JP2001177336A - Planar antenna for receiving broadcast waves - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planar antenna for receiving broadcast waves, that is suitably used for single frequency network SFN relaying for television broadcast waves. SOLUTION: This planar antenna for receiving broadcast wave is an antenna, where a plurality of antenna elements 12 is arranged on an antenna reflecting flat plate 11. An interference-preventing body 13 having a nearly cylindrical conductor face is provided at the end of the antenna reflector in parallel with the end. Then a side lobe level in the 90-degree direction at the side to which the interference preventing body is provided is reduced, and the antenna is made compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plane antenna for receiving broadcast waves, which is suitable for relaying, for example, television broadcast waves.

[0002]

[Related Background Art] An SNF (Single Frequency Network) that provides the same television broadcast wave at the same transmission frequency to an adjacent area from a plurality of broadcast stations and relay stations.
rk) In relaying, for example, as shown in FIG. 5, a broadcast wave transmitted from a transmitting antenna 1 of a broadcasting station is received by a receiving antenna 2 of the relay station, and the received broadcasting wave is transmitted by a transmitting antenna 3 of the relay station. From to the next relay station,
Alternatively, it is performed by broadcasting to the area covered by the relay station. In particular, in terrestrial digital broadcasting, OFDM (Orthogonal Frequency D) which is resistant to interference (ghost)
Since the ivision multiplexing (orthogonal frequency division multiplexing) modulation method is used, the SNF relay can be effectively performed, and the frequency can be effectively used.

The receiving antenna 2 in such a relay station
And the transmitting antenna 3 are provided exclusively near the upper part of the broadcasting tower 4. Therefore, it is important to ensure the effect of the broadcast wave (radio wave) radiated from the transmitting antenna 3 wrapping around to the receiving antenna 2, that is, to ensure the isolation between the antennas 2 and 3.

[0004]

The antenna 2,
In order to ensure the isolation between the antennas 3, a so-called pencil beam antenna such as a parabolic antenna may be used as the receiving antenna 2. However, when a planar array antenna having a structure as shown in FIG. 6 is used as the receiving antenna 2, for example, the power distribution and the phase distribution of the plurality of antenna elements 5 are adjusted so as to have a Chebyshev distribution or the like in the ± 90 ° direction. It is necessary to take measures such as reducing the side lobe level or increasing the antenna reflector 6 as much as possible to eliminate unnecessary radiation in the ± 90 ° direction. Note that this planar array antenna is provided on an antenna reflector 6 serving as a grounded body.
For example, a plurality of antenna elements (radiating elements composed of microstrip antennas) 5 are arranged at predetermined intervals via a dielectric layer 7.

However, it is theoretically (calculated) possible to adjust the power distribution and the phase distribution in order to reduce the side lobe level in the ± 90 ° direction. The tolerance for dimensional errors is narrow,
Since the power distribution and the phase distribution are disturbed by the isolation between the antenna elements 5, it is difficult to obtain desired antenna characteristics.

Further, the antenna radiation plate 6 is enlarged to 90 °
In order to eliminate unnecessary radiation in the direction, a reflector at infinity is theoretically necessary. Even if a sufficiently large antenna reflector 6 is used, it is difficult to obtain a sufficient gain for the size (opening surface of the reflector 6). Further, there is a problem that the antenna shape becomes considerably large. It is also considered that an auxiliary reflector 8 is provided at the end of the antenna radiation plate 6 at right angles to the main surface of the antenna reflector 6,
A considerably large auxiliary reflector 8 is required.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object to reduce the side lobe level in the 90 ° direction while having a compact shape, and to be provided in close proximity to a transmitting antenna. However, it is an object of the present invention to provide a broadcast wave receiving planar antenna that can significantly reduce the influence of the radio wave wraparound.

[0008]

In order to achieve the above object, a broadcast wave receiving planar antenna according to the present invention comprises a plurality of antenna elements arranged on a flat antenna reflector having a predetermined size. For example, it is suitable for use in relaying television broadcast waves, and particularly, at the end of the antenna reflector, an interference preventing body having a substantially cylindrical conductor surface is provided in parallel with the end. Features.

Preferably, the interference preventing member has a length substantially equal to the width of the end of the antenna reflector, and its longitudinal direction is set to the end of the antenna reflector. The antenna reflector is provided so as to be electrically connected to the antenna reflector. Incidentally, the anti-interference body having a substantially cylindrical conductor surface may be a metal cylinder or a cylindrical tube, or a metal film may be formed on the surface of the cylindrical or cylindrical tube of a material as appropriate, or may be formed by plating. It may be something. Further, it may be a polygonal column whose cross-sectional shape is octagonal or decagonal and can be regarded as forming a substantially columnar surface.

