JP2008288936A - Waveguide antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna for digital television broadcast reception capable of stably receiving from a low-pass channel of a UHF to a high-pass channel by changing the resonance frequency of a waveguide antenna, at a low cost. <P>SOLUTION: The antenna for digital television broadcast reception has a waveguide 105 including a capacity mounting board 102, a capacity changeover switch 103 and a feeder line 104, the material of which is the same metal plate 101, wherein a main opening plane 106 is provided at the front of the waveguide. Five or more feed points 107 being connection points between the feed line and the metal plate are provided, a capacitor point 108 being a connection point between the capacity mounting board and the metal plate is provided, and the impedance matching degree of the waveguide is improved by switching the positions of the feed points and the capacitor of the capacitor point so that the best matched state can be achieved to each of UHF band channels used in digital television broadcasting. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a digital television broadcast receiving antenna and a digital television broadcast receiver, and more particularly to a digital television broadcast receiving antenna and a digital television for receiving a digital television broadcast in a free arrangement indoors. Related to John Broadcast Receiver.

  Conventional analog television broadcasts will continue in the current 1-12 ch VHF broadcast band (-222 MHz) and UHF broadcast band (470 MHz-770 MHz) until the end of analog broadcast in July 2011. However, when a broadcast electric wave with a weak electric field is received, a reduction in reception level of several dB greatly affects the image quality, and when receiving a radio wave in an urban area, an unpleasant ghost image is generated due to a reflected wave from a building. Therefore, it is necessary to install and use an antenna having a high gain in the direction of the incoming radio wave and a low gain in the direction of the reflected radio wave at a position where the incoming radio wave is as strong as possible. Therefore, as a conventional antenna installation method, a method in which an antenna having directivity in the horizontal direction is supported by a metal support and installed at a high position on the roof has been adopted.

  Further, on the transmitting side for transmitting the broadcast wave of the analog television broadcast, horizontal polarization has been adopted as the polarization direction of the broadcast wave. This is because when receiving horizontally polarized waves with the antenna on the receiving side, the current level induced in the metal support of the antenna is less affected by the disturbance of the received electric field. This is because a wave and a non-directional transmission antenna in the horizontal direction have been realized.

  And, as an antenna on the analog television broadcast radio wave receiving side, the resistance to wind is small, the equivalent reception area of the antenna is large, that is, the reception band is wide, and the gain can be increased easily by increasing the number of elements. For this reason, current-induced dipole antennas have been used exclusively.

  In addition, it is also possible to receive the broadcast wave of the analog television broadcast by an indoor antenna that does not require antenna wiring from the wall to the receiver, regardless of the outdoor antenna as described above. Conventionally, a current induction type dipole antenna is exclusively used because it has a wide reception band and can be realized at a low cost with a simple configuration (see, for example, Patent Document 1).

  On the other hand, in digital television broadcasting that has become widespread in recent years, when receiving broadcast waves with relatively strong electric fields in urban areas, even if there are reflected waves from buildings, the analog television broadcast is In contrast, since a ghost image is not generated in principle, the usefulness of the indoor antenna that requires no antenna wiring from a wall as an antenna for receiving digital television broadcasts has been attracting attention.

  And it is widely known that digital television broadcasting has the characteristic that there is no deterioration in image quality unless the reception level of radio waves falls below a threshold, and if the indoor antenna is used, the receiver can be freely placed indoors. Because there is an advantage that can be received, even when receiving a broadcast electric wave of a weak electric field more than an analog television broadcast, it is desired to receive the broadcast electric wave of a digital television broadcast with an indoor antenna, and its realization has been expected. It was.

  Here, when it is considered that the digital television broadcast receiving antenna is realized by an indoor antenna, the indoor antenna for receiving the digital television broadcast also has a physical merit that a gain is not wasted. And an antenna capable of directing the directivity in the direction of arrival of radio waves by electronic control is required.

