JP2012084944A - On-vehicle diversity antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle diversity antenna device, solving the conventional problem of a deteriorated SN ratio in the case of being unable to configure sufficient high-frequency grounding between a film antenna ground portion and a flange of a window frame portion.SOLUTION: The on-vehicle diversity antenna device uses: a first film antenna 1a, having a monopole antenna element 11a and a ground pattern 22a, disposed substantially perpendicular thereto, which are respectively connected to power feed portions 10a, 20a; and a second film antenna 1b having relationship of line symmetry with respect to an axis parallel to the antenna element 11a. In the case of insufficient high-frequency grounding because of a large distance D between a vehicle window edge 62 and a flange 61, each of the film antennae 1a, 1b is pasted onto window glass 60 in a state that a certain section (W) on the end side of each of the ground patterns 22a, 22b is overlapped along a line (63) close to the vehicle window edge 62. Each reception signal of the antennae 1a, 1b is amplified by each of amplifier units 50a, 50b, so as to output to a synthesizer.

Description

  The present invention relates to an in-vehicle diversity antenna apparatus, and more particularly to an apparatus for receiving broadcast radio waves by a diversity reception method by sticking a pair of film antennas to a windshield or rear glass of a vehicle.

  In recent years, reception systems capable of viewing television (TV) broadcasts in vehicles such as automobiles have become widespread, and in particular, the viewing rate of terrestrial digital TV broadcasts started after December 2003 has improved dramatically. In conjunction with the popularization of car navigation systems using GPS and global positioning system, various in-vehicle digital signal receivers have been developed and put on the market, but film antennas are used as antennas. As shown in Patent Documents 1 and 2 below, a transparent plastic film in which an antenna element, a ground pattern (or ground wire), and a power feeding portion are arranged and formed is attached to a window glass of an automobile or the like.

In addition, in the in-vehicle digital signal receiving device, the reception level often fluctuates greatly due to the occurrence of fading due to the characteristics of in-vehicle. Therefore, how good terrestrial digital TV broadcasting can be stably received. A variety of diversity reception systems using film antennas have been proposed.
Here, the diversity reception method is a method of combining the reception signals of a plurality of antennas installed separately from each other, but in the reception signal after combining, it is possible to avoid an extreme decrease in reception level by mutual complement of each antenna, A more stable reception state can be obtained.

  On the other hand, when multiple antennas are used, broadcast radio waves always reach each antenna with different path lengths, and when a car is traveling in the city, it is affected by buildings and has a complicated multipath state. For this reason, the combined received signal is inevitably distorted due to the complicated phase difference caused by them, and noise is mixed into the demodulated received signal.

  With respect to this problem, in Patent Document 3 and the like below, the phase of the received signal of one TV antenna out of two TV antennas spaced apart from each other is shifted by a plurality of phase shifters. The output signal of each phase shifter and the output signal of the other TV antenna are combined by a combiner, and a plurality of combined received signals combined by the combiner and the output signal of the other TV antenna are A vehicle-mounted TV diversity system has been proposed that compares the received signals synthesized by the synthesizers, selects the received signal of the highest level by the received signal changeover switch, and sends it to the TV.

As a further problem, in the case of a film antenna attached to a window glass of an automobile or the like, if the antenna element is arranged along a car window frame made of a metal material that easily reflects radio waves, the influence of the reflected radio waves is reduced. The signal-to-noise ratio of the received signal greatly affects whether the ground circuit is properly taken and whether the ground circuit is configured with respect to the antenna element. Therefore, the configuration of the film antenna is extremely important for reducing the error rate when demodulating and decoding the received signal of digital terrestrial TV broadcasting.
In addition, in the invention of Patent Document 1, the film antenna in which the antenna element is arranged along the ground wire in a mode in which the ground wire is arranged along the vehicle window frame and the ground wire is interposed with respect to the vehicle window frame. is suggesting.

