Adcock Antenna Research Articles

基于谱估计的短波信号测向算法

针对短波沃森瓦特测向系统，提出了一种基于波束形成的测向算法，该算法将沃森瓦特接收机的三个通道输出进行线性组合，形成阵列测量矢量，采用最小方差无失真波束形成器进行空域滤波测向。与传统沃森瓦特算法相比，该方法充分利用了爱德考克天线的阵列孔径。计算机仿真表明，所提算法的测向精度优于传统算法。 An algorithm based on beamforming is proposed for shortwave direction finding with a Watson- Watt (WW) system. It constructs an array measurement vector by the linear combination of the outputs of the three receiving channels of a WW system, and then utilizes the Minimum Variance Distortionless Response (MVDR) beamforming to perform spatial filtering. Compared to the traditional WW algorithm, the proposed method takes advantage of the full aperture of the Adcock antenna array, which leads to its better accuracy of direction finding, and it has been demonstrated by computer simulations.

Robust direction of arrival estimate method in FM‐based passive bistatic radar with a four‐element Adcock antenna array

This study examines the problem of direction of arrival (DOA) estimation in FM-based passive bistatic radar using a four-element Adcock antenna array. The authors investigate the influence of the target echo, involved in the reference signal, on the DOA estimation of the corresponding target considered. Analysis shows that, unlike the pure reference signal case, a weak target echo involved in the reference signal may not affect the detection of the corresponding target. It can often have a significant impact on the estimation of a target's DOA; thus typical DOA estimate methods degrade heavily. A robust method is proposed to cope with this problem. Simulation and experimental results demonstrate the effectiveness of the method.

Direction finding in frequency-modulated-based passive bistatic radar with a four-element Adcock antenna array

The Adcock antenna array is widely used in electronic warfare for direction finding of emitter sources. However, in frequency modulated (FM)-based passive bistatic radar (PBR) the traditional Adcock antenna-based direction finding methods cannot work well because weak target echoes are embedded in the background of strong direct signals, multipath and clutter echoes. A method using a four-element Adcock antenna array is developed for horizontal plane 360° target direction measurements for FM-based PBR. By using numerical simulations, the performance of the proposed method is studied for both single and multiple targets, and finally its effectiveness is demonstrated for real data.

Application of the MUSIC method for direction of arrival estimation using the ADCOCK antenna arrays

The MUSIC based Direction of Arrival estimation using the ADCOCK antenna arrays is considered. Starting from signal model formulation, the cost function of the MUSIC algorithm and the ambiguity functions for the ADCOCK antenna array have been formulated. Some simulation results and some preliminary results of the verification in practice are presented.

An Analysis of Errors in Long Range Radio Direction Finder Systems

Modern radio direction finding equipment and techniques have advanced to such a degree that it is possible to obtain accurate bearings on a signal from halfway around the globe. These successes have resulted largely from recent electrical and mechanical refinements in the modern Adcock antenna df system. Although the system has been described before, and applications demonstrated, to the writer's knowledge there has not been a complete investigation of its potentialities. An analysis would seem desirable because of the great utility of the system. The following material develops a rigorous mathematical analysis of the errors that are mostly encountered in the design and installation of a new direction finding station. A detailed treatment of the effect of variations in the antenna spacing is presented in support of the author's recommendations for obtaining higher efficiency in the upper frequency ranges of a given station.

Null Characteristics of the Rotating Adcock Antenna System

It has been the usual practice when designing a rotating Adcock antenna system to allow a spacing of one-half wavelength between opposite dipoles at the highest intended frequency of operation. A mathematical analysis of this antenna system is presented, and it is shown that an optimum spacing for the most clearly defined nonmultiple nulls approaches a full wavelength. Useful design formulas are developed and typical response curves are presented graphically.

Ultra-High-Frequency Radiosonde Direction Finding

A simple radio direction finder, operating at 183 megacycles, for observing the flight of meteorological balloons is described. An Adcock antenna and a single-dipole antenna system, including a corner-type reflector as shield against ground-reflected waves, were used for measuring the azimuthal and the elevation angles of an incoming electromagnetic wave. Shielding characteristics of the corner-type reflector for various wire spacings, focal lengths, and wire lengths are given. The direction finder has an accuracy of ¼ degree in the determination of the azimuthal angles. An accuracy of ½ degree is easily obtained in the determination of the elevation angles when a stationary transmitter is used as target on top of Mt. Wilson at a distance of seven miles. Larger errors in the elevation angles were observed when the target transmitter was sent aloft on balloons.

Radio Direction Finding at 1.67-Meter Wavelengths

Different antenna systems such as the Adcock, V-type, double-V-type, parabolic, and the H-type were tested for measuring both the vertical and the azimuthal angles of an incident wave at the wavelength of 1.67 meters. A null method using the Adcock antenna for defining the azimuthal angle and the H antenna for determining the vertical angle was found to be most satisfactory for high angles of incidence. As the frequency used is too high for sky-reflected waves, erroneous directions attributed to the effect of sky waves at longer wavelengths are eliminated. With the antenna system one and one-half wavelengths above ground and with the ground surface dry and homogeneous and no reflecting objects in the immediate vicinity, the direction of the incident wave thus determined agrees within ½ degree with the optical direction in the azimuthal angle and within ±½ degree in the vertical angle. But when the ground is wet, the error in the vertical angle may reach as high as 3¾ degrees. A mathematical analysis of the reception by these two types of antenna systems, taking into consideration the ground-reflected waves, is given. The theoretical response agrees well with the experimental one.

The Compensated-Loop Direction Finder

One of the serious limitations of the null-type radio direction finder has been the "night-effect" error caused by the horizontally polarized component of the downcoming sky wave, which is picked up in the horizontal elements of the loop. Two types of attack on this problem are represented by the "Adcock antenna" and the "compensated loop." The Adcock antenna is effective because of its construction without horizontal elements, but suffers from low pickup of the desired vertically polarized components. On the other hand, the compensated loop consists of a standard loop plus an auxiliary horizontal antenna mounted on the loop, from which is obtained a voltage for neutralizing the undesired loop pickup. The latter system offers the greater advantages in terms of good pickup and compactness of structure, but has not received adequate consideration by previous investigators. This paper presents an analysis of the compensated loop in the general case, together with the results of detailed calculations for direction finders covering a wide range of wavelengths, with two specific examples for 550 and 1100 meters. The analysis shows that when the earth has a high reflection coefficient the system is capable of providing complete or nearly complete neutralization with no tuning required other than an initial adjustment, and even with poor earth conditions, substantial reduction in errors is obtainable.