It is also possible to provide an interference preventing member at the end of the antenna reflector without separating it, but it is also possible to provide it at a slight distance L.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flat antenna for receiving broadcast waves according to an embodiment of the present invention will be described below with reference to the drawings. This broadcast wave receiving planar antenna is suitable for use in, for example, the relay of television broadcast waves, and is generally rectangular as shown in FIGS. 1 (a) and 1 (b). A plurality of antenna elements (radiating elements) 12 composed of, for example, microstrip antennas are arranged on a flat antenna reflector 11 of a predetermined size having a shape. In particular, at an end of the antenna reflector 11, It has a structure in which an interference preventing body 13 having a substantially cylindrical conductor surface is provided in parallel with the end. In the figure, reference numeral 14 denotes a radome made of, for example, FRP resin provided on the upper surface of the antenna reflector 11 so as to cover the antenna element (radiating element) 12. 1 in the figure
Reference numeral 5 denotes a stay for attaching the interference preventing body 13 to the end of the antenna reflector 11.

Specifically, this broadcast wave receiving flat antenna is for receiving digital terrestrial broadcast waves in the 470-770 MHz band, for example, the UHF band, and the antenna reflector 11 has a vertical dimension (vertical direction) H. Is made of a rectangular conductor (metal plate) having a size of 1200 mm and a horizontal dimension (horizontal direction) W of 1200 mm. Further, a plurality of, for example, four antenna elements (microstrip antennas) 12 provided on the antenna reflector 11 are arranged in a vertical direction of 0.5.
are arranged in a square at an installation interval of 0.8λ in the horizontal direction.

In practice, these antenna elements (microstrip antennas) 12 have a thickness of, for example, one.
The antenna reflector 11 is formed on a dielectric substrate (not shown) having a thickness of about 0 to 25 mm.
Is formed. However, it is not necessary to use a dielectric substrate. Specifically, it is also possible to form the antenna element 12 by a metal plate and arrange the antenna element 12 on the antenna reflector 11 with a predetermined height. In this case, an air layer having a predetermined thickness is provided between the antenna reflector 11 and the antenna element 12.

Thus, an end of the antenna reflector 11;
For example, the anti-interference bodies 13 provided at both ends in the vertical direction have a length substantially equal to the width of the end of the antenna reflector 11, and are formed from a rod-shaped body having a substantially cylindrical conductor surface with an outer diameter of 80 mmφ. Become. The anti-interference body 13 may be made of a material having conductivity such as metal, but may be formed by forming a conductive metal film on the surface of an insulating material or by plating. Is also good. In addition, the interference prevention body 13
As shown in FIGS. 2 (a) to 2 (c), the cross-sectional structure of FIG. 2 (a) to (c) shows that a columnar body or a cylindrical body (pipe), and further, a substantially substantially cylindrical surface is formed. It may be an octagon that can be considered or a polygonal prism having a larger number of faces. Further, as shown in FIG. 2D, a semi-circular arc (semi-cylindrical column) having a substantially cylindrical surface only on the antenna reflector 11 side may be used.

The anti-interference body 13 has its longitudinal direction parallel to the end of the antenna reflector 11 and is separated from the end of the antenna reflector 11 directly or via a stay 15 by a predetermined distance L. And is electrically coupled to the antenna reflector 11. The mounting height position of the interference preventing member 13 is determined by the surface formed by the antenna reflector 11 and the antenna surface formed by the antenna element 12.
3 is set so as to be included in the range of the height of the interference prevention body 13 specified by the diameter D.

FIG. 3 shows a plane antenna (40 mmφ, 8 mm) for receiving broadcast waves provided with interference preventing members 13 having different diameters D.
2 shows simulation results of antenna characteristics in the vertical direction between a 0 mmφ, 120 mmφ) and a broadcast wave receiving planar antenna without the interference preventive body 13 (without the interference preventive body 13). However, in this simulation, an anti-interference body 13 was directly attached to the end of the antenna reflector 11, and an antenna provided with four antenna elements 12 was prepared as described above. The diameter D of the interference preventing body 13 is actually 20 mmφ, 80 mm.
mmφ, 40mmφ, 60mmφ, 80mmφ, 100mm
φ, 120 mmφ, 140 mmφ, 0 (without interference preventing body 13) were prepared, and their antenna characteristics were verified.

As shown in the simulation results, the provision of the interference preventing member 13 at the end of the antenna reflecting plate 11 allows the antenna characteristic in the vertical direction (direction in which the interference preventing member 13 is provided) to be particularly ± 90. It was found that the side lobe level in the ° direction was improved by about 10 dB. Moreover, it has been confirmed that when the diameter D of the interference preventing body 13 is a certain size, and in this example, when the diameter D is 80 mmφ, the best effect of improving the antenna characteristics can be expected.

FIG. 4 shows a plane antenna for receiving a broadcast wave provided with the above-mentioned interference preventing body 13 of 80 mmφ, wherein the mounting distance (separation distance) L of the interference preventing body 13 to the antenna reflector 11 is 0 mm, 40 mm, 80mm, 2
The simulation results of the antenna characteristics in the vertical direction when the distance is changed to 00 mm are shown in comparison. However, in this simulation, the interference preventing body 13 is actually used.
The antenna characteristics were verified by changing the mounting interval L of each in 20 mm steps.

