JP5514568B2 - Glass antenna - Google Patents

Description

  The present invention relates to a glass antenna in which an antenna pattern and a feeding point that is mounted on a side corner portion of the glass surface and supplies power to the antenna pattern are formed on a glass surface.

  The glass antenna on which the antenna pattern is formed on the rear window of the vehicle is superior in appearance because there is no protrusion on the design surface compared to the conventional rod antenna, there is no fear of breakage, wind noise does not occur, etc. Widely used.

  A glass antenna on which an AM (Amplitude Modulation) / FM (Frequency Modulation) antenna pattern is mounted is also widely used. Conventionally, an RFC between the bus bar and the ground constituting an anti-fogging energizing heater (hereinafter referred to as defogger) is used. A glass antenna that can use this defogger as an antenna by inserting a (high-frequency choke coil) is known (see, for example, Patent Document 1 (FIG. 8)).

JP-A-57-188102 ("FIG. 8")

  Patent document 1 is demonstrated based on the following figure. As shown in FIG. 5, the glass antenna 100 </ b> A used in the vehicle includes an FM main antenna element 103 mounted between the AM antenna element 101 and the defogger 102, and an FM sub antenna element mounted below the defogger 102. 104 and FM diversity antenna are constructed. An RFC 105 of 1.0 μH, for example, is connected between each bus bar of the defogger 102 and a ground (not shown). The AM antenna element 101 is provided with a feeding point 106a, the FM main antenna element 103 is provided with a feeding point 106b, and the FM sub-antenna element 104 is provided with a feeding point 106c.

By the way, the reception performance of the diversity antenna configured by the FM main antenna element 103 and the FM sub antenna element 104 described above has been evaluated using the indices (1) to (4) listed below.
(1) The directivity of each frequency of the FM main antenna element 103 and the FM sub antenna element 104 is omnidirectional in each of horizontal polarization (hereinafter referred to as H polarization) and vertical polarization (hereinafter referred to as V polarization). Sensitivity averaged over time (hereinafter referred to as directivity average sensitivity)
(2) Sensitivity obtained by further averaging the directivity average sensitivity in the FM frequency band (hereinafter referred to as frequency average sensitivity) and its minimum value (3) FM main antenna element 103, FM respectively for H polarization and V polarization Average sensitivity and minimum value of directivity after diversity combining of the directivity of each frequency of the sub-antenna element 104 (select the higher sensitivity at each measurement point of 0 ° to 360 °) (4) FM main antenna Difference in frequency average sensitivity between element 103 and FM sub-antenna element 104

  However, these indexes are not necessarily correlated with the audibility when actually traveling in the FM broadcasting region of North America. Therefore, as an index that can be more correlated, in the FM main antenna element 103, the directivity of each frequency of H polarization and V polarization is added in all directions (hereinafter referred to as H / V synthesis), and the minimum directivity is obtained. A method of evaluating by value was adopted.

  The reason why this H / V synthesis is used as an index is that there is a correlation between the directivity when actually measured in the field and the directivity after H / V synthesis measured in the anechoic chamber. In North America, there are many FM broadcasts with circular polarization, and it is considered that the evaluation using the H / V synthesis index is more in line with the actual radio wave environment than the index for each of the H polarization and the V polarization. It is done.

  By the way, the target value of the minimum directivity after H / V synthesis is 45 dBuV in a 60 dBuV / m electric field (after amplifier gain subtraction, in order to prevent sound fluctuation due to stereo / mono switching in a weak electric field. , Optimally 47 dBuV / m or more) is required. In addition, consideration must be given to reducing mutual interference between the FM main antenna element 103 and the FM sub-antenna element 104 so that the diversity antenna can obtain good reception performance even in an environment where FM broadcast waves arrive by multipath. There is also.

  In order for the above-described minimum directivity after H / V synthesis to be equal to or greater than the target value, it is necessary that the directivity of each of the H polarization and the V polarization covers portions with low sensitivity. is there. In order to form a glass antenna having such directivity, for example, as shown in the glass antenna 100B of FIG. 6, the feeding point 106b of the FM main antenna element 103 is formed at substantially the center of the upper side of the glass surface. It turned out that “upper side feeding” should be used.

  However, in the case of “upper side feeding”, as shown in the glass antenna 100A of FIG. 5, an antenna amplifier having a higher cost than that in the case of “side feeding” feeding from the side corner portion of the glass surface is used. There is a need. The reason is due to the order of assembling parts at the vehicle production factory. Specifically, the rear glass peripheral part is assembled in the order of an antenna amplifier, a roof interior material, and a rear glass. At this time, if an insertion-type antenna terminal is mounted on the upper side of the glass, it is hidden by the roof interior material, so that the operator cannot perform the insertion operation.

