JP2006074192A - Antenna for vhf/uhf band - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plate type dipole antenna capable of being made broad in band, low in cost, small in size and high in performance with a simple configuration. <P>SOLUTION: First and second plate type dipole antennas 11a and 11b are arranged symmetrically one over the other at a designated interval and their center part is held by a holding substrate 12. The plate type dipole antennas 11a and 11b are constituted by arranging dipole antenna elements 13a and 13b made of nearly rectangular metal plates at a specified interval Db. The dipole antenna elements 13a and 13b have overall lengths L set to about 0.35λa, heights H set to about 0.1λa, thicknesses set to about 0.0015λa, and the interval Db set to about 0.008λa. Further, a plate type folding element 15 is provided on the back side of the dipole antenna elements 13a and 13b. Then the dipole antennas 13a and 13b are fed from feed points 14a and 14b provided on the holding substrate 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antenna used for transmitting and receiving terrestrial television broadcast waves and communication radio waves from, for example, a VHF band to a UHF band.

  Terrestrial Integrated Services Digital Broadcasting (ISTB-T) has already started broadcasting in the Kanto, Kinki, and Chukyo regions since 2003, and in other regions by 2006 is planned.

In the terrestrial digital broadcasting, radio waves in the UHF band are used, and the frequency band is scheduled to expand to 470 to 770 MHz (13 to 62 channels).
2. Description of the Related Art Conventionally, a two-wire dipole antenna is known as a wideband antenna that receives UHF band TV broadcast radio waves (see, for example, Patent Document 1).

As shown in FIG. 12, the conventional two-wire dipole antenna has a first dipole antenna element 1a, 1b constituted by an aluminum pipe and a second dipole antenna element 2a, 2b in parallel at a predetermined interval. The central portion is held by a holding substrate 3 made of an insulating material, and the dipole antenna elements 1a and 2a and the dipole antenna elements 1b and 2b are electrically connected by metal plates 4a and 4b, respectively. Then, power is supplied to a feeding point 5 provided on the holding substrate 3 on the first dipole antenna element 1a, 1b side.
JP 2003-273737 A

  The conventional two-wire dipole antenna has a wide band, but has a disadvantage that the number of parts is larger than that of a half-wave dipole antenna or a biconical antenna. Further, the wideband feed point impedance of the two-wire dipole antenna is 200 to 300Ω, and an impedance conversion circuit is required to match the characteristic impedance of a commonly used television broadcast receiving coaxial cable, 75Ω.

  FIG. 13 shows an example of the voltage standing wave ratio of the two-wire dipole antenna. The horizontal axis represents frequency (MHz) and the vertical axis represents voltage standing wave ratio (VSWR). The conventional two-wire dipole antenna has a wide band as shown in FIG. 13, but it is difficult to obtain good characteristics over a wide band, such as a VSWR of 2.0 or more in a specific frequency range. is there.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a broadband, small, and high-performance antenna from the VHF band to the UHF band.

  The antenna according to the present invention includes a first folded dipole antenna formed by loading a folded element on one surface of a plate-shaped dipole antenna element, and a folded element loaded on one surface of the plate-shaped dipole antenna element. A second folded dipole antenna, holding means for holding the first folded dipole antenna and the second folded dipole antenna symmetrically at a predetermined interval, and feeding the first and second folded dipole antennas And a power feeding means.

  According to the present invention, by arranging the plate-like first and second folded dipole antennas vertically (laterally) symmetrically, the directivity of the horizontal polarization vertical plane (vertical polarization horizontal plane) is sharp and high due to the stack effect. Gain. Since the antenna is loaded with a folded element having a size smaller than the height of the plate-shaped dipole antenna element, the impedance step-up effect, which is a feature of the folded dipole antenna of different thickness, and the feeding of the two antennas are provided. By connecting the points in parallel, it is possible to connect a power supply unit and a general coaxial cable with an impedance of 75Ω to a wide band without impedance conversion, thereby realizing a wide band and high gain antenna.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
1A and 1B show a configuration of an antenna 10A according to a first embodiment of the present invention. FIG. 1A is a plan view, FIG. 1B is a front view, and FIG. 1C is a side view. The first embodiment shows a configuration example when implemented in a UHF band receiving broadband antenna.