From this simulation result, when the mounting interval L of the interference preventing body 13 is set to 0 mm, it is approximately 90 °.
The side lobe level in the direction can be reduced as a whole.
It was confirmed that the side lobe level in the ° direction could be significantly reduced locally.

By providing the anti-interference body 13 at the end of the antenna reflector 11, the side lobe in the 90 ° direction can be reduced because the diffraction of the radio wave generated at the end of the antenna reflector 11 is substantially cylindrical. It is considered that the interference is prevented by the anti-interference body 13 having the conductor surface of FIG. This is because even if a quadrangular pole-shaped rod-shaped conductor is provided at the end of the antenna reflector 11 in the same manner as the interference preventing body 13, the effect of reducing the side lobe level in the 90 ° direction cannot be expected so much. In view of this, when this quadrangular prism-shaped conductor is used, it is considered that the reflection components of the radio waves generated at the end of the antenna reflector 11 are aligned in a certain direction, and as a result, the diffraction is hardly disturbed. Because.

Therefore, in order for the rod-shaped conductor provided at the end of the antenna reflector 11 to function as the interference preventing body 13, the rod-shaped conductor has a substantially columnar conductor surface and reflects the radio wave reflection component in various directions. It is considered that it is necessary to play a role of disturbing the diffraction of radio waves generated at the end of the antenna reflector 11. Therefore, as described above, even if the cross-sectional shape is a polyhedron and can be regarded as forming a substantially cylindrical conductor surface, it can function as the interference preventing body 13.

Thus, according to the broadcast wave receiving planar antenna having the above-described configuration, only the interference preventing member 13 is provided at the end of the antenna reflector 11, and the 90 ° direction on the side where the interference preventing member 13 is attached is provided. 10 dB side lobe
To some extent. Moreover, the antenna reflector 11
, In other words, the antenna reflector 11
Even when the shape is small, the side lobe in the 90 ° direction can be reduced by the interference prevention body 13 attached to the end, and unnecessary reflection components can be suppressed. As a result,
Even when the broadcast wave receiving planar antenna is provided side by side with the transmitting antenna, sufficient isolation from the transmitting antenna can be ensured, and the size of the antenna can be reduced. Therefore, it is easy to suppress interference with an antenna of the same frequency band installed adjacently, and it is extremely useful, for example, to use the antenna as an SFN relay antenna described above.

The present invention is not limited to the above embodiment. For example, regarding the number of antenna elements 12 provided on the antenna reflector 11 and the arrangement pattern thereof,
What is necessary is just to determine according to the specification of the frequency of a broadcast wave, required antenna gain, etc. Also, the antenna element 12
Also, it is possible to use a device other than the microstrip antenna. Further, the anti-interference body 13 may be longer than the width of the end portion of the antenna reflector 11, but this is slightly disadvantageous from the viewpoint of reducing the size of the antenna. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0024]

As described above, according to the present invention, an interference preventing member having a substantially cylindrical conductor surface is provided at the end of the antenna reflector in parallel with the end, so that this interference can be prevented. The side lobe level in the 90 ° direction on the side where the body is provided can be effectively reduced, and the shape can be made compact. Therefore, even when the broadcast wave receiving planar antenna is provided side by side with the transmitting antenna, the interference between these antennas can be effectively suppressed, so that the antenna is extremely useful for use as, for example, an SFN relay antenna. Some effects are obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a broadcast wave receiving planar antenna according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of the structure of an interference preventing body used in the broadcast wave receiving planar antenna shown in FIG. 1;

FIG. 3 is a diagram illustrating a change in antenna characteristics when the size (diameter D) of the interference preventing body is changed in the broadcast wave receiving flat antenna illustrated in FIG. 1;

4 is a distance L between an end of an antenna reflector and an interference preventing member in the broadcast wave receiving flat antenna shown in FIG. 1;
The figure which shows the change of the antenna characteristic when changing.

FIG. 5 is a schematic configuration diagram of an antenna system for relaying television broadcast waves.

FIG. 6 is a diagram showing a general configuration example of a planar array antenna.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Antenna reflector 12 Antenna element (microstrip antenna) 13 Interference prevention body 14 Radome 15 Stay

Claims (2)

[Claims] 1. A broadcast wave receiving flat antenna in which a plurality of antenna elements are arranged on a flat antenna reflector having a predetermined size, wherein a substantially cylindrical conductor surface is provided at an end of the antenna reflector. A broadcast wave receiving flat antenna, wherein an interference preventing body having the following is provided in parallel with the end. 2. The antenna reflection body has a length substantially equal to a width of an end of the antenna reflector, and a longitudinal direction thereof is provided so as to match an end of the antenna reflector. 2. The broadcast wave receiving planar antenna according to claim 1, wherein the planar antenna is electrically connected to a plate.