  Therefore, it is necessary to mount a relatively expensive contact type antenna terminal that does not require insertion work on the upper side of the glass. Since the contact type antenna amplifier is more expensive than the plug-in type, it is currently not used in low-priced models.

  However, when a plug-in type antenna amplifier is used, it is necessary to make the glass antenna 100A by the “side feeding” shown in FIG. There is a drop in directivity after H / V synthesis. The reason for this will be described below with reference to FIGS.

  When the configuration of the glass antenna 100B by the “upper side feeding” shown in FIG. 6 is electrically expressed, the schematic diagram shown in FIG. 7 is shown. FIG. 8 shows the directivity and gain of the FM main antenna element 103 after H / V combination in the case of “upper side feeding” and the case of “side feeding”. ) Respectively. In both FIG. 8A and FIG. 8B, the directivity of H polarization is represented by a dotted line, the directivity of V polarization is represented by a solid line, and the directivity after HV synthesis is represented by a thick line.

  As shown in the schematic diagram of FIG. 7, the “upper side feeding” glass antenna 100B is capacitively coupled between the FM main antenna element 103 and the AM antenna element 101 and between the AM antenna element 101 and the defogger 102, respectively. 151 and 152 function as a λ / 4 monopole antenna 150 using the vertical lines of the AM antenna element 101 and the defogger 102. The glass antenna 100B can be regarded as a V-polarized monopole antenna from the vehicle longitudinal direction, and can be regarded as an H-polarized monopole antenna from the lateral direction of the vehicle because the glass surface is nearly horizontal. . Therefore, as shown in FIG. 8A, the directivity covers a portion where the directivity of each of the H polarization and the V polarization is low in sensitivity.

  However, in the glass antenna 100A by the side feeding shown in FIG. 5, the FM main antenna element 103 does not have an ideal monopole shape as shown in FIG. 7, and the directivity thereof is as shown in FIG. As a result, the directivity after H / V synthesis is degraded (hatched portion in the figure).

  An object of the present invention is to provide a glass antenna that improves reception performance in all directions without causing a drop in directivity after H / V synthesis.

The invention according to claim 1 is a glass antenna in which an antenna pattern and a feeding point that is mounted on a side of the glass surface and supplies power to the antenna pattern are formed on a glass surface. A first antenna element having a first antenna pattern composed of a plurality of horizontal conductors orthogonal to a vertical conductor, and mounted on the top of the first antenna element and positioned at the top of the first antenna pattern A second antenna element having a second antenna pattern that is capacitively coupled to the horizontal conductor and having a reception band different from that of the first antenna element, and is mounted below the first antenna element. An anti-fogging energizing heater comprising a plurality of horizontal conductors orthogonal to one horizontal conductor capacitively coupled to the horizontal conductor located at the bottom of one antenna pattern , The sides of the glass surface, characterized in that a side edge.

  According to a second aspect of the present invention, in the glass antenna according to the first aspect, a third antenna element mounted on a lower portion of the anti-fogging energizing heater and performing diversity reception in cooperation with the second antenna element. And.

  According to a third aspect of the present invention, in the glass antenna according to the first aspect, the anti-fogging energizing heater is used also as a third antenna element that performs diversity reception in cooperation with the second antenna element. It is characterized by that.

In the invention according to claim 1, the glass antenna is mounted on the first antenna element composed of a plurality of horizontal conductors orthogonal to one vertical conductor and on the first antenna element, and the first antenna A second antenna element capacitively coupled to the horizontal conductor located at the top of the pattern, and mounted at the bottom of the first antenna element, and capacitively coupled to the horizontal conductor located at the bottom of the first antenna pattern An anti-fogging energizing heater composed of a plurality of horizontal bus bars orthogonal to one vertical bus bar, and the side of the glass surface was the side .

According to the inventors' evaluation, by mounting the second antenna element on top of the first antenna element, it is possible to obtain directivity similar to that in the case of “upper side feeding” while being “side feeding”. all right. Therefore, a contact-type antenna amplifier is not required, the assembly of parts is facilitated, and the cost of the antenna amplifier can be reduced. Further, the second antenna element is adjusted for receiving a specific frequency band by capacitively coupling the second antenna element with a horizontal conductor located at the top of the first antenna element, and the second antenna The vertical conductor of the first antenna element functioning as a part of the element and the vertical bus bar of the anti-fogging energizing heater can be mounted substantially at the center of the glass surface. Accordingly, it is possible to provide a glass antenna that improves reception performance in all directions without causing a drop in directivity after H / V synthesis. Further, since the side of the glass surface is the side, the same directivity as in the case of “upper side feeding” can be obtained while being “side feeding”.

