一种修正的渐近无偏E脉冲雷达目标识别方法

为了进一步改善低信噪比条件下E脉冲目标识别方法的性能,该文理论分析了渐近无偏E脉冲目标识别方法,指出其存在E脉冲二次滤波使其能量识别数失效和回波中不同极点互藕产生新极点分量从而降低目标识别概率等缺陷,在此基础上提出了一种先互相关再E脉冲滤波的修正渐近无偏E脉冲雷达目标识别新方法,并对其渐近无偏性进行了理论证明。基于三种不同尺寸有限长细导线目标理论计算后时响应的仿真实验表明,该文提出方法的性能大大优于传统E脉冲和渐近无偏E脉冲雷达目标识别方法。     

Performance of an automated radar target discrimination schemeusing E pulses and S pulses

Previous studies have demonstrated the viability of natural resonance based target discrimination using extinction pulses (E pulses) and single-mode pulses (S pulses). These studies qualitatively demonstrated the principles of resonance annihilation by forcing the interrogating pulse to have zeros at the complex natural resonance frequencies of the target. Here a quantitative scheme for evaluating discrimination using the E pulse and the S pulse is given. The performance of an automated E-pulse and S-pulse discrimination scheme is evaluated using numerically derived scattering data with varying amounts of noise     

An asymptotically unbiased E-pulse-based scheme for radar target discrimination

This communication proposes an E-pulse-based scheme for radar target discrimination that provides asymptotically correct results for any level of additive white noise contaminating the radar signal. After multiple sampling of the signal dispersed by the target, it is analytically shown that the cross correlation between the output signals of the E-pulse designed for the standard target, corresponding to two different sampling periods, is asymptotically , regardless of the amount of contaminating noise. The results obtained by simulation have allowed us to propose a discrimination criterion that produces better results than the original E-pulse technique at very low signal-to-noise ratio (SNR) levels.     

一种基于傅里叶级数的E脉冲识别波形综合方法

为了直接发射E脉冲进行雷达目标识别,本文从理论上推导了产生特定矩形基编码脉冲信号傅里叶级数系数的一般性表达式;提出了一种基于傅里叶级数的E脉冲目标识别波形综合方法;给出了参数设计原则以及综合E脉冲波形的系统组成框图;并利用细导线散射场数据仿真了理论E脉冲和综合E脉冲目标识别性能;验证了本文提出的方法的可行性。     

Extinction pulses synthesis for radar target discrimination using /spl beta/-splines, new E-pulse conditions

The extinction pulse method has been proven to be a suitable method for radar target discrimination using the natural resonance annihilation concept. The standard procedure for extinction pulse (E-pulse) construction is based on an expansion on subsectional polynomials. In this paper it is proposed a new formalism for E-pulse construction using /spl beta/-splines. This formalism allows the E-pulse polynomial basis expansion to be treated in a unified theoretical framework and leads to a simplification of the original problem due to the linear nature of all the involved parameters. This new formulation has been also used to impose new conditions over the spectral contents of the E-pulses. These E-pulses constructed using the new conditions annihilate better the natural modes in the late-time radar target response, and provide a better discrimination rates than the classical scheme.     

The singularity expansion method and its application to targetidentification

The singularity expansion method (SEM) for quantifying the transient electromagnetic (EM) scattering from targets illuminated by pulsed EM radiation is reviewed. SEM representations for both induced currents and scattered fields are presented. Natural-resonance-based target identification schemes, based upon the SEM, are described. Various techniques for the extraction of natural-resonance modes from measured transient response waveforms are reviewed. Particular attention is given to the aspect-independent (extinction) E-pulse and (single-mode) S-pulse discriminant waveforms which, when convolved with the late-time pulse response of a matched target, produce null or mono-mode responses, respectively, through natural-mode annihilation. Extensive experiment results for practical target models are included to validate the E-pulse target discrimination technique. Finally, anticipated future extensions and areas requiring additional research are identified     

Detection of Depth Changes of a Metallic Target Buried in a Frequency-Dependent Lossy Halfspace Using the E-Pulse Technique

The extinction pulse (E-pulse) technique has been widely applied to the problem of free-space radar target identification. In this paper, the possibility of applying the same E-pulse technique to a subsurface target recognition scheme is investigated. In particular, the detection of depth changes of a metallic target is considered with numerical examples that determine the depth of a hip prosthesis model buried inside representative human tissue.     

