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# Communications, Radar and Signal Processing, IEE Proceedings F

## Filter Results

Displaying Results 1 - 23 of 23
• ### Editorial. Adaptive arrays

Publication Year: 1983, Page(s):1 - 2
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• ### Adaptive array processing. A tutorial

Publication Year: 1983
| | PDF (746 KB)

An array is defined as a set of sensors, for example antennas or acoustic transducers. The outputs from these sensors can be processed in an adaptive manner to respond to an unknown interference environment in an attempt to optimise the performance of the system in some defined manner. The paper is intended as an introduction to, and to some extent a survey of, some of the methods used in adaptive... View full abstract»

• ### A complex gradient operator and its application in adaptive array theory

Publication Year: 1983, Page(s):11 - 16
Cited by:  Papers (30)
| | PDF (673 KB)

The problem of minimising a real scalar quantity (for example array output power, or mean square error) as a function of a complex vector (the set of weights) frequently arises in adaptive array theory. A complex gradient operator is defined in the paper for this purpose and its use justified. Three examples of its application to array theory problems are given. View full abstract»

• ### Adaptive algorithms in the space and time domains

Publication Year: 1983, Page(s):17 - 21
| | PDF (413 KB)

The basic similarities and essential differences between adaptive processing structures in the space and time domains are considered. Attention is focused on the fact that a cascade structure is required to decorrelate the signals received from different elements of an antenna array, while a very different and more efficient lattice filter structure may be used to decorrelate successive samples of... View full abstract»

• ### Eigenfilter approaches to adaptive array processing

Publication Year: 1983, Page(s):22 - 28
Cited by:  Papers (10)
| | PDF (840 KB)

High-resolution methods of spectral estimation have recently found application in the processing of data received by spatially distributed arrays of sensors. These techniques have been used for estimation of the directional power illuminating the array and have proved useful as a first step in the analysis and classification of possible targets. Several desirable qualities are offered by these spa... View full abstract»

• ### Transversal filter techniques for adaptive array applications

Publication Year: 1983, Page(s):29 - 35
| | PDF (759 KB)

The performance of current cancellation systems is limited when broadband cancellation is required. The paper covers some of the work performed at Plessey (Roke Manor) to overcome these problems by using an adaptive transversal filter. The paper begins by considering some of the effects which limit broadband performance of current cancellation equipment. Secondly, assuming that each tap weighting ... View full abstract»

• ### Rapid interference suppression using a Kalman filter technique

Publication Year: 1983, Page(s):36 - 40
| | PDF (593 KB)

Directional interference suppression is based on a recursive estimation procedure of the state of a filter forming the directional interference spectrum. For the stationary filter, this leads to an iterative solution of the Wiener-Hopf matrix equation. It can be shown that the number of samples required for convergence is related to the number of degrees of freedom of the filter. The nonstationary... View full abstract»

• ### Comparison of directional and derivative constraints for beamformers subject to multiple linear constraints

Publication Year: 1983, Page(s):41 - 45
| | PDF (530 KB)

Optimum beamformers with multiple linear constraints are usually designed under the assumptions of plane-wave signals and an ideal propagation medium. In acutal operating conditions these ideal assumptions do not hold; for example, signal suppression can arise from beam steering angle errors if the optimum weights are calculated from the signal-plus-noise cross-spectral matrix. To overcome this, i... View full abstract»

• ### Convergence time of sidelobe cancellation systems

Publication Year: 1983, Page(s):46 - 56
| | PDF (1181 KB)

A computer program has been written for the statistical investigation of the transient response of adaptive arrays of the radar sidelobe cancellation type, using multiple parallel feedback correlation loops. The expressions for the response are derived, the program is described in general terms, and some results are presented for a particular array, giving an indication of the performance availabl... View full abstract»

• ### Multifunction adaptive processor for small antenna arrays

Publication Year: 1983, Page(s):57 - 62
| | PDF (694 KB)

The design and operation of a compact processor for small adaptive arrays is described. The control law is based on the minimisation of the array output power subject to a linear weight constraint. This choice enables the processor to be used in a wide range of applications using relatively simple control techniques to avoid cancellation of the wanted signal. Practical results supporting many of t... View full abstract»

• ### Problems associated with correlation-loop adaptive antennas employing hard limiting

Publication Year: 1983, Page(s):63 - 66
| | PDF (382 KB)

There are many applications of adaptive antennas where it is desirable to set an adjustable threshold below which received signals are not nulled by the adaptive process. This may be achieved with a gradient descent adaptive control algorithm by a suitable choice of integration loss and update gain factors. Generally, the gradient estimate is obtained by a correlation process, and the hardware des... View full abstract»

• ### UHF circular arrays incorporating open-loop null steering for communications

Publication Year: 1983, Page(s):67 - 77
Cited by:  Papers (1)
| | PDF (1425 KB)

The paper describes an experimental wideband antenna and adaptive signal processing system which has the ability to exhibit an omnidirectional azimuth radiation pattern which can be modified in real time to minimise the effects of unwanted interference. The philosophy behind the use of circular antenna arrays for this system and brief details of their directional properties are given. To enable th... View full abstract»

