结果证明了该实现方法的可行性.     

中频PCM/DPSK信号软件解调的一种实现方法

本文根据中频PCM/DPSK信号的解调原理提出了软件解调的一种实现方法,完成了对软件解调算法的理论阐述和数学推导,并根据推导出的数学模型在Matlab平台下进行软件设计,最后进行了仿真测试和实验验证,仿真结果和实验结果证明了该实现方法的可行性。     

基于软件无线电的FM正交调制器的实现

基于软件无线电(SDR)的思想,介绍了一种新型FM调制方法———正交调制,并利用Xilinx的高级系统级FPGA仿真工具System Generator for DSP对这种正交调制方法进行建模、仿真。实验结果表明,用正交调制的方法可以方便地实现FM调制。用数字方法为实现FM调频广播或超短波FM电台提供新的解决方案。     

一种FM信号调制解调数字化实现方法研究

针对陆军某通信电台应用需求,本文提出了一种基于软件无线电设计思想的FM信号调制解调数字化实现方法,给出了数字化实现FM信号调制解调的原理架构及实现步骤,并与传统的模拟实现方式进行对比,最后对数字化实现过程进行了仿真验证.该方法已实际应用于项目,性能达到了军标要求.     

软件无线电中FM调制解调算法的DSP实现

介绍了FM调制解调的数字化实现方法 ,给出了基于DSP芯片TMS32 0C32DSP实现的FM调制解调算法功能模块及其主要源代码。该功能模块已应用于超短波FM电台上     

几种FM数字解调算法比较

探讨了3种FM数字解调的算法,给出相应的公式推导,并由此得出了算法和系统模块。在此基础上,通过对TI公司的TMS320C54x系列DSP实际应用,分析了各种方法的优缺点及各自的应用场合,并对一段信号,采用3种方式解调的结果进行了比较。     

数字正交FM解调方案门限效应的研究

介绍了FM解调方案的门限效应。针对传统调频解调方案中的解调门限值高以及降低解调门限的方案难以实现的不足,在研究传统模拟调频解调方案的基础上,分析了数字FM解调方案的门限性能。理论推导证明,数字正交FM解调方案的门限效应低于模拟解调方案。因此,可以采用数字正交解调方案降低其解调门限,而不需采用较难设计和控制的反馈系统,这极大地降低了调频系统实现的复杂度。最后计算机仿真的结果显示,该方案比传统模拟解调方案门限约低2dB。     

PCM/FM遥测序列软解调研究

为了提高PCM/FM信号解调系统的性能,本文研究一种多符号检测(Multi-Symbol Detection,MSD)技术.首先针对PCM/FM在硬件解调中存在的一系列问题,引入MSD软件解调方法;随后研究MSD在低信噪比下解调同步的实现;最后进行算法仿真,结果表明,在误码率10-4处时,检测性能比传统非相干鉴频算法可提高近3 dB,性能十分理想.     

FM信号数字化解调算法的改进与实现

针对FM(调频)信号数字化解调中叉积鉴频法存在占用资源大、精度低和只适用于窄带信号解调的缺点,采用了一种改进的解调算法,该算法通过改变对I路和Q路信号的处理方法,避免计算近似反正切值,最大限度降低了算法复杂程度,实现了占用资源小、精度高和满足窄带和宽带信号的解调。经MATLAB软件仿真并利用Quartus II 11.0软件基于Cyclone III芯片设计仿真,验证了该算法是可行的。     

软件无线电技术研究与实现

文章针对软件无线电技术中使用的双边带调幅（AM）、模拟频率调制（FM）和差分相移键控（DPSK）信号在解调过程中的软件算法,从理论上进行了较严密的推导与论证,并给出了软件接收机的构成及检测算法的实现方法。     

