JP5617736B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device that has two antennas on the same substrate and can reduce mutual coupling between the antennas.

  Conventionally, systems that use the same frequency band on the same substrate have been developed in communication devices. For example, a 2.4 GHz band communication system such as Bluetooth (registered trademark) or wireless LAN can be used. When designing antennas having the same frequency on the same substrate, there is a problem that the antennas influence each other, and as a result, the performance of each antenna deteriorates. For this reason, in order to reduce the mutual coupling of the respective antennas, it is necessary to increase the distance between the respective antennas, and the antenna area increases, leading to an increase in the size of the entire apparatus.

  As a countermeasure against such mutual coupling, for example, Patent Document 1 discloses an antenna mutual coupling neutralizer that neutralizes coupling between a pair of patch antennas used in a mobile communication system. A configuration has been proposed that provides two capacitors, first and second terminations, and is selected to neutralize the reverse mutual coupling between the paired patch antennas over a predetermined frequency band.

  Patent Document 2 proposes an antenna device having a pair of L-shaped folded monopoles arranged symmetrically on a ground plate, a bridge portion, a radiating strip portion, a feeding strip portion rising at a right angle, and a short-circuit strip portion. Has been.

Japanese Patent Laid-Open No. 10-178314 JP 2009-206847 A

However, the following problems remain in the above-described conventional technology.
That is, in the mutual coupling neutralizer described in Patent Document 1, in order to neutralize the reverse mutual coupling between the paired patch antennas over a predetermined frequency band, the capacitor is formed in a predetermined size. There is a need to. In addition, it is necessary to inject with the same amplitude and opposite phase drawn from each antenna, the antenna layout becomes complicated, and it is difficult to easily adjust the antenna and mutual coupling including downsizing.
Further, in the antenna device described in Patent Document 2, since the mutual coupling between elements is adjusted by the distance from the end of the feed strip portion to the bridge portion, unstable elements are large, productivity is low, and at the same time, miniaturization is reduced. It was difficult. Furthermore, adjacent short-circuit strip portions are coupled to each other, and are coupled to each other via the ground due to the influence of the high-frequency current to the ground side, which is influenced by the design conditions such as the ground size and the antenna size. Realization of bond suppression was difficult.

  The present invention has been made in view of the above-described problems, and can save space, reduce the mutual coupling between the antennas, and can flexibly adjust the mutual coupling level and the like. The purpose is to provide.

  The present invention employs the following configuration in order to solve the above problems. That is, the antenna device of the first invention includes an insulating substrate body, a ground surface patterned with metal foil on the surface of the substrate body, a first antenna element, a second antenna element, and an intermediate element, The first antenna element and the second antenna element are arranged apart from each other, and separate feeding points are provided at base ends arranged on the ground plane side, respectively, in a direction away from the ground plane. At least a base end side extending portion extending from a feeding point, wherein the intermediate element is spaced apart from the ground plane and the base end side extending portion of the first antenna element and the second antenna element A pair of both end extending portions having an inductance component are connected to the base end side extending portion and the pair of both end extending portions Wherein the inductor and the capacitor are connected in parallel to constitute a mutual coupling reduction unit between.

  In this antenna apparatus, the intermediate element is disposed apart from the ground plane and has a pair of ends extending with an inductance component in the proximal end side extending portion of the first antenna element and the proximal end side extending portion of the second antenna element. Since the existing part is connected and the inductor and the capacitor are connected in parallel between the pair of extending parts at both ends to constitute the mutual coupling suppressing part, the antenna constituted by the first antenna element and the second antenna It is possible to reduce mutual coupling with an antenna constituted by elements, and to obtain high-performance antenna characteristics. That is, a high frequency to the ground surface is obtained by the inductance component obtained by the pair of both end extending portions of the intermediate element, the stray capacitance between the pair of both end extending portions and the ground surface, and the parallel resonance of the inductor and the capacitor. While suppressing the flow of current and making the impedance between the antennas high impedance, the mutual coupling level can be suppressed. Further, the mutual coupling suppression level, the mutual coupling bandwidth, and the suppression are set by appropriately setting the inductance of the inductor and the capacitance of the capacitor in the parallel resonance portion provided in the central portion of the first antenna element and the second antenna element. The mutual coupling frequency can be adjusted flexibly.

