JP4528155B2 - Antenna device - Google Patents

Description

  The present invention relates to a small antenna for receiving television broadcasts and the like, and more particularly to a shared receiving antenna for terrestrial digital television broadcasts and conventional terrestrial analog television broadcasts.

  Terrestrial digital TV broadcasting will start in December 2003 in the three major metropolitan areas of Tokyo, Osaka, and Nagoya, and is scheduled to start in other regions by 2006. One of the features of terrestrial digital is that it is possible to prevent data reception leakage with the bit error correction function etc. until the radio field intensity drops below a predetermined value compared to conventional analog broadcasting. Therefore, there is an advantage that there is little disturbance of the image due to a decrease in radio field intensity or ghost.

  As for television receivers, thin televisions using thin displays such as liquid crystal displays or plasma displays are becoming mainstream from conventional cathode ray tubes. A flat-screen TV can be installed on a wall because it does not take depth, and it can be moved freely to the room you want to see because it is small and lightweight. Furthermore, it can be sufficiently received by an indoor antenna by terrestrial digital television broadcasting.

  This type of indoor antenna needs to have wideband voltage standing wave characteristics and directivity characteristics in order to cover the VHF band (90 to 108 MHz, 170 to 222 MHz) and UHF band (470 to 770 MHz) with one antenna. Therefore, it has a VHF receiving rod antenna and a UHF receiving antenna element as shown in Patent Document 1 and Patent Document 2.

  Such an indoor antenna can be folded and retracted when the antenna is transported or stored, but when used, the rod antenna is extended to receive the lower limit frequency of 90 MHz in the VHF band. There is a need to. As for downsizing, a technique called “alternative self-complementary antenna” in a broadband planar antenna as shown in Non-Patent Document 1 has been disclosed.

Japanese Utility Model Publication No. 60-25134 JP 2001-274609 A Furuya Tsuneo, Ishisone Takayuki, Makiaki Yasuto “A Mutual Self-Complementary Antenna and Its Application to High-Gain Broadband Antenna”, IEICE Technical Report, AP77-43, July 1997, P35-40

  FIG. 7 is a configuration diagram showing a configuration of a conventional indoor antenna. The indoor antenna 100 includes two rod antennas 102 and 103, a lid body 104 having a UHF receiving element 105, a storage portion 106 for storing them, and a case main body 101 that can store or deploy a fall prevention plate 107. is doing.

  When the indoor antenna 100 as shown in FIG. 7 is used, the rod antennas 102 and 103 are extended and the antenna length is set to about 80 cm so as to be equal to the quarter wavelength of the lower limit frequency of the VHF frequency band. When the antenna is extended, the position of the center of gravity changes, and there is a risk of falling, so the tipping prevention plate 107 stored in the case body is extended and used, requiring a space of about 100 cm in width and about 20 cm in depth. There was a problem that conversion was difficult.

  Furthermore, since there are movable parts such as rod antennas, there are problems that it is difficult to improve strength against wind and rain, and to prevent rust and dust when used as an outdoor antenna installed on a veranda.

  As for downsizing, it is possible to make a planar antenna using the mutual self-complementary antenna shown in Non-Patent Document 1, but it is necessary to make it equal to a quarter wavelength of the lower limit frequency in the VHF band. There is a problem that it becomes a planar antenna having a side length of about 80 cm and cannot be miniaturized.

  In order to solve the above problems, an antenna device according to the present invention includes a dielectric substrate, an antenna pattern formed on a surface of the dielectric substrate, and a dielectric A power supply section that feeds power to the antenna pattern, and the antenna pattern is arranged on the lower half of the dielectric substrate and is arranged on a central axis extending in the vertical direction. Disposed in the upper half of the dielectric substrate and supplemented to the lower sub-pattern, including a lower sub-pattern including a linear conductive wire and branch-shaped linear conductive wires branched alternately from the linear conductive wire in the left-right direction at equal intervals. A pair of upper sub-patterns, and the lower sub-pattern and the upper sub-pattern have a saw-tooth pattern in a part of the branch-like linear conductors.

