JP2005124061A - Loop antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a loop antenna device having almost no flat-face directivity or capable of setting desired flat-face directivity. <P>SOLUTION: The loop antenna device is composed of a dielectric substrate mounted on a conducting flat plate and an antenna element, which includes a conductor pattern formed on the substrate. Both ends of the conductor pattern are connected to the conducting flat plate and formed in a shape like a belt on the circumferential face of the dielectric substrate. The antenna element is composed of a conductor and the conductor pattern. One end of the conductor is connected to the conductor pattern and the other end of it is connected to a power feeding point on the conducting flat plate. In the antenna element, a pair of half-loop-shaped elements from the end connected to the conducting flat plate to the end of the conductor connected to the power feeding point has a symmetrical shape, and a dielectric substrate has a width wider than the belt-shaped conductor pattern at the circumferential face, where the belt-shaped conductor pattern is formed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention generally relates to a loop antenna device, and more particularly to a loop antenna device having a conductor pattern formed on a surface of a dielectric substrate as a part of an antenna element.

  Conventionally, as shown in FIG. 1A, a pair of symmetrical loops in which two loop-shaped antenna elements each having a length corresponding to one wavelength (λ) are arranged and fed at one point. A double-loop antenna is known as an antenna element made of (see, for example, Patent Document 1).

  The double loop antenna has an advantage that high gain and wide band antenna characteristics can be obtained as compared with the monopole antenna.

Further, as shown in FIG. 1B, there is also known a double / half loop antenna in which a double loop antenna is cut in half at the center and provided on a ground plane (conductor flat plate). As in the case of the single loop, the dual / half-loop antenna also functions as an antenna equivalent to the double-loop antenna shown in FIG. 1A by combining the actual conductor portion and the electric image portion by the principle of mirror image. .
Japanese Utility Model Publication No. 2-86208

  As shown in FIG. 2A, in the double loop antenna, currents flowing through the antenna elements # 1 to # 3 are in phase during resonance. This twin loop antenna can be approximated to three dipole antennas as shown in FIG. In this situation, the electromagnetic waves from the respective elements # 1 to # 3 are in a relationship of strengthening each other in the Y direction and in a relationship of weakening each other in the X direction.

  Therefore, the conventional twin loop antenna has a characteristic that the radiation in the Y direction is relatively strong and the radiation in the X direction is relatively weak, and the horizontal plane (XY plane) directivity is approximately elliptical.

  The present invention is intended to improve the antenna directivity unique to such a loop antenna, and provides a loop antenna device in which the horizontal plane directivity is substantially omnidirectional or any horizontal plane directivity can be set. The main purpose is to do.

  In order to achieve the above object, a first aspect of the present invention is a loop antenna device having a dielectric substrate placed on a conductive plate and an antenna element including a conductor pattern formed on the substrate. The conductor pattern has both ends connected to a conductor flat plate, is formed in a strip shape on the outer peripheral surface of the dielectric substrate, the antenna element passes through the dielectric substrate, and one end forms a conductor pattern. The other end is connected to the feeding point on the conductor flat plate, and the conductor pattern, and from the end connected to the conductor flat plate to the end of the conducting wire connected to the feeding point A pair of half-loop elements having a symmetrical shape, and the dielectric substrate has a wider width on the outer peripheral surface on which the band-shaped conductor pattern is formed than the band-shaped conductor pattern. Antenna device A.

  According to this aspect, the electric field is strengthened in the conventional low gain direction and the electric field is weakened in the conventional high gain direction in the antenna horizontal plane as compared with the bi-half loop antenna in which no dielectric passes through the loop. Therefore, the horizontal plane directivity of the twin / half loop antenna can be made substantially uniform in all directions.

  In order to achieve the above object, a second aspect of the present invention is a loop antenna device having a dielectric substrate placed on a conductive plate and an antenna element including a conductor pattern formed on the substrate. The conductor pattern has one end connected to the conductor flat plate, the other end connected to a feeding point provided on the conductor flat plate, and is formed in a strip shape on the outer peripheral surface of the dielectric substrate. The element is a loop antenna device having a half-loop shape, and the dielectric substrate has a wider width than the belt-like conductor pattern on the outer peripheral surface on which the belt-like conductor pattern is formed.