  In the invention according to claim 2, the third antenna element that performs diversity reception in cooperation with the second antenna element is mounted below the anti-fogging energizing heater. For this reason, the third antenna element can be mounted as far as possible from the second antenna mounting position, thereby reducing the degree of mutual interference between the second antenna element and the third antenna element. Therefore, it is possible to construct a diversity antenna that can obtain good reception performance even in a multipath environment.

  In the invention according to claim 3, the anti-fogging energizing heater is used as a third antenna element that performs diversity reception in cooperation with the second antenna element. Therefore, it is possible to construct a diversity antenna in which the number of parts is reduced and good reception performance can be obtained while further cost reduction is achieved.

It is a figure which shows an example of the antenna pattern of the glass antenna which concerns on the Example of this invention. It is the figure which showed the directivity characteristic of the glass antenna shown in FIG. 2 in contrast with the prior art example. It is the figure which showed the receiving sensitivity of the glass antenna shown in FIG. 2 with the graph. It is a figure which shows the modification of the antenna pattern of FIG. It is a figure which shows an example of the antenna pattern of the conventional glass antenna. It is a figure which shows the other example of the antenna pattern of the conventional glass antenna. FIG. 7 is a schematic diagram when the antenna pattern of FIG. 6 is viewed electrically. It is the figure which showed the directivity characteristic of the conventional antenna pattern.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

(Configuration of Example)
First, the structure of the Example of this invention is demonstrated based on drawing.
As shown in FIG. 1, the glass antenna 10 according to the embodiment has an AM antenna element 20, an FM main antenna element 30, a defogger 40, and an FM sub antenna element 60 mounted on the glass surface of the rear glass 10. Yes. Electric power is supplied to the AM antenna element 20 through a feeding point 71, the FM main antenna element 30 through the feeding point 72, and the FM sub antenna element 60 through the feeding point 73. These feeding points 71 to 73 are formed at the left side corner portion toward the rear glass 10 (side feeding).

  The AM antenna element 20 is a first antenna element having a first antenna pattern composed of a plurality of horizontal conductors 22 (22a to 22e) orthogonal to one longitudinal conductor 21. The FM main antenna element 30 is mounted on the top of the AM antenna element 20 and is capacitively coupled to the horizontal conductor 22a located at the top of the antenna pattern constituting the AM antenna element 20 at 50 pF or less.

  The defogger 40 is mounted on the lower part of the AM antenna element 20 and a plurality of horizontal conductors orthogonal to one vertical conductor 41 capacitively coupled to the horizontal conductor 22e located at the lowermost part of the antenna pattern of the AM antenna element 20. 42. A 1.0 μH RFC 50 is inserted between the bus bars 41 and 42 constituting the defogger 40 and the ground, and the defogger 40 is used as a part of the FM main antenna element 30.

  The FM sub-antenna element 60 is mounted below the defogger 40 and performs diversity reception in cooperation with the FM main antenna 30.

(Operation of Example)
The glass antenna 1 according to the embodiment is characterized in that, first, the FM main antenna element 30 whose power is “side-side fed” by the feeding point 72 is mounted on the upper side of the AM antenna element 20. The FM main antenna element 30 was capacitively coupled with the horizontal conductor 22a located at the top of the AM antenna element 20 with a capacitance of 50 pF or less. Second, the FM sub-antenna element 60 is mounted below the defogger 50 and is separated from the mounting position of the FM main antenna element 30 as much as possible.

  As described above, by mounting the FM main antenna element 30 on the upper part of the AM antenna element 20, directivity similar to that in the case of “upper side feeding” can be obtained while being “side feeding”. In addition, by receiving capacitive coupling between the horizontal conductor 22a located at the top of the antenna pattern (horizontal conductor 22) of the AM antenna element 20 and the FM main antenna element 30, the element length of the FM main antenna element 30 is received. The vertical conductor 21 of the AM antenna element 20 that functions as a part of the FM main antenna element 30 and the vertical conductor 41 of the defogger 40 are mounted substantially at the center of the rear glass 10. it can.

  Further, by mounting the FM sub antenna element 60 as far as possible from the FM main antenna element 30, the degree of mutual interference between the two antennas is reduced. Therefore, it is possible to receive excellent diversity even in an environment where FM broadcast waves arrive by multipath.

  In the following, these grounds will be described based on the directivity characteristic chart for each FM band shown in FIGS. 2A and 2B and the reception sensitivity characteristic chart of the FM band shown in FIG.

  FIG. 2 shows the directivity and gain of the FM main antenna element 30 after HV synthesis, measured together with the H polarization and V polarization before synthesis for each FM reception period number (88 MHz, 98 MHz, 108 MHz). FIG. 2 shows a glass antenna 1 of Example 1 (FIG. 2A) having the antenna pattern shown in FIG. 1 and a conventional glass antenna 100A (FIG. 2B) having the antenna pattern shown in FIG. It is shown against. In both cases, the directivity of H polarization is indicated by a dotted line, the directivity of V polarization is indicated by a solid line, and the directivity after HV synthesis is indicated by a bold line.