Japanese Patent Laid-Open No. 7-122920 JP 2003-115713 A JP 2000-252895 A

By the way, in the case of terrestrial digital TV broadcasting in Japan, a multi-carrier system is adopted as a carrier wave, and information such as voice, video, data, etc. is divided and modulated into a plurality of carrier waves and transmitted. It is said that it is hard to be affected by the accompanying fading.
In the case of a received signal for terrestrial digital TV broadcasting, some high-frequency noise is completely removed in the demodulation process, and even if there is strong noise, it becomes mosaic as block noise or is not seen at all. It is not reflected in the video as a ghost unlike TV broadcasting.

Therefore, in the in-vehicle receiver for digital terrestrial TV broadcasting, it is important to ensure a good signal-to-noise ratio by rationally configuring the earth circuit while ensuring a stable reception state by the diversity reception method using the film antenna. If this is effectively realized, it is possible to suppress decoding errors and reproduce high-quality video and audio.
However, in the case of a film antenna, the ground element part is connected to a metal part that is conducted to the vehicle body using a conductive tape or the like, and the flange (conductive metal) that is provided in the vehicle window frame. In some cases, the high-frequency ground by capacitive coupling is used.
In the former case, the metal portion that can be directly connected to the vehicle window frame is not always exposed, and even if it is possible, connecting with a conductive tape or the like impairs the aesthetic appearance of the vehicle window.
In the latter case, there is no such problem, but the placement position of the flange differs depending on the vehicle, and the high frequency grounding can be effectively taken depending on the distance between the window edge of the vehicle window and the flange and the case where it is not so effective. Even if it is not effective, it is basically desirable to increase the ground area (equipotential surface).

  Accordingly, the present invention provides a vehicle-mounted diversity antenna device that uses a pair of film antennas to form a high-frequency ground between the ground element portion of each film antenna and the flange on the vehicle window frame side. An object of the present invention is to ensure a sufficient grounding condition even when it cannot be configured effectively, and to always obtain a good SN ratio with high sensitivity.

  In the present invention, the antenna-side power feeding part and the ground-side power feeding part are arranged close to each other, and one end of the monopole antenna element is connected to the antenna-side power feeding part and has a shorter length than the monopole antenna element. Is arranged in parallel with the monopole antenna element, and one end of the ground wire extends to the ground-side feeding part, and one end of a belt-like earth pattern extending in a direction perpendicular to the monopole antenna element has the ground-side feeding part A first film antenna connected to each other, a second film antenna having an axisymmetric relationship with respect to an axis parallel to the monopole antenna element with respect to the first film antenna, and an amplifier circuit And a case attached to the feeding area of each film antenna and an output cable. A pair of amplifier units each having a signal input terminal connected to the tena side power supply unit and a ground terminal connected to the ground side power supply unit, and outputting the antenna reception signal amplified by the amplifier circuit as a cable, and each of the amplifier units The first film antenna and the second film antenna on the line along the window edge of the vehicle window glass. A vehicle-mounted diversity antenna characterized in that it is attached to the window glass in such a manner that the tip side fixed sections of each of the ground patterns overlap each other, or in a mode in which the tips of the respective ground patterns face each other. Related to the device.

The first and second film antennas in the present invention are monopole antennas, and the ground pattern arranged perpendicular to the antenna element constitutes a high-frequency ground with the conductive metal on the vehicle window frame side, In combination with the ground wire arranged in parallel with the monopole antenna element, the S / N ratio as an antenna is improved.
The first and second film antennas are a pair of antennas that are in line symmetry with each other with respect to an axis parallel to the monopole antenna element. Is configured.
As pointed out in the above [Problems to be solved by the invention], there is a problem of whether or not a ground circuit can be effectively secured by a vehicle, but (a) a flange or the like in a vehicle window frame extends from the edge of the window glass surface. In the case where they are separated from each other, it is difficult to form a high-frequency ground due to capacitive coupling, so it is desirable to increase the S / N ratio by widening the ground circuit of each film antenna. In the case where is near the edge of the window glass surface, there is not much problem with the S / N ratio, and it may be better to arrange the film antennas apart in order to obtain the diversity effect more effectively.
In the present invention, since the first and second film antennas are configured as a pair of antennas having a line symmetry as described above, each film is placed with the monopole antenna element facing the inside of the window glass. Under the condition that the ground pattern of the antenna is located on a line along the window edge of the window glass of the vehicle, in the case of (a), the front end side sections of the mutual ground pattern are overlapped, and (b) In this case, each film antenna can be attached to the window glass surface with the tips of the ground patterns facing each other.