  According to this aspect, compared to a half-loop antenna in which no dielectric passes through the loop, the electric field is strengthened in the conventional low gain direction and the electric field is weakened in the conventional high gain direction in the antenna horizontal plane. The horizontal directivity of the half-loop antenna can be made substantially uniform in all directions.

  A third aspect of the present invention for achieving the above object is a loop antenna apparatus having an antenna element including a conductor pattern formed on a dielectric substrate, wherein the conductor pattern is fed at a predetermined position. Connected to a point, formed in a strip shape on the outer peripheral surface of the dielectric substrate, the antenna element has a loop shape, and the dielectric substrate is formed on the outer peripheral surface on which the strip-shaped conductor pattern is formed. The loop antenna device has a wider width than the strip-shaped conductor pattern.

  According to this aspect, the electric field is strengthened in the conventional low gain direction and the electric field is weakened in the conventional high gain direction in the antenna horizontal plane as compared with the loop antenna in which no dielectric passes through the loop. The horizontal plane directivity of the antenna can be made substantially uniform in all directions.

  In the first to third embodiments, the dielectric forming the “dielectric substrate” is, for example, ceramic. Epoxy resin such as glass epoxy, polyether resin such as PPO, BT resin, Teflon (registered trademark) Any dielectric material such as PTFE resin may be used.

  In the first to third aspects, since the effective dielectric constant of the dielectric substrate changes depending on the selection of the dielectric constant ε of the dielectric substrate and / or the setting of the length of the lateral width, both these parameters are set. By selecting appropriately, a desired horizontal plane directivity can be obtained.

  In the first to third aspects, a strip-like groove is provided on the outer peripheral surface of the dielectric substrate, the conductor pattern is formed in the groove, and a desired vertical direction is formed according to the depth of the groove. It is also possible to obtain surface directivity.

  Further, as an application example of the present invention, two loop antenna devices according to the first aspect are combined, a concave portion is provided on a contact surface with the conductor flat plate of one of the loop antenna devices, and the other loop antenna device is provided. Is designed to be accommodated in the recess when installed on the conductor flat plate, and is a two-frequency compatible loop in which the feeding line and feeding point are shared for both the loop antenna devices and impedance matching is taken. An antenna device is also possible.

  According to the present invention, it is possible to provide a loop antenna device in which the horizontal plane directivity is substantially omnidirectional or an arbitrary horizontal plane directivity can be set.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the accompanying drawings. Note that the basic concept, main hardware configuration, operating principle, basic control method, and the like of an antenna device having a loop-shaped antenna element are known to those skilled in the art, and thus detailed description thereof is omitted.

  First, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 3 is a perspective view of the loop antenna device 300 according to the present embodiment.

  The loop antenna device 300 includes an antenna composed of a conductor pattern 302 formed on a substantially rectangular parallelepiped ceramic base 301 and a central conductor 304 connecting the conductor pattern 302 and the feeding point 303 through a hole formed in the ceramic base 301. It has an element. For convenience, the thickness of the conductor pattern 302 is not shown in FIG.

  As shown in the figure, the loop antenna device 300 is a twin / half loop antenna and is installed on a ground plane (conductor flat plate) 305. The ground plane 305 may be any conductor as long as it can function as a ground.

  The formation method of the conductor pattern 302 may be arbitrary, and for example, the same method (for example, vapor deposition) as in the case of the microstrip antenna can be used.

  For example, the central conductor 304 is inserted into a hole formed in the ceramic substrate 301 after the conductor pattern 302 is formed, and is soldered to the conductor pattern 302.

  In this way, the conductor pattern 302 is formed on the ceramic base 301 that is a dielectric, and this is connected to the feeding point 303 by the conductive wire 304, whereby the half ring of the half-loop antenna element is the dielectric. It is assumed that the ceramic penetrates and the center conductor 304 is surrounded by the ceramic.