• ### Direction finding using an adaptive null tracker

Publication Year: 1983, Page(s):78 - 83
| | PDF (682 KB)

Signals received by a multiple-element array can be processed by an adaptive null steering algorithm which treats the signals¿¿ as jammers¿¿, thereby potentially forming discrete nulls in the directions of arrival of individual signal components. Use of a null tracker can therefore be proposed as a means of direction finding, and, since the null widths can be made narrower than the width of a be... View full abstract»

• ### Perturbation adaptive array processor for airborne application

Publication Year: 1983, Page(s):84 - 90
| | PDF (818 KB)

The adaptive processor here described uses a perturbation algorithm embodied in a microprocessor, and has been used with a four-element array. The resulting system is of low cost and great flexibility, with particular advantages for installation in aircraft. The transient response is shown to be of the same form as that of an LMS algorithm for small perturbations, and a simulation shows the deviat... View full abstract»

• ### Coefficient perturbation adaptive HF array

Publication Year: 1983, Page(s):91 - 97
| | PDF (997 KB)

Algorithmic details and the experimental performance of a large-scale HF adaptive antenna array implemented on a computer-controlled beam steering system are described. The results are obtained in the medium-wave and lower short-wave bands and show that ionospheric reflection can have deleterious effects on the ability to cancel interference sources. Some of the problems encountered in developing ... View full abstract»

• ### Adaptive antenna design considerations for satellite communication antennas

Publication Year: 1983
| | PDF (1483 KB)

Satellite communication systems must often be designed to operate in the presence of interfering signal sources. Conventionally, bandspreading via signal modulation is often used to combat such unwanted interference. Recently, interest has been focused on supplementing the conventional interference reduction achieved via bandspreading by using antenna radiation pattern shaping achievable with adap... View full abstract»

• ### Experimental open-loop canceller for radar

Publication Year: 1983, Page(s):109 - 113
| | PDF (729 KB)

The paper describes experimental work to investigate the feasibility of applying the open-loop interference cancellation technique to radar-type signals. Design of experimental equipment is described advantages over the closed-loop canceller but, with currently available components, lacks dynamic range and good wideband performance. View full abstract»

• ### Open-loop adaptivity for rotating antennas

Publication Year: 1983, Page(s):114 - 117
| | PDF (573 KB)

The application of adaptivity in the form of a sidelobe canceller to a rotating radar antenna requires that the adaptive weights employed should be updated at a rate high enough to avoid degradation due to movement of the main beam. The paper describes the design and performance of an experimental sidelobe canceller using a hybrid analogue/digital solution. A dedicated digital processor computes t... View full abstract»

• ### Experimental linear phased array with partial adaptivity

Publication Year: 1983, Page(s):118 - 124
| | PDF (921 KB)

Although much has been published concerning the theoretical aspects of adaptive antenna arrays, practical results are scarce. A phased array with partial adaptivity is described, and preliminary experimental results showing its performance against multiple noise jammers are presented and discussed. The factors which limit the cancellation which can be achieved by such an adaptive phased array are ... View full abstract»

• ### Adaptive clutter suppression for airborne phased array radars

Publication Year: 1983, Page(s):125 - 132
| | PDF (935 KB)

The problem of clutter suppression is more serious for airborne than for ground-based radars because the ground returns become Doppler coloured owing to platform motion. Therefore the clutter power depends on both the azimuth and the Doppler frequency. Such two-dimensional spectra can only be suppressed by two-dimensional filters, which require sampling of the echo field in both space and time. Th... View full abstract»

• ### Detection of narrowband sources by an array

Publication Year: 1983, Page(s):133 - 138
| | PDF (574 KB)

Adaptive array techniques which seek to optimise the passive detection of an acoustic narrowband source under ideal conditions are well established. The paper gives details of a frequency-domain technique which has modest hardware requirements and yet is capable of operation in a highly nonstationary environment. In addition, the algorithm enhances both signal/noise gain and detectability when mis... View full abstract»

• ### Performance assessments of a time-domain adaptive processor in a broadband environment

Publication Year: 1983, Page(s):139 - 146
| | PDF (901 KB)

The paper is a study of a time-domain adaptive array processor operating in a broadband environment. The processor is a variant of that due to Widrow; in particular processing is carried out in octave bands and sensor data are not time shifted. The constraint system consists of four to seven linear point and gradient constraints, together with a soft norm constraint. Computations assume full adapt... View full abstract»

• ### Performance of stochastic gradient descent adaptive beamforming using sonar data

Publication Year: 1983, Page(s):147 - 151
| | PDF (518 KB)

Using sonar data characterised by the presence of a strong interference, adaptive beamforming is performed by the stochastic gradient descent algorithm in the frequency domain. The weights are constrained to have a unity response in the look direction. Convergence rates are estimated from averaged adaption curves, and, in most cases, these are found to be in reasonable agreement with theoretical v... View full abstract»