  Further, since the digital television broadcast is preferably broadcast in the horizontally polarized wave so that the radio wave can be received even by an analog television broadcast receiving antenna that has already been widely used, the digital television broadcast reception is performed. As the indoor antenna for use, an antenna capable of receiving horizontally polarized waves is preferable.

  In view of the above, an antenna using a magnetic current induced in an opening provided in a metal plate or metal box as a radiation source (hereinafter referred to as a “magnetic current induction type antenna”) is a conventional indoor antenna. Compared with the current-induced antennas used, it can receive horizontal polarized waves with a vertically elongated shape, so the installation area is small and the directivity is almost omnidirectional in the horizontal direction. If it is noticed that it has the characteristic that it does not need to be directed, this magnetic current induction type antenna can meet the requirements for the digital television broadcast receiving antenna as described above, and it is a room for receiving a digital television broadcast. It is promising as a unit antenna element of an antenna (see, for example, Patent Document 2 and Patent Document 3).

In addition, a waveguide antenna for receiving digital television broadcasts has been proposed that can be mounted on or incorporated in a thin television receiver without greatly reducing the thinness that is characteristic of the thin television receiver. (For example, refer to Patent Document 4).
Japanese Utility Model Publication No. 5-80014 (Page 2, Fig. 1) JP 58-15303 (page 7, FIG. 8) Japanese Patent Laid-Open No. 2003-124738 (page 6, FIG. 1-3) Japanese Patent Laying-Open No. 2005-102142 (page 17, FIG. 6)

  However, the magnetic current induction type antenna considered to be promising as the conventional antenna for receiving digital television broadcasts is considered suitable as an antenna for receiving digital television broadcasts. An antenna for receiving digital television broadcasting using an induction type antenna has not been realized so far.

  This is mainly because, like the current induction type dipole antenna, the magnetic current induction type unit antenna element has a high resonance strength Q value, and is scheduled for digital television broadcasting from 470 MHz to 710 MHz (USA is from 470 MHz to This is considered to be due to the inability to receive broadband broadcast radio waves up to 810 MHz).

  In other words, in order to receive broadband broadcast radio waves ranging from 470 MHz to 710 MHz (USA is 470 MHz to 810 MHz), a plurality of unit antenna elements having different resonance frequencies are combined, or the Q value of the unit antenna elements is lowered and this is reduced. However, the former is not practical because the antenna is larger than the current-induced dipole antenna, and the latter has a reactance change range required for the tuning element provided in the unit antenna element. It was difficult to realize it by becoming large.

  As for a digital television broadcast receiver, a means for realizing an antenna directivity in the direction of arrival of broadcast radio waves by electronic control and having the antenna portion not protruding while the antenna is mounted or built in is as follows. Was not provided.

  In order to solve the above problems, Japanese Patent Application Laid-Open No. 2005-102142 has already been proposed in order to realize a thin television receiver by incorporating a magnetic current induction type waveguide antenna. Therefore, there is a demand for a waveguide antenna that can be manufactured using a metal plate that is all processed by sheet metal without using a dielectric or magnetic material.

  In addition, when used in extremely strong electric field areas such as directly under the transmitting antenna of a broadcasting station, varactor diodes are used to vary the tuning frequency of the antenna. Therefore, a waveguide antenna that does not use a varactor diode is required, because it may cause interference to other wireless devices.

  In order to solve the above-mentioned two problems in a magnetic current induction type waveguide antenna, in order to change the resonance frequency of the waveguide, it has an open waveguide structure in which one end is short-circuited and the other end is opened. When adopting a configuration that switches the capacitance added to the waveguide, there is a problem that if the resonance frequency is changed, the feeding position that matches the input impedance of the tuner differs for each frequency, and matching cannot be achieved in the entire band. .

  Furthermore, the waveguide thickness suitable for incorporation in a thin television receiver is generally about 20 mm to 50 mm. In this case, it has been empirically known that the operating band matched to −6 dB or less of the aperture waveguide antenna is generally about 50 MHz. There was a problem that a configuration covering the entire UHF band was necessary. Of course, since analog UHF broadcasting is mixed in addition to digital broadcasting during the period until analog broadcasting is stopped, a configuration that covers the frequency range of 470 MHz to 770 MHz, which is an analog UHF broadcasting band, is desired.

