JP2006121219A - Multi-resonance planar antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-resonance planar antenna with a simple structure capable of obtaining a plurality of resonance frequencies. <P>SOLUTION: The multi-resonance planar antenna is configured with: a dielectric antenna board 10; a ground electrode layer 16 located on a lower side of the dielectric antenna board 10; an SDARS planar antenna radiation element 11 located on an upper side of the dielectric antenna board 10; a feeding point 15 provided to the SDARS planar antenna radiation element 11; and an annular GPS parasitic planar antenna radiation element 12 located on the upper side of the dielectric antenna board 10, electromagnetically coupled to the SDARS planar antenna radiation element 11, and for surrounding the SDARS planar antenna radiation element 11 at a prescribed gap. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multi-resonant planar antenna having a plurality of resonance frequencies.

  In general, a receiving antenna used for receiving services such as GPS (Global Positioning System) and SDARS (Satellite Digital Audio Radio Service) is a flat antenna (patch antenna) that can be easily reduced in size and thickness. Yes.

  The frequency bands of GPS and SDARS are different from each other. For this reason, in order to use both GPS and SDARS services, it is necessary to separately prepare a GPS reception antenna and a SDARS reception antenna, which leads to an increase in the number of components.

  Therefore, recently, a multi-resonant antenna that supports a plurality of frequency bands has attracted attention.

As such a multi-resonant antenna, a laminated antenna in which a plurality of antenna elements are laminated is known (for example, see Patent Document 1). Also known is a structure in which a rectangular patch antenna and a loop antenna are arranged on an antenna substrate and the rectangular patch antenna and the loop antenna are individually fed (see, for example, Patent Document 2).
JP 2003-283240 A JP 2003-152445 A

  However, since the laminated antenna as in Patent Document 1 has an extremely complicated structure, the workability is poor and the manufacturing cost increases.

  In addition, although the antenna of Patent Document 2 is not a laminated structure, it has a configuration in which a feeding unit for a rectangular patch antenna and a feeding unit for a loop antenna are separately provided, resulting in an increase in the number of parts around the feeding unit. Become. Further, since the antenna of Patent Document 2 is premised on that the rectangular patch antenna and the loop antenna operate independently of each other, the rectangular patch antenna is used in order to avoid the interaction between the rectangular patch antenna and the loop antenna. It is necessary to form a loop antenna at a sufficient distance from the antenna, thereby causing an increase in the area of the entire antenna.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a multi-resonance planar antenna capable of obtaining a plurality of resonance frequencies with a simple structure.

  In order to solve the above-described problem, a multi-resonant planar antenna according to the first aspect of the present invention includes a dielectric antenna substrate, a ground electrode layer disposed on a lower surface of the dielectric antenna substrate, and the dielectric antenna substrate. A planar antenna radiating element disposed on the upper surface, a feeding point provided on the planar antenna radiating element, and a predetermined gap that is disposed on the upper surface of the dielectric antenna substrate and is electromagnetically coupled to the planar antenna radiating element. And an annular parasitic planar antenna radiating element surrounding the planar antenna radiating element.

  In this multi-resonant planar antenna, an annular parasitic planar antenna radiating element is disposed so as to surround the planar antenna radiating element with a predetermined gap electromagnetically coupled to the planar antenna radiating element. The point is provided only on the planar antenna radiating element. The parasitic planar antenna radiating element operates in a parasitic manner by electromagnetic coupling with the planar antenna radiating element. With such a one-point feeding method, two resonant frequencies, a resonant frequency corresponding to a planar antenna radiating element and a resonant frequency corresponding to an annular parasitic planar antenna radiating element, can be obtained. In comparison, the structure can be simplified, and the number of parts around the power feeding section can be reduced.

  According to a second aspect of the present invention, in the configuration of the first aspect, the width w of the gap is such that 0 <w ≦ 0, where λ is a free space wavelength at resonance of the parasitic planar antenna radiating element. 002λ.

  By arranging an annular parasitic planar antenna radiating element around the planar antenna radiating element with an extremely narrow gap in this way, the mutual coupling between the planar antenna radiating element and the parasitic planar antenna radiating element is effectively utilized. In particular, it is possible to improve the gain on the parasitic planar antenna radiating element side.

  According to a third aspect of the present invention, the planar antenna radiating element has a rectangular shape, and one of the two corners facing each other in the diagonal direction of the planar antenna radiating element. Is formed with a first cutout portion for degenerate separation, the parasitic planar antenna radiating element has a rectangular shape, and a set corresponding to the other corners of the planar antenna radiating element. A second notch for degenerate separation is formed at the corner.

  With this configuration, one of the planar antenna radiating element and the parasitic planar antenna radiating element can have right-handed circular polarization characteristics, and the other can have left-handed circular polarization characteristics.