As shown in FIG. 1, the antenna 10A according to the first embodiment of the present invention includes a first plate-shaped dipole antenna 11a and a second plate-shaped dipole antenna 11b, for example, while maintaining a predetermined distance Da in the vertical direction. It arrange | positions symmetrically and the center part is hold | maintained by the holding substrate 12 which consists of an insulating material. The first and second plate-shaped dipole antennas 11a and 11b are generally formed in the same shape. The distance Da between the plate-shaped dipole antennas 11a and 11b is appropriately set within a range of 0.01λa to 0.25λa, for example. The λa is, for example, the lower frequency in the frequency range 470 to 770 MHz of the TV broadcast radio wave in the UHF band, and the wavelength of 470 MHz.
In the plate-like dipole antennas 11a and 11b, plate-like dipole antenna elements 13a and 13b, 13a 'and 13b' made of, for example, a substantially rectangular metal plate are arranged on the left and right sides with a predetermined distance Db. The first and second plate-shaped dipole antennas 11a and 11b are electrically connected between the plate-shaped dipole antenna elements 13a and 13a ′ and between the plate-shaped dipole antenna elements 13b and 13b ′ at the portion of the holding substrate 12, respectively. Connected to. Further, feeding points 14a and 14b are provided on the holding substrate 12, and the feeding conductors 14a and 14b are provided with, for example, an inner conductor of a coaxial cable (not shown) having a characteristic impedance of 75Ω and an end portion of the outer conductor, respectively. They are connected by electrical connection means such as bolts and nuts. For example, the inner conductor of the coaxial cable is connected to the feeding point 14a, and the outer conductor is connected to the feeding point 14b. The first and second plate-shaped dipole antennas 11a and 11b are not formed by connecting the dipole antenna elements 13a and 13a and the dipole antenna elements 13b and 13b with the holding substrate 12 respectively. Electrical connection may be formed by integrally forming the antenna elements 13a and 13a ′ and the dipole antenna elements 13b and 13b ′.

  The dipole antenna elements 13a, 13b and 13a ′, 13b ′ have, for example, a total length L of about 0.35λa, a height H of about 0.06λa or more, a thickness t of about 0.002λa or less, and a distance Db of 0.006. It is set to ~ 0.025λa. The distance Db between the dipole antenna elements 13a, 13b and 13a ′, 13b ′ need not be set to a constant value. For example, the outer end is 0.006λa, and the holding substrate 12 is 0.025λa. You may set to the inclination space | interval.

  As a preferred example of the above embodiment, the value of each part is set such that the total length L is about 0.35λa, the height H is about 0.1λa, the thickness t is about 0.0015λa, and the interval Db is about 0.008λa. it can.

  Further, folding elements 15 and 15 'formed of a metal plate are provided on the back side of the plate-shaped dipole antennas 11a and 11b. The folding elements 15 and 15 'are provided on the back side of the plate-like dipole antennas 11a and 11b, for example, so as to be positioned along the approximate center. In this case, since the impedances at the feeding points 14a and 14b vary depending on the positions of the folding elements 15 and 15 ', the positions of the folding elements 15 and 15' are set so that the impedance becomes, for example, 75Ω. The folding elements 15 and 15 ′ may be formed integrally with the plate-like dipole antenna elements 13a and 13b and 13a ′ and 13b ′, or may be formed into a plate-like shape by using any connecting means such as soldering or screwing. It may be connected to a dipole antenna element.