  The present invention solves the above-mentioned conventional problems, and can be mounted on or built in a thin television receiver without greatly losing its characteristic thinness, and is being used or planned for digital television broadcasting. Low-cost digital television using a magnetic current induction type unit antenna element that can be tuned to a wide-band broadcasting radio wave ranging from 470 MHz to 770 MHz in the analog UHF broadcasting band in addition to 470 MHz to 710 MHz (USA is 470 MHz to 810 MHz) An object of the present invention is to provide an antenna for receiving a John broadcast and a digital television broadcast receiver that can be mounted or incorporated without protruding the antenna.

  In order to solve the above-described conventional problems, the waveguide antenna of the present invention is a waveguide having one end short-circuited and the other end opened, in order to change the resonance frequency of the waveguide to at least two or more. A capacitor mounting unit, at least two feeding points for receiving a resonance frequency changed by the capacitor mounting unit, and a changeover switch for switching between the resonance frequency and the position of the feeding point. Is.

  Furthermore, in the waveguide antenna of the present invention, the first frequency range from 470 MHz to 770 MHz, the second frequency range from 470 MHz to 810 MHz, or the television broadcast in which the first and second frequency ranges are expanded. The UHF band to be generated is divided into at least two or more bands and switched.

  Furthermore, in the waveguide antenna of the present invention, the changeover switch is characterized by steplessly switching the resonance frequency to be divided and the feeding point.

  According to the waveguide antenna of the present invention, it can be mounted or built in a thin television receiver without greatly losing its characteristic thinness, and is also being used or planned for digital television broadcasting. For receiving low-cost digital television broadcasts that can be tuned to broadband broadcast radio waves ranging from 470 MHz to 770 MHz in the analog UHF broadcast band in addition to 710 MHz (USA is 470 MHz to 810 MHz) and using a magnetic current induction type unit antenna element An antenna and a digital television broadcast receiver that can be mounted or incorporated without protruding the antenna can be provided.

  In the following, embodiments of the waveguide antenna of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
Hereinafter, the waveguide antenna according to the first embodiment will be described with reference to FIGS.

  First, the configuration of the waveguide antenna according to the first embodiment will be described with reference to FIGS.

  FIG. 1 is a perspective view in which a cable of a waveguide antenna and a capacitive mounting board are mounted according to Embodiment 1 of the present invention.

  FIG. 2 is a perspective view of only the waveguide of the waveguide antenna according to the first embodiment of the present invention.

  FIG. 3 shows three views of the waveguide antenna according to the first embodiment of the present invention.

  In FIG. 1, a digital TV broadcast receiving waveguide antenna 100 includes a metal plate 101, a capacitive mounting substrate 102 shown as an example of a capacitive mounting portion, a capacitive switching switch 103, and a feeder line 104. A wave tube 105 is provided. A main opening surface 106 is provided in front of the waveguide 105, and five feeding points 107, which are connection points between the feeding line 104 and the metal plate 101, are provided to connect the capacitive mounting substrate 102 and the metal plate 101. A capacity point 108 which is a point is provided.

  As shown in FIG. 2, the feature of the shape of the waveguide 105 can be divided into a waveguide upper surface 109 having an uneven portion and a flat waveguide lower surface 110. , A feeding point terminal extraction hole 111 is provided at the feeding point 107, and a capacitance point terminal extraction hole 112 is provided at the capacitance point 108. A notch is formed in the metal plate 101 on the waveguide lower surface 110 at the feeding point 107, and further bent upward to take out the feeding point lower surface terminal 113 from the feeding point terminal extraction hole 111.