  FIG. 4 is a cross-sectional view of the loop antenna device 300 of FIG. 3 cut along the XZ plane on the conductor pattern 302. As shown in the drawing, two half loops constituted by the conductor pattern 302 and the conductive wire 304 are filled with ceramic inside.

Here, considering the radiation in the X direction where the gain is weak in the conventional dual (.half) loop antenna, the electromagnetic wave 401 radiated in the X direction from the antenna element # 1 (= the central conducting wire 304) is generated in the ceramic substrate 301. Therefore, a phase difference is generated between the current 402 and the current 402 passing through the conductor pattern 302. Here, by appropriately selecting the dielectric constant of the ceramic substrate 301 epsilon, in the X-direction far field P _1, an electromagnetic wave from the case of conventional dielectric without antenna elements # 1 to 3 were destructively with each other It can be a mutually reinforcing relationship.

FIG. 5 is a top view of the loop antenna device 300 of FIG. As shown in the drawing, W ₁ and W ₂ > 0 in order to make the dielectric penetrate through the loop.

Here, in the case of radiation in the Y direction where the conventional dual (.half) loop antenna has a strong gain, the electromagnetic wave 501 radiated in the Y direction from the antenna element # 1 (= the central conducting wire 304) Therefore, the phase is shifted as compared with the case of traveling in the air. On the other hand, the electromagnetic wave 502 radiated from the antenna elements # 2 and 3 which are part of the conductor pattern 302 formed on the side surface of the ceramic base 301 travels in the air without passing through the dielectric. Here, by appropriately selecting the lateral width W ₂ (or W ₁ ) of the ceramic substrate 301, the antenna elements that have strengthened each other in the Y-direction far field P ₂ due to the same phase in the case of no conventional dielectric. The electromagnetic waves from # 1 to # 3 can be made to weaken each other.

As described above, according to the present embodiment, by appropriately selecting the dielectric constant ε of the ceramic substrate 301, it is possible to increase the radiation in the X direction where the gain is relatively weak in the conventional double loop antenna, By appropriately designing the lateral widths W ₁ and W ₂ of the ceramic substrate 301, the radiation in the Y direction, which has a relatively strong gain in the conventional dual loop antenna, can be weakened. In addition, the horizontal plane directivity of the double loop antenna, which is elliptical and non-uniform depending on the shape, can be made to be substantially uniform in all directions.

  Next, Embodiment 2 of the present invention will be described with reference to FIGS. The loop antenna device according to the present embodiment has a configuration that is substantially similar to that of the first embodiment described above. However, in Example 1, the aim is mainly to achieve uniform horizontal plane directivity in all directions, whereas in this example, the shape of the ceramic substrate is appropriately designed to be strong or weak in a specific direction. The aim is to achieve a desired horizontal plane directivity with gain.

  More specifically, in Example 1 described above, it is assumed that the ceramic base 301 is a substantially rectangular parallelepiped, and the horizontal plane directivity is mainly considered in the four directions of the X direction (+/−) and the Y direction (+/−). However, the shape of the ceramic substrate of the loop antenna device according to the present invention is not limited to a rectangular parallelepiped, but can be any shape, and in this embodiment, the shape is devised.

  FIG. 6 is a top view of an example of the loop antenna device according to the present embodiment. The same components as those in the first embodiment are denoted by the same reference numerals.

  When the ceramic base 301a of the loop antenna device shown in FIG. 6 focuses on electromagnetic waves emitted radially from the central conductor 304, the width of the dielectric is short in the direction A and the width of the dielectric in the direction B as shown in the figure. Is long. Therefore, as described above, the antenna gain is strong in the direction A and the antenna gain is weak in the direction B.

  Therefore, according to the loop antenna device shown in FIG. 6, the antenna horizontal plane directivity having directivity with respect to the direction A rather than the direction B can be realized.