  The folded elements 15 and 15 ′ are preferably plate-shaped dipole antenna elements having a thickness of 0.0015λa and a height Ha of 0.0015λa or more which are the same as those of the plate-shaped dipole antenna elements 13a, 13b and 13a ′ and 13b ′. Is set to be smaller than the height H. The folding width Wa of the folding element is set to about 0.05λa.

  By loading the folding elements 15 and 15 'on the back surfaces of the plate-like dipole antennas 11a and 11b as described above, the plate-like dipole antenna constitutes a folded dipole antenna having a different thickness.

  In the antenna 10A according to the first embodiment, when a high-frequency signal is fed to the feeding points 14a and 14b, a plate-shaped dipole antenna element from the feeding points 14a and 14b as indicated by an arrow a in FIG. A high-frequency current flows along the periphery of 13a, 13b and 13a ', 13b', and the same operation as that of the two-wire dipole is performed.

  As shown in the above embodiment, when the length L of the plate-like dipole antenna elements 13a, 13b and 13a ′, 13b ′ is set to a value shorter than a half wavelength, for example, 0.35λa, the resonance frequency band is shifted to a high frequency range. However, the size H of the plate-like dipole antenna elements 13a, 13b and 13a ', 13b' is compared with the diameter (about 0.015λa) of the aluminum pipe of the antenna element of the conventional dipole antenna constituted by the aluminum pipe. By setting the size sufficiently larger than 0.06λa, the electrical length is corrected with the reactance. Further, the distance Db between the plate-shaped dipole antenna elements 13a, 13b and 13a ′, 13b ′ is set in the range of 0.006 to 0.025λa, and the length of the distance Db is set to 0.06λa or more, thereby providing a dipole antenna. The same effect as the two-wire dipole can be achieved while maintaining the same shape as the above, and it is possible to increase the bandwidth and correct the impedance. Therefore, a good VSWR (voltage standing wave ratio) characteristic can be realized while miniaturizing the antenna.

  FIG. 2 shows the VSWR characteristics of the antenna 10A according to the first embodiment in the frequency range of 470 to 770 MHz of UHF band TV broadcast radio waves, with the horizontal axis representing frequency (MHz) and the vertical axis representing VSWR. Is. This VSWR characteristic shows a favorable characteristic over the above frequency range.

  3 shows horizontal polarization horizontal plane directivity (dB scale polar coordinates) at a frequency of 470 MHz of the antenna 10A according to the first embodiment, and FIG. 4 shows horizontal polarization horizontal plane directivity at a frequency of 770 MHz. It is.

  FIG. 5 shows the horizontal polarization vertical plane directivity at a frequency of 470 MHz of the antenna 10A, and FIG. 6 shows the horizontal polarization vertical plane directivity at a frequency of 770 MHz.

  According to the first embodiment, the total length L of the plate-shaped dipole antenna element can be shortened to about 0.35λa, and the size can be reduced as compared with the conventional UHF band antenna. Furthermore, the width of the folding element is about half the width of a general folding dipole, and the size can be reduced as compared with a general folding dipole.

  In carrying out the present invention, the plate-like dipole antenna element and the folded element are formed as a single part that can be processed by a press or the like, so that it can be formed by stamping or bending by a press, and the assembly man-hour can be reduced. Further, regarding the material of the plate-shaped dipole antenna element, it can be composed of a wide variety of electric conductors such as aluminum which is inexpensive and excellent in durability, a brass material which can be soldered, and a stainless material which is excellent in strength.

