JP2011066713A - Integrated antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an integrated antenna that has high isolation between a transmitting/receiving antenna and a receiving antenna forming diversity. <P>SOLUTION: An antenna 110 for telephone has a diversity structure comprising: an antenna 111 for TRx for transmitting/receiving at a specified frequency band; and an antenna 112 for Rx for only receiving, and a parasitic element 113 is arranged adjacent to the antenna 111 for TRx. The parasitic element 113 is bent like an L shape in the vicinity of its ground point 113b, so that the ground point 113b becomes close to a feed point 112a of the antenna 112 for Rx. Thus, high isolation between the antenna 111 for TRx and the antenna 112 for Rx is achieved. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an integrated antenna mounted on a vehicle, and more particularly to an in-vehicle integrated antenna in which a telephone antenna is further integrated with an antenna such as ETC or VICS.

  Conventionally, an integrated antenna has been developed in which the antennas used for ETC (Electronic Toll Collection System), VICS (Vehicle Information and Communication System), GPS (Global Positioning System), etc. are integrated on a common ground. Has been. For example, in Patent Document 1, the VICS antenna and the GPS antenna are arranged on one composite substrate, and the ETC antennas having different directivities are arranged on another substrate, and these two substrates are shared by one. Located near the center of the ground. A substrate ground is formed on almost the entire surface of the substrate opposite to the surface on which each antenna is mounted.

  On the other hand, in recent years, there has been a growing need to mount a telephone antenna for use in a mobile phone or the like in a vehicle, and it is difficult to secure a space for installing a telephone antenna. It is highly desired. The telephone antenna uses a frequency band of 800 MHz. Further, in order to obtain suitable reception characteristics, it is desired that the telephone antenna has a diversity configuration. As an in-vehicle integrated antenna provided with a telephone antenna having a diversity configuration, for example, an antenna described in Patent Document 2 is known.

  FIG. 14 shows an example of an integrated antenna including a telephone antenna having a diversity configuration. In the integrated antenna 900 shown in the figure, a GPS antenna 902 is disposed substantially at the center of the common ground plane 901, and the common ground plane 901 functions as the ground of the GPS antenna 902. Further, telephone antennas 903 and 904 are arranged on the left and right sides of the GPS antenna 902, respectively.

  The telephone antennas 903 and 904 are antennas that operate in the same frequency band. By using this antenna to configure diversity, high reception characteristics can be obtained. Here, the telephone antenna 903 is a transmission / reception antenna (hereinafter referred to as a TRx antenna), and the telephone antenna 904 is a reception-only antenna (referred to as an Rx antenna).

  As the telephone antennas 903 and 904, inverted F-type antennas as shown in FIG. 15 can be used. FIG. 15 is a perspective view showing telephone antennas 903 and 904, and illustration of the GPS antenna 902 is omitted. Each of the telephone antennas 903 and 904 has a feeding point connected to the feeding cables 905 and 906 and a grounding point connected to the common ground plane 901. Further, the parasitic element 907 is disposed substantially parallel to the telephone antenna 903 so that the telephone antenna 903 has a suitable radiation characteristic. The parasitic element 907 has a grounding point connected to the common ground plane 901 and does not have a feeding point.

JP 2004-056773 A JP 2007-124016 A

  However, when the diversity antenna is configured by incorporating the TRx antenna and the Rx antenna into the integrated antenna, there is a problem that a transmission wave from the TRx antenna leaks to the Rx antenna. That is, there is a problem that it is difficult to ensure sufficient isolation between the TRx antenna and the Rx antenna. In particular, when a parasitic element as shown in FIG. 15 is disposed close to the TRx antenna, there is a problem that the isolation between the TRx antenna and the Rx antenna is significantly reduced.

  Accordingly, the present invention has been made to solve the above problem, and an object thereof is to provide an integrated antenna having high isolation between the TRx antenna and the Rx antenna constituting the diversity.