Optimization method versus E-pulse method in the context of targetdiscrimination

The performances of the optimization method and the extinction pulse method are evaluated for idealized data as well as experimental data from scaled-model targets. Although both methods use the late-time response to discriminate targets, the discriminant waveform is synthesized differently; from the target pole singularities in the E-pulse method, and from an energy maximization in the optimization method. Responses from waveforms synthesized using calculated wire data and laboratory measured data are presented, and the early-time energy confinements produced by the two methods are found to be generally comparable. The robustness of the optimization and E-pulse methods in the presence of noise is demonstrated by results for calculated and measured data     

A general E-pulse scheme arising from the dual early-time/late-timebehavior of radar scatterers

A duality between the temporal late-time response and the spectral early-time response of a radar target is used to form the basis for a general E-pulse technique. Examples, using the ultrawide-band measurements of an aircraft model, reveal that E-pulse cancellation is possible both in the time domain for the late-time component and in the frequency domain for the early-time component. Applications to radar target discrimination and clutter cancellation are described, and the aspect dependence of early-time discrimination is investigated     

Radar-Target Identification via Exponential Extinction-Pulse Synthesis

New contributions to noncooperative radar-target discrimination using only the scattered response of conductive objects are presented in this paper. The technique studied is the extinction-pulse (E-pulse), which makes use of natural resonances as discrimination features. The E-pulse expansion using complex exponential functions as basis functions is proposed, obtaining new E-pulses with characteristics completely different from those in the literature. Specifically, a weighting factor is added to modulate the exponential frequency, providing E-pulses with better discrimination capability. Numerical results achieved in the discrimination between thin straight wires of different lengths show that the proposed exponential E-pulses improve the discrimination results with respect to other types of E-pulses in the literature.     

Extended E-pulse technique for discrimination of conducting spheres

The study presented is on the influence of forced-E-pulse duration in the discrimination capacity of the E-pulse technique, applied to spherical targets. This analysis allows three ranges of E-pulse durations to be considered and an optimum duration of the forced E-pulse to be obtained. The results obtained allow the discrimination technique to be extended in order to determine if the radius of an “unknown” sphere is longer or shorter than the radius of the “expected” one     

Bit error probability of distributed Turbo coded relay systems over quasi-static Rayleigh fading channels

As is known, distributed Turbo coding (DTC) performs close to the theoretic outage probability bound of a relay channel when correct decoding is assumed at the relay. However, decoding error is inevitable in practical fading channels due to the error-prone feature of radio channels, and the decoding error propagation in DTC scheme will severely degrade the error performance of the relay system. As a result, it is necessary to evaluate the error performance of the DTC scheme in multi-hop relaying wireless systems in practical fading channels. Moreover, the theoretical method of analysis provides an effective tool for obtaining the error performance besides lengthy simulations. In this article, the concept of equivalent signal-to-noise ratio (SNR) of the two-hop relay channel and the method of computing equivalent SNR are developed, and then the upper bound on the bit error probability (BEP) of DTC relay systems is analyzed by use of Turbo code's distance spectrum, the concept of uniform interleaver, the limit-before-averaging technique, and the union bound method. Both theoretical analysis and numerical simulation are implemented for relay systems with DTC scheme over quasi-static Rayleigh fading channels. The results show that the upper bound approaches the simulation results in the medium to high SNR region.     

一种基于广义似然比检测的雷达目标识别新方法

为了实现发射周期内目标的实时识别,首先建立了E脉冲激励下目标回波的二元假设检验模型,在此基础上导出了识别目标的广义似然比检测量,并从理论上给出了计算目标识别概率的解析表达式.基于数值计算的三种细导线目标散射场数据的仿真实验以及理论计算结果表明,本文提出的基于广义似然比检测目标识别新方法的实验目标识别性能与其理论计算值是一致的,且其目标识别性能优于直接发射E脉冲目标识别方法.     

Performance comparison of selection combining schemes for binary DPSK on nonselective Rayleigh-fading channels with interference

This paper is concerned with the error performance analysis of binary differential phase shift keying (DPSK) with differential detection over the nonselective Rayleigh-fading channel with selection diversity reception and with an additive, correlated, Gaussian interference process in each diversity channel. The fading process is assumed to have an arbitrary Doppler spectrum with arbitrary Doppler bandwidth. The selection schemes investigated are: 1) the selection combining (SC) scheme based on signal-to-noise power ratio (SNR); 2) the SC scheme based on signal-plus-noise (S+N); and 3) the SC scheme based on maximum output (MO). New, exact, closed-form bit-error probability (BEP) expressions are derived, and a performance comparison among the three SC schemes and combining diversity reception is given. The results obtained reduce to previously known results when the correlated interference process is absent, and when the fading process does not fluctuate over the duration of several symbol intervals. The results indicate that the performance of each scheme depends on the tradeoff between the number of diversity branches, the SNR, the interference level, and the correlation of the interference process. However, the SC-(S+N) scheme generally performs worse than the SC-SNR scheme, the SC-MO scheme and combining diversity reception scheme. The findings presented here are not only of fundamental theoretical value, but are also of practical interest to the designers of future mobile communication systems.     

