RU2248075C1 - Loop antenna - Google Patents

Abstract

FIELD: radio engineering; transmitting antennas for operation in ultrahigh-frequency band.

SUBSTANCE: proposed loop antenna has two multiturn loops. Planes of turns in each loop are parallel to each other and size of each turn is much smaller than operating wavelength. Each multiturn loop is sectionalized and capacitor is inserted in each section; all sections are cascaded and turns of adjacent sections are wound in opposing directions. Axes of both loops are in same horizontal plane and relatively perpendicular; centers of multiturn loops are spaced from their intersection point through 0.2 to 0.32 of wavelength at intermediate frequency of operating frequency band.

EFFECT: provision for attaining omnidirectional pattern in horizontal plane at vertical polarization of radiated waves.

1 cl, 3 dwg

Description

The invention relates to radio engineering and is intended, in particular, for use as a transmitting antenna for digital broadcasting by the earth wave in the decameter wavelength range.

For this purpose, omnidirectional antennas in the horizontal plane are needed, which ensure the emission of vertically polarized waves. The vertical size of the antennas should be small (significantly less than the working wavelength) for ease of placement on the roofs of buildings.

Known loop antenna for the range of decameter waves, in which the planes of the frames are vertical, therefore, the antenna can emit vertically polarized waves [1]. However, this antenna is directed in the horizontal plane, in addition, its frame size is large (comparable to the wavelength).

Known loop antenna, omnidirectional in the plane of the frame [2]. However, when the plane of the frame is oriented horizontally, this antenna emits horizontally polarized waves. In addition, its size is large (comparable with the wavelength).

Known loop antenna, which can emit radio waves with different polarization, and the radiation pattern in the horizontal plane is close to omnidirectional [3]. However, the dimensions of the antenna are large: the perimeter of the frame is half the length of the working wavelength. This antenna, like the ones mentioned above [1, 2], contains a small number of turns in the frame (in this case, one), therefore, such antennas can effectively radiate only if the dimensions of the turns of the frames are large enough (comparable to the wavelength).

A loop antenna is known that contains a multi-turn frame, the turns of which are parallel to each other, and the dimensions of each of the turns are much smaller than the working wavelength, with the multi-turn frame made sectioned and a capacitor included in each section, while the sections are connected in cascade, and the turns in adjacent sections are made with the opposite direction of the winding [4] (prototype). This antenna is capable of efficiently emitting at a relatively small coil size. However, in order to ensure the emission of vertical polarized radio waves, the planes of the turns of the frame must be vertical, therefore, the axis of the frame must be horizontal; in this case, the directivity pattern in the horizontal plane is uneven - there will be deep dips in the direction of the frame axis.

The present invention solves the problem of obtaining an omnidirectional radiation pattern in the horizontal plane with a small vertical antenna size and with sufficient radiation efficiency (i.e. high radiation resistance, efficiency) of vertically polarized radio waves.

To achieve this technical result, in a known loop antenna containing a multi-turn frame, the planes of the turns of which are parallel to each other, and the dimensions of each of the turns are much smaller than the working wavelength, with the multi-turn frame made sectioned and a capacitor included in each section, while the sections are connected between a cascade, and the turns in adjacent sections are made with the opposite direction of winding, the second same multi-turn frame is introduced, and the axes of both frames lie in the same horizon cial plane and perpendicular to each other, and the centers of multiturn frames are removed from the point of intersection of the axes to a distance of 0.2 ... 0.32 wavelength at the average frequency of the operating frequency band.

Figure 1 shows a schematically proposed loop antenna, a top view.

Figure 2 shows a multi-turn frame (the second of two identical) - the main component of the proposed antenna.

Figure 3 shows the radiation patterns in the horizontal plane of the proposed loop antenna.

The proposed loop antenna contains two multi-turn frames 1 and 2 (figure 1). The axes of the multi-turn frames are mutually perpendicular and are located in the same horizontal plane. Thus, the planes of the turns of multi-turn frames are vertical; in this case, the planes of the turns of the multi-turn frame 1 are perpendicular to the planes of the turns of the multi-turn frame 2. The centers of the multi-turn frames are removed from the point of intersection of the axes by a distance l (Fig. 1) equal to 0.2 ... 0.32 wavelength at the average frequency of the working frequency band of the frame antennas. Multi-turn frames 1, 2 are connected by feeders 3, 4 of equal length with a signal source 5 (transmitter feeder, if necessary, with a matching device, not shown in Fig. 1). Multi-turn frame (figure 2) is made in the form of sections 6 connected in cascade. Each section contains a coil 7, consisting of one or more turns, and a capacitor 8. The planes of all turns of a multi-turn frame are parallel to each other; turns in adjacent sections are made with the opposite direction of winding (in Fig.2, the beginning of the coils are indicated by dots).

The proposed loop antenna operates as follows (see figure 1). The energy from signal source 5 through feeders 3 and 4 enters the multi-turn frames 1 and 2 and is emitted by them. Due to the fact that the planes of the turns of the multi-turn frames 1 are perpendicular to the planes of the turns of the multi-turn frames 2 and due to the shift of the centers of the multi-turn frames by a distance l, the radiation in the horizontal plane is sufficiently uniform: the aforementioned range of values for l ensures uneven radiation pattern within ± 1.5 dB (the ratio of the minimum radiation pattern to the maximum of at least 0.7). The interval of values of l was obtained on the basis of this criterion by numerical electrodynamic modeling. Figure 3 shows the radiation patterns in the horizontal plane of the proposed antenna: curve 1 for l = 0.25, curve 2 for l = 0.2 and curve 3 for l = 0.32. The prototype radiation pattern is also shown there - one multi-turn frame with a horizontal axis (curve 4). Partitioned multi-turn frames provide high radiation resistance, due to which the efficiency of the frame antenna sufficient for practical purposes is obtained and its coordination with the feeder is facilitated.

Used sources

1. US patent No. 6342861, CL. H 01 Q 7/00 (national class. 343/741; 343/834), publ. 01/29/2002.

2. Patent of Russia No. 2.180.151, cl. H 01 Q 9/00, publ. 02.27.02, BI No. 6.

3. Application WO No. 227862, cl. H 01 Q 1/24; H 01 Q 7/00, publ. 04/04/2002.

4. USSR author's certificate No. 854232, cl. H 01 Q 7/00, publ. 05/27/96, BI No. 15.

Claims (1)

A loop antenna containing a multi-turn frame, the planes of the turns of which are parallel to each other, and the dimensions of each of the turns are much smaller than the working wavelength, the multi-turn frame is made sectional, and a capacitor is included in each section, while the sections are connected in cascade, and the turns in adjacent sections are made with the opposite direction of winding, characterized in that a second same multi-turn frame is inserted into it, the axes of both frames lying in the same horizontal plane and mutually perpendicular are pendicular, and the centers of the multi-turn frames are removed from the point of intersection of the axes at a distance of 0.2 .... 0.32 wavelength at the average frequency of the working frequency band.

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