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.     

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 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.     

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.     

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。     

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.     

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。     

On Optimum Sampled-Data FM Demodulation

Since the introduction of large-scale integration (LSI) techniques, there has been a continuing effort to develop digitalization techniques for communication equipment amenable to LSI implementation. Hopefully, this will permit expanded capability in the equipment while taking advantage of the cost reliability attributed of LSI. In this paper, a digitalized or sampled-data FM demodulator recursive algorithm is synthesized and its signal-to-noise ratio performance compared with the optimum analog demodulator and the conventional limiter discriminator demodulator. The demodulator is shown to exhibit threshold extension capability and automatic time-varying gain (bandwidth) adjustments from acquisition through tracking of the incoming modulated signal.     

MSK信号的数字解调新方法

近年来通信信息的数字解调技术引起了人们的广泛关注，本文根据MSK信号的数学特征，提出了一种基于MSK信号特殊点FFT的实部或虚部比较判决的方法来实现MSK信号的数字解调。推导了在高斯白噪声背景下该方法的误码情况。计算机仿真结果表明该算法是简单、有效的。与传统的MSK最佳解调方法相比本算法对载波频偏不敏感，可以应用于一些通信侦察和截获的场合。     

一种JTIDS信号测向新方法

JTIDS信号的高跳速、宽频段、窄脉冲对测向提出了挑战,同时,现代战争的超视距打击能力使得其通信终端距离侦察设备越来越远,如何及时截获并测量其方位,不但要解决高灵敏度接收的问题,还要解决高精度测向问题。提出了一种基于JTIDS信号特点的测向方法,能够实现远距离侦收和高精度测向,同时系统是最简单的。     

一种单边带调制/解调新方法

本文在分析了常规的单边带调制/解调方法的弱点之后,提出了一套基于复信号滤波和数字信号内插/抽取原理的单边带调制/解调新方法。该方法不仅有助于减小单边带调制/解调过程中的信号失真,而且便于采用数字信号处理方法实现。计算机仿真和DSP实现的结果表明,该方法具有推广应用的价值。     

Approximate FM Demodulation Using Zero Crossings

This paper deals with approximate methods for demodulating FM signals using their zero crossings. A first-order (linear) interpolation method is devised and analyzed. Computer programs were then prepared to compare this first-order interpolator to the more usual zero-order interpolator. Higher order interpolation is briefly discussed, and the results of using a second-order interpolator are compared to those using the lower order methods.     

光纤光栅传感信号解调方法的研究

光纤光栅编码信号解调是实现光纤光栅传感器实用化的关键技术之一。简单介绍了光纤布拉格光栅传感器的工作原理,并从波长转化量分类角度对光纤光栅的几种解调方法进行了分析比较。     

CPM信号的微积分解调算法分析

连续相位调制（Continuous Phase Modulation）是一类包络恒定且相位连续的调制方式,具有很高的带宽和功率利用率,优良的包络和相位特性使其适用于空间通信。在分析CPM信号的模型基础上,研究了基于微积分的代数运算方法来完成对CPM信号的解调,该方法几乎不需要任何的先验信息和参数信息就能实现信号的盲解调,目的能够降低接收机的复杂度,是一种优秀的CPM信号解调方式。