  In this way, by changing the thickness of the dielectric through which the electromagnetic wave radiated from the central conductor 304 passes, the relationship between the electromagnetic waves radiated from the antenna elements # 1 to # 3 in a specific direction is weakened or strengthened. Can be set to

  The ceramic substrate 301a shown in FIG. 6 is merely an example, and for example, a substantially cross-shaped ceramic substrate 301b as shown in FIG. 7 or a substantially octagonal ceramic substrate 301c as shown in FIG. 8 is possible.

  Furthermore, since the shape of the ceramic substrate in the loop antenna device according to the present invention can be arbitrarily designed in the height direction (that is, the direction perpendicular to the ground plane 305), for example, as shown in FIG. By making the ceramic substrate around the body pattern 302 higher than the height of the conductor pattern, the antenna gain can be weakened even in the Y direction upward. That is, a desired vertical surface directivity can be obtained by making a difference in height between the conductor pattern 302 and the ceramic substrate.

  An example of the loop antenna device according to the present embodiment shown in FIG. 9 can be easily manufactured by, for example, forming a belt-like groove on the outer periphery of the ceramic substrate and depositing a conductor pattern on the bottom surface of the groove. is there.

  Thus, according to the present embodiment, desired horizontal and vertical plane directivities can be realized by appropriately designing the shape of the ceramic substrate.

  Next, Embodiment 3 of the present invention will be described with reference to FIGS. The loop antenna device according to the present embodiment has a structure in which two loop antenna devices according to the first embodiment having different sizes are stacked, and is capable of supporting two frequencies.

  FIG. 10 is an assembly diagram of the two-frequency loop antenna device according to the present embodiment. In the present embodiment, two large and small loop antenna devices 300 according to the first embodiment are used. The smaller loop antenna device is basically the same as the loop antenna device 300, and the larger loop antenna device 300a is sufficient to completely accommodate the smaller loop antenna device 300 on the contact surface with the ground plane 305. A recess (recess) of a size is provided.

  FIG. 11 is a cross-sectional view of the dual-frequency loop antenna device according to the present embodiment cut along the XZ plane on the conductor pattern 302.

  As shown in the figure, the outer loop antenna device 300a and the inner loop antenna device 300 share a feeding point 303 and a central conductor 304a. By adopting impedance matching for both in such a configuration, the outer and inner loop antennas can resonate at different frequencies, and as a result, the entire apparatus can be adapted to two frequencies.

  Further, a gap 1101 is provided between the inner wall of the recess provided in the ceramic base 301e of the outer loop antenna device 300a and the surface of the inner loop antenna device 300 (particularly, the surface of the conductor pattern 302). Since the effective dielectric constant changes when the conductor pattern 302 is sandwiched between the dielectrics from above and below, the inner loop is designed by designing the ceramic substrate 301e (indentation) so as to ensure such a gap 1101. The antenna device 300 can function in the same manner as in the first embodiment.

  Thus, according to the present embodiment, it is possible to realize a loop antenna device that can easily cope with two frequencies by using two loop antenna devices according to the present invention.

  It should be noted that also in this embodiment, the shape of the ceramic base can be arbitrarily designed according to the desired directivity.

  The first to third embodiments of the present invention have been described above. However, the “ceramic substrate” in the above description is not limited to ceramic, and may be a substrate formed of any material as long as it is a dielectric. For example, a substrate formed of a dielectric material such as an epoxy resin such as glass epoxy, a polyether resin such as PPO, a PTFE resin such as BT resin or Teflon (registered trademark) can be considered as an alternative.

  The present invention can be used as an omnidirectional antenna or a directional antenna in a communication system such as a wireless LAN. The content of the communication method and data to be communicated is not limited.