The antenna device according to a second aspect of the present invention is the antenna device according to the first aspect, wherein the first antenna element and the second antenna element are orthogonal to the proximal end extending portion from the distal end of the proximal extending portion. In the first antenna element and the second antenna element, a distal end side extending portion extending in the opposite direction to each other, and one end connected to the middle of the proximal end extending portion, and the other end from the feeding point And a ground connection extending portion connected to the ground surface at a spaced position, and a high impedance passive element is connected to the ground connection extending portion.
In other words, in this antenna device, the first antenna element and the second antenna element are connected to the ground plane in such a manner that one end is connected in the middle of the proximal-side extension portion and the other end is connected to the ground plane at a position away from the feeding point. Since the high-impedance passive element is connected to the ground connection extending part, each antenna element constitutes an inverted F-type antenna and the high-impedance passive element generates high-frequency current to the ground plane. Flow is suppressed. Thereby, the space | interval of a 1st antenna element and a 2nd antenna element can be narrowed further, and it becomes possible to achieve size reduction further.

According to a third aspect of the present invention, there is provided the antenna device according to the second aspect, wherein an antenna element of a dielectric antenna is provided at a distal end portion of the distal end side extending portion.
That is, in this antenna device, since the antenna element of the dielectric antenna is provided at the distal end portion of the distal end side extending portion, the distal end extending portion can be shortened by selecting an antenna element that is a dielectric antenna, and the antenna device is small. And higher performance.

An antenna device according to a fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, an adjustment passive element is connected to the base end side extending portion.
That is, in this antenna device, since the adjustment passive element is connected to the proximal end side extending portion, the resonance frequency and the like of the first antenna element and the second antenna element can be adjusted by setting the adjustment passive element. Become.

The present invention has the following effects.
According to the antenna device of the present invention, the intermediate element is disposed apart from the ground surface and has an inductance component in the proximal end side extending portion of the first antenna element and the proximal end side extending portion of the second antenna element. Since the pair of both end extending portions are connected and the inductor and the capacitor are connected in parallel between the pair of both end extending portions to form the mutual coupling suppressing portion, the antenna configured by the first antenna element And the antenna composed of the second antenna element can be reduced, and downsizing and high-performance antenna characteristics can be obtained. Therefore, when designing two antennas that use the same frequency band such as Bluetooth (registered trademark) or wireless LAN on the same substrate, the deterioration of antenna performance due to mutual coupling is suppressed without greatly separating the distance between the antennas. It is possible to save space (smaller and thinner). Furthermore, it is possible to flexibly adjust the mutual coupling level and the mutual coupling frequency band, and it is possible to take measures against mutual coupling corresponding to various applications and devices.

In one Embodiment of the antenna device which concerns on this invention, it is a top view which shows an antenna device. In this embodiment, it is a typical equivalent circuit diagram which shows an antenna device. In this embodiment, they are a perspective view (a), a plan view (b), a front view (c), a bottom view (d), and a rear view (e) showing an antenna element. In this embodiment, it is a graph which shows the return loss measurement result of antenna A, antenna B, and these mutual coupling. It is a graph which shows the return loss measurement result of the mutual coupling between the antenna A and the antenna B when there is no mutual coupling suppression part. It is a graph which shows the return loss measurement result of mutual coupling in the case where the distance of antenna A and antenna B when there is no mutual coupling suppression part is small and large, and the case of this embodiment. In this embodiment, it is a graph which shows the return loss measurement result of a mutual coupling at the time of changing a capacitance.

