摘要:

The paper is devoted to the problem of estimating the angular position of targets detected by using the sequential-probability ratio test. An estimation algorithm, which uses the final value of the cumulative variable of the detection test, has been analysed by assuming a scanning step equal to one half the −3 dB antenna mainbeam aperture. The estimation algorithm is carried out by a decision-directed estimator. Its performance has been evalued by numerical computation: the estimate is affected by a negligible bias error and the error standard deviation is lower than one fifth of the antenna aperture.

DOI:10.1049/ip-f-1.1985.0034

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Sequential techniques for signal detection are becoming increasingly important in radar applications. In the paper the authors focus their attention on the sequential probability ratio test (SPRT), used for radar target detection. This test was proposed and analysed for the first time by Wald, who developed a method to approximately determine the performance of the SPRT. Unfortunately, this method is not valid in radar applications, so an exact analysis of the SPRT is required. In the work the authors present the exact analysis of the SPRT in the following cases: (i) coherent detection, (ii) incoherent detection with nonfluctuating target and (iii) incoherent detection with a Swerling-II-type fluctuating target. The results are summarised in a set of graphs which are useful for both design and analysis purposes.

DOI:10.1049/ip-f-1.1985.0035

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A new approach to the problem of depth-of-field limitations and distortion in long wavelength imaging systems is proposed. The method exploits the backward propagation imaging algorithm and can be utilised in circumstances where data are recorded in the close near-field region. The fundamental theory of the technique is provided, and images from both simulations and experiment are presented as examples of the process.

DOI:10.1049/ip-f-1.1985.0036

出版商:IEE    

年代:1985

数据来源: IET

摘要:

In the telephone network, an echo is generated at the hybrid junction that connects four-to two-wire lines. A conventional echo suppressor or canceller is designed on the assumption that the echo is actually induced. In contrast, in our method, using a bilateral opto-isolator circuit, the echo is suppressed at its origin. This bilateral opto-isolator circuit has not only the property of bilateral transmission, but also the same property of suppression of impedance fluctuation as is characteristic of a buffer amplifier. Experimental results show that the degradation of echo return loss can be kept within a few decibels, even under the severe condition that the line impedance changes from being very small to very large. However, the bilateral opto-isolator circuit in previous work had the shortcoming that the operating frequency range showing the effect of echo suppression was narrow (below 1 kHz). In this paper, a method of echo suppression using an improved bilateral opto-isolator circuit is proposed. The operating frequency range is widenend from below 1 kHZ to several tens of kiloHertz.

DOI:10.1049/ip-f-1.1985.0037

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The paper presents the results of a detailed evaluation of the modified forward-backward linear prediction (FBLP) method used for angle of arrival estimation in a low-angle tracking radar environment. The results are based on real radar data pertaining to an angular separation of less than one standard beamwidth between the direct and image components impinging on the radar antenna. The results confirm the superior performance of this method compared to a conventional FFT beamformer. The paper also includes a brief review of the modified FBLP method.

DOI:10.1049/ip-f-1.1985.0038

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The performance of superposed quadrature amplitude modulation (SQAM) systems, in a nonlinearly-amplified multichannel environment, in the presence of additive white Gaussian noise (AWGN), intersymbol interference (ISI), adjacent-channel interference (ACI) and cochannel interference (CCI), is investigated. This study is an extension of our previous work which was restricted to the performance study of SQAM modems in single-channel AWGN systems. Typical system configurations are analysed by means of computer simulations. Our results demonstrate that SQAM modems outperform OQPSK, MSK and IJF-OQPSK (or SQORC) modems.

DOI:10.1049/ip-f-1.1985.0039

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The paper address the design of timed stochastic gradient-search adaptive lattice filters for applications in channel equalisation. Timing the lattice, i.e. freezing the PARCOR recursion, has previously been shown to offer a significant reduction in the algorithm noise of gradient adaptive lattice filters. Here we further simulate the effects of freezing the recursion, and show the point at which the PARCOR coefficient update process may be stopped and the adaptive combiner operation initiated.

DOI:10.1049/ip-f-1.1985.0040

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The resolution of binary signals in Middleton's class A narrowband non-Gaussian noise for both coherent and incoherent threshold or weak-signal detection is treated. A specific relative crosscorrelation coefficientpis defined for narrowband binary signals, and it is then shown that: (i) forcoherentdetection, ‘antipodal’ (p= −1) signals are best, i.e. they give the smallest error probabilityPein the threshold regime, and (ii) forincoherentdetection, ‘orthogonal’ (p= 0) signals are best. Threshold performance, i.e.Pe, is a monotonic function ofNSL, whereNis the number of large (independent) data samples,Sis the normalised signal-to-noise ratio andLis Fisher's information measure for the noise statistics.

DOI:10.1049/ip-f-1.1985.0042

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A packet-switching network with both end-to-end and local flow-control mechanisms is considered. End-to-end control is accomplished by window flow control and local control by using buffer management schemes between the input and transit traffic at the nodes. A queueing model of a semiclosed network is developed, which includes blocking models for the flow-control mechanisms and still retains a product form for the equilibrium distribution. Analytical expressions for network-performance measures are given and the effects of different buffer management schemes on these measures is studied using numerical techniques.

DOI:10.1049/ip-f-1.1985.0043

出版商:IEE    

年代:1985

数据来源: IET