(Second Embodiment)
Next, an antenna according to a second embodiment of the present invention will be described. FIG. 7 is a front view showing the configuration of the antenna 10B according to the second embodiment of the present invention.
As shown in FIG. 7, the antenna 10B according to the second embodiment is less likely to induce current in the center of the plate-shaped dipole antenna elements 13a and 13b than the antenna 10A shown in the first embodiment. For example, rectangular voids 18a, 18b and 18a ′, 18b ′ are formed in the portion. The widths and heights of the gaps 18a, 18b and 18a ′, 18b ′ are preferably formed to be about 2/3 or less of the widths and heights of the plate-like dipole antenna elements 13a, 13b and 13a ′, 13b ′, respectively. The

  Even when the air gap is formed at the center of the plate-shaped dipole antenna element as described above, the same operation and effect as those using the plate-shaped dipole antenna element shown in the first embodiment can be obtained. Further, by forming a gap in the center of the plate-shaped dipole antenna element, it is possible to reduce the weight of the element and reduce the wind receiving area. Note that the shape of the gap may be formed in an arbitrary shape, for example, a circle, an ellipse, a trapezoid, or the like as long as the above effect is achieved.

(Third embodiment)
FIG. 8 shows a configuration of an antenna according to a third embodiment of the present invention, where (a) is a plan view, (b) is a front view, and (c) is a side view.
The antenna according to the third embodiment is an example in which the antenna 10C shown in the first embodiment is applied to the antenna 10C with a reflector using the radiator. That is, a reflector 21 is provided behind the antenna 10A shown in the first embodiment at a predetermined interval, and the holding substrate 12 of the antenna 10A is supported through a support column 22 at the center of the reflector 21. is doing. The reflector 21 is formed in a square shape, for example, and is sufficiently large with respect to the antenna 10A.

  According to the reflector-equipped antenna 10C according to the third embodiment, the gain in the forward direction can be improved and the performance can be improved as compared with the antenna 10A shown in the first embodiment.

  In the third embodiment, the case where the antenna 10A of the first embodiment is used as a radiator is shown. However, an antenna in which a gap is provided in the center of the plate-shaped dipole antenna element shown in the second embodiment. 10B may be used.

(Fourth embodiment)
FIG. 9 shows a configuration of an antenna according to a fourth embodiment of the present invention, in which (a) is a front view and (b) is a side view.
The antenna according to the fourth embodiment is an example in which the antenna is implemented in a corner reflector antenna 10D using the antenna 10A shown in the first embodiment as a radiator. That is, a corner reflector 25 is provided behind the antenna 10A shown in the first embodiment at a predetermined interval, and the holding substrate 12 of the antenna 10A is supported through a support column 26 at the center of the corner reflector 25. is doing.
According to the corner reflector antenna 10D according to the fourth embodiment, the forward gain can be improved and the performance can be improved as compared with the antenna 10A shown in the first embodiment. Further, the directivity in the horizontal plane can be controlled by changing the angle α of the corner reflector 25. Although the case where the antenna 10A of the first embodiment is used as the radiator has been described, the antenna 10B having a gap in the center of the plate-like dipole antenna element shown in the second embodiment may be used.

(Fifth embodiment)
FIG. 10 shows the configuration of an antenna according to a fifth embodiment of the present invention, where (a) is a front view and (b) is a side view.

  The antenna according to the fifth embodiment shows an example in which the antenna is implemented in the indoor antenna 10E using the antenna 10A shown in the first embodiment as a radiator.

  That is, the indoor antenna 10E is configured by providing the antenna 10A shown in the first embodiment on the base 27 made of an insulating member.

  By using the antenna 10 </ b> A shown in the first embodiment as a radiator, the indoor antenna 10 </ b> E can be downsized to reduce the installation space, and the performance can be improved.

  In the fifth embodiment, the antenna 10A according to the first embodiment is used as a radiator. However, an antenna having a gap at the center of the plate-shaped dipole antenna element shown in the second embodiment. 10B may be used.

(Sixth embodiment)
FIG. 11 shows the configuration of an antenna according to a sixth embodiment of the present invention, in which (a) is a side view and (b) is a plan view.

  The antenna according to the sixth embodiment is an example in which the antenna is applied to a Yagi antenna 10F having the antenna 10A shown in the first embodiment as a radiator.

