JPH03149907A - Array antenna - Google Patents

Abstract

PURPOSE:To improve the directivity by constituting a resonator with a radiation element to radiate a radio wave in an objective direction and plural reflecting exciting elements and radiating elements arranged in a plane not including the objective direction. CONSTITUTION:The principle is adopted for the array antenna that the radiation in the objective direction is increased more as the radiation in undesired directions is suppressed from the standpoint of that the total energy radiating from the antenna is constant, and the array antenna that the radiation energy toward upward into sky and downward to ground being the energy radiating in the undesired directions in a three-dimensional space is converted effectively for the use in the objective direction (horizontal direction) is realized. The array antenna is configurated by adding exciting elements 4, 5 to Yagi antennas 2, 3. Accordingly, the waste radiating energy other that the forget direction is effectively utilized. Thus, when the array antenna is applied to ground communication or television broadcast, the energy having been radiated in sky and toward ground in conventional antennas is effectively joined for the use in horizontal directions, and when the array antenna is applied to satellite communication, the energy having been radiated in horizontal directions conventional antennas is effectively added for the use in upward directions. Thus, the gain increase is obtained.

Description

[Detailed Description of the Invention] (Industrial field in Icheon) The present invention is applicable to dipole antennas, Yagi antennas, reflector antennas, etc. used in a wide range of fields such as radio, television, communication equipment, and radar, and can improve the antenna gain. It is effective in improving radiation and suppressing radiation or reception in unnecessary directions.

(Prior Art) It has been known that the requirements for array antennas have become stricter in order to improve the directivity characteristics of the antenna. Furthermore, it was difficult to suppress radiation (reception) in unnecessary directions.

(Problems to be Solved by the Present Invention) The present invention configures the antenna element arrangement and excitation method using a design principle different from that of the conventional one, so that radio wave energy radiated in unnecessary directions can be effectively directed toward the target direction. The array antenna of the present invention achieves high gain and suppression of directional characteristics, and is effective in increasing receiver sensitivity and eliminating ghost interference for TV antennas that require unidirectional characteristics. be.

(Object of the Invention) The present invention is to realize an array antenna that increases the gain of the antenna in the target direction and further improves the characteristics of suppressing radio wave radiation in unnecessary directions or arrival of radio waves from unnecessary directions.

(Means for solving the problem) Sharp directivity is required to efficiently radiate radio waves in the target direction.

Conventionally, when considering the directional characteristics of an antenna, attention has been focused only on the in-plane characteristics including the direction in which radio waves are radiated. Furthermore, the design policy has been to increase the directional characteristics in the target direction.

The present invention focuses on the conventional design principle from the opposite direction.If the combined energy radiated from the antenna is constant, suppressing radiation in unnecessary directions will increase radiation in the target direction. This is based on the principle, and the goal is to realize an array antenna that can effectively direct radiated energy toward the sky or the ground in a three-dimensional space, in the desired direction (horizontal direction).

Conventional broadside arrays and end-fire arrays are arranged in a plane that includes the target direction. That is, in a terrestrial television antenna, antenna elements are arranged horizontally. Although antenna elements have radio wave radiation characteristics in the vertical direction as well, no consideration has been given to radiation or reception energy in this direction.

FIG. 4 shows the figure-8 directivity characteristic of a well-known dipole antenna.

It is expressed as a directional characteristic 2 in a plane including the antenna element 1.

FIG. 2 is a diagram showing the directivity characteristic from the dipole antenna of FIG. 1 in a plane orthogonal to the antenna element, and the directivity in this plane is omnidirectional. This means that an array antenna such as a Yagi antenna that combines two dipole elements will radiate wasteful energy in the vertical direction if the intended direction of radiation is the horizontal direction.

Focusing on the principle that if this useless directional characteristic is suppressed three-dimensionally, the gain in the target direction will be improved accordingly, the present invention has constructed a resonant array antenna using a three-dimensional element arrangement.

FIG. 3 shows the basic element arrangement and directivity characteristics according to the present invention. Excitation elements 3 and 4 are placed above and below the single Goupole shown in Figure 2.
, and adjust the distance from 1 and the dimensions of 3 and 4 so that both 3 and 4 act as radiators for 1, a resonator effect occurs between 3 and 4, suppressing the radiation in the vertical direction. Stronger radiation occurs in the horizontal direction
It was confirmed through experiments that this resulted in an increase in db. When calculating using the method of moments, if we use a half-wavelength dipole for the radiating element l and the same half-wavelength elements for the excitation radiating elements 3 and 4, there will be an increase of about 7 dB, and if we use elements with a wavelength of 0.55 for 3 and 4. It is shown that the gain in the X direction for the half-wavelength Gypole increases by about 5.7 dB.

The feed point impedance is approximately 33+j25 ohms compared to 76+142 ohms of the standard half-wavelength Guypole, so impedance matching is required.

(Function) According to the configuration of the array antenna according to the present invention, wasteful radiation energy in directions other than the target direction can be effectively utilized. If applied to terrestrial communications or television, it will effectively add energy directed toward the sky or the ground in the horizontal direction; if applied to antennas that emit or receive radio waves upwards, such as in satellite communications, the horizontal direction will be unnecessary. Energy can be directed upwards. This results in an increase in gain.