(A) It is the schematic of the conventional double loop antenna. (B) It is the schematic of the conventional twin and half loop antenna. (A) It is the schematic which shows the electric current which flows into the conventional double loop antenna at the time of resonance. (B) It is the schematic which shows three dipole antennas equivalent to the twin loop antenna of Fig.2 (a). It is a perspective view of the loop antenna apparatus which concerns on Example 1 of this invention. It is sectional drawing which cut the loop antenna apparatus which concerns on Example 1 of this invention on the conductor pattern at XZ plane. It is a top view of the loop antenna apparatus which concerns on Example 1 of this invention. It is a top view of an example of the loop antenna apparatus which concerns on Example 2 of this invention. It is a top view of another example of the loop antenna apparatus which concerns on Example 2 of this invention. It is a top view of another example of the loop antenna apparatus which concerns on Example 2 of this invention. It is a perspective view of another example of the loop antenna apparatus which concerns on Example 2 of this invention. It is an assembly drawing of the loop antenna device corresponding to 2 frequencies which concerns on Example 3 of this invention. It is sectional drawing which cut | disconnected the 2 frequency corresponding | compatible loop antenna apparatus which concerns on Example 3 of this invention on the conductor pattern at XZ plane.

Explanation of symbols

300, 300a Loop antenna device 301, 301a, 301b, 301c, 301d, 301e Ceramic substrate 302 Conductor pattern 303 Feeding point 304, 304a Conductor 305 Ground plate 401, 402, 501, 502 Electromagnetic wave 1101 Air gap

Claims (8)

A loop antenna device having a dielectric substrate placed on a conductive plate and an antenna element including a conductor pattern formed on the substrate,
The conductor pattern is connected to a conductor flat plate at both ends, and is formed in a strip shape on the outer peripheral surface of the dielectric substrate,
The antenna element includes a conductive wire that passes through the dielectric substrate, has one end connected to a conductor pattern and the other end connected to a feeding point on a conductor plate, and the conductor pattern. A pair of half-loop elements from the end connected to the flat plate to the end of the conducting wire connected to the feeding point has a symmetrical shape,
The loop antenna device according to claim 1, wherein the dielectric substrate has a wider width on the outer peripheral surface on which the strip-shaped conductor pattern is formed than the strip-shaped conductor pattern. A loop antenna device having a dielectric substrate placed on a conductive plate and an antenna element including a conductor pattern formed on the substrate,
The conductor pattern has one end connected to the conductor flat plate, the other end connected to a feeding point provided on the conductor flat plate, and is formed in a strip shape on the outer peripheral surface of the dielectric substrate,
The antenna element has a half-loop shape,
The loop antenna device according to claim 1, wherein the dielectric substrate has a wider width on the outer peripheral surface on which the strip-shaped conductor pattern is formed than the strip-shaped conductor pattern. A loop antenna apparatus having an antenna element including a conductor pattern formed on a dielectric substrate,
The conductor pattern is connected to a feeding point at a predetermined position, and is formed in a strip shape on the outer peripheral surface of the dielectric substrate,
The antenna element has a loop shape,
The loop antenna device according to claim 1, wherein the dielectric substrate has a wider width on the outer peripheral surface on which the strip-shaped conductor pattern is formed than the strip-shaped conductor pattern. The loop antenna device according to any one of claims 1 to 3,
A loop antenna device, wherein a dielectric constant of the dielectric substrate is selected according to desired horizontal plane directivity. The loop antenna device according to any one of claims 1 to 3,
A loop antenna device characterized in that the width is set according to a desired horizontal plane directivity. The loop antenna device according to any one of claims 1 to 3,
A loop antenna device, wherein a belt-like groove is provided on an outer peripheral surface of the dielectric substrate, and the conductor pattern is formed in the groove. The loop antenna device according to claim 6, wherein
A loop antenna apparatus, wherein the depth of the groove is set according to desired vertical plane directivity. A loop antenna device for two frequencies, which is a combination of two loop antenna devices according to claim 1,
A concave portion is provided on a contact surface with the conductor flat plate of one of the loop antenna devices,
Designed to be housed in the recess when the other loop antenna device is installed on the conductor flat plate,
A dual-frequency loop antenna apparatus characterized by sharing a feeding line and a feeding point for both the loop antenna apparatuses and taking impedance matching.

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