  According to a fourth aspect of the present invention, in the configuration of the first aspect, the present invention further includes a pair of notches formed on an inner peripheral edge of the parasitic planar antenna radiating element and facing each other with the planar antenna radiating element interposed therebetween. It is characterized by doing.

  Since the impedance of the parasitic planar antenna radiating element can be adjusted by providing a pair of notches on the inner peripheral edge of the parasitic planar antenna radiating element in this way, the best axial ratio of the parasitic planar antenna radiating element The gain at can be improved.

  According to the present invention, it is possible to realize a multi-resonance planar antenna capable of obtaining a plurality of resonance frequencies with a simple structure.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the structure of a multi-resonant planar antenna according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1A is a plan view of the multi-resonant planar antenna according to the present embodiment as viewed from above, and FIG. 1B is a side view of the multi-resonant planar antenna. FIG. 2 is a cross-sectional view taken along the line II of FIG.

  This multi-resonant planar antenna is realized as a microstrip antenna having two resonance frequencies, for example, a GPS band (1.5 GHz) and an SDARS band (2.6 GHz in Japan and 2.3 GHz in the United States). In this multi-resonant planar antenna, a ground electrode layer 16 is formed on the lower surface of the dielectric 10 functioning as a dielectric antenna substrate, and the upper surface of the dielectric 10 is arranged so as to face the ground electrode layer 16. One antenna radiating element 11 and a second antenna radiating element 12 are arranged. As the dielectric 10, for example, an air layer substrate or the like can be used in addition to a resinous substrate.

  The first antenna radiating element 11 is a planar antenna radiating element for SDARS. The first antenna radiating element 11 is made of a conductive material (patch) such as a copper foil formed on the upper surface of the dielectric 10. The first antenna radiating element 11 has a rectangular shape, and one set of corners (a pair of corners in the upper left and lower right in the figure) of the two corners facing each other in the diagonal direction. ) Are formed with cut-out portions 11a and 11b for degeneration and separation cut at 45 degrees, respectively. The first antenna radiating element 11 can have a left-handed circular polarization characteristic by the cut-out portions 11a and 11b for degeneracy separation.

  The first antenna radiating element 11 is provided with a feeding point 15 at a position offset from the center thereof. The feed point 15 is connected to a low noise amplifier (LNA) 17 disposed immediately below the ground electrode layer 16 through a feed line 15 a penetrating the dielectric 10.

  The second antenna radiating element 12 is a planar antenna radiating element for GPS, and is realized as an annular parasitic planar radiating element having no feeding point. The second antenna radiating element 12 is made of an annular conductive material such as a copper foil formed on the upper surface of the dielectric 10. The second antenna radiating element 12 is disposed around the first antenna radiating element 11 via a gap 13 including a predetermined gap so as to be electromagnetically coupled to the first antenna radiating element 11.

  That is, the second antenna radiating element 12 is formed on the upper surface of the dielectric 10 so as to surround the first antenna radiating element 11, and the rectangular inner periphery of the second antenna radiating element 12 and the first antenna are formed. A gap 13 separates the rectangular outer periphery of the radiating element 11. The second antenna radiating element 12 operates in a parasitic manner by electromagnetic coupling with the first antenna radiating element 11.

In the present embodiment, the width of the gap 13 is used in order to efficiently receive GPS band radio waves by utilizing the interaction between the second antenna radiating element 12 and the first antenna radiating element 11. Is set extremely narrow. According to the experiments of the present inventors, the width w of the gap 13 is
0 <w ≦ 0.002λ
It is preferable that

  Here, λ is a free space wavelength at the time of resonance of the second antenna radiating element 12. The resonance frequency of the second antenna radiating element 12 is designed to be a GPS center frequency of 1.575 GHz. In this embodiment, the width w of the gap 13 is set to 0.3 mm.

  With this structure, it becomes possible to receive radio waves in the GPS band by utilizing the interaction between the second antenna radiating element 12 and the first antenna radiating element 11, and it is possible to increase the gain for the radio waves in the GPS band. It becomes. Also, with this structure, the external dimensions of the second antenna radiating element 12 can be made smaller than when a single GPS antenna with the same performance is configured under the same conditions.

  One corresponding to the corner of the first antenna radiating element 11 on the side where the notches 11a and 11b are not formed, out of the two corners facing each other in the diagonal direction of the second antenna radiating element 12. Cutout portions 12a and 12b for degenerative separation are formed at corners of the set (a pair of corners in the figure, upper right and lower left), respectively. The second antenna radiating element 12 can have a right-handed circularly polarized wave characteristic by the degenerate separation notches 12a and 12b.