基于MATLAB的遥测PCM/FM信号解调仿真

为解调遥测体制中常用的PCM/FM信号,在受到鉴频电路的启发后,提出了非相干包络检波算法,这种算法共包括限幅、求导、低通滤波3个步骤。详细讲述了这种解调算法的基本原理和实现过程,并对一些关键步骤做了着重说明,最后用MATLAB进行了仿真,画出了误码性能曲线。仿真结果表明该方法不仅能够有效抑制各种干扰、具有较好解调性能,而且原理简单、运行效率高。     

一种PCM/FM接收机的定时同步设计和实现

时钟同步是接收机的关键问题,传统模拟解调灵活性差,调试复杂。针对测控中常用的PCM/FM体制,介绍了一种全数字接收机的定时同步方法,采用数字转换跟踪环估计定时误差,通过内插计算和反馈控制采样时钟完成误差校正。同步计算全部由软件实现,设计灵活。Matlab仿真及VHDL代码的硬件实测结果表明,该方法同步时间快、定时精度高,适合FPGA实现。     

带内数模混叠同播中的OFDM对FM的干扰分析

OFDM与FM带内数模混叠同播是中国发展数字调频的一项重要候选技术,评估OFDM对FM解调的影响是选择OFDM与发射功率比的重要参考依据.在给出了三种常见调频解调算法公式的基础上,通过仿真评估了OFDM对FM解调失真度和信噪比的影响.仿真结果表明,在OFDM与FM发射功率比高于-11 dB时发生明显的捕获效应.     

Interferometric demodulation of optical FM signals and its relation to modal distortion in optical multimode fibers

A general theoretical analysis of two-beam interference between modulated light signals is presented. It is demonstrated that a Michelson interferometer (MI) with short path difference can be used for demodulation of optical frequency modulation (FM) signals. The demodulated signal is usually a wide-band FM signal charaeterized by an effective FM index βeffin the order of 10-100, and the "conversion efficiency" of the demodulation is given by the ratio between the actual βeff-value and its low-frequency limit. For incoherent applications interference must generally be avoided as the demodulated wide-band signal generates harmonic distortion of high order. The close connection between interferometric demodulation and modal distortion in multimode fibres is demonstrated. An improved theory of modal distortion is presented and numerical examples of modal distortion are calculated. In practical cases the amount of distortion can be estimated on the basis of the fiber dispersion, the frequency deviation of the laser and the amount of spatial filtering.     

FM解调的性能分析与测试方法

在无线通信中,调频调制（FM）方式因其抗噪性能好、实现简单被广泛应用。分析了FM解调的信噪比性能,给出了一种FM解调信噪比的测试方法。     

Demodulation Procedure for Very Wide-Band FM

Since conventional FM demodulators are incapable of accurately demodulating very wide-band frequency-modulated signals, a new approach to the problem is needed. Based upon a theorem by Sandberg, a practical procedure is presented for demodulating not only typical FM signals but also those employing modulation bandwidths and/or frequency deviations on the order of the cartier frequency. The proposed demodulator utilizes an iterative recovery procedure. The first iteration is analogous to demodulation by a conventional zero crossing discriminator and results in severe distortion of the modulation under wide-band conditions. This distortion is reduced by successive iterations. Because, in practice, the iterative process is truncated after a finite number of terms, a procedure for computing the coefficients of these terms for minimum mean-squared error is given. Using computer simulation, the demodulation technique is demonstrated to work effectively for several very wide-band FM signals.     

Modeling and simulation of FM detection by zero-crossing in thepresence of noise and FH interference

A signal model for a frequency-hop (FH) spread spectrum system and an FM system is presented, and the demodulation of an FM signal in the presence of interfering FH and noise is described. The FM receiver presented uses a zero-crossing scheme for demodulation. To demonstrate the zero-crossing technique, two algorithms are developed and examined. The results show that for many applications, FM systems could reasonably coexist with frequency-hopping spread-spectrum systems. Furthermore, zero-crossing demodulation schemes are shown to be useful with microprocessor-based detector systems