  Hereinafter, an embodiment of an antenna device according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, the antenna device 1 according to the present embodiment includes an insulating substrate main body 2, a ground surface GND, a first antenna element 3, Two antenna elements 4 and an intermediate element 5 are provided.
The first antenna element 3 and the second antenna element 4 are arranged to be separated from each other, and are provided with separate feeding points FP at the base ends arranged on the ground plane GND side and away from the ground plane GND. And a first antenna element 3 and a second antenna element extending in a direction orthogonal to the proximal end extending portion E1 from the distal end of the proximal end extending portion E1. 4 and a distal end side extending portion E2 extending in opposite directions to each other.

The first antenna element 3 and the second antenna element 4 are connected to the ground plane GND at one end connected in the middle of the base end side extending portion E1 and the other end separated from the feeding point FP. It has an extending part E3. High-passive passive elements P1 and P3 are connected to these ground connection extending portions E3, respectively.
Furthermore, adjustment passive elements P2 and P4 are connected in the middle of each base-end extending portion E1.
For example, inductors, capacitors, or resistors are employed as the high impedance passive elements P1 and P3 and the adjustment passive elements P2 and P4.

  The intermediate element 5 is spaced apart from the ground plane GND and is arranged between the intermediate portion of the proximal end side extending portion E1 of the first antenna element 3 and the intermediate portion of the proximal end side extending portion E1 of the second antenna element 4. A pair of both end extending portions 5a having an inductance component are connected, and an inductor 5L and a capacitor 5C are connected in parallel between the pair of both end extending portions 5a to constitute a mutual coupling suppressing portion. That is, the pair of both end extending portions 5a of the intermediate element 5 are formed in a pattern that is narrower than the connecting portion 5b between the inductor 5L and the capacitor 5C, which is a parallel resonance portion, as shown in FIG. , Having an inductance component L. Further, stray capacitances C are respectively generated between the pair of both end extending portions 5a and the ground plane GND.

In addition, although the inductor 5L and the capacitor 5C, which are passive elements, are connected in parallel to the mutual coupling suppressing unit, a plurality of inductors or capacitors may be connected in parallel so as to allow parallel resonance.
In order to secure a large mutual coupling suppression level, it is desirable to set the capacitance of the capacitor 5C to a high impedance with respect to a desired resonance frequency.

If it is desired to give priority to the mutual coupling bandwidth over the mutual coupling suppression level, it is desirable to set the capacitance of the capacitor 5C to a low impedance with respect to a desired resonance frequency.
Based on these capacitance setting conditions, by setting the desired resonance frequency using the inductance of the inductor 5L, the mutual coupling suppression level and the suppression frequency can be flexibly adjusted.

  In addition, an antenna element AT of a dielectric antenna is provided at the distal end portion of each distal end side extending portion E2. These antenna elements AT are loading elements that do not self-resonate at a desired resonance frequency, and are chip antennas in which a conductor pattern 22 such as Ag is formed on the surface of a dielectric 21 such as ceramics as shown in FIG. is there. These antenna elements AT may select elements having different lengths, widths, conductor patterns 22 and the like according to the setting of the resonance frequency and the like, and may select the same elements. In addition, these antenna elements AT are installed along the extending direction of the distal end side extending portion E2. In other words, the distal end extending portion E2 and the antenna element AT are arranged in parallel along the end sides of the opposing ground surface GND.

The substrate body 2 is a general printed circuit board, and in this embodiment, a printed circuit board body made of a rectangular glass epoxy resin or the like is employed.
For example, a core wire of a coaxial cable (not shown) connected to a high-frequency circuit is connected to the feed point FP, and the ground wire of the coaxial cable is connected to the ground plane GND.

Note that the antenna occupation area (region where the ground plane GND around the antenna region including the first antenna element 3, the second antenna element 4, and the intermediate element 5 is removed) is preferably larger as antenna characteristics, and other configurations are as follows. It is preferable to set the following conditions.
That is, it is desirable that the distance between the first antenna element 3 and the second antenna element 4 be set at a quarter or more away from the wavelength of the desired resonance frequency.

Further, it is desirable that the high impedance passive elements P1 and P3 have a high impedance with respect to a desired resonance frequency in consideration of suppression of a high-frequency current toward the ground plane GND.
In addition, the pair of both end extending portions 5a connected to the base end side extending portion E1 