The in-vehicle diversity antenna device of the present invention has the following effects.
When receiving digital terrestrial TV broadcasts or the like with a film antenna, it becomes a problem whether or not a ground circuit can be sufficiently configured with a conductive metal part such as a flange provided on the window frame part of the vehicle. Even when the conditions are bad, the ground patterns of the two film antennas are partially overlapped so that a large ground area can be shared with each other, enabling reception with a good S / N ratio while ensuring a diversity effect, When the conditions are good, it is possible to obtain a sufficient diversity effect by arranging each film antenna with a higher degree of freedom.

It is the top view (A) of the 1st film antenna in the state before sticking to the window glass of a motor vehicle (state before use), and the top view (B) of a 2nd film antenna. It is a disassembled perspective view of a 2nd film antenna. It is a side view which shows the attachment state of the amplifier unit with respect to a film antenna. It is the figure which looked at the state which overlapped the earth pattern on the upper edge part of the windshield of a motor vehicle, and was affixed on the 1st and 2nd film antenna from the vehicle interior. It is the figure which expanded the attachment part of the 1st and 2nd film antenna in FIG. FIG. 6 is a block circuit diagram of an on-vehicle receiver for digital terrestrial TV broadcasting when the film antenna sticking method shown in FIGS. 4 and 5 is adopted. It is the figure which looked at the state which stuck the 1st and 2nd film antenna to the upper edge part and side edge part of the windshield of a car (state which stuck without overlapping an earth pattern) from the inside of a car. It is the figure which expanded the attachment part of the 1st film antenna in FIG. It is the figure which looked at the state (state which stuck without overlapping an earth pattern) which stuck the 1st and 2nd film antenna on the both-sides edge part of the windshield of a car from the car interior. FIG. 10 is a block circuit diagram of an on-vehicle receiver for digital terrestrial TV broadcasting when the first and second film antenna sticking methods shown in FIGS. 7 and 9 are used.

Hereinafter, embodiments of an in-vehicle diversity antenna device of the present invention will be described in detail with reference to the drawings.
First, FIG. 1 is a plan view of a pair of film antennas in a state before being attached to an automobile window glass (a state before use), and each antenna has a basic configuration as a 1/4 wavelength monopole antenna. It is used as a diversity antenna applied to an in-vehicle receiver for digital terrestrial TV broadcasting.

FIG. 2A relates to the first film antenna 1a, and its electrical elements include an antenna-side power feeding part 10a and a ground-side power feeding part 20a having a substantially square planar shape, and one end of the antenna-side power feeding part 10a. The connected monopole antenna element 11a, the ground wire 21a arranged in parallel along the monopole antenna element 11a, one end of which is connected to the ground-side feeding unit 20a, and the direction perpendicular to the monopole antenna element 11a It is composed of a ground pattern 22a, one end of which is connected to the ground-side power feeding section 20a.
However, the monopole antenna element 11a is provided with a branching element 12a on the tip end side thereof so as to have broadband characteristics, and a slit 23a is formed in the longitudinal direction of the earth pattern 22a.
Each electrical element is formed by punching a thin copper plate, and black paint is applied to the front and back surfaces of the monopole antenna element 11a, the ground wire 21a, and the ground pattern 22a except for the front and side surfaces of the power feeding portions 10a and 20a. Is applied and, as will be described later, the film sheet 40a is attached in a manner covered with an overcoat 41a in the arrangement relationship of FIG.

On the other hand, FIG. 1B shows a second film antenna 1b, which is in a line-symmetric relationship with respect to the axis 30 parallel to the monopole antenna element 11a with respect to the first film antenna 1a.
Therefore, the description relating to each element of the second film antenna 1b is omitted, and in FIG. 1B, the reference numerals indicating the elements such as the respective power feeding portions, the monopole antenna element, the earth wire, and the earth pattern are also given. The subscript “a” attached to the element of one film antenna 1a is changed to “b”.