  A first aspect of the integrated antenna of the present invention is an integrated antenna in which a telephone antenna is arranged on a common ground plane together with another antenna, and the telephone antenna has at least a radiating portion of the common ground plane. A first antenna and a second antenna disposed in parallel with each other in proximity to two opposing edges; a parasitic element disposed in parallel with and adjacent to the first antenna; The grounding point side of the parasitic element is bent toward the second antenna side, and the grounding point of the parasitic element is connected to the feeding point of the first antenna and the second antenna. It is arranged between the feeding point of the antenna.

  According to another aspect of the integrated antenna of the present invention, when the wavelength of the transmission / reception wave of the telephone antenna is λ, the distance between the first antenna and the second antenna is 0.11λ or more and 0.14λ or less. The grounding point of the parasitic element is disposed at a distance of 0.09λ or less from the feeding point of the second antenna.

  In another aspect of the integrated antenna of the present invention, the feeding point and grounding point of the second antenna are bent toward the first antenna, and the feeding point and grounding point of the second antenna are the first antenna. It is arranged close to the feeding point of the antenna.

  According to another aspect of the integrated antenna of the present invention, when the wavelength of the transmission / reception wave of the telephone antenna is λ, the distance between the first antenna and the second antenna is 0.11λ or more and 0.14λ or less. The grounding point of the parasitic element is disposed at a distance of 0.06λ or less from the feeding point of the second antenna.

  Another aspect of the integrated antenna of the present invention is characterized in that the radiating portion, the feeding point, and the grounding point of the first antenna are linearly arranged along the edge of the common ground plane.

  In another aspect of the integrated antenna of the present invention, the first antenna is a transmission / reception antenna.

  Another aspect of the integrated antenna of the present invention is characterized in that the first antenna and the second antenna are inverted F-type antennas.

  ADVANTAGE OF THE INVENTION According to this invention, the integrated antenna which has high isolation between the antenna for TRx and the antenna for Rx which comprises diversity can be provided.

It is a top view of the integrated antenna which concerns on 1st Embodiment of this invention. It is a perspective view of the integrated antenna which concerns on 1st Embodiment. It is a graph which shows the VSWR characteristic, gain characteristic, and isolation characteristic of the integrated antenna which concerns on 1st Embodiment. It is a graph which shows the VSWR characteristic of a 1st comparative example, a gain characteristic, and an isolation characteristic. It is a graph which shows the VSWR characteristic of the 2nd comparative example, a gain characteristic, and an isolation characteristic. It is a graph which shows the VSWR characteristic of a 3rd comparative example, a gain characteristic, and an isolation characteristic. It is a comparison figure of isolation of a 1st embodiment and the 1st-3rd comparative example. It is a perspective view which shows the structure of the integrated antenna of 2nd Embodiment. It is a graph which shows the VSWR characteristic, gain characteristic, and isolation characteristic of the integrated antenna of 2nd Embodiment. It is a perspective view which shows the structure of the integrated antenna of 3rd Embodiment. It is a graph which shows the VSWR characteristic, gain characteristic, and isolation characteristic of the integrated antenna of 3rd Embodiment. It is a perspective view which shows the structure of the integrated antenna of 4th Embodiment. It is a graph which shows the VSWR characteristic of a 4th comparative example, a gain characteristic, and an isolation characteristic. It is the top view and side view of an integrated antenna provided with the antenna for telephones of the conventional diversity structure. It is a perspective view of the telephone antenna using an inverted F antenna.

  An integrated antenna according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. Each component having the same function is denoted by the same reference numeral for simplification of illustration and description. The integrated antenna of the present invention is an integrated antenna for a vehicle equipped with an antenna such as ETC or VICS, and further integrated with a telephone antenna.

  An integrated antenna according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view showing the configuration of the integrated antenna 100 of the first embodiment, and FIG. 2 is a perspective view of the integrated antenna 100. The integrated antenna 100 of this embodiment is configured by integrating a telephone antenna 110 with another antenna 101. FIG. 1 shows an embodiment in which a GPS antenna is mounted as an example of another antenna 101. However, the GPS antenna 101 is not shown in FIG. In the present embodiment, the present invention is not limited to this. For example, an ETC antenna may be further mounted adjacent to the GPS antenna 101. The ETC antenna is placed at a predetermined angle with respect to the common ground plane 102.

