Wireless Direction Finding Research Articles

Sound and fury: sound and vision in early U.K. air defence

To mount an effective national air defence after the outbreak of the First World War, Great Britain required early warning and tracking of aggressors beyond visual range. To achieve this, the early warning provided by wireless interception, ‘listening in’ to attackers’ radio traffic and tracing its origin by wireless direction finding, and acoustic (sound) location, tracking enemy aircraft engine noise – techniques almost totally independent of the ability to see the enemy – increasingly enabled fighters to attain the necessary height and position for interception, mobile gunners to set up their artillery, and blackouts to deny enemy dirigibles and aircraft accurate acquisition of their targets. The system relied upon the telephone, and later wireless, both acoustic means, to communicate information speedily between interceptors and listeners, control centres, and defence assets such as guns, aircraft and civilian air-raid warnings. These defences developed to prove effective against two overlapping phases of strategic bombing assault, first by Zeppelin dirigibles, and later by bomber aircraft. In both cases, wireless and acoustic techniques, though imperfect, provided a necessary early warning impossible to achieve by visual means.

Assessment of the Impact of Orthogonal Directional Pattern Generating Algorithms on the Accuracy of Wireless Direction Finding by BS-MUSIC and BS-Capon Methods

The paper considers the MUSIC and Capon methods for determination of radio radiation coordinates, possessing a superresolution property, which assumes that two signal sources spaced less than at the Rayleigh limit can be represented as individual peaks on the spatial direction finding relief graph. A computational burden problem arises in such spectrum estimation algorithms; it can be solved by the methods of building so-called orthogonal directional patterns, reducing computational complexity and antenna array dimension. A multibeam array pattern (spatial channel) is formed for this purpose, and then the signals are pre-processed by means of these spatial channels focused in a certain region. The paper gives numerical estimations of accuracy for determination of radio radiation source coordinates by the classical MUSIC and Capon methods, and also after preliminary transformation by orthogonal directional patterns (BS-MUSIC and BS-Capon) versus signal/noise ratio, the number of beams and averaging time of the correlation matrix. A great number of methods of mutually orthogonal spatial channel formation are presented; among them the most well-known discrete Fourier transform, spherical sequences and Taylor series expansion. It is worth noting that to date no comparative studies of the accuracy characteristics of such methods (BS-MUSIC and BS-Capon) has been performed. It is found that the accuracy of the BS-MUSIC and BS-Capon methods increases with the increase in the number of spatial channels from four to five. In this case the accuracy of the method for channel generating by spherical discrete sequences is the highest in the majority of the considered interference cases.

Correction of the amplitude-phase distribution of electromagnetic field in the context of wireless direction finding problem

A technique for correcting the amplitude-phase distribution of the aperture field in the antenna array has been investigated. The optimal number of points for placing the reference oscillator was determined. The specified number provides for achieving the efficiency of superresolution algorithms. A correction technique based on presenting the antenna array in the form of large-radius array consisting of ideal noninteracting elements was proposed. This technique involves the use of only one reference point. Using the MUSIC method, as an example, the direction finding characteristics were calculated for the techniques under consideration.

Method for estimating the number of signals in problems of wireless direction finding with a small observation period

A new algorithm for estimating the number of signals received by the antenna array has been proposed. As confirmed by simulation and field tests, this algorithm features smaller computational costs and ensures more accurate estimates at short observation times.

Application of Spherical Trigonometry to Problems in Wireless Direction Finding

Mathematical theory for tackling various problems encountered in Wireless Direction Finding is given. Primary among these problems is locating accurately—by calculation or otherwise—the position of an unknown transmitter, knowing its bearings from two known D/F stations. The theory assumes importance in high frequency D/F work, when the transmitter sought to be located may be very far off from D/F stations and over the area the earth cannot be presumed flat.

Wireless Direction Finding

Wireless Direction Finding

Wireless Direction Finding

THE appearance of the fourth edition of this book will do much to dispel the impression, prevalent in some quarters, that the technique of radio direction finding has been rendered obsolete by the introduction and development of radar in recent years. As the author explains in his introductory chapter, there are several fields in which direction finding will still have commitments for many years to come. The relative simplicity of the equipment required to give guidance to ships and aircraft, and particularly to those in distress, makes it an invaluable aid to navigation ; in another field, the network of direction finders provides the only means so far available of locating radio transmitting stations, and such information is frequently required under peacetime conditions as well as in time of war. Wireless Direction Finding By R. Keen. Fourth edition. Pp. xii + 1059. (London: Iliffe and Sons, Ltd., 1947.) 45s. net.

Wireless Direction Finding

Wireless Direction Finding

Wireless Direction Finding

Wireless Direction Finding

Wireless Direction Finding. By R. Keen, B.Eng. Published by Iliffe and Sons, Ltd. (Third edition.) Price 25/-.

An abstract is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content.

Wireless Direction Finding

THE art of navigating any mobile craft depends essentially on being able to determine the position of that craft with relation to a fixed point or points; the position may either be obtained in the form of a bearing on, and a distance from, any known fixed point, or of simultaneous bearings from two or more fixed points, which bearings are laid off on a chart and denote, by their intersection, the position of the craft at the time.

A device for maintaining isochronism in low-power electric motors

In connection with the driving of a wireless direction finding rotating beacon it was found necessary to devise means of controlling a motor so as to obtain accurate constancy of speed over wide ranges of mains variation.In the first instance experiments were made with a governor such as that used in the Baudot printing-telegraph system, but it was found that it did not absorb sufficient power to enable it to be used on the direction-finding rotating beacon. With a view to diminishing the amount of power that need be absorbed by the governor, an electric circuit arrangement for the supply of power to the electric motor used to drive the beacon was devised, and finally an eddy-current governor with clock control was designed. The clock control is intended to enable two beacons to be run with alternate periods of transmission, without the possibility of serious overlapping of these periods. The accuracy of the governor control is of the order of 0.05 per cent with 30 per cent mains-voltage fluctuations, while the clock control limits the cumulative error to less than 1 degree of azimuth.