A notch is made in the metal plate 101 on the waveguide lower surface 110 at the capacitance point 108, and further bent upward to take out the capacitance point lower surface terminal 114 from the capacitance point terminal extraction hole 112.
A cut is made in the metal plate 101 on the waveguide upper surface 109 at the feeding point 107, and the feeding point upper surface terminal 115 is taken out.

  A cut is made in the metal plate 101 on the waveguide upper surface 109 at the capacitance point 108, and the capacitance point upper surface terminal 116 is taken out.

  As shown in FIG. 3, the detailed configuration of the waveguide upper surface 109 is divided into a waveguide upper surface convex portion 109a and a waveguide upper surface concave portion 109b. The feed point terminal extraction hole 111 and the capacitance point terminal extraction hole 112 are guided. The wave tube upper surface recess 109b is opened. When the waveguide 105 is viewed from the main opening surface 106, the opening oblique bending portion 117 is provided so that the opening surface is rectangular.

  Here, the open waveguide as in the present application is generally used as an antenna by using a magnetic current accompanying an electric field appearing on the open face of the waveguide as a radiation source. The opening width of the waveguide is ½ wavelength or more of the operating frequency, and the waveguide length is ¼ wavelength of the in-tube wavelength when the opening on one side is short-circuited, and the opening on one side is opened. If it is, it is used by resonating with a half wavelength of the guide wavelength.

  In order to reduce the cost of such an open waveguide, the open waveguide of the present application is made of the same metal plate.

  Next, the input terminal position 126, that is, the feed point terminal as shown in FIG. 1, is shown in FIGS. 4 to 6 which are simplified diagrams as the waveguide antenna 120 of the digital television broadcast receiving waveguide antenna 100 in the first embodiment. The relationship between the position 107, the input impedance, and the resonance frequency will be described.

  In FIG. 4, the input impedance of the waveguide antenna 120 will be described. In the waveguide antenna 120 whose length L130 is equal to or less than a half wavelength, since the electric field E124 generated so as to wind the magnetic current M123 generated in the opening enters the waveguide outer wall perpendicularly, the radiated electric field is disturbed by the waveguide outer wall. Therefore, the electric radiation pattern is substantially the same as that of the electric dipole antenna 125 in which the electric field E124 and the magnetic field H are interchanged.

That is, since the waveguide antenna 120 can be regarded as a slot antenna that is complementary to the electrical dipole antenna 125, the input impedance Zm at the opening 121 of the waveguide antenna and the electrical dipole antenna 125 are based on the principle of Babenet. Zm · Zj = (60π) ² between the input impedance Zj of
There is a relationship.

The input impedance of the electric dipole antenna 125 is such that when the length L130 is shorter than λo / 2, the negative reactance component increases rapidly, but the change of the resistance component is gradual, and the negative reactance component is reduced by the matching element. The input impedance in the case of canceling and resonating is in the range of approximately 70 to 50Ω. Therefore, from the equation of the input impedance Babenet at the opening 121 of the resonant waveguide antenna of length L130,
Zm = (60π) ² / Zj = (60π) ² / (70-50) = 508-710Ω
Become close.

In FIG. 5, the input terminal position of the waveguide antenna will be described. When the distance A131 from the opening 121 to the input terminal is changed in the waveguide antenna having a length L130 and a depth ¼ of the guide wavelength λg at the resonance frequency, the input impedance is 0 (distance A131 = [λg / 4 132]): Short-circuit portion 122) <Input impedance <Zm (distance A131 = 0: impedance at opening 121)
The pure resistance value in the range of That is, it is between 0Ω and (500 to 700) Ω. Therefore, by selecting an appropriate distance A131, it is possible to match the tuner input impedance to 75Ω.

  In FIG. 6, the resonance frequency and input impedance of the waveguide antenna will be described. Even with the same length L130 and depth D133 as in FIG. 5, it is possible to resonate at a lower frequency by adding a capacitor C127 between the waveguide inner walls. Here, the closer to the opening 121, the greater the effect of the capacitor C127, that is, the resonance frequency can be greatly changed with a small capacitance value. Therefore, the closer to the short circuit portion, the smaller the effect.