  Further, in the antenna device according to the present invention, the front antenna pattern includes a VHF antenna part located on the outside and a UHF antenna part located on the inside, and the VHF antenna part and the UHF antenna part are connected by a choke coil. It is characterized by.

  Further, in the antenna device according to the present invention, the sawtooth pattern includes a rectangular or triangular tooth portion, and the tooth includes at least two kinds of widths.

  Furthermore, in the antenna device according to the present invention, when the lower sub-pattern is folded upward on the horizontal axis, the tooth tip of the sawtooth pattern faces the tooth tip of the upper sub-pattern.

  When the present invention is used, the antenna outer shape of the VHF band can be reduced in size, and further, the antenna device can be simplified by sharing with the UHF band shared antenna. In addition, by using a planar antenna such as a rod antenna with no moving parts, there is an effect that it can be easily combined with a thin television.

  In addition, according to the present invention, the dimensional accuracy at the time of mass production can be stabilized and the weight can be reduced and the price can be reduced by adopting a configuration in which a pattern is printed by etching a copper-clad printed circuit board.

  One of the practically used wideband antennas is a log periodic antenna. The input impedance repeats a constant change logarithmically with respect to frequency, and is approximately constant impedance. In general, it is considered that an antenna having a logarithmic periodic structure can have a constant impedance, but in practice, a constant impedance is guaranteed when the antenna has a self-complementary structure. Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  FIG. 1 is an external view showing an external appearance of an antenna device using a self-complementary antenna in the first embodiment. The antenna device includes an antenna body 41, a cable (not shown) that transmits a television broadcast received by the antenna, and a support portion 42 that supports the antenna body 41.

  The antenna body 41 has an antenna structure called a self-complementary antenna. The principle of the self-complementary antenna is 60π (about 188Ω: 1/2 of the characteristic impedance of free space) regardless of the frequency when it is composed of an infinitely large planar conductor. The antenna body 41 has a constant directivity, is as small and efficient as possible with respect to frequency, has few orthogonal braided wave components, and can be directly connected by a coaxial cable even with a balanced self-complementary antenna (balun The antenna itself has a balancing action even if it is not used).

  FIG. 2 is a configuration diagram showing configurations of the antenna substrate 32, the coaxial cable 27, and the support portion 42 that are made of conductors by removing the antenna cover of the antenna device using the self-complementary antenna in the first embodiment. is there. The conductor pattern of the antenna substrate 32 has a structure in which the conductor pattern is overlapped with a portion without the conductor pattern by rotating the conductor 90 degrees around the feeding point F or turning it back with the CD axis which is a horizontal axis.

  The conductor pattern of the antenna substrate 32 in FIG. 2 has the same width of the AF-FB serving as a trunk functioning as a transmission line, and each corner of the quadrilateral ABCD is 90 degrees. In addition, the branches of the conductor from the trunk are alternately branched at equal intervals, and the lengths of the outer circumference and the inner circumference of the branches are the same as the sides constituting the adjacent quadrangle. With this configuration, a suitable VSWR can be obtained.

The width of the trunk that functions as the transmission path of the antenna substrate 32 in FIG. 2 is connected to the FB using a Semi-rigid coaxial cable (for example, a diameter of 3.6 mm). The same width (eg 6
mm). The CD gap (the gap between the ACD triangle and the BDC triangle) is preferably concentrated to 188Ω when the value is equal to the width of the trunk.

  Further, in the first embodiment, the shape of the outer peripheral portion of the conductor pattern is a rectangular saw-tooth shape, and the length of the end portion constituted by four sides is one wavelength of the lower limit frequency.

  When the coaxial cable 27 is directly fed as shown in FIG. 2, the generation of an unbalanced current is generally a problem. However, in the antenna body 41 of the present embodiment, the antenna itself has an effect as a wideband balun. The balanced current is not a problem in practical use, and the number of parts can be reduced.

