JPH073928B2 - Antenna device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an antenna device which enables directivity control when the beam width of the directivity in the horizontal plane of a dual-frequency resonant base station antenna in land mobile communication is variable. is there.

"Prior Art" Conventionally, a base station antenna for land mobile communication is sometimes configured to control the beam width from 60 ° to 180 ° in the horizontal plane directivity so as to cope with an increase in subscriber capacity. If the radio zone shape can be set relatively arbitrarily with one antenna, there is an advantage that the service area configuration becomes easy.

FIG. 3 shows a configuration example of a conventional variable beam width antenna when a single frequency resonates. 1 is a dielectric substrate of a printed dipole antenna, 2 is a printed dipole antenna, and 4 is a reflector. The angle of this reflector can be changed mechanically arbitrarily. Further, 5 is a feeding terminal, and 7 is a ground surface of the printed dipole antenna. Here, the distance between the reflector and the center of the printed dipole antenna is d, and the width of the reflector in the variable portion is W.

The control of the beam width in the horizontal plane is performed mechanically by the opening angle α of the reflector.
It can be relatively easily realized by changing the value of, but the distance d between the reflector and the center of the printed dipole antenna and the width W of the reflector in the variable portion influence. As is well known, this antenna is called a corner reflector antenna.

FIG. 4 shows a measurement example and a theoretical value of the beam width with respect to the divergence angle of a conventional variable beam width antenna when a single frequency resonates, and the beam width in the horizontal plane increases as the divergence angle increases. There is a tendency. At this time, the width W of the reflector is 0.56 wavelength, the distance d between the reflector and the center of the printed dipole antenna is 0.28 wavelength, and the solid line is the theoretical value. Thus, in the case of a single frequency, a variable beam width antenna can be easily realized. However, in an antenna in which two frequencies resonate with one antenna, it is not easy to match the directivities of the two when the beam width is changed.

FIG. 5 shows a conventional example in which a reflector is arranged on a two-frequency resonant printed dipole antenna. 1 is a dielectric substrate of the printed dipole antenna, 2 is a printed dipole antenna, and 3 is a parasitic element made of a metal conductor. Reference numeral 5 is a power feeding element, and 4 is a reflector, and the angle of the reflector can be changed. When the beam width of the directivity in the horizontal plane is changed at the time of two-frequency resonance, the frequency at which the printed dipole antenna at 2 resonates and the frequency at which the parasitic element made of the metal conductor at 3 resonates are different from each other. Since the distance d between the reflector and the parasitic element made of the printed dipole antenna 2 or the metal conductor 3 is different depending on the wavelength ratio, the directivity in the horizontal plane is different. Here, the directivity of the printed dipole antenna is theoretically easily obtained because it is the same as the conventional one.
When there are two parasitic elements sandwiching the print dipole antenna, it is complicated to theoretically determine the directivity, and thus the characteristics are experimentally determined.

FIG. 6 shows an example of measurement of the beam width of the directivity in the horizontal plane with respect to the opening angle of the antenna. (A) is a measurement example at a second high frequency, and (b) is a measurement at a first low frequency. Here is an example. The resonance frequency of the parasitic element is higher than the resonance frequency of the printed dipole antenna and is about 1.7 times, the width W of the reflector is 0.5 wavelength, the distance d between the reflector and the center of the printed dipole antenna is 0.2 wavelength, and the parasitic power is not fed. The width of the device is 0.06 wavelength. The wavelength at this time indicates the wavelength at the first low frequency. From this result, the beam width tends to increase as the antenna divergence angle increases for both frequencies. Between the two frequencies, as the antenna opening angle increases, the beam width tends to increase at the higher frequencies. For example, when a 180 ° beam is obtained at a low frequency, a beam width of 220 ° is obtained at a high frequency, and a beam width difference of 40 ° or more occurs. Further, when the antenna opening angle is small, the beam width tends to become narrower as the frequency becomes lower, resulting in an error of 15 ° to 20 °. Each set value shown in FIG. 6 is the best value in the measurement example of the divergence angle with respect to the beam width.

"Problems to be solved by the invention" When a system that uses two different frequencies in land mobile communication is shared by one antenna, the service area differs if the directivity in the horizontal plane when the beam width is changed is different, and the system design is different. There was a problem that became complicated.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a two-frequency resonant land mobile communication base station antenna device that has the same directivity in the horizontal plane when the beam width is changed at two frequencies.