  It is the outer shape of the second antenna radiating element 12 that affects the circular polarization characteristics of the second antenna radiating element 12. For this reason, the notch portions 11a and 11b of the first antenna radiating element 11 located on the inner peripheral side of the second antenna radiating element 12 have circular polarization characteristics of the second antenna radiating element 12. Does not affect.

  Further, a pair of notches 14a for adjusting the impedance of the second antenna radiating element 12 are disposed on the inner peripheral edge of the second antenna radiating element 12 at positions facing each other with the first planar antenna radiating element 11 in between. 14b is formed. In the present embodiment, the cutout portions 14a and 14b are positions rotated clockwise by 45 degrees with respect to the longer diagonal of the second antenna radiating element 12 (the line connecting the upper left and the lower right). In other words, the second antenna radiating element 12 is formed at the center of the upper side and the center of the lower side, respectively, of the inner periphery.

  Each of the notches 14a and 14b has, for example, a rectangular shape, and the width and depth thereof are set to the same level as the width w of the gap 13, in this example, about 0.3 mm.

  The positions and sizes of the notches 14a and 14b are adjusted while observing the input impedance of the second antenna radiating element 12 using a measuring instrument such as a network analyzer. With the cutout portions 14a and 14b, it is possible to optimally adjust the impedance of the second antenna radiating element 12 so that the best axial ratio of the second antenna radiating element 12 becomes the impedance matching point. Further, the shape of each of the notches 14a and 14b is not limited to a rectangle.

  Next, a configuration example of the low noise amplifier (LNA) 17 will be described with reference to FIG.

  The low noise amplifier (LNA) 17 includes a single diplexer 21 and two amplifiers (AMP) 22 and 23. The diplexer (Diplexer) 21 is configured to pass a high-frequency signal corresponding to the frequency band of the GPS band and a high-frequency signal corresponding to the frequency band of the SDARS band.

  A high-frequency signal in the GPS band received by the multi-resonant planar antenna is sent to an amplifier (AMP) 22 via a diplexer (Diplexer) 21 and amplified by the amplifier (AMP) 22 and then externally connected via, for example, a coaxial cable or the like. Is output. A high frequency signal in the SDARS band received by the multi-resonant planar antenna is sent to an amplifier (AMP) 23 through a diplexer (Diplexer) 21, and after being amplified by the amplifier (AMP) 23, for example via a coaxial cable or the like. Output to the outside.

  The low noise amplifier (LNA) 17 can extract signals corresponding to the GPS band and the SDARS band even in an environment where signals of both the GPS band and the SDARS band are received simultaneously. The signal received by the multi-resonance planar antenna is amplified by a low noise amplifier (LNA) 17 and then led out through a single coaxial cable or the like, and the GPS band and the SDARS band by a diplexer provided on the receiver side. You may make it take out the signal corresponding to each.

  FIG. 4 shows the VSWR characteristics of the multi-resonant planar antenna of the present embodiment. The horizontal axis of the graph in FIG. 4 indicates frequency, and the vertical axis indicates VSWR. As can be seen from the graph of FIG. 4, the multi-resonance planar antenna of this embodiment has two resonance frequencies of 1.575 GHz corresponding to GPS and 2.642 GHz corresponding to SDARS.

  FIG. 5A shows a radiation pattern in the GPS band of the multi-resonant planar antenna of this embodiment, and FIG. 5B shows an elevation angle of −90 degrees to +90 degrees in the radiation pattern of FIG. This is an enlarged view of the gain characteristics within the range of. The width w of the gap 13 is set to 0.3 mm. As can be seen from FIGS. 5A and 5B, the multi-resonant planar antenna of this embodiment operates well as a right-handed circularly polarized antenna for the GPS band.

  FIG. 6A shows a radiation pattern in the SDARS band of the multi-resonant planar antenna of this embodiment, and FIG. 6B shows an elevation angle of −90 degrees to +90 degrees in the radiation pattern of FIG. This is an enlarged view of the gain characteristics within the range of. The width w of the gap 13 is set to 0.3 mm. As can be seen from FIGS. 6A and 6B, the multi-resonant planar antenna of this embodiment operates well as a left-handed circularly polarized antenna for the SDARS band.

  7 and 8 show radiation patterns corresponding to the GPS band and the SDARS band when the width w of the gap 13 is set to 0.5 mm.

  As can be seen from comparison between FIGS. 5 and 7 and FIGS. 6 and 8, the case where the width w of the gap 13 is 0.3 mm as compared with the case where the width w of the gap 13 is 0.5 mm. Can get high gain. Further, it has been experimentally confirmed that if the width w of the gap 13 is 0.4 mm (λ = 0.002) or less, a practically sufficient gain can be obtained.

