摘要:

Adaptive antenna arrays are aerial arrays which are able to adjust themselves automatically and electronically to meet particular constraints. In this paper, arrays in which the reception of interfering signals is minimised are considered. The theory of a particular form of these arrays, the linear uniformly spaced array of identical elements, is introduced and some of the possible adaptation algorithms are considered.

DOI:10.1049/ip-f-1.1980.0037

出版商:IEE    

年代:1980

数据来源: IET

摘要:

Adaptive arrays are aerial arrays which are able to adjust themselves automatically and electronically to meet particular constraints. The IBA's steerable adaptive broadcast equipment (s.a.b.r.e.) is designed for the reception of u.h.f. television signals where the constraint is that of minimising the level of cochannel interference relative to the wanted signal. The paper describes the first practical implementation, which has been in operation in the Channel Islands since March 1977, and also considers the future applications of adaptive arrays.

DOI:10.1049/ip-f-1.1980.0039

出版商:IEE    

年代:1980

数据来源: IET

摘要:

Current generation sonar systems employ high temporal and spatial resolution to achieve acceptable operational performance. This, together with the physical mechanisms of acoustic propagation in the ocean, places a number of constraints on the implementation of beam-forming systems for sonar applications that are in many ways unique; in particular:(a) Low sonar operating frequencies and the use of wide processing and analysis bandwidths necessitate the use of broadband beam-forming techniques, often using true time-delay rather than phase-delay realisation.(b) Large arrays of sensors are required for high spatial resolution and the beam-forming system must be capable of forming and processing from these large numbers of independently steered beams in parallel to achieve useful angular cover, as well as good angular resolution.(c) The sensor arrays themselves are often mounted on mobile platforms, for example on surface ships, and the effects of platform motion on array data must be considered if the intrinsic system resolution is to be maintained.(d) The array geometries employed are often constrained by platform requirements rather than by those of the sonar and consequently sonar beam-forming systems must be able to process data from various diverse array geometries, for example from conformal and cylindrical, as well as planar sensor arrays. This paper outlines the impact of such factors on sonar beam-forming implementations and describes some of the techniques that have been developed, together with their practical realisation using state-of-the-art digital l.s.i. technology.

DOI:10.1049/ip-f-1.1980.0040

出版商:IEE    

年代:1980

数据来源: IET

摘要:

Development of digital methods for antenna beam forming in the receiving mode of a radar can be advantageous in providing the system with a high degree of flexibility in ‘beam-pattern management’ for countering e.c.m. and providing multiple functions efficiently. The justification for incorporating digital methods and various possible arrangements are discussed first. The main body of the paper is a review of the mathematical basis for operating in the digital domain, and includes an analysis of the main causes of error so that a broad assessment of the precision of the method, compared with more conventional and better documented types, can be made. The relationship between complexity of realisation on the one hand, with signal bandwidth, number of elements and number of simultaneous beams on the other, is also discussed. In this context brief comments are made on anticipated advances in device technology. The function of controlling the beam-formation process is summarised from the point of view of allowing corrections to the weight values in real time to be made to compensate for errors in the antenna, its feeds and the multiple receiving channels, and providing an adaptive control of the beam patterns to optimise performance against jamming. The paper ends with a description of the operation of a small experimental digital beam former.

DOI:10.1049/ip-f-1.1980.0041

出版商:IEE    

年代:1980

数据来源: IET

摘要:

A multichannel coherent optical correlator and a noncoherent optical vector-matrix processor are described and their application to the processing of data from an adaptive phased-array radar are discussed.

DOI:10.1049/ip-f-1.1980.0042

出版商:IEE    

年代:1980

数据来源: IET

摘要:

A description of the ELRA phased array radar at FFM in Germany is given. This phased array, comprising separate active transmitting and receiving antennas, acts as a test bed for a wide variety of radar waveforms and signal-processing techniques. Emphasis is placed in the present paper on a description of the array hardware and the test or adjustment procedures used to achieve the desired radiation patterns of the arrays.

DOI:10.1049/ip-f-1.1980.0043

出版商:IEE    

年代:1980

数据来源: IET

摘要:

A review of microwave devices for power generation and low-noise amplification in active array modules is given. Various configurations of active array module are discussed and particularly full attention is given to the use of microwave phase-locked loops to achieve the required gain and accurate phase control. The noise performance and response to pulse-compression waveforms for such loops is also considered. It is suggested that considerable benefits may be obtained by performing phase shifting and signal processing at i.f. or baseband and that this leads to the possibility of optical-fibre interfaces with modules, much simplifying the interconnection problem. The realisation of a phase-locked loop module with phase shift applied at i.f. and constructed in thick-film microstrip form for use at X band is described.

DOI:10.1049/ip-f-1.1980.0044

出版商:IEE    

年代:1980

数据来源: IET

摘要:

The use of gallium arsenide as a material for monolithic microwave circuits where active devices, such as f.e.t.s, diodes etc., are integrated onto the same piece of material as passive components is now receiving considerable attention in Europe and the USA. The paper concentrates on the specific role of monolithic circuits in phased-array-radar applications with descriptions of the use of f.e.t.s in switches, phase shifters, attenuators, receivers and transmitters. A summary of GaAs f.e.t. device performance is included allowing some insight into the noise figures, output powers and efficiencies obtained from low-noise and power amplifiers, respectively, at frequencies in S- and X-band. Some examples of GaAs monolithic circuit designs are given and methods of using active as against passive matching to achieve higher packing densities are described. The yield and cost of monolithic techniques is reviewed in the light of present and predicted circuit design and technology improvements. The impact of such costs on the realisation of phased-array systems with large numbers of elements is reviewed.

DOI:10.1049/ip-f-1.1980.0045

出版商:IEE    

年代:1980

数据来源: IET

摘要:

Use of multiple active devices in phased-array radars to generate r.f. power is becoming more interesting, owing to the technical advantages of solid-state components. Because the solid-state components have peak-power limitations instead of the mean-power limitations of traditional components, it is more cost effective to transmit signals with a high duty factor. Furthermore, one of the most important features of phased-array radars is the capability of performing simultaneous tracking on several targets. A method of interleaving pulse sequences for the multitarget tracking function, thus using a high duty factor, is reported. In particular, a technique of selecting the pulse repetition frequency (p.r.f.) and the transmission frequency is described, depending on the estimated radial velocity of each target, its accuracy, clutter spectral characteristics, and the interleaving algorithm efficiency. A simulation has been performed to evaluate the packing efficiency as a function of the pulse length, the duty factor of the transmitter, the number of targets and their range distribution. Consequently, a typical partitioning of the radar frame time among the different functions (tracking, search, confirmation etc.) has been determined for fixed and rotating phased-array antennas. Finally, an evaluation of computer loading to implement multitarget tracking is given.

DOI:10.1049/ip-f-1.1980.0046

出版商:IEE    

年代:1980

数据来源: IET

摘要:

A technique for cancer treatment using focused microwave arrays to induce hyperthermia is developed. The system as initially proposed consists of orthogonal linear-phased arrays whose focusing properties are allied to the weakness of malignant cells to excessive heat. A two-dimensional computer simulation of the power dissipation inside a cylindrical body, with uniform permittivity and attenuation, shows that the array system could provide sufficient localised heating within the attenuating medium. The feasibility of operating without a matching dielectric is examined, but the results so far obtained are inferior in some important respects to those obtained with a matching dielectric.

DOI:10.1049/ip-f-1.1980.0047

出版商:IEE    

年代:1980

数据来源: IET