  However, since the resonant electric field distribution in the tube changes depending on the resonant frequency, in order to use the waveguide antenna 120 in a well-matched state, it is preferable to switch the input terminal position for each band. In addition, when the resonance frequency is changed by the capacitor C127, the degree of matching can be improved by shortening the distance A131 in a low frequency band, that is, close to the opening 121.

  From the above description, when the important items are summarized in FIG. 7 in order to use the digital television broadcast receiving waveguide antenna 100 in a well-matched state like the waveguide antenna 120, the capacitor C127 is a portion close to the opening 121. The distance A131 from the opening 121 to the input terminal position 126 is preferably switched by the arbitrary capacitance changeover switch 140 that can be changed to an arbitrary value, and the frequency range is preferably divided into bands.

  Further, as shown in FIG. 7, by using the slider-type contactless step-change switching device 141 as 107, the movable feeding point 142 is realized, so that it is best for each UHF band channel used for television broadcasting. It is possible to realize the matching state.

  However, for the purpose of balancing the cost and performance, a method of configuring five or more fixed feeding points 107 as a guide as shown in FIGS. 1 to 3 is preferable.

  The present invention does not require an external antenna connected by a cable, an indoor antenna protruding outside, or an external device that receives a broadcast wave and relays and retransmits it to a receiver, and can be digitally arranged freely in a room. It is useful for realizing a low-profile digital television broadcasting receiver that can enjoy television broadcasting at a low cost.

The figure which shows the waveguide antenna in Embodiment 1 of this invention The figure which shows the waveguide antenna which removed the capacitive mounting board | substrate and the feeder in Embodiment 1 of this invention The figure which shows the waveguide antenna when the capacitor mounting board and the feeder line are removed and viewed vertically from three directions in the first embodiment of the present invention Explanatory drawing about the input impedance of the waveguide antenna in the first embodiment of the present invention Explanatory drawing about the input terminal position of the waveguide antenna in the first embodiment of the present invention Explanatory drawing about the resonant frequency and input impedance of the waveguide antenna in the first embodiment of the present invention 1 is a configuration diagram for realizing the best matching state for each UHF band channel used for television broadcasting using a waveguide antenna in the first embodiment of the present invention.

Explanation of symbols

100 Digital TV Broadcasting Waveguide Antenna 101 Metal Plate 102 Capacitance Mounting Board 103 Capacitance Switch 104 Feed Line 105 Waveguide 106 Main Opening Face 107 Feed Point 108 Capacitance Point 109 Waveguide Top Surface 110 Waveguide Bottom Surface 111 Feed Point terminal extraction hole 112 Capacitance point terminal extraction hole 113 Feeding point lower surface terminal 114 Capacitance point lower surface terminal 115 Feeding point upper surface terminal 116 Capacitance point upper surface terminal 117 Opening oblique bent portion 120 Waveguide antenna 121 Opening portion 122 Short-circuit portion 123 Magnetic current M
124 Electric field E
125 Electric dipole antenna 126 Input terminal position 127 Capacitance C
130 length L
131 Distance A
132 λg / 4
133 depth D
140 Arbitrary capacity changeover switch 141 Slider type contactless stepless changeover device 142 Movable feed point

Claims (3)

A waveguide with one end shorted and the other end open,
A capacity mounting portion for changing the resonance frequency of the waveguide to at least two or more;
A waveguide antenna comprising: at least two or more feeding points for receiving a resonance frequency changed by the capacitance mounting unit; and a changeover switch for switching a position of the resonance frequency and the feeding point.   A first frequency range of 470 MHz to 770 MHz, a second frequency range of 470 MHz to 810 MHz, or at least two UHF bands used for television broadcasting in which the first and second frequency ranges are expanded The waveguide antenna according to claim 1, wherein the waveguide antenna is switched in a divided manner. 2. The waveguide antenna according to claim 1, wherein the change-over switch switches a resonance frequency to be divided and a feeding point in a stepless manner.

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