基于双频EBPSK-MODEM的雷达通信机研究

为了解决双频连续波雷达在测距中的整周期模糊度问题,同时实现雷达通信一体化,该文提出一种基于双载频双路扩展的二元相移键控(EBPSK)调制解调器的综合电子系统,实现了基本的雷达与通信功能,其中一路只发送连续波,与另一路EBPSK调制信号进行比相接收,输出高精度测距信息;用冲激滤波器对另一路EBPSK调制信号进行解调。通过把EBPSK调制信号的相位跳变信息转变为幅度冲激,在连续波背景中再现目标的雷达脉冲回波,该滤波器的输出是大量程测距信息;将两组数据融合后,系统可输出高精度大量程的雷达测距值。同时利用EBPSK调制信号和冲击滤波辅助解调的特殊优势进行高频谱利用率的数字通信。     

Rake‐Based Cellular Radar Receiver Design for Moving Target Detection in Multipath Channel

In this paper, we design a rake‐based cellular radar receiver (CRR) scheme to detect a moving target located in a multipath environment. The modules of Doppler filter banks, threshold level test, and target detection module are newly introduced into the conventional rake receiver so that it can function as a radar system. The proposed CRR tests the Doppler‐shift frequency and signal‐to‐noise ratio of the received signal against predefined threshold levels to determine detection and then calculates target velocities and ranges. The system performance is evaluated in terms of detection probability and the maximum detection range under a Nakagami‐n channel that reflects the multipath environment.     

基于PN与OFDM技术的射频隐身雷达信号设计

飞机必须具有良好的射频隐身性能,以降低无源探测系统对飞机的探测距离及识别效果,从而使飞机及其机载雷达等电子设备减少被截获、被干扰甚至被摧毁的可能性。提出了机载雷达射频隐身信号的设计原Ⅻ,根据此原则设计和研究了基于伪随机码调制与正交频分复用技术的雷达信号。所设计的雷达信号具有较低的峰均功率比,通过基于数字信道化接收机无源探测系统的仿真实验,验证了该雷达信号相对常用的线性调频雷达信号具有更好的射频隐身性能。     

Power allocation and range performance considerations for a dual-frequency EBPSK/MPPSK system

Extended binary phase shift keying/M-ary position phase shift keying (EBPSK/MPPSK)-MODEM provides radar and communication functions on a single hardware platform with a single waveform. However, its range estimation accuracy is worse than continuous-wave (CW) radar because of the imbalance of power in two carrier frequencies. In this article, the power allocation method for dual-frequency EBPSK/MPPSK modulated systems is presented. The power of two signal transmitters is adequately allocated to ensure that the power in two carrier frequencies is equal. The power allocation ratios for two types of modulation systems are obtained. Moreover, considerations regarding the range of operation of the dual-frequency system are analysed. In addition to theoretical considerations, computer simulations are provided to illustrate the performance.     

Information, error, and imaging in deadtime-perturbed doubly stochastic Poisson counting systems

The detection of a fluctuating signal in the presence of noise is considered for a doubly stochastic Poisson counting system that is subject to fixed nonparalyzable detector deadtime. Explicit expressions are obtained for the likelihood-ratio detection of a modulated source of arbitrary statistics in the presence of Poisson noise counts. Receiver operating characteristics (ROC curves) are presented for an unmodulated (amplitude-stabilized) source with detector dead-time as a parameter; increasing deadtime causes a decrease in the probability of detection for a fixed false-alarm rate. Probability of error curves are presented for an amplitude-stabilized source, both in the absence of modulation and in the presence of triangular modulation, illustrating the deleterious effects of modulation, noise, and deadtime on receiver performance. Expressions for the average mutual information and channel capacity of the system are obtained and graphically presented for the simple counting receiver and for the maximum-likelihood counting receiver; the channel capacity decreases with decreasing signal level and with increasing deadtime and modulation depth. Representative examples of the appropriate counting distributions are provided. Finally, a maximum-likelihood estimate of the mean signal level is obtained for a simple image detection system with a deadtime-perturbed counting array. An expression for the statistical confidence level of the estimate is also obtained. The results are valid for an arbitrary deadtime-perturbed doubly stochastic Poisson counting system and as such are expected to find application in a broad variety of disciplines including photon counting and lightwave communications, operations research, nuclear particle counting, and neural counting and psychophysics.     