Outage analysis of opportunistic multi-antenna relay selection in decode-and-forward relay networks

This article studies the closed-form expressions of outage performance for opportunistic relay under aggregate power constraint in decode-and-forward(DF)relay networks over Rayleigh fading channels,assuming that multiple antennas are available at the relay node.According to whether instantaneous signal-to-noise ratio(SNR)or average SNR can be utilized for relay selection,two opportunistic relay schemes,opportunistic multi-antenna relay selection(OMRS)and average best relay selection(ABRS)are proposed.The performances of both two schemes are evaluated by means of theoretical analysis and simulation.It is observed that OMRS is outage-optimal among multi-antenna relay selection schemes and closely approaches the beamforming(BF)scheme known as theoretical outage-optimal.Compared with previous single-antenna opportunistic relaying(OR)scheme,OMRS brings remarkable performance improvement,which is obtained from maximum ratio combining(MRC)and beamforming techniques.It is also shown that the performance of ABRS in asymmetric channels is close to OMRS in the low and median SNR range.     

Bayesian Multi-Object Filtering With Amplitude Feature Likelihood for Unknown Object SNR

In many tracking scenarios, the amplitude of target returns are stronger than those coming from false alarms. This information can be used to improve the multiple-target state estimation by obtaining more accurate target and false-alarm likelihoods. Target amplitude feature is well known to improve data association in conventional tracking filters, such as probabilistic data association and multiple hypothesis tracking, and results in better tracking performance of low signal-to-noise ratio (SNR) targets. The advantage of using the target amplitude approach is that targets can be identified earlier through the enhanced discrimination between target and false alarms. One of the limitations of this approach is that it is usually assumed that the SNR of the target is known. We show that the reliable estimation of the SNR requires a significant number of measurements, and so we propose an alternative approach for situations where the SNR is unknown. We illustrate this approach in the context of multiple targets for different SNRs in the framework of finite set statistics (FISST). Furthermore, we illustrate how this can be incorporated into approximate multiple-object filters derived from FISST, including probability hypothesis density (PHD) and cardinalized PHD (CPHD) filters. We present simulation results for Gaussian mixture implementations of the filters that demonstrate a significant improvement in performance over just using location measurements.     

Subsectional-polynomial E-pulse synthesis and application to radartarget discrimination

A new family of extinction-pulses (E-pulses), called subsectional-polynomial E-pulses, is presented. This new type of E-pulse is constructed by choosing polynomials of degree Q as subsectional basis-functions in the E-pulse expansion. The main feature of this family of E-pulses is that the waveforms are continuous and smooth. Several topics concerning the E-pulse technique are investigated, such as: insensitivity to the exact number of natural modes present in the target response; aspect-angle independence; and effects of additive white Gaussian noise. Numerical results, using the response of a thin cylinder and a sphere, show that the subsectional-polynomial E-pulses improve the results obtained using subsectional-rectangular E-pulses     

Multi-antenna Decode and Forward Relay Selection over Nakagami-m Fading Channels

This paper analyzes the performance of opportunistic relay under aggregate power constraint in Decode-and-Forward (DF) relay networks over independent, non-identical, Nakagami-m fading channels, assuming multiple antennas are available at the relay node. According to whether instantaneous Signal-to-Noise Ratio (SNR) or average SNR can be exploited for relay selection, two opportunistic relay schemes, opportunistic multi-antenna relay selection (OMRS) and average best relay selection (ABRS) are proposed. The closed form expressions of outage probability and error performance for binary phase shift keying (BPSK) modulation of OMRS and ABRS are determined using the moment generating function (MGF) of the total signal-to-noise ratio (SNR) at the destination. Simulations are provided to verify the correctness of theoretical analysis. It is observed that OMRS is outage-optimal among multi-antenna relay selection schemes and approaches the Beamforming (BF) scheme known as theoretical outage-optimal very closely. Compared with previous single-antenna Opportunistic Relaying (OR) scheme, OMRS brings remarkable performance improvement obtained from maximum ratio combining (MRC) and beamforming, which proves that multiple antennas at the relays could provide more array gain and diversity order. It also shows that the performance of ABRS in asymmetric channels is close to OMRS in the low and median SNR range.     

Impact of fixed power allocation in wireless energy harvesting NOMA networks

The time switching‐based relaying (TSR) scheme is considered in energy harvesting protocol to implement with its advantage to nonorthogonal multiple access (NOMA) system. In particular, decode‐and‐forward (DF) mode is proposed to employ in relay to forward signal to serve two far NOMA users. There are two main metrics including outage probability and ergodic rate, which are derived in exact expressions with respect to varying performance under impacts of energy harvesting fractions. To evaluate system performance, outage event and related capacity are illustrated, and we tailor performance gap among two NOMA users and such gap can be controlled by selecting of appropriate power allocation factors assigned for each user to obtain optimal performance. By examining node arrangement, target rates and varying transmit signal to noise ratio (SNR), it can be further achieved performance in several situations of such NOMA. As important result, the considered NOMA system outperforms than the conventional multiple access scheme, and this expected result is confirmed in numerical result and theoretical results. We also explore impacts of transmit power at source, noise power, the other key parameters of energy harvesting scheme to exhibit outage, and ergodic performance. Simulation results are presented to corroborate the proposed methodology.