  The GPS antenna 101 is disposed in a substantially non-contact manner at the center of the common ground plane 102, and the common ground plane 102 functions as a reflector for the GPS antenna 101. The telephone antenna 110 has a diversity configuration including a TRx antenna 111 that transmits and receives in a predetermined frequency band and an Rx antenna 112 that performs only reception, and both antennas 111 and 112 are GPS antennas 101. Are arranged in parallel to the left and right ends of the common base plate 102. A parasitic element 113 is disposed in the vicinity of the TRx antenna 111, and at least a portion of the parasitic element 113 in the longitudinal direction is parallel to the TRx antenna 111. The parasitic element 113 is provided to improve the radiation characteristics of the telephone antenna 110. Although the parasitic element 113 is disposed in the vicinity of the TRx antenna 111 here, the parasitic element 113 is not limited to this and may be disposed in the vicinity of the Rx antenna 112.

  Hereinafter, the use frequency band of the TRx antenna 111 is defined as a transmission / reception frequency band F1, and the use frequency band of the Rx antenna 112 is defined as a reception frequency band F2. As an example, each frequency band is assumed to be F1 = 824 to 925 MHz and F2 = 843 to 875 MHz, and characteristics when adjusted appropriately in each frequency band will be described below.

  Here, inverted F-type antennas are used as the TRx antenna 111 and the Rx antenna 112, and each of them is disposed substantially parallel to two opposing edges on the common ground plane 102. The feed points 111 a and 112 a of the TRx antenna 111 and the Rx antenna 112 are connected to a predetermined cable to be fed, and the ground points 111 b and 112 b are connected to the common ground plane 102.

  In the telephone antenna 110 of the present embodiment, the grounding point 113b of the parasitic element 113 is brought close to the feeding point 112a of the Rx antenna 112, thereby realizing high isolation between the TRx antenna 111 and the Rx antenna 112. The configuration is to let In order to bring the grounding point 113b of the parasitic element 113 close to the feeding point 112a of the Rx antenna 112, the parasitic element 113 is bent in an L shape near the grounding point 113b, and a grounding point 113b is provided at the tip thereof. ing. As a result, the grounding point 113b is disposed on the center side of the common ground plane 102, and is disposed close to the feeding point 112a of the Rx antenna 112. The grounding point 113b is connected to the common ground plane 102.

  An example of the dimensions of the telephone antenna 110 will be described below, where λ is the wavelength of the radio wave transmitted and received by the telephone antenna 110. When the distance between the TRx antenna 111 and the Rx antenna 112 is 0.11λ to 0.14λ, the distance between the ground point 113b of the parasitic element 113 and the feed point 112a of the Rx antenna 112 is set to 0. It is preferable that the angle is not more than 09λ. By bringing the grounding point 113b of the parasitic element 113 close to the feeding point 112a to a distance of 0.09λ or less, it is possible to realize high isolation between the TRx antenna 111 and the Rx antenna 112. .

  In the following, the distance between the TRx antenna 111 and the Rx antenna 112 is 0.13λ, and the distance between the ground point 113b of the parasitic element 113 and the feed point 112a of the Rx antenna 112 is close to 0.07λ. It will be described that a high isolation characteristic is obtained between the TRx antenna 111 and the Rx antenna 112. The characteristics of the telephone antenna 110 are shown in FIG. In the same figure, (a) and (b) are the VSWR (Voltage Standing Wave Ratio) characteristics of the TRx antenna 111 and the Rx antenna 112, respectively, and (c) and (d) are the TRx antenna 111 and the Rx antenna 112, respectively. (E) shows the isolation characteristic (S21) between the TRx antenna 111 and the Rx antenna 112, respectively.