基于PWHT的LFM-PRBC雷达信号截获与特征提取

线性调频-伪随机二相编码调相复合调制雷达信号(LFM-PRBC)融合了两者的优点,弥补了单一信号的不足,是一种性能较好的低截获概率雷达信号,给传统雷达截获接收机带来挑战。提出了将周期Wigner Hough变换(PWHT)与相关检测相结合的方法,通过在信号的周期WignerHough域搜索峰值,检测复合调制雷达信号并实现其特征提取。通过理论分析和计算机仿真验证,该方法能实现高斯白噪声背景下低信噪比复合调制信号的截获与特征提取。     

Optimum Versus Suboptimum Detection Under the Poisson Regime--Application to Optical Communications Using Biphase and Quadriphase Modulated Subcarriers

The performance of a maximum likelihood receiver whose input is the photoelectric current created by a modulated light beam is studied for a number of discrete modulation schemes. The performance is compared with that of a classical microwave receiver, i.e., one designed to optimize detection in a Gaussian channel. Such a receiver has the advantages of availability, simplicity, ease of implementation, and greater tolerance to slow photodetector response and is an obvious candidate for suboptimum detection. Procedures for calculating receiver performance in the Poisson regime by the tilted probability density technique are described and applied specifically to modulation schemes employing one or more subcarriers that are biphase or quadriphase modulated. Results indicate that the classical receiver falls noticeably short of the optimum only at or near 100 percent modulation, where it may require at worst up to 30 percent more light power in order to equal the maximum likelihood receiver. When modulation is incomplete, or when background radiation is significant, the difference in performance is generally much smaller.     

Subjective evaluation of companded frequency modulation and continuously variable slope delta modulation single channel per carrier satellite communication systems

A comprehensive series of subjective tests are carried out on narrow-band companded F.M. and continuously controlled delta modulation SCPC satellite systems. In order to resolve discrepancies reported in the literature both Youden square and mean opinion scale listening tests have been applied. Both white noise and modulated noise reference conditions are employed and the performance of the systems, in terms of signal to noise and equivalent Q factor are given for various C/N₀ fixed and mobile-maritime performance requirements.     

On the performance evaluation of a multifrequency-tone envelope detector

The performance of an envelope detector receiver for tone detection applications is evaluated in terms of probability of false alarm and probability of correct detection as functions of the receiver type, signal and noise parameters. The single tone case is considered first. The analysis is then carried out for L (>1) simultaneous tones and it is shown how the results found for the single tone case can be conveniently exploited for evaluating the performance in the more general case. Curves of the probability of detection versus system parameters are also explicitly given for some typical system configurations.At last some practical considerations are discussed with reference to a prototype implementation of an envelope detector receiver for tone transmissions.     

Quickest physical‐layer MGD anomaly detection for jamming attacks in centralized modulated wideband converter‐based ROC curve

In wireless communication systems, physical‐layer security menaces have evolved from jammers. Jammers, due to their furtive nature, make wireless communication systems vulnerable. The novelty in this work is to combine centralized modulated wideband converter, which is a networking system developed from the modulated wideband converter–based sub‐Nyquist sampling theory with a multivariate Gaussian distribution (MGD) anomaly detector‐based receiver operating characteristic curve that plot the detection rate (DR) versus false alarm rate (FAR) at various threshold values. We supposed the presence of a group of jammers in the spectrum corrupted with the primary source signal and noise. The received primary signal at each cognitive radio (CR) receiver is converted in to a digital signal using an analog‐to‐information converter. Each CR receiver give minimum number of samples denoted N₁. All these compressed samples from every CR receiver are collected in the form of matrix called compressed sampling matrix, which is considered directly as the input of the MGD detector. The intelligent MGD detector proposed in the level of fusion center is based on the characteristics of the MGD. The numerical results show that this new system of combination detects faster anomalies perfectly in the presence of jammers in the spectrum in real‐time scenarios. Performance evaluation is performed in terms of DR versus FAR at different detection threshold values, under the presence of attacks in the system. By employing well‐known machine learning algorithms called MGD, the performance of this new proposed system shows good.     