Suppressing radiation in unnecessary directions improves directivity,
Unidirectional antennas can also improve the effect of suppressing unnecessary waves.

(Example) FIG. 4 shows a configuration diagram of a well-known three-element Yagi antenna. Element 1 is a radiator, 2 is a waveguide, and 3 is a reflector. This Yagi antenna is used to transmit and receive radio waves in the X direction including the entire array of elements, but it emits unnecessary radio waves similar to non-directional radio waves in the upper and lower directions.

FIG. 5 shows a configuration in which excitation elements 4 and 5 according to the present invention are added above and below. - Figure 6 shows the horizontal plane directivity of the array antenna with the configuration of Figure 5. In the figure, the dotted line 1 indicates the optimum directivity of the conventional three-element Yagi antenna, and the solid line 2 indicates the directivity of the present invention. It can be seen that although a gain increase of 1 dB was obtained in the target X direction, the rearward characteristic increased by 3 dB.

This is because backward radiation from the excitation element increases.

FIG. 7 shows an arrangement in which the arrangement of FIG. 5 is modified and the excitation elements are tilted backward by 25 degrees.

FIG. 8 is a diagram of the configuration of FIG. 7 viewed from the Y-axis direction. Figure 8
According to the configuration shown in FIG. 9, the front-to-back ratio of directivity is significantly improved.

FIG. 9 shows the directivity in the horizontal plane XY and in the vertical plane xz. The dotted line shows the directivity of the conventional five-element Yagi antenna, and the solid line shows the directivity of the total five-element array antenna, which is the three-element Yagi plus two excitation elements according to the present invention. The gain is increased by 1 dB compared to the 5-element Yagi antenna, and the rear characteristics are further improved by about 18 dB. In this way, for the same five-element Yagi antenna, the antenna of the present invention can increase the forward gain by +1 dB and the rear suppression by 18 dB.

(Modified Embodiment) The present invention is based on the principle of effectively utilizing unnecessary radiant energy in the target direction, and is based on the principle of arranging reflectors on both sides of the radiator in a plane that does not include the target direction. . Since the radio waves radiated by the radiator return to the radiator and make use of the effect of reinforcing each other's radiation, the same effect can be obtained even if a feed type element is used as the excitation element.

The effect of the principle of the present invention can be seen depending on the shape of the excitation element, not only the linear shape but also the planar or three-dimensional shape.

The configuration according to the principles of the present invention can also be applied to the feed section for a general open single-sided antenna. Further, the number of excitation elements may be increased to two or more.

(Effects of the Invention) When the array antenna having the configuration of the present invention is used, radio wave radiation in unnecessary directions is directed toward the target direction, so that gain can be improved.

Since the excitation element configured according to the present invention acts as a reflector, the unnecessary direction suppression effect is improved by arranging the excitation element in the unnecessary direction.

Like the Yagi antenna (a configuration that combines a radiator, a waveguide, and a reflector increases the number of elements and performs an optimal design, which makes it difficult to design each element length and element spacing, etc.), but the configuration of the present invention Since a simple combination of radiators is sufficient, the design conditions are easy.

[Brief explanation of the drawing]

ml indicates the eight-figure directivity on a plane including the half-wavelength dipole antenna and the antenna element. FIG. 2 shows that the directivity of the half-wavelength Goupole, which is the same as in FIG. 1, is omnidirectional in a plane orthogonal to the antenna element. FIG. 3 shows that the directivity changes as shown in 5 by adding excitation elements 3 and 4 of the present invention in the same plane as FIG. Figure 4 shows a three-element Yagi antenna commonly used. Figure 5 shows the excitation element 4 of the present invention in the three-element Yagi antenna of Figure 4.
A configuration diagram with 5 and 5 added is shown. FIG. 6 shows the directional characteristics of the configuration shown in FIG. The dotted line shows the Yagi antenna, and the solid line shows the directivity of the antenna according to the present invention. m) shows an arrangement in which the excitation elements are tilted 25 degrees from the vertical line with respect to the configuration of FIG. FIG. 8 is a diagram showing the arrangement of FIG. 7 on the xz plane. FIG. 9 shows the directivity of the same five-element array according to the invention (FIG. 7) compared to the directivity of a five-element Yagi antenna. (Symbols/Symbols) Figure 3 shows an element arrangement according to the basic principle of the present invention, - In the figure, 1 is a radiation element, 2 is a directivity in the vertical plane, 3 and 4 are excitation elements according to the present invention, and 5 is a radiation element according to the present invention. The directivity due to the antenna and X indicate the radiation target direction. FIG. 7 shows one embodiment in which the present invention is combined with a Yagi antenna. Element l is a radiator, 2 is a waveguide, 3 is a reflector, and 4 and 5 are excitation elements according to the invention.

Claims (1)

[Claims] An array antenna in which a radiating element for radiating radio waves in a target direction, a plurality of reflective excitation elements arranged in a plane that does not include the target direction of radiation, and the radiating elements are arranged to form a resonator.