As described above, FIG. 1 is a plan view of the film antennas 1a and 1b before use, and FIG. 2 shows a layer structure related to the second film antenna 1b in FIG.
In FIG. 2, 40b is a film sheet, 41b is an overcoat, 42b and 43b are separators, and electric elements [feeding portions 10b and 20b, monopole antenna element 11b (including branch element 12b), ground wire 21b, ground The pattern 22b] is adhered and arranged on one side of a film sheet 40b having a strong adhesive layer, and the upper side thereof is covered with an overcoat 41b so that the electrical element is sandwiched to constitute a state in use of the film antenna 1b. is doing.

And the other surface of the film sheet 40b is a surface that is adhered to the window glass surface in the usage state of the film antenna 1b, and an adhesive layer having the required adhesiveness is formed on the same surface. The separator 43b is temporarily attached to the separator 42b, and the separator 43b formed in the substantially same plane shape as the separator 42b is temporarily attached so as to cover the surface on the overcoat 41b side.
Here, the separators 42b and 43b on the respective temporary attachment surfaces are in an attached state so that they can be easily peeled off. The separator 42b is divided into four by a predetermined line (broken line in the figure), and the separator 43b is separated from the separator 42b. Although they have substantially the same planar shape, only the part indicated by * in FIGS. 1 and 2 is formed longer than the separator 43b.
Note that the first film antenna 1a is also in a line symmetrical relationship as described above, and the layer configuration including the separators 42a and 43a, the temporary attachment relationship, and the like are the same as those of the second film antenna 1b.

  Based on the layer configuration of each of the film antennas 1a, 1b and the separators (42a, 43a), (42b, 43b), the film antennas 1a, 1b in the state of FIG. The separators 42a and 42b are peeled off sequentially from each other, and the peeled surfaces are attached to the required positions of the window glass, and then the separators 43a and 43b are peeled off from the parts indicated by * Only the antennas 1a and 1b are stuck and left on the window glass to remove the separators 43a and 43b.

1 indicate that the amplifier units 50a and 50b are attached to the portions where the feeding portions (10a, 20a) and (10b, 20b) of the film antennas 1a and 1b are disposed.
Specifically, as shown in FIG. 3, each of the amplifier units 50a and 50b includes cases 51a and 51b each including a board on which a low-noise high-frequency amplifier is mounted, and coaxial cables 52a and 52a that output signals amplified by the high-frequency amplifier circuit. 52b, but the lower sides of the cases 51a and 51b are in contact with the antenna-side power feeding portions 10a and 10b and the ground-side power feeding portions 20a and 20b of the film antennas 1a and 1b attached to the window glass 60 of the automobile, respectively. The signal input terminals 53a, 53b to be connected and the ground terminals 54a, 54b are protruded, and the cases 51a, 51b are provided at the portions where the feeding portions (10a, 20a), (10b, 20b) of the film antennas 1a, 1b are provided. By sticking, the contact connection is ensured.

Next, how to attach the film antennas 1a and 1b to the window glass (front glass) 60 of the automobile will be described.
[Example 1]
First, FIG. 4 shows a case where the film antennas 1a and 1b are attached by being attached to the upper edge side of the window glass 60, and FIG. 5 is an enlarged view of the attachment portion.
By the way, among the conductive members constituting the window frame portion of the automobile, the flange 61 that holds the gasket that seals and supports the peripheral portion of the window glass 60 is arranged closest to the window edge, The flange 61 is configured as an edge portion of the inner panel or the outer panel, and is electrically connected to the vehicle body frame.
Therefore, it is reasonable to configure the ground circuit of the film antennas 1a and 1b attached to the window glass 60 with high-frequency grounding by capacitive coupling with the flange 61 on the window frame side. The structure of the part varies, and the efficiency of the high-frequency grounding inevitably differs.