  Thus, the gain for the GPS band and the SDARS band can be improved by setting the width w of the gap 13 to 0.4 mm (λ = 0.002) or less, and 0.3 mm in this example. Particularly for the GPS band, the second antenna radiating element 12 and the first antenna radiating element are set by setting the width w of the gap 13 to 0.4 mm (λ = 0.002) or less, in this example, 0.3 mm. 11 can be used effectively, and the gain can be greatly improved.

  Next, with reference to FIG. 9, the impedance adjustment by the notches 14a and 14b formed at the inner periphery of the second antenna radiating element 12 will be described.

  FIG. 9A shows VSWR characteristics with respect to the GPS band before impedance adjustment. The position of the best axial ratio point of the second antenna radiating element 12 is mainly determined by the notches 12a and 12b for degeneracy separation. For this reason, as shown in FIG. 9A, the best impedance point of the second antenna radiating element 12 may deviate from the best axial ratio. Since the notches 14a and 14b are formed on the inner peripheral edge of the second antenna radiating element 12, the impedance of the second antenna radiating element 12 can be adjusted, which is shown in FIG. 9B. Thus, the impedance best point can be matched with the vicinity of the axial ratio best point. Note that in FIG. 9B, the impedance best point and the axial ratio best point almost overlap each other, so that they are shown as one point. Thereby, the gain at the best axial ratio can be improved.

  As described above, in the multi-resonance planar antenna according to the present embodiment, the feeding point 15 is provided only on the first antenna radiating element 11 and the extremely narrow gap 13 is placed around the first antenna radiating element 11. By adopting a one-point feed structure in which two antenna radiating elements 12 are arranged, the structure can be simplified as compared with the laminated antenna. Further, since the antenna characteristics on the low frequency side corresponding to the second antenna radiating element 12 can be improved by the interaction between the first antenna radiating element 11 and the second antenna radiating element 12, the second antenna Even if the area of the radiating element 12 is not increased, desired antenna characteristics for the low frequency side can be obtained.

  In the present embodiment, the case where each of the first antenna radiating element 11 and the second antenna radiating element 12 is rectangular has been described. However, the first antenna radiating element 11 and the second antenna radiating element 12 are Each may be formed in a circular shape.

  In this embodiment, SDARS and GPS have been described as examples. However, the present invention can be similarly applied to other frequency bands.

  Furthermore, the present invention is not limited to the above embodiment, and various modifications can be made.

The figure which shows the structure of the multiple resonance planar antenna which concerns on one Embodiment of this invention. Sectional drawing which shows the structure of the multiple resonance planar antenna of the embodiment. The block diagram which shows the structural example of the low noise amplifier provided in the multi-resonance planar antenna of the embodiment. The figure which shows the VSWR characteristic of the multi-resonance planar antenna of the embodiment. The 1st figure which shows the radiation pattern characteristic in the GPS band of the multi-resonance plane antenna of the embodiment. The 1st figure which shows the radiation pattern characteristic in the SDARS zone | band of the multi-resonance planar antenna of the embodiment. The 2nd figure which shows the radiation pattern characteristic in the GPS band of the multi-resonance planar antenna of the embodiment. The 2nd figure which shows the radiation pattern characteristic in the SDARS band of the multi-resonance planar antenna of the same embodiment. The figure for demonstrating the impedance adjustment of the multi-resonance planar antenna of the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Dielectric material, 11 ... 1st antenna radiation element, 12 ... 2nd antenna radiation element, 13 ... Gap, 14a, 14b ... Notch part for impedance adjustment, 15 ... Feeding point, 16 ... Ground electrode layer, 17 ... low noise amplifier.

Claims (4)

A dielectric antenna substrate;
A ground electrode layer disposed on a lower surface of the dielectric antenna substrate;
A planar antenna radiating element disposed on an upper surface of the dielectric antenna substrate;
A feeding point provided in the planar antenna radiating element;
An annular parasitic planar antenna radiating element that is disposed on the top surface of the dielectric antenna substrate and surrounds the periphery of the planar antenna radiating element with a predetermined gap electromagnetically coupled to the planar antenna radiating element. A featured multi-resonant planar antenna. The width w of the gap is λ, which is a free space wavelength at resonance of the parasitic planar antenna radiating element.
0 <w ≦ 0.002λ
The multi-resonant planar antenna according to claim 1, wherein The planar antenna radiating element has a rectangular shape, and a first notch for degenerate separation is provided at one of the two corners facing each other in the diagonal direction of the planar antenna radiating element. Part is formed,
The parasitic planar antenna radiating element has a rectangular shape, and a second cutout portion for degenerate separation is formed at one set of corners corresponding to the other corners of the planar antenna radiating element. The multi-resonant planar antenna according to claim 1, wherein:   The multi-resonant planar antenna according to claim 1, further comprising a pair of notches formed on an inner peripheral edge of the parasitic planar antenna radiating element and facing each other with the planar antenna radiating element interposed therebetween.

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