JPH01125003A - Reflector for yagi antenna - Google Patents

Abstract

PURPOSE:To prevent an interference wave from backward, and also, to effectively utilize the frequency by choosing a large value for the front-to-back ratio of a Yagi antenna. CONSTITUTION:A reflector is constituted of two stages of reflectors A, B. That is, as for the reflector A of a first stage, short elements R2, R3 are arranged in two lines and long elements R1, R4 are arranged by one line each in the upper and the lower parts of said elements by opening its center. Length of the element is L1 L2, and the long elements R1, R4 and the short elements have about one wavelength of the working frequency and about half wavelength, respectively. As for the reflector B of a second stage, long elements R6, R7 are arranged in two lines, and in its upper and lower parts, short reflecting elements R5, R8 are arranged by one line each. That is, as for the reflector A and the reflector B, the positions of the long elements and the short elements are replaced. Length of the reflecting element is L4 L3, and the long elements and the short elements have about one wavelength of the working frequency and about half wavelength, respectively. In such a way, the radio interference of a television broadcast can be obviated, and the title reflector is useful as a high quality television receiving antenna.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a reflector for a Yagi antenna that has a large front-to-back ratio (F/B) and can prevent interference waves from the rear. Regarding.

[Prior art and its disadvantages] In order to eliminate the single viewing of TV broadcasts, many satays are used.
There is a growing problem of lack of channels. Therefore, the use of television synchronized broadcasting, which uses frequencies efficiently, is being considered. However, in the case of TV synchronized broadcasting,
Another major problem is the generation of ghosts due to radio wave interference. One way to solve this problem is to improve the performance of the receiving antenna.

[Object of the Invention] The present invention has been made in view of the above points, and its purpose is to provide a reflector for a Yagi antenna that can improve the front/back ratio (F/B) of the antenna. be.

[Key Points of the Invention] In the reflector of the Yagi antenna, the reflector is configured in two stages, with two rows of short elements arranged in the first stage and one row each of long elements with the center open above and below it. The eyes are placed at the rear of the first stage by swapping the positions of the long and short reflective elements, and the antenna's front-to-back ratio (F/8
).

[Embodiments of the Invention] A reflector for a Yagi antenna according to an embodiment of the present invention will be described below with reference to the mouth side. The first factor shows the shape of the entire antenna, which includes 20 waveguide elements D1 to D2G, a feeding element P1, a reflecting element R1, and a feeding element P1.
~R8 are arranged. The radius of the waveguide elements D1 to 020 is 0.3 CI, and one feeding element P is arranged on the right side of the waveguide element D1.

Here, - reflective element R
1 to R4 constitute a reflector A, and reflecting elements R4P to R8 constitute a reflector←B.

Figure 2 (A) shows the first stage reflector A, with short elements R2, R
3 with two rows and the center open above and below it, long elements R1, R
4 are arranged in one column each.

The length of the element is Ll 4L2, and the long element R1°R4
is about one wavelength of the operating frequency, and the short element is about half a wavelength.

Also, the spacing between the first stage reflective elements is 6.2C- from the center to the shortest element, and 16.0cm from the center to the longest element.
It is.

Moreover, FIG. 2(A) shows the second stage reflector B, and the right part 9 of the first stage reflector A. It is located at OC-. The long elements Re and R7 are arranged in two rows, and the short reflective elements R5 and R8 are arranged one row each above and below. That is, reflector A and reflector B have long elements and short elements interchanged in position. The length of the reflective element is L4~L
3, the long element is about one wavelength of the operating frequency, the short element is about half a wavelength of the operating frequency, and the spacing between the reflective elements is 4.5 and 10.3 C- from the center.

Next, each reflector A shown in FIGS. 2(A) and (B),
FIGS. 3 and 4 show graphs of frequency versus F/B when F/B is arranged in the first or second stage as shown in FIG. 1. Here, the frequency is expressed as KL (K-2π/λ) based on the length of the feeding element, and the vertical axis is from 120 degrees to
The ratio between the electric field in the 240 degree direction and the maximum radiated electric field strength (0 direction) is expressed in decibels. Here, since the directivity is symmetrical, 120 to 180 degrees are plotted every 2 degrees, and the line connecting the smallest value of this line group is F/B.
It represents.

In addition, long reflective elements R1, R4 and short reflective elements R2, R
3, a steep peak as shown in FIG. 3 can be obtained.

Also, even if the reflector is one stage, the F/B is 24d or more.
B can be obtained, but the band is K L −1,65 ~
It is only satisfied within a narrow range of 1.80.

Also, when KL is small, the area where F/B is large is 1
The direction is 20 degrees, and the point where F/B is small is the direction of 180 degrees, and most F/B is determined in the direction of 180 degrees. However, the side lobe becomes large from around K L -1,6, resulting in complicated directivity. Here, even if the length of the reflective element is extended to about four times the length of the feeding element, F/B is not improved. In this way, the F/B characteristic in the case of one stage of reflective elements is 24
It rarely exceeded dB, and even if it did, it was within a narrow range.

Therefore, by installing reflectors A and B as shown in Figure 2 (A) and (B) and arranging reflectors A and B with different lengths three-dimensionally, two peaks can be obtained at 180 degrees F/B. , and high F/B can be obtained over a wide frequency range (K
L -1,55~2.20), therefore, when used for UHF TV, it is for LM band (470~660M1b)
and for the MH band (518 to 770 MTo). In the case of this reflector, when the lengths of the elements of reflectors A and B are as shown in FIG. 4, the band is the widest. As shown in Figure 4, F/B is 30
The band above [dB] is quite wide (K
L-'1.75-1.95).

By forming the reflector in a two-stage structure in this manner, it is possible to obtain a good F/B over a wide range of UHF television bands, for example. This reflector can also be used for VHF television or communication antennas. Furthermore, even if the number of waveguides is reduced, the influence of F/B is small.

[Effects of the invention] As detailed above, according to the present invention, it is possible to eliminate interference in television broadcasting by improving the F/B, so that frequencies can be used effectively, and it can be used as a high-definition television receiving antenna. An excellent Yagi antenna reflector can be provided.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a reflector of a Yagi antenna according to an embodiment of the present invention, Figure 2 is a plan view showing the configuration of the first and second stage reflectors, and Figure 3 is a diagram showing the configuration of the reflector. FIG. 4 is a graph showing the frequency vs. KL characteristic when the reflector is in one stage, and FIG. 4 is a graph showing the frequency vs. KL characteristic when the reflector is in two stages. P... Feeding element, D1-D20... Waveguide element, R1
-R8...Reflection element. Applicant's agent Patent attorney Takehiko Suzue L Figure 3 L Figure 4

Claims (1)

[Claims] In the Yagi antenna reflector, the reflector is configured in two stages, the first stage has two rows of short elements, the top and bottom of which are arranged one row each of long elements with the center open, and the second stage has the above-mentioned reflecting elements. A reflector for a Yagi antenna in which the positions of the long and short elements are switched and placed behind the first stage.