The film antennas 1a and 1b are attached to the inner surface of the window glass 60 so that the ground patterns 22a and 22b are along the window edge 62 of the window glass 60. In the case of FIGS. Since the distance D of the window edge 62 of the window glass 60 is large, the distance between the ground patterns 22a, 22b and the flange 61 is also large.
Therefore, if the film antennas 1a and 1b are separated and attached individually, high-frequency grounding cannot be obtained sufficiently, and the S / N ratio of the received signals of the film antennas 1a and 1b is deteriorated.

Therefore, as shown in FIGS. 4 and 5, when the film antennas 1a and 1b are attached to the window glass, a fixed section on the tip side of each of the ground patterns 22a and 22b is used as the window edge 62 of the window glass 60. It is made to overlap on the line which followed closely (line 63).
As a result, the film antennas 1a and 1b are connected in high frequency in the overlapping section W of the ground patterns 22a and 22b, so that the ground area of the film antennas 1a and 1b is increased and high-frequency grounding with the flange 61 is facilitated. .
That is, it is possible to improve the SN ratio of the received signals of the film antennas 1a and 1b while performing diversity reception with the two film antennas 1a and 1b.

The in-vehicle receiver for digital terrestrial TV broadcasting including the film antennas 1a and 1b has a circuit configuration as shown in FIG.
That is, the reception signals of the film antennas 1a and 1b are amplified by the high frequency amplifiers included in the cases 51a and 51b of the amplifier units 50a and 50b, and guided to the combiner 71 by the coaxial cables 52a and 52b. Are output to the tuner / decoder 72, channel selection and MPEG signal demodulation / decoding are performed, and the decoded video / audio signals are output to the TV monitor 73.
In FIGS. 4 and 6, reference numeral 77 denotes a remote control light receiver. The operator controls the tuner / decoder 72 using a remote control light transmitter (not shown) to perform channel selection and volume adjustment. it can.

As shown in FIG. 4, the TV monitor 73 is installed on the upper surface of the dashboard 74, etc., but the synthesizer 71 and the tuner / decoder 72 are installed in the dashboard 74, and the film antennas 1a and 1b are connected to each other. The received signal is guided from the roof (ceiling) 75 to the synthesizer 71 in the dashboard 74 through the inside of the A pillar 76 by the coaxial cables 52a and 52b.
In that case, for the entire ground circuit (the ground-side power feeding portions 20a and 20b of the film antennas 1a and 1b)-(the high-frequency amplifier of the amplifier units 50a and 50b)-(the outer conductor of the coaxial cables 52a and 52b)-( The circuit is composed of the path of the combiner 71)-(the outer conductor of the coaxial cable)-(the tuner / decoder 72), but the wired connection to the vehicle body of the ground circuit is made only in the tuner / decoder 72.

  Therefore, the film antennas 1a, 1b and the ground point of the tuner / decoder 72 are far away from each other, and the ground to the vehicle body is secured in each film antenna 1a, 1b to achieve a good S / N ratio for the received signal. Although it is necessary for this, according to this embodiment, even if the flange 61 is separated from the window edge 62, the ground patterns 22a and 22b of the film antennas 1a and 1b are overlapped so that a common ground having a large area can be obtained. It can be configured as a pattern (E in FIG. 6), and the high frequency grounding with the flange 61 can be effectively taken to improve the S / N ratio. As a result, the received signals of both film antennas 1a and 1b are weakened due to fading. In this case, it is possible to prevent a situation in which the signal is hidden by noise and decoding errors frequently occur.

[Example 2]
In the first embodiment, the ground patterns 22a and 22b of the film antennas 1a and 1b are overlapped. However, in the case of an automobile in which the flange is arranged near the window edge, the ground patterns 22a and 22b are used. Therefore, it is not necessary to overlap the ground patterns 22a and 22b.
Therefore, the end portions of the ground patterns 22a and 22b of the film antennas 1a and 1b may be arranged so as to face each other on a line (line 63) that is close to the window edge 62 of the window glass 60.