  The VSWR characteristic of the TRx antenna 111 is adjusted to be sufficiently low in the transmission / reception frequency band F1 shown in FIG. Further, the VSWR characteristic of the Rx antenna 112 is also adjusted to be sufficiently low in the reception frequency band F2 shown in FIG. Similarly, the gain characteristic is adjusted so that the gain characteristic of the TRx antenna 111 is sufficiently high in the transmission / reception frequency band F1, and is adjusted so that the gain characteristic of the Rx antenna 112 is sufficiently high in the reception frequency band F2. . In this case, the isolation characteristic between the TRx antenna 111 and the Rx antenna 112 has a small S21 in a wide frequency band including the transmission / reception frequency band F1 and the reception frequency band F2, as shown in FIG. It can be seen that high isolation is obtained.

  Next, as a comparative example with the telephone antenna 110, the conventional telephone antenna (hereinafter referred to as the first comparative example) shown in FIGS. 14 and 15 in which the parasitic element 909 is formed in a straight line. The isolation characteristics and the like will be described with reference to FIG. FIG. 4 shows the VSWR characteristics, (c) and (d) the gain characteristics, and (e) the isolation characteristics (S21), as in FIG. However, the TRx antennas 111 and 903, the Rx antennas 112 and 904, and the common ground planes 201 and 907 all have the same shape and the same dimensions. In the integrated antenna 900 shown in FIGS. 14 and 15, the ground point 907 b of the parasitic element 907 is disposed at a position farther from the feed point 904 a of the Rx antenna 904 than the integrated antenna 100.

  From a comparison between FIG. 3E and FIG. 4E, in this embodiment, a higher isolation characteristic (lower S21) than in the first comparative example is obtained, and the ground point 113b of the parasitic element 113 is set to Rx. It can be seen that higher isolation characteristics can be obtained by bringing the antenna 112 closer to the feeding point 112a. In addition, in the VSWR characteristic and the gain characteristic, there is no significant difference between the present embodiment and the first comparative example. Therefore, the parasitic element 113 is bent in an L shape so that the ground point 113b is an Rx antenna. The antenna characteristics such as the gain characteristics are not deteriorated even if the power feeding point 112a is close to 112.

  In the present embodiment, the distance between the ground point 113b of the parasitic element 113 and the feed point 112a of the Rx antenna 112 is close to 0.07λ. However, as another second comparative example, this distance is set to 0. The isolation characteristic in the case where the distance exceeds 09λ, for example, 0.1λ will be described below with reference to FIG. FIG. 5 is a graph showing VSWR characteristics, gain characteristics, and isolation characteristics of the second comparative example. The VSWR characteristics shown in FIGS. 5A and 5B and the gain characteristics shown in FIGS. 5C and 5D are all the same as those of the first comparative example shown in FIG. Also, it can be seen that the isolation characteristic shown in FIG. 5E is slightly higher than that of the first comparative example, but is lower than that of the present embodiment.

  From the antenna characteristics of the second comparative example, even if the parasitic element 113 is bent in an L shape and the grounding point 113b is brought close to the feeding point 112a of the Rx antenna 112, the distance is 0.09λ. If it exceeds, it can be seen that the isolation characteristics cannot be made sufficiently high. In the integrated antenna 100 of this embodiment, when the distance between the TRx antenna 111 and the Rx antenna 112 is 0.11λ to 0.14λ, the ground point 113b of the parasitic element 113 and the Rx antenna 112 are fed. The distance from the point 112a is preferably 0.09λ or less.

  As still another comparative example, a third comparative example in which the distance between the TRx antenna 111 and the Rx antenna 112 is 0.14λ, which is the largest in the range of 0.11λ to 0.14λ, will be described below. Explained. In order to increase the isolation between the TRx antenna 111 and the Rx antenna 112, it is preferable to increase the distance between them. However, since there is a need to make the integrated antenna as small as possible, the TRx antenna 111 is required. And the Rx antenna 112 cannot be made sufficiently large. Therefore, as a third comparative example, the parasitic element is not linearly bent like the first comparative example but is linear, and the distance between the TRx antenna 111 and the Rx antenna 112 is set to FIG. 6 shows antenna characteristics when 0.14λ, which is 0.02λ larger than the comparative example.