  As apparent from FIG. 2 (a), the drop in the directivity after H / V synthesis is conspicuous in any of the respective frequency bands (88MHz, 98MHz, 108MHz), whereas in FIG. 2 (b). As is apparent, according to the first embodiment, the directivity after HV synthesis is such that the directivity of each of the H-polarized wave and the V-polarized wave covers portions where the sensitivity is low in each frequency band. It has become. Thus, it can be understood that the directivity is improved in all directions without causing a drop in the directivity after H / V synthesis.

  FIG. 3 is a diagram in which the directivity minimum gain after HV synthesis by the FM main antenna element 30 is measured when the antenna output in a 60 dBuV / m electric field is plotted on the vertical axis and the frequency is scaled on the horizontal axis. . In FIG. 3, the solid line represents the target value, the dotted line represents the conventional example, and the thick solid line represents Example 1.

  As is clear from FIG. 3, the minimum gain is 45 dBuV or more which is the target value in all FM reception frequency bands, and the recommended value is 47 dBuV or more in most of the frequency bands. You can see that it has improved.

(Effect of Example)
According to the glass antenna 1 which concerns on the Example of this invention, the directivity similar to the case of upper side electric power feeding is obtained, although it is side electric power feeding. Therefore, a contact-type antenna amplifier is not required, and the assembly of the parts is facilitated, so that the cost of the antenna amplifier can be reduced and the number of man-hours can be reduced. Further, the FM main antenna element 30 is capacitively coupled to the horizontal conductor 22a located at the uppermost part of the AM antenna element 20, so that the length of the FM main antenna element 30 is adjusted for FM frequency band reception, and the FM main antenna The vertical conductor 22a of the AM antenna element 20 functioning as a part of the element 30 and the vertical conductor 41 of the defogger 40 can be mounted at substantially the center of the glass surface of the rear glass 10.

  In addition, an FM sub antenna element 60 that performs diversity reception in cooperation with the FM main antenna element 30 is mounted below the defogger 40, and the FM sub antenna element 60 is separated as much as possible from the mounting position of the FM main antenna element 30. Therefore, it is possible to construct a diversity antenna that can reduce the degree of mutual interference between antennas, and thus can obtain good reception performance even in a multipath environment.

(Modification)
Note that the same effect as described above can be obtained by using the configuration shown in FIG. 4 as a modification in which the FM sub-antenna element 60 is shared with the defogger 40 instead of the antenna pattern described above. In this case, since the number of parts is reduced, it is possible to construct a diversity antenna that can obtain good reception performance while further reducing cost.

  The glass antenna 1 according to the present invention is applied to a vehicle window glass, in particular, a rear glass 10 to obtain a remarkable effect. The trend of reducing the cost of vehicle parts is becoming stronger day by day, and the effect obtained by the present invention is great while further cost reduction is required for antennas.

  DESCRIPTION OF SYMBOLS 1 ... Glass antenna, 10 ... Rear glass, 20 ... AM antenna element, 21 ... Vertical conductor, 21 (22a-22e) ... Horizontal conductor, 30 ... FM main antenna element, 40 ... Defogger (electric heating heater for anti-fogging), DESCRIPTION OF SYMBOLS 41 ... Vertical conductor, 42 ... Horizontal conductor, 50 ... RFC, 60 ... FM subantenna element, 71, 72, 73 ... Feeding point.

Claims (3)

On the glass surface, an antenna pattern, and a feeding point that is mounted on a side of the glass surface and supplies power to the antenna pattern, is a glass antenna,
A first antenna element having a first antenna pattern comprising a plurality of horizontal conductors orthogonal to one longitudinal conductor;
A second antenna pattern mounted on the first antenna element and capacitively coupled to the horizontal conductor located at the top of the first antenna pattern and having a reception band different from that of the first antenna element A second antenna element having a first antenna element and a vertical conductor mounted at a lower part of the first antenna element and capacitively coupled to the horizontal conductor located at a lowermost part of the first antenna pattern. An anti-fogging energizing heater composed of a plurality of horizontal conductors ,
The glass antenna is characterized in that the side of the glass surface is a side . A third antenna element mounted under the anti-fogging energizing heater and performing diversity reception in cooperation with the second antenna element;
The glass antenna according to claim 1, further comprising:   2. The glass antenna according to claim 1, wherein the anti-fogging energizing heater is also used as a third antenna element that performs diversity reception in cooperation with the second antenna element.

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