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.     

模拟调制信号正交解调的抗载频失配性能分析

文章通过对模拟调制信号中两种典型的调制信号AM信号和FM信号进行数字正交解调的研究,探讨分析了该方法相较于相干解调所具有的较强抗载频失配能力,推导了AM、FM正交解调方法所允许的最大载频偏差△fmax,为实际应用提供了理论依据。     

基于多相滤波的PCM/FM正交解调

传统的相干正交解调方法,需要提取同频同相的载波,从而增加了解调的难度。根据遥测系统脉冲编码调制/调频（PCM/FM,Pulse Code Modulation-Frequency Modulation）信号的特点,采用基于多相滤波的解调方法。该方法通过多相滤波的方式来实现正交变换,不需要在接收端恢复同频同相的载波,从而降低了传统解调方法中电路实现的难度。通过MATLAB对信号进行调制解调的仿真,比较了不同解调方法对信号的解调效果,并在表格中显示了解调的误码率数据,从而验证了该方法的可行性和优越性。     

一种基于GPU的PCM/FM信号多符号检测算法

PCM/FM信号的非相干鉴频解调存在门限效应,将多符号检测技术引入PCM/FM信号的解调中,可以提高约3 dB的解调增益.多符号检测多采用FPGA实现系统功能,存在硬件设计周期较长、 硬件平台通用性低和升级难度大等问题,距离软件无线电设计理念有较大的差距.针对传统硬件实现的问题,设计了基于GPU的多符号检测实现方法,根...     

调频信号FM-AM转换数字解调研究

研究了FM—AM转换时频分析的理论及其实现方法,利用高斯滤波器设计了调频信号的调制特征分析滤波器组,并以正弦调频和线性调频两类调频信号为例,进行了数字解调分析。仿真结果表明,在信噪比为5dB时,利用FM—AM转换时频分析技术,可以有效地提取载波调频的特征信息。     

调频信号数字解调算法的改进与实现

介绍了一种调频离散信号无盲区解调算法,以适应各种载波下调频离散信号的变频和解调。首先获取数字载波,然后对频谱进行分析以获得完整信号频谱,再进行数字变频以获得多相滤波正交解调条件,最后通过二阶数字差分算法,从而实现调制信号的无失真解调。试验结果表明：该算法解决了调频信号解调时遇盲区无法解调的情况,实现调频离散信号无盲区数字解调,提高了频谱利用率。     

一种用于信号分析的数字正交解调电路设计

阐述了数字正交解调的原理以及与传统模拟正交解调相比所体现出的优越性。详细介绍了一种用于信号分析的数字正交解调电路设计方案和工作原理,并结合信号分析类仪器的特点和要求说明电路的硬件和软件设计方法。通过对数字滤波环节的仿真和在具体应用中所得到的实验结果说明设计电路的优越性。     

基于分数阶Fourier变换的正交多载波水声通信系统研究

针对传统OFDM系统在应对深度频率选择性衰落信道时性能下降和多普勒频偏造成子载波相互干扰的问题,提出采用正交的线性调频(LFM)信号作为载波,基于分数阶Fourier变换(FRFT)的正交多载波水声通信方案。该方案选用相同调频斜率,不同中心频率,频带相互重叠的正交LFM作为子载波进行信息调制,以分数阶Fourier变换作为调制解调方法来传输信息。为应对水声信道的多途效应,采用在数据帧与帧之间插入保护间隔(GI)来减小码间干扰。提出结合QDPSK和分数阶域载波位置修正抑制多普勒效应,简化系统复杂度。该方案最高通信速率可达3.6kbit/s,通过仿真研究和湖试实验验证了该方案的有效性与可行性。     

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。     

超宽带正交解调接收机的误差分析与数字补偿方法

本文提出了超宽带正交解调接收机的误差分析方法，并且针对超宽带线性调频信号，分析了超宽带正交解调误差对脉冲压缩的影响，然后提出了超宽带正交解调误差的数字补偿方法，在实际系统中获得了比较理想的脉冲压缩输出响应。     

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.     

Demodulation of multi-gigahertz frequency-modulated optical signals in an injection-locked distributed feedback laser oscillator

A new type of wavelength selective optical receiver that allows the demodulation of multi-gigaHertz frequency modulated (FM) optical signals is demonstrated by detecting FM light-induced changes in the forward voltage of an optically injection-locked distributed feedback semiconductor laser operating at far above the lasing threshold. A bandwidth as wide as 2 GHz is reported together with an FM demodulation efficiency of 52 mu V/GHz.<>     

Phase tracking and demodulation with delay

Algorithms are described for estimating carrier phase by a maximum-likelihood procedure similar to the Viterbi algorithm for decoding a digital sequence. These algorithms avoid the constraint of physical realizability imposed by a phase-locked loop and allow a processing lag in estimation. An approximate analysis suggests that threshold extension can be achieved thereby. Computer simulations demonstrate the improved performance for demodulation of FM and for tracking of phase modulation due to dynamic maneuvers.     

一种调频信号数字正交解调方法

本文提出了一种对调频信号进行数字解调的方法。该方法利用DDS产生的数字正交载波将调频信号进行数字下变频,利用FIR抽取滤波器和数字微分器在基带进行信号处理,从而得到调制信号。仿真结果显示,该方法在较低信噪比环境下能够准确地恢复调制信号。     

Algorithmic Measurement of Digital Instantaneous Frequency

This paper presents an algorithmic method for measuring the instantaneous frequency of a uniformly sampled FM signal. The measured parameter, termed digital instantaneous frequency, is defined in a manner similar to that used to describe frequency-modulated, continuous-time signals. The measurements are derived from an adaptive linear prediction spectral estimates. The proposed algorithm is utilized in the development of a digital processor for FM demodulation which operates on a uniformly sampled FM signal, and its output is a sampled sequence of the estimated demodulated message. The performance of the digital processor is demonstrated and compared with that of a conventional FM discriminator.     

Error rate performance of digital FM mobile radio withpostdetection diversity

An analysis of bit error rate (BER) in a binary digital FM system with postdetection diversity is presented. Expressions for the average BER due to additive white Gaussian noise (AWGN), random FM noise and delay-spread in the multipath channel are derived for reception using differential demodulation (DD), and frequency demodulation (FD) assuming independent fading signals. Calculated results for MSK show that the BER performance is strongly dependent on the RMS-delay/bit-duration ratio and that the delay-spectrum shape is of no importance when the receiver predetection filter product is optimized for the effect of AWGN. The effect of fading correlation on the diversity improvement is also analyzed for a two-branch case with multiplicative Rayleigh fading signals. Expressions for the average BER due to AWGN and random FM noise are derived. Calculated results are shown for the average BER due to random FM noise assuming a horizontally spaced antenna system at a mobile station. It is shown that the use of small antenna spacings leads to a diversity improvement greater than that obtainable for the case of independent AWGN     

Postdetection selection diversity effects on digital FM land mobile radio

The postdetection selection diversity effects on a binary digital FM system are theoretically analyzed in the fast Rayleigh fading signal environment encountered in the typical UHF or microwave land mobile radio channels. Both differential and discriminator detections are considered for demodulation of digital FM signal. The average error rate is presented by a simple closed form including both effects of Rayleigh envelope fading and random FM noise. A few examples of numerical results for minimum shift keying (MSK) are graphically presented.     

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。