  FIG. 3 is a configuration diagram showing a configuration of the antenna substrate 32 etched on the glass epoxy substrate having the conductive thin film of the dielectric substrate in the second embodiment, and a fine antenna pattern is formed by the etching processing. is there.

  First, the feeding point F will be described. Power is supplied to the antenna body 41 by the coaxial cable 27. Specifically, the ground 28 of the coaxial cable 27 is connected to the pattern 21 via the feeder line 25, and similarly, the core wire 29 of the coaxial cable 27 is connected to the pattern 23 via the feeder line 26. In these loops, from the feeding point, the first to seventh laps function in turn as the UHF band, and the eighth to ninth laps function as the VHF band.

  The trunk-like FB patterns 21 and 22 and the FA patterns 23 and 24 are fed by the coaxial cable 27, and each trunk-like pattern is connected to the outer trunk-like pattern by the choke coil 31 as shown in the G section. ing. With this configuration, the inside of the antenna main body 41 functions as a UHF band antenna and also functions as a VHF band antenna as a whole via the choke coil 31.

  Next, the inner antenna pattern will be described. The high frequency fed from the feeding point F includes the outer periphery of the pattern 2 having the same side length, the inner periphery of the pattern 3 via the gap, the outer periphery of the pattern 1, and the pattern 4 via the gap. It is radiated as an electromagnetic wave from the pattern connecting the inner circumference of the. Similarly, electromagnetic waves are also radiated from the inner periphery of the pattern 6, the outer periphery of the pattern 3, the inner periphery of the pattern 5, the pattern connecting the outer periphery of the pattern 4 (first periphery) and the outer periphery (second to ninth periphery). .

  The first to seventh laps of the outer circumference of the inner pattern 14 constituting the seventh circumference, the inner circumference of the pattern 15, the outer circumference of the pattern 13, and the rectangular sawtooth shape provided on the inner circumference of the pattern 16 It acts as an antenna. Furthermore, the antenna pattern of the antenna substrate 32 has a structure in which the portion with the antenna pattern overlaps the portion without the antenna pattern by rotating the conductor 90 degrees around the feeding point F or turning it back with the CD axis which is the horizontal axis. The directions of the serrated teeth are opposite. At this time, the teeth facing each other may be in positions where the tip portions face each other, or in positions where the tip portions mesh with each other, and are not limited to providing a saw-tooth shape on the seventh and ninth circumferences.

  The pattern of connecting the outer periphery of the outer pattern 18, the inner periphery of the pattern 19, the outer periphery of the pattern 17, the inner periphery of the pattern 20, and the inner UHF band antenna function as a VHF band antenna, thereby reducing the size of the antenna. Has been realized.

  In addition, the interval between the sawtooth teeth is determined by the frequency and outer dimensions of the UHF band and the VHF band, and is arranged at different intervals, and the length of each side of each circumference is equal to the length of the other side. .

  One of the important antenna devices described above is constant directivity. There is a demand for an antenna in which the radiation pattern does not change at least with no change in the maximum radiation direction over a wide frequency range. The antenna device according to the present embodiment is an antenna device that has a substantially constant directivity over a frequency range of 1:10.

  FIG. 4 is a schematic diagram showing a symbol and a coordinate system of the antenna device using the self-complementary antenna in the present embodiment. Here, each symbol and coordinate system are defined as shown in FIG.

  The plane of polarization of the electric field has a plane of polarization in the Y-axis direction, and has substantially the same orthogonal polarization component as the linearly polarized antenna. The results of measuring the E-plane pattern D (θ) on the YZ plane and the E-plane pattern D (φ) on the XZ plane from the VHF band to the UHF band are shown below.

  FIG. 5 is a D (θ) directivity pattern in the YZ plane of the antenna device using the self-complementary antenna according to this embodiment. The pattern of D (θ) does not change so much with the change of frequency, and shows the same value as the half-value angle of the half-wave dipole antenna (for example, 78 degrees to 84 degrees). Similarly, the maximum radiation direction does not change from the Z-axis direction due to the change in frequency, and there is almost no radiation in the Y-axis direction.