  That is, the antenna 10A shown in the first embodiment is provided as a radiator on the arm 31 of the Yagi antenna 10F, and a plurality of waveguides 32 are provided at predetermined intervals in front of the antenna. A reflective arm 33 is mounted on the arm 31 at a predetermined interval behind the antenna 10A, and a plurality of reflective elements 34 are provided on the reflective arm 33 in the vertical direction at a predetermined interval.

  As described above, by using the antenna 10A shown in the first embodiment as the radiator of the Yagi antenna 10F, the gain of the radiator itself can be improved, so that the performance can be improved as compared with the conventional Yagi antenna. Can do.

  In the sixth embodiment, the case where the antenna 10A of the first embodiment is used as a radiator has been described. However, an antenna in which a gap is provided in the center of the plate-shaped dipole antenna element shown in the second embodiment. 10B may be used.

In each of the above embodiments, the case where the plate-shaped dipole antenna element is formed of a metal plate has been described, but it is needless to say that the dipole antenna element may be formed of metal foil on the antenna substrate.
Further, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements without departing from the scope of the invention in the implementation stage.

The structure of the antenna which concerns on 1st Embodiment of this invention is shown, (a) is a top view, (b) is a front view, (c) is a side view. It is a figure which shows the VSWR characteristic of the antenna which concerns on the same embodiment. It is a figure which shows the horizontal polarization horizontal plane directivity in the frequency of 470 MHz of the antenna which concerns on the same embodiment. It is a figure which shows the horizontal polarization horizontal plane directivity in the frequency of 770 MHz of the antenna which concerns on the same embodiment. It is a figure which shows the horizontal polarization vertical surface directivity in the frequency of 470 MHz of the antenna which concerns on the same embodiment. It is a figure which shows the horizontal polarization vertical surface directivity in the frequency of 770 MHz of the antenna which concerns on the same embodiment. It is a front view which shows the structure of the antenna which concerns on 2nd Embodiment of this invention. The structure of the antenna which concerns on 3rd Embodiment of this invention is shown, (a) is a top view, (b) is a front view, (c) is a side view. The structure of the antenna which concerns on 4th Embodiment of this invention is shown, (a) is a front view, (b) is a side view. The structure of the antenna which concerns on 5th Embodiment of this invention is shown, (a) is a front view, (b) is a side view. The structure of the antenna which concerns on 6th Embodiment of this invention is shown, (a) is a side view, (b) is a top view. It is a top view which shows the structure of the conventional 2-wire type dipole antenna. It is a figure which shows the VSWR characteristic of the conventional 2-wire type dipole antenna.

Explanation of symbols

  10A ... Antenna according to the first embodiment, 10B ... Antenna according to the second embodiment, 10C ... Antenna with reflector according to the third embodiment, 10D ... Corner reflector antenna according to the fourth embodiment, 10E ... Fifth embodiment Indoor antenna according to embodiment, 10F ... Yagi antenna according to sixth embodiment, 11a ... first plate-like dipole antenna, 11b ... second plate-like dipole antenna, 12 ... holding substrate, 13a, 13b, 13a ', 13b' ... plate-shaped dipole antenna element, 14a, 14b ... feeding point, 15, 15 '... folding element, 18a, 18b, 18a', 18b '... gap, 21 ... reflector, 22 ... support column, 25 DESCRIPTION OF SYMBOLS ... Corner reflector, 26 ... Support pillar, 27 ... Base, 31 ... Arm, 32 ... Waveguide, 33 ... Reflective arm, 34 ... Reflective element.

Claims (1)

  A first folded dipole antenna in which a folded element is loaded on one surface of a plate-shaped dipole antenna element, and a second folded dipole antenna in which a folded element is loaded on one surface of a plate-shaped dipole antenna element Holding means for holding the first folded dipole antenna and the second folded dipole antenna symmetrically at a predetermined interval in the vertical direction, and feeding means for feeding power to the first and second folded dipole antennas And an antenna.

Images