SU1734147A1 - Loop aerial - Google Patents

Abstract

The invention relates to radio communication and can be used in the radio reception technique of electrically small antennas in radio communication systems, broadcasting, radio navigation. In a frame antenna, the screen is designed as a conductive plate, the dimensions of which exceed the frame dimensions, and is mounted along the frame axis perpendicular to its plane . Replacing a closed screen with a conductive plane provides a simplified design. The ability to change the dimensions of the conductive plane allows you to slightly change the shape of the beam antenna. 4 il.

Description

The invention relates to radio, in particular to the technique of receiving radio signals by electrically small antennas. It can be used by users of signals from broadcasting systems, radio communications, radio navigation, etc.

Analogs are known in which the efficiency of a loop antenna in the zero reception region is enhanced by a second, orthogonal to the first loop antenna located and a summing stage combining the signals of both antennas. A metal screen serves the same purpose, weakening the influence of the frames on each other.

The disadvantage of such antennas is the low efficiency inherent in frame antennas with a small electrical length,

Closest to the present invention is an antenna comprising several vertical wire turns. The antenna is shielded in such a way that the half-turns 2 belonging to one side of the frame are enclosed in a grounded metal screen 3, therefore the signal induced in them is smaller than the signal induced in half-turns 1. The result is a decrease in the compensation of the signal induced in half-turns 1 by the signal induced in shielded half-turns 2 and an increase in the magnitude of the output signal.

The disadvantage of the prototype device is the corresponding increase in the output signal level, a decrease in the directional properties of the loop antenna, and the complexity of the design.

The purpose of the proposed loop antenna is to simplify the design while maintaining the directional properties.

The goal is achieved by the fact that in a frame antenna containing a vertical wire frame and a grounded shield, the screen is made in the form of a conductive plate, which is placed symmetrically and normally to the plane of the frame, while the dimensions of the conductive plate ai, 61 are

Yu

with

V4 CO Ј VI

from the ratio of ah, 61 b, where a, b - the corresponding size of the frame.

Unlike the prototype antenna, in which the shielding is performed by a closed screen, in the proposed antenna, the shielding is performed by a conductive plate, which simplifies the design. In addition, the symmetrical arrangement of the conductive plate, the dimensions of which are not less than the size of the frame, ensures that the radiation pattern is preserved, which, in addition, can be changed within certain limits by changing the screen size.

Fig. 1 is a schematic diagram of a framework antenna; in fig. 2,3,4 - diagrams explaining the operation of the antenna.

The proposed frame antenna consists of an electromagnetic signal sensor in the form of a vertical wire frame, the semi-turns 1 and 2 of which are located symmetrically with respect to the grounded conductive surface 3, also located vertically.

The dimensions of the conductive surface 3 (width a and height b) must be no less than the corresponding dimensions a and b of the wire frame, i.e. Ata, 61 6. Conductive surface 3 is located symmetrically between half-threads 1 and 2 and the normal plane of the frame.

Frame antenna works as follows.

When receiving a vertically polarized electromagnetic wave from azimuths of 0 and 180 ° in semi-turns 1 and 2, signals ei and e2, respectively, are sent, respectively, in magnitude and phase (see Fig.2a), but directed oppositely in the contour of the frame, therefore the output the signal is 0 (see fig.2a). When receiving from azimuths of 90 and 270 °, the induced signals ei and 62 are still equal in size, but their phases are different, so that in the absence of a separating conductive surface 3, the output signal would correspond to the difference differential (see Fig. 26) , and the radiation pattern is shaded in FIG. 3 with a maximum equal to evyh. The presence of a conductive surface is 3

It changes the ratio of ei and e2. When received from the azimuth of 90 ° in half-turns 1, the signal ei is induced, and in half-turns 2-62 it is 62 0. This means that eV et. If the shielding is not ideal or the azimuth differs significantly from 90 °, then e2 0 and the magnitude of the output signal decreases. The degree of gain in the magnitude of the output signal depending on the degree of shielding (ratio e2 / ei) and electrical dimensions of the loop antenna (angle values

d

a-g in radians) is shown in dependencies in FIG. 4. The magnitude of the gain for electrically small antennas (0.01) may be 20 dB or more.

If the dimensions of the conductive surface 3 slightly exceed the dimensions of the frame, then the radiation pattern with azimuths significantly different from 90 ° will be different from the original one, since the effect of compensating ei and e2 signals and reducing the output signal will appear, which is equivalent to narrowing the radiation pattern .

An experimental test was carried out on a 250-mm framework antenna (three turns) with a conducting surface of 980x1400 mm in size at a frequency of 1125 kHz (I-270 m). The signal source is a local radio station, the signal level indication was carried out using a CMB-6.5 selective microvoltmeter. Signal levels were compared in the directions of maximum reception with and without a screen. The ratio of signal levels is 11 dB.

Claims (1)

Claims of the invention A frame antenna comprising a wire frame and a grounded shield, characterized in that, in order to simplify the construction, the screen is made in the form of a plate that is arranged along the axis of the vertical wire frame orthogonal to its plane, while the dimensions of the conducting plate ai and bi are chosen from the ratios ai a, 61 6, where a and o are the corresponding dimensions of the wire frame. -J L s a L X about / Out ./ 270  l / x. Q d 0.7 d 0.3 0.01 iff 2 / ti