"Means for Solving the Problems" According to the present invention, the above-mentioned objects are achieved by the means described in the claims. That is, the present invention provides a printed dipole antenna that resonates at a first frequency formed on a dielectric substrate provided on one surface of a reflector for controlling directivity substantially perpendicular to the reflector. In a two-frequency antenna in which two parasitic elements made of a metal conductor that resonates at the second frequency are arranged to face each other in parallel with the electric field axis, a parasitic element made of a metallic conductor that resonates at the second frequency is received. A waveguide element made of a metal conductor and having a length equal to or less than the length of the parasitic element is arranged at a front side in the direction at intervals of about a quarter wavelength or less. .

[Embodiment] FIG. 1 is a view showing an embodiment of the present invention, in which 1 is a dielectric substrate, 2 is a printed dipole antenna formed on the dielectric substrate 1 at which a first frequency resonates, and 3 is a printed circuit board. The parasitic element 4 made of a metal conductor having a second frequency resonating, which is arranged to face the electric field axis with the printed dipole antenna interposed therebetween, is a reflector, and the angle of the variable portion can be varied. Further, 5 is a feeding terminal, 6 is a second parasitic element (waveguide element) for directivity control made of a metal conductor arranged on the front side of the parasitic element 3, and 7 is a ground plane of the printed dipole antenna. is there.

As can be seen from FIG. 6 which is a conventional measurement result, the beam width at the high frequency is broader than that at the low frequency.

The beam width can be sharpened by applying the operation of the Yagi antenna in which a parasitic element is placed in front of the radiating element. However, it is not clear that a directivity element can be controlled by further installing a waveguide element on the front surface side of the parasitic element without affecting the first low frequency. However, it became clear from the measurement results shown below that the directivity can be controlled.

FIG. 2 is a measurement example of the beam width of the directivity in the horizontal plane with respect to the antenna opening angle when the length of the parasitic element 6 and the distance between the parasitic element 3 and the parasitic element 6 are optimized.
(A) shows the second high frequency, and (b) shows the first low frequency. From this result, there is almost no difference even if the antenna opening angle is increased. Further, even when the antenna opening angle is narrow, there is no phenomenon of beam width reversal at low frequency and high frequency as shown in FIG. 6, and the characteristics are extremely good. Each set value at this time is as shown in the figure.

In the present invention, the antenna structure in which the second frequency resonates is equivalently a three-element Yagi antenna. Therefore,
The directivity changes depending on the distance between the waveguide element 6 and the parasitic element 3 and the length of the waveguide element 6. In order to make the directivity the sharpest, the distance between the waveguide element 6 and the parasitic element 3 is approximately 1/4.
It is necessary to make the length of the waveguiding element of wavelength 6 a little shorter than 1/2 wavelength. In this way, the directivity at the second frequency is controlled by changing the distance between the waveguide element 6 and the parasitic element 3 and the waveguide element length 6 so that the directivities at the two frequencies match. There will be an optimum value.

It is well known that the three parasitic elements and the waveguide elements 6 shown in FIG. 1 can be formed on the same dielectric substrate.

"Effects of the Invention" As is apparent from the above description, according to the present invention, the waveguide element for directivity control is simply installed on the front surface side of the parasitic element where the second frequency resonates. There is an advantage that the beam widths in the horizontal plane directivity at the first frequency and the second frequency can be substantially matched.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a beam width variable antenna with dual frequency resonance according to the present invention, and FIG. 2 is a diagram showing a relationship between an antenna opening angle and a beam width of a beam width variable antenna with dual frequency resonance according to the present invention, FIG. 3 is a diagram showing a configuration example of a conventional single-resonance variable beam width antenna, and FIG. 4 is a diagram showing a relation of an antenna opening angle to a beam width of a conventional single-resonance variable beam width antenna. FIG. 6 is a diagram showing a configuration example of a conventional beam width variable antenna with dual frequency resonance, and FIG.
It is a figure which shows the relationship of the antenna opening angle with respect to the beam width of the beam width variable antenna of a frequency resonance. 1 ... Dielectric substrate, 2 ... Printed dipole antenna, 3 ... Parasitic element where second frequency resonates, 4 ...
Reflector, 5 ... Feed terminal, 6 ... Waveguide element for controlling directivity in horizontal plane at second frequency, 7 ... Ground plane of printed dipole antenna.

Claims (1)

[Claims] 1. A printed dipole antenna having a first frequency resonating, which is formed on a dielectric substrate provided substantially perpendicular to the reflecting plate on one surface of a reflecting plate for controlling directivity. In a two-frequency antenna in which two parasitic elements made of a metal conductor that resonates at a second frequency are arranged opposite to each other in parallel to the electric field axis, the receiving direction of the parasitic element made of a metal conductor that resonates at the second frequency Forward, and 4
An antenna device, wherein waveguide elements made of a metal conductor having a length equal to or less than the length of the parasitic element are arranged at intervals of one-half wavelength or less.