In this case, as shown in FIG. 4, the film antennas 1a and 1b may be spaced apart at the upper window edge of the window glass 60. However, as shown in FIG. If the other film antenna 1b is arranged on the window edge along the window edge along the A-pillar 76, the polarization diversity functioning as an antenna having different polarization planes can be formed. This is effective as a vehicle-mounted diversity antenna.
FIG. 8 is an enlarged view of a portion where the film antenna 1a is attached in FIG. 7. In this case, since the distance D ′ between the flange 61 ′ of the window frame and the window edge 62 ′ is small, the film is inevitably produced. The distance between the ground pattern 22a of the antenna 1a and the flange 61 'can be narrowed, and a high-frequency ground is effectively obtained by mutual capacitive coupling.
Although the film antenna 1b side is omitted, naturally high frequency grounding is obtained under the same conditions.

Furthermore, not only the configuration of the polarization diversity as described above, but also sufficient high frequency grounding can be obtained between the ground patterns 22a and 22b of the film antennas 1a and 1b and the flange 61 'as shown in FIG. As shown in FIG. 9, the film antennas 1a and 1b may be arranged on the window edges along the A pillars 76 on both sides.
In this case, the film antennas 1a and 1b are arranged in a state of being largely separated on both sides of the window glass 60, which is advantageous in obtaining a diversity effect.

  The in-vehicle receiver for digital terrestrial TV broadcasting in the second embodiment has a circuit configuration as shown in FIG. 10, and sufficient high-frequency grounding can be secured by the ground patterns 22a and 22b of the film antennas 1a and 1b (see FIG. 10). 10 Ea, Eb), it is possible to output a received signal having a good S / N ratio to the tuner / decoder 72 while obtaining a more effective diversity effect.

  INDUSTRIAL APPLICABILITY The present invention can be applied to an in-vehicle receiver for terrestrial digital TV broadcasting as a diversity receiving antenna device in which a pair of film antennas are attached to a vehicle window glass.

1a, 1b ... Film antenna, 10a ... Antenna side feeding part, 11a, 11b ... Monopole antenna element, 12a, 12b ... Branch element, 20a ... Earth side feeding part, 21a, 21b ... Earth wire, 22a, 22b ... Earth pattern 23a, 23b ... slit, 30 ... axis parallel to the monopole antenna element, 40a, 40b ... film sheet, 41a, 41b ... overcoat, 42a, 42b, 43a, 43b ... separator, 50a, 50b ... amplifier unit, 51a , 51b ... Case (built-in high frequency amplifier), 52a, 52b ... Coaxial cable, 53a, 53b ... Signal input terminal, 54a, 54b ... Earth terminal, 60 ... Window glass, 61 ... Flange, 62 ... Window edge, 63 ... Window A line along the edge, 71 ... synthesizer, 72 ... tuner / decoder, 73 ... TV monitor, 74 ... dashboard, 75 ... roof, 76 ... A pillar, 77 ... remote receiver.

Claims (1)

The antenna-side feeding part and the ground-side feeding part are arranged close to each other, and one end of the monopole antenna element is connected to the antenna-side feeding part, and a ground wire having a shorter length than the monopole antenna element is provided. One end of the band-shaped earth pattern that is arranged in parallel with the monopole antenna element and extends in a direction perpendicular to the monopole antenna element is connected to the ground side power supply section. A first film antenna,
A second film antenna having a line-symmetric relationship with respect to an axis parallel to the monopole antenna element with respect to the first film antenna;
An amplifier circuit is built in, and is composed of a case and an output cable that are attached to the feeding region of each film antenna, and the case has a signal input terminal connected to the antenna side feeding unit and the ground side feeding. A pair of amplifier units that output the antenna reception signal amplified by the amplifier circuit to a cable.
It consists of a synthesizer that synthesizes the amplified received signal output from each amplifier unit by cable,
In a mode in which the first film antenna and each of the second film antennas are on the line along the window edge of the window glass of the vehicle, the constant sections on the front end side of the respective ground patterns overlap each other. Alternatively, the vehicle-mounted diversity antenna device is characterized in that the ground patterns are stuck on the window glass so that the tips of the ground patterns face each other.

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