A constant false alarm rate frame detector for satellite‐based automatic identification system

Frame detection is an important step in satellite‐based automatic identification system for its contributions in verifying the presence of automatic identification system signal before frame synchronization. In this paper, a constant false alarm rate frame detector is proposed, which exploits the feature implied in the training sequence, to realize frame detection in the presence of additive white Gaussian noise and frequency offset. False alarm probability is related with a threshold, which is independent of the signal and noise. For fixed false alarm probability, the relationship between detection performance and E_b/N₀ is analyzed. Simulations prove that the proposed detector outperforms the detector based on cyclic autocorrelation when message collisions exist. Copyright © 2016 John Wiley & Sons, Ltd.     

对称的扩展二元相移键控调制解调方法研究

为了提高扩展二元相移键控(Extended Binary Phase Shift Keying, EBPSK)系统的抗衰落性能, 并简化解调器结构, 提出了一种对称的扩展二元相移键控(Symmetric-EBPSK, S-EBPSK)调制方式, 以“0”、“1”码元对称的调制波形为主要特征, 采用简单有效的冲击滤波加比较判决的方法来完成解调, 并从理论上推导了S-EBPSK系统的功率谱, 及加性高斯白噪声(Additional White Gaussian Noise, AWGN)信道下系统的理论误码率公式.仿真结果表明了所提方案实现简单有效, 且无论在AWGN信道还是衰落信道下, 均表现出了明显的性能优势.     

Successive interference cancelation for a CDMA system with diversity reception in non‐Gaussian noise

A large class of physical phenomenon observed in practical wireless systems exhibits non‐Gaussian behavior. The performance of many multiuser detectors can degrade substantially in the presence of such impulsive ambient noise. In this paper, multiuser detection of space coded MIMO and code division multiple access (CDMA) signals under impulsive noise with diversity reception are investigated. We analyze and derive the probability of bit error (P_b) performance of a successive interference cancelation (SIC) system under impulsive noise and maximal ratio combining. We use Middleton's class A model for the noise distribution. Furthermore, we employ post detection SIC as the robust multiuser detection technique for combating the impulsive noise at specific noise parameters in a CDMA setting. The performance of the system under power imbalance is also shown. Novel analytical derivations for both combining techniques are presented, and simulations were performed, which confirm the theoretical results. Copyright © 2011 John Wiley & Sons, Ltd.     

Near optimal detection of signals in impulsive noise modeled with asymmetric α-stable distribution

There has been great interest in symmetric α-stable distributions which have proved to be very good models for impulsive noise. However, most of the classical non-Gaussian receiver design techniques cannot be extended to the symmetric α-stable noise case since these techniques require an explicit compact analytical form for the probability density function (PDF) of the noise distribution which α-stable distributions do not possess. A new analytical representation has been suggested for the symmetric α-stable PDF which is based on scale mixtures of Gaussians. Based on this new analytical representation, this paper introduces a novel near-optimal receiver for the detection of signals in symmetric α-stable noise. The performance of the new receiver is very close to the locally optimum receiver and is significantly better than the performance of previously suggested sub-optimum receivers. The new technique has important potential in radar, sonar, and other applications     

On the error probability of linearly modulated signals on Rayleighfrequency-flat fading channels

Consideration is given to optimal detection of linearly modulated signals subject to multiplicative Rayleigh-distributed distortion and additive white Gaussian noise. For coherent detection, regenerated amplitude and phase references are employed at the receiver to compensate for amplitude and phase deviations from the correct values. A system model is formulated under the assumption of perfect symbol timing and in the absence of intersymbol interference, producing a final additive noise term, applied just before the detection, which contains the effects of the original additive and multiplicative distortions and of the errors in the phase and amplitude references. By determining the probability density function of this final noise term for arbitrary types of linear modulation, it is possible to perform exact calculations of error probabilities     

Performance analysis of spectrally encoded hybrid WDM-OCDMA network employing optical orthogonal modulation format against eavesdropper