  FIG. 6 is a D (φ) directivity pattern in the XZ plane of the antenna device using the self-complementary antenna in this embodiment. D (φ) has a maximum value in the Z-axis direction, and radiation in the X-axis direction is lower than that. From the above, the directivity pattern and polarization plane of the antenna device in this embodiment are similar to those of the single-wavelength loop antenna, and even if the antenna is miniaturized using the self-complementary antenna pattern, the antenna performance is affected. I understand that I don't.

  As described above, when the present invention is used, it is possible to reduce the size of the VHF band antenna, and to simplify the antenna device by using the VHF band antenna and the UHF band antenna in common. Due to the directivity, it can be easily installed in the optimum direction.

  In addition, by using a planar antenna such as a rod antenna with no moving parts, there is an effect that it can be easily combined with a thin television.

  Furthermore, the antenna body 41 has constant directivity, is as small and efficient as possible with respect to frequency, has few orthogonal polarization components, and can be directly connected by the coaxial cable 27 even if it is a balanced self-complementary antenna. It contributes to the reduction of the number of parts.

  Furthermore, according to the present invention, the dimensional accuracy at the time of mass production can be stabilized, and the weight can be reduced and the price can be reduced by adopting a configuration in which a pattern is printed by etching a copper-clad printed circuit board. Note that the substrate is not limited to glass epoxy, and can be suitably implemented even by using cheaper paper epoxy or the like.

It is an external view which shows the external appearance of the antenna apparatus using the self-complementary antenna in this embodiment. It is a block diagram which shows the structure of an antenna board | substrate and other components by removing the antenna cover of the antenna apparatus using the self-complementary antenna in 1st Embodiment. It is a block diagram which shows the structure of the antenna board | substrate in 2nd Embodiment. It is a schematic diagram which shows the symbol and coordinate system of an antenna apparatus using the self-complementary antenna in this embodiment. It is a directivity characteristic figure which shows the D ((theta)) directivity pattern in the YZ plane of the antenna apparatus using the self-complementary antenna in this embodiment. It is a directivity characteristic figure which shows the D ((phi)) directivity pattern in the XZ plane of the antenna apparatus using the self-complementary antenna in this embodiment. It is a block diagram which shows the structure of the conventional indoor antenna.

Explanation of symbols

  1-24 patterns, 25, 26 feeder, 27 coaxial cable, 28 ground, 29 core wire, 31 choke coil, 32 antenna board, 41 antenna body, 42 support section, 100 indoor antenna, 101 case body, 102, 103 rod antenna , 104 Lid, 105 receiving element, 106 storage, 107 fall prevention plate.

Claims (4)

In an antenna device that receives radio waves of TV broadcasting,
A dielectric substrate;
An antenna pattern formed on the surface of the dielectric substrate;
A power feeding unit that is disposed at the center of the dielectric substrate and feeds power to the antenna pattern;
Have
The antenna pattern is
A trunk-like linear conductor arranged on the central axis extending in the vertical direction and arranged on the lower half of the dielectric substrate, and branch-like linearly branched from this linear conductor in the left-right direction at equal intervals A lower sub-pattern including a conductor;
An upper sub-pattern disposed in the upper half of the dielectric substrate and complementary to the lower sub-pattern;
Have
The lower sub-pattern and the upper sub-pattern have a sawtooth pattern in a part of the branch-like linear conducting wire. The antenna device according to claim 1,
The front antenna pattern is
It has a VHF antenna part located outside and a UHF antenna part located inside,
An antenna device, wherein the VHF antenna unit and the UHF antenna unit are connected by a choke coil. In the antenna device according to claim 1 or 2,
The sawtooth pattern includes a rectangular or triangular tooth portion, and the tooth includes at least two kinds of widths. In the antenna device according to any one of claims 1 to 3,
An antenna device characterized in that when the lower sub-pattern is folded upward on the horizontal axis, the tooth tip of the sawtooth pattern faces the tooth tip of the upper sub-pattern.

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