  The VSWR characteristics shown in FIGS. 6A and 6B and the gain characteristics shown in FIGS. 6C and 6D are all the same as those in the first comparative example shown in FIG. In addition, it can be seen that the isolation characteristic shown in FIG. 6E is similar to that of the first comparative example and is lower than that of the present embodiment. From this, it can be seen that even if the distance between the TRx antenna 111 and the Rx antenna 112 is increased from 0.13λ to 0.14λ, it is difficult to sufficiently improve the isolation characteristics. Rather than slightly increasing the distance between the TRx antenna 111 and the Rx antenna 112, the grounding point 113 of the parasitic element 113 is closer to the feeding point 112a of the Rx antenna 112 as in this embodiment. The isolation between the Rx antenna 111 and the Rx antenna 112 can be increased.

  Regarding the isolation characteristics between the TRx antenna and the Rx antenna, the lowest value of the isolation characteristic in the first embodiment (the highest value of S21) was compared with the lowest value in the first to third comparative examples. The results are shown in FIG. In FIG. 7, the horizontal axis is the distance between the ground point of the parasitic element and the feed point of the Rx antenna, and the vertical axis is the isolation (with the sign of S21 reversed). Is the lowest value plotted. Reference numeral 10 denotes the isolation magnitude in the first embodiment, and reference numerals 11 to 13 denote the isolation magnitudes in the first to third comparative examples, respectively. From the figure, it can be seen that the isolation 10 between the Rx antenna 111 and the Rx antenna 112 in the first embodiment is sufficiently higher than in the first to third comparative examples.

  An integrated antenna according to a second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a perspective view showing the configuration of the integrated antenna 200 of the second embodiment. In addition, illustration of the GPS antenna 101 which is an example of another antenna is abbreviate | omitted here. In the integrated antenna 200 of the present embodiment, in addition to bending the parasitic element 113 in an L shape, the Rx antenna 212 of the telephone antenna 210 is also bent in an L shape so that the parasitic element 113 is connected. The point 113b and the feeding point 212a of the Rx antenna 212 are further brought closer to each other. When the distance between the TRx antenna 111 and the Rx antenna 212 is 0.11λ to 0.14λ, the distance between the ground point 113b of the parasitic element 113 and the feed point 212a of the Rx antenna 212 is 0.06λ or less. It is good to do.

  As described above, the isolation characteristic when the grounding point 113b of the parasitic element 113 and the feeding point 212a of the Rx antenna 212 are brought closer to each other will be described with reference to FIG. FIG. 9 is a graph showing VSWR characteristics, gain characteristics, and isolation characteristics of the present embodiment. Here, the distance between the grounding point 113b of the parasitic element 113 and the feeding point 212a of the Rx antenna 212 is 0.04λ. When the isolation characteristic of the present embodiment shown in FIG. 9E is compared with the isolation characteristic of the first embodiment shown in FIG. 3E, the present embodiment is higher than the first embodiment. It can be seen that isolation characteristics can be obtained.

  An integrated antenna according to a third embodiment of the present invention in which the distance between the grounding point of the parasitic element and the feeding point of the Rx antenna is further reduced will be described with reference to FIG. FIG. 10 is a perspective view showing the configuration of the integrated antenna 300 of the third embodiment. Also here, illustration of the GPS antenna 101 which is an example of another antenna is omitted. In the present embodiment, in order to further reduce the distance between the ground point 113b of the parasitic element 113 and the feed point 312a of the Rx antenna 312, the Rx antenna 312 is further bent 90 degrees at the portion connected to the ground point 312b. Thus, the feeding point 312a is brought close to the ground point 113b of the parasitic element 113. In the embodiment shown in FIG. 10, the distance between the ground point 113b of the parasitic element 113 and the feed point 312a of the Rx antenna 312 is set to 0.1 by bending the Rx antenna 312 at a portion connected to the ground point 312b. It is set to 03λ.

