JPS6161281B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna used for receiving television broadcasts, particularly for receiving VHF bands.

For this type of antenna, in order to increase the front-to-back ratio and eliminate interference waves from the rear, it is necessary to install a large number of waveguides or use a large reflector with multiple elements or a mesh. Attempts are being made to However, in both cases, there was a problem that only a small improvement in the front-to-back ratio could be obtained even though the number of antenna elements was increased.

Therefore, as shown in FIG. 9, the applicant's company installed linear waveguides at a position in front of the radiator 3 and above and below the plane formed by the linear waveguide group 2'. I tried arranging the waveguides 2a and 2a. However, as shown by line A in Figure 5, the front-back ratio (if the reflected wave arrives from behind the antenna, D/
u (desired wave/reflected wave)) only reached the allowable limit (25 db) for channel 1, and it was not possible to improve the overall signal to the allowable limit. Moreover, it was not possible to reach the detection limit of 30db. For further improvement, as shown in FIG.
We also tried placing waveguides above and below the waveguide group 2', but this had a poor front-to-back ratio like the one in Figure 9 (shown by line B in Figure 5).We tried to improve the front-to-back ratio. I couldn't do it.

Therefore, as long as the configuration does not become complicated, even if the front-to-back ratio reaches the detection limit, it is desirable to
It was hoped that an improvement plan would be provided that exceeds the allowable limits in all three areas.

The present invention has been devised to meet the above requirements. That is, the present invention was created after taking various improvement measures, and by combining a linear waveguide and two folded waveguides under specific conditions, channel 1 can reach the detection limit. We have succeeded in providing a configuration in which the overall front-to-back ratio can be improved as shown by line C in Figure 5. Moreover, the VHF has a relatively simple structure.
The aim is to provide a low-frequency television antenna.

The drawings showing the embodiments of the present application will be described below. In antenna A, 1 is boom, 2, 2...
A plurality of linear waveguides are arranged in parallel in the front part of the boom 1, and these plurality constitute a waveguide group 2', and as is well known, they are arranged to guide incoming radio waves. There is. Numeral 3 is a radiator that picks up and receives incoming radio waves, and 4 is a power feeding section thereof, which transmits the signal received by the radiator 3 to a power feeding line 4' without loss.
Reference numeral 5 denotes an auxiliary boom that extends vertically and vertically at the rear of the boom 1, and is made of synthetic resin for the purpose of weight reduction. 7,7,
7 is a reflector, which constitutes a reflector group. Reference numeral 9 denotes an auxiliary boom that extends perpendicularly to the boom 1 and in the vertical direction thereof at a position in front of the radiator 3, and is made of a synthetic resin material. Reference numerals 10 and 10 indicate folded waveguides, which are attached to the upper and lower ends of the auxiliary boom 9, and are disposed at positions above and below the plane formed by the waveguide group 2', respectively. As shown by the two-dot chain line in FIG. 1, these may be arranged in two or more locations as an upper and lower pair. Note that 11 is a mast provided to support the antenna A, and the boom 1 is attached to the top of the mast.

Next, the folded waveguide 10 will be explained. 1
Reference numeral 2 denotes an element holder, which is made of synthetic resin and is fixed to the auxiliary boom 9 using a set screw 13, as shown in FIG. Reference numerals 14 and 14 denote waveguide elements, each of which is formed into a folded type, that is, a U-shape, as clearly shown in FIG. A connecting body 15 is provided to electrically connect the free end portions 14a of the opposing waveguide elements 14, 14, and is formed using a metal piece. Note that a conducting wire may be used for this purpose. Reference numeral 16 denotes a fastener for mechanically fixing the free end 14a of the waveguide element 14 and the connecting body 15 to the element holder 12, and for electrically connecting the free end 14a and the connecting body 15. It is made of metal rivets. Note that a threaded rod or other material may be used for this purpose. Reference numeral 18 denotes a cover that is fitted onto the element holder 12, and is connected to the connecting body 15 and the fastener 16.
It is provided so as to cover the connection part with.

Next, we designed and manufactured an antenna with the above structure for use in the low band of a television, and measured its gain and front/rear ratio characteristics, as shown in Figures 4 and 5, respectively.
Characteristics as shown by the solid line in the figure were obtained. In these figures, the broken lines indicate the characteristics of the conventional structure shown in FIG.

As is clear from these figures, it was confirmed that good characteristics similar to the conventional ones can be obtained in terms of gain, and in addition, an extremely large improvement can be obtained in terms of front-to-back ratio.

Moreover, FIGS. 6 to 8 show the results of measuring the directional characteristics. As is clear from these figures, it was also confirmed that sharper directivity characteristics can be obtained compared to conventional products.

As described above, in the present invention, since the folded waveguides 10 and 10 are placed above and below the radiator 3 in front of the radiator 3, the synergistic effect of this and the reflector group results in It has a feature that it can have a much larger front-to-back ratio compared to conventional structures, and is particularly effective when used as a countermeasure against ghosts.

[Brief explanation of the drawing]

The drawings show an embodiment of the present application, and Fig. 1 is a perspective view, Fig. 2 is a front view, Fig. 3 is an enlarged sectional view of the element holder portion, Fig. 4 is a gain characteristic diagram, and Fig. 5 is a front and rear view. Ratio characteristic diagram, Figures 6 to 8 are directional characteristic diagrams,
FIGS. 9 and 10 are schematic diagrams of antennas with conventional configurations. 1...Boom, 2...Waveguide, 3...Radiator,
7...Reflector, 10...Folded waveguide.

Claims (1)

[Claims] 1. The boom is equipped with, in order from the radio wave arrival side, a waveguide group consisting of a plurality of linear waveguides arranged in parallel, a radiator, and a reflector group consisting of a plurality of reflectors. A VHF antenna characterized in that folded waveguides are arranged in front of the radiator and above and below the plane formed by the linear waveguide group, respectively. TV low frequency antenna.