In this paper, the spectrally encoded hybrid WDM-OCDMA network employing 60 Gbps non-return to zero/differential quadrature phase shift keying (NRZ/DQPSK) orthogonally modulated data signal operating over 100 km SMF+DCF has been proposed. In proposed hybrid WDM-OCDMA network, the orthogonal modulation formats are used to enhance per channel capacity and the spectral amplitude optical coding for enhancing the confidentiality of data from unauthorized user or eavesdropper. The impact of input power, transmission distance and energy per bit to noise power spectral density ratio (E_b/N₀) on the performance of WDM-OCDMA network in terms of output optical power, timing diagram, BER, Q-factor and probability of error free code detection has been investigated. It can also be determined that orthogonal modulation formats are promising option to increase per channel capacity as compared to conventional modulation format and these are less vulnerable to chromatic dispersion (CD) and polarization mode dispersion (PMD). Meanwhile, the performance of proposed hybrid network is compared with existing OCDMA network which show the feasibility of proposed WDM-OCDMA network in future generation optical networking.     

Differential modulation for asynchronous two‐way relay systems over frequency‐selective fading channels

We propose two schemes for asynchronous multi‐relay two‐way relay (MR‐TWR) systems in which neither the users nor the relays know the channel state information. In an MR‐TWR system, two users exchange their messages with the help of N_R relays. Most of the existing works on MR‐TWR systems based on differential modulation assume perfect symbol‐level synchronization between all communicating nodes. However, this assumption is not valid in many practical systems, which makes the design of differentially modulated schemes more challenging. Therefore, we design differential modulation schemes that can tolerate timing misalignment under frequency‐selective fading. We investigate the performance of the proposed schemes in terms of either probability of bit error or pairwise error probability. Through numerical examples, we show that the proposed schemes outperform existing competing solutions in the literature, especially for high signal‐to‐noise ratio values. Copyright © 2016 John Wiley & Sons, Ltd.     

Polarization modulated direct detection optical transmissionsystems

A novel polarization modulated direct detection (PM-DD) system suitable both for binary and multilevel transmission is presented. At the transmitter the optical field is polarization modulated by a standard modulator. The receiver is based on the estimation of the Stokes parameters of the received optical field by means of a direct-detection optical front end and baseband electrical processing. The Poincare sphere rotation induced by the fiber is compensated by means of a purely electronic algorithm and the decision is performed in the Stokes space. The system performance is evaluated by an analytical model when the only relevant noise source is the receiver thermal noise and when erbium-doped optical amplifiers introduce amplified spontaneous emission (ASE) noise. The system is completely compatible with a direct-detection-based optical network, and it is possible to implement efficient multilevel modulation formats     

A New Approach to Bivariate Hoyt Distribution and its Application in Performance Analysis of Dual-Diversity Receivers

Novel infinite series based expressions for the bivariate Hoyt distribution are derived. More specifically, expressions for the joint probability density function (JPDF) and the joint cumulative distribution function (JCDF) of two Hoyt fading envelopes are derived, and proposed for use in performance analyses of dual-branch diversity receivers operating over correlated Hoyt fading channels. Using these reasonably simple and mathematically tractable expressions, we evaluate the performance of a dual-branch selection combining (SC) diversity receiver in terms of the outage probability (P _out ) and the average bit error probability (ABEP) criteria. The ABEP performance is evaluated for binary differential phase-shift-keying (BDPSK) and binary non-coherent frequency-shift keying (BNFSK) modulation schemes.     

Direct detection optical overlapping PPM-CDMA communication systemswith double optical hardlimiters

Direct detection optical code-division multiple-access (CDMA) communication systems involving overlapping pulse-position modulation (OPPM) is considered. Double optical hardlimiters placed before and after the correlator at the receiver side is proposed for this system. The performance (in terms of the bit error probability) of this system is evaluated taking into account the effect of both the multiple-user interference and the photodetector shot noise. Both the receiver dark current and thermal noise are ignored in our analysis since their effect is very minor. The performance of the above receiver is compared to that of the OPPM-CDMA correlator receiver without hardlimiters, OPPM-CDMA optimum receiver, and OOK-CDMA optimum receiver. Our results reveal that, for given pulsewidth and throughput constraints, significant improvement in the performance is acquired when adding double optical hardlimiters to the correlator of the OPPM-CDMA receiver. Moreover the performance of this system is asymptotically close to the optimum OPPM-CDMA system and is considerably superior to the optimum OOK-CDMA system. It is also reported that the capacity of the proposed system is about 5.3 times greater than that of the optimum OOK-CDMA system