  The isolation characteristics when the ground point 113b of the parasitic element 113 and the feed point 312a of the Rx antenna 312 are further brought closer as described above will be described with reference to FIG. FIG. 11 is a graph showing VSWR characteristics, gain characteristics, and isolation characteristics of the present embodiment. When the isolation characteristic of the present embodiment shown in FIG. 11E is compared with the isolation characteristic of the second embodiment shown in FIG. 9E, the present embodiment is higher than the second embodiment. It can be seen that isolation characteristics are obtained.

  In any of the above embodiments, the TRx antenna 111 is linear and arranged parallel to the left end side of the common ground plane 102. As a fourth comparative example, the TRx antenna 111 is also bent in an L shape. An example of the integrated antenna is shown in FIG. In this figure, the TRx antenna 911 is bent in an L shape with respect to the integrated antenna 300 of the third embodiment, so that the feeding point 911a of the TRx antenna 911, the grounding point 113b of the parasitic element 113, and Rx The feed points 312a of the antennas 312 are close to each other.

  In FIG. 12, the distance between the ground point 113b of the parasitic element 113 and the feed point 312a of the Rx antenna 312 is 0.03λ, which is the same as in the third embodiment. FIG. 13 shows VSWR characteristics, gain characteristics, and isolation characteristics in the fourth comparative example configured as described above. From FIG. 13 (e), when the TRx antenna 911 is also bent in an L shape and the feeding point 911a is brought close to the feeding point 312a of the Rx antenna 312, the isolation characteristic is deteriorated. Accordingly, it is preferable that the ground point 113b of the parasitic element 113 and only the feed point 312a of the Rx antenna 312 are brought close to each other, and the TRx antenna 111 arranged linearly is used as the TRx antenna.

  Note that the description in the present embodiment shows an example of the integrated antenna according to the present invention, and the present invention is not limited to this. The detailed configuration, detailed operation, and the like of the integrated antenna in this embodiment can be changed as appropriate without departing from the spirit of the present invention.

100, 300, 400, 500, 600, 700, 900 Integrated antenna 101, 902 GPS antenna 102, 201, 602, 802, 901 Ground plane 602a Current blocker 110, 310, 510, 903, 904 Telephone antenna 111 For TRx Antenna 111a, 112a, 312a Feeding point 111b, 112b, 113b, 312b, 513b Grounding point 112, 312 Rx antenna 113, 513, 909 Parasitic element 120, 320, 520 Telephone board 121, 122, 322, 521 Antenna element Forming part 123 Substrate main part 424, 724 Base plate 425 Separation slit

Claims (7)

An integrated antenna in which a telephone antenna is integrated with another antenna on a common ground plane,
The telephone antenna is
A first antenna and a second antenna having at least a radiating portion disposed adjacent to and parallel to two opposite sides of the common ground plane;
A parasitic element provided in proximity to and in parallel with the first antenna, and configured to diversity,
The grounding point side of the parasitic element is bent toward the second antenna, and the grounding point of the parasitic element is disposed between the feeding point of the first antenna and the feeding point of the second antenna. An integrated antenna characterized by When the wavelength of the transmission / reception wave of the telephone antenna is λ, the first antenna and the second antenna are arranged with a distance of 0.11λ or more and 0.14λ or less, and the parasitic element 2. The integrated antenna according to claim 1, wherein a grounding point is disposed at a distance of 0.09λ or less from a feeding point of the second antenna. The feeding point and grounding point of the second antenna are bent toward the first antenna, and the feeding point and grounding point of the second antenna are arranged close to the feeding point of the first antenna. The integrated antenna according to claim 1, wherein: When the wavelength of the transmission / reception wave of the telephone antenna is λ, the first antenna and the second antenna are arranged with a distance of 0.11λ or more and 0.14λ or less, and the parasitic element The integrated antenna according to claim 3, wherein the ground point is disposed at a distance of 0.06λ or less from the feeding point of the second antenna. The radiating portion, the feeding point, and the grounding point of the first antenna are arranged in a straight line along the edge of the common ground plane. Integrated antenna. The integrated antenna according to any one of claims 1 to 5, wherein the first antenna is a transmission / reception antenna. The integrated antenna according to any one of claims 1 to 6, wherein the first antenna and the second antenna are inverted F-type antennas.

Images