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。     

中频PCM/FM信号全软化FM解调的一种实现方法

本文介绍了中频PCM/FM信号全软化FM解调系统的组成、解调原理及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。     

A New Demodulation Method Improving FM System Interference Immunity

As a result of investigation of interference into FM systems, a new algorithm for the process of demodulation is proposed. When compared to the method using the conventional limiter-discriminator, it offers better immunity against the baseband interference noise. Desired signal processing is performed by the functional devices added to the conventional limiter-discriminator in such a way that this new demodulator can be optimized in the sense of the minimum baseband interference noise. The statistics of the wanted and interfering signals must be known. Several examples involving interference problems in FDM-FM radio-relay systems carrying multichannel telephone signals are elaborated to illustrate the performances of the proposed demodulator. FDM-FM, PSK, or FSK systems are considered the cause of the interference. The noise power ratio (NPR) at the output of the conventional limiter-discriminator and the improvement factor offered by the new demodulator, obtained on digital computer, are presented versus baseband frequency in the form of diagrams. Different IF filters in FDM-FM receiver and transmit filters in the interfering systems are taken into account. The improvement offered by the proposed demodulator is of such a degree that some of the important restrictions in planning different radio systems could be relaxed.     

基于SystemView的调频信号的调制解调仿真

调频信号是模拟调制系统中最常用的调制信号,如何高效准确地从调频信号中解调出原来原始信号是当今研究的一个重要课题。根据模拟通信系统中调频信号解调的基本原理得出具体实现方法,并通过使用SystemView软件对其中一种方法进行了仿真验证,仿真结果与理论结果基本吻合。     

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。     

Improved Demodulation of Sampled FM Signals in High Noise

Simulation results are presented which are very convincing in favor of FM demodulators driven by in-phase and quadraturephase signals. Application of the extended Kalman filtering algorithms to the appropriate signal model directly yields demodulators in which the error covariance equations are uncoupled from the state estimate equations. These demodulators perform a little better than others derived using different nonlinear filtering techniques and the necessary approximations to achieve "decoupling." More significantly, these demodulators using in-phase and quadrature-phase sampled signals are readily augmented to achieve demodulation with delay by the application of fixed-lag smoothing algorithms. Simulations highlight the attractive trade-offs between demodulation complexity and performance results for this class of demodulator.     

一种新的宽带信号正交分量的解调方法

在D通道均匀DFT分析滤波器组基础上给出了一种新的信号正交分量的解调结构 ,为解调宽带信号 (B fc)的正交分量 ,系统采用两组D通道均匀DFT分析滤波器组通带互补方法 ,以克服单组滤波器中滤波器的非理想性所造成的信号失真。在频域中当信号频谱处于两个或更多个滤波器通道时 ,通过频谱组合办法直接得到实信号的正半谱或负半谱。在载波频率已恢复的情况下给出了IQ正交分量的解调算法。仿真证明该系统结构和算法的正确性和高效性     

编码16DAPSK 信号解调译码新方法

基于子载波采用16阶差分幅度相移键控(16DAPSK)的正交频分复用(OFDM)系统,提出并分析了编码16DAPSK信号的一种新的简单易行的比特软输出解调译码方法。仿真结果表明,在高斯信道、平坦Rayleigh衰落信道和多径Rayleigh衰落信道下,采用编码速率为3/4的punctured卷积码与16DAPSK信号的硬输出解调译码方法相比,系统的误码性能可改善约1.2dB。新方法应用在日本CRL开发的100Mbps毫米波16DAPSK-OFDM宽带移动接入实验系统,将进一步提高系统误码性能。     

DPSK-PM调制信号数字解调方法研究

针对卫星USB测控系统中常用的DPSK-PM调制技术，设计了一种简单的数字解调方法。在介绍算法原理的基础上，对解调算法进行了仿真，仿真结果证明了该方法的有效性。该方法对于航天测控链路信息对抗仿真平台的建立具有指导意义。     

一种低信噪比下的 RFID 信号解调方法

针对实际环境中RFID信号微弱且易受干扰的情况,提出了一种低信噪比条件下的解调方法,对以前的方法进行了改进,采取了基于自适应拟合的降噪除干扰算法,并设计了一种新的同步结构。通过理论分析和计算机仿真结果表明,该方法能在较低的信噪比容限下,正确地解调出RFID信号,性能优于原有方法,可为低信噪比条件下RFID的信号处理以及远距离RFID技术的应用提供更有效的解决途径。     

一种短波衰落信道下FSK信号FFT解调方法

对传统FSK信号的多种解调方法进行了简单介绍,在短波衰落信道下,由于多径和衰落的影响,其解调性能严重恶化,甚至不能得到正确的比特流。提出了一种基于时频域的FFT的FSK信号解调方法,利用FSK信号不同频率点处的功率谱峰值进行检测判决,并详细介绍了其实现方法。对其在高斯白噪声下的性能进行了仿真,性能与非相干包络解调理论性能相当,而对衰落信号,相比其他解调方法,此解调方法也可以给出较好的解调效果,适用于工程应用。     

141A信号盲解调算法研究

针对非协作通信中MIL-STD-188-141A(141A)信号盲解调的需求,在分析总结现有几种解调算法优缺点的基础上,对基于频号信息的滑动快速傅里叶变换(Fast Fourier Transform,FFT)解调算法提出了改进,应用离散时间傅里叶变换(Discrete Time Fourier Transform,DTFT)算法计算信号精细频偏对信号进行校频预处理,统计获取141A信号的实际频号信息。对校频预处理后的信号应用基于实际频号信息的滑动FFT解调算法进行解调。应用仿真信号对改进的解调算法进行仿真,仿真结果表明,改进的解调算法相比原解调算法能够适应更大的信号频偏,解调效果良好。     

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.     

Demodulation Method for Continuous Phase Modulation Signals Based on Least-Squares Method

Continuous phase modulation (CPM) schemes are attractive for telecommunication systems, which are limited in terms of the bandwidth and signal power due to their high spectral efficiency. In this paper we present a method for the demodulation of continuous phase modulation signals based on least-squares method (LSM). This method (CPM-LSM) is based on the optimal linear estimation of information symbols from the phase of the received signal by solving the overdetermined system of equations using the least squares method. Mathematical substantiation for the application of the proposed CPM-LSM method is presented. Preliminary experimental results of modeling using Geo-Mobile Radio (GMR-2) signals indicate that the method is robust with respect to carrier phase errors. Another feature of CPM-LSM method is that it does not use unique words (symbol patterns for amplitude/phase alignment). The latter fact is very important since unique words usually occupy up to twenty percent of transmitted packet size. The absence of unique words can substantially increase the information throughput.     

A New Microwave Amplifier for Multichannel FM Signals Using a Synchronized Oscillator

Because of the excellent results of the noise-loading test on an IMPATT oscillator that is phase-locked to an external FM driving signal, a new microwave amplifier for multichannel FM signals using a synchronized oscillator is proposed. An IMPATT oscillator, injection-synchronized with an FM signal, is regarded as an amplifier and its noise characteristics for multichannel signals are evaluated with the noise-loading method as recommended by the International Radio Consultative Committee. The results show that when this oscillator satisfies the noise characteristics for 960 telephone message channels, it assures a gain of approximately 15 dB at 11 GHz, and in this sense, this oscillator can be regarded as an amplifier for multimessage channels. The degradation of SNR of this amplifier is less than 2 dB. This excellent result is obtained because of the following. In the video band, the modulation suppression of an FM driving signal in the injection-synchronized oscillator, such as the IMPATT, is very small, while the oscillator noise, which dominates the entire output characteristic, is considerably reduced by the synchronizing action of the oscillator. This amplification continues up to the high-frequency range in which this principle of operation applies.     

脉冲噪声下数字调制信号的自适应解调

提出基于自适应滤波解调α稳定分布脉冲噪声下的常规数字调制信号的方法。采用归一化最小平均p范数自适应滤波算法的自适应滤波器,跟踪信号任一码元间隔内的单一频率,根据自适应滤波器权值的收敛值可以解调相应的码元。计算机仿真结果表明,此自适应滤波解调方法性能优越,抗脉冲干扰强,同时算法计算速度快,易于实现,具有很好的实用价值。     

调频信号的数字合成方法

调频信号作为一种常见信号在电子技术的各个领域，特别是通信领域有着广泛的应用。因此调频信号的合成就成为了其中关键性的一项技术。传统的调频信号通常是通过模拟方法合成的。但是模拟合成有频率不稳定、参数设置不可量化等缺点，而用数字合成的方法就可以解决这些问题。数字频率合成通常采用DDS技术，调频信号的数字合成也基于这项技术。本文首先介绍了DDS的基本原理。然后提出用双DDS结构实现调频信号数字合成的方法。由于把调制波形的幅度量化成了频率字，构成了一个输出频率字的DDS。因此只要改变这个DDS波形RAM中的数据。就可以产生任意以周期信号为调制波形的调频信号，并且调制频率和深度都精确可调。     

一种基于数字测频的PCM/DPSK解调方法

本文提出了一种新颖的PCM／DPSK数字信号解调方法。通过数字测频算法,获取PCM／DPSK信号频率突变点,根据DPSK调制原理,实现PCM／DPSK信号的解调。文中详细介绍了此种解调方法的基本原理及实现过程,分析了解调过程中多普勒频率对解调结果的影响。计算机仿真结果表明,此方法比相干解调性能优越,抗干扰能力强,便于软件编程及DSP器件实现,具有一定的应用价值。     

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.     

Alpha稳定分布脉冲噪声下MPSK信号的自适应解调

通信系统经常工作在理稳定分布脉冲噪声环境下。提出了一种基于自适应滤波算法对脉冲噪声下MPSK信号的解调方法。高斯噪声是α稳定分布噪声的一个特例,提出的解调方法同样也适于高斯噪声下MPSK信号的解调。仿真结果表明,无论是在高斯噪声还是脉冲噪声下此方法都有很好的韧性,同时该算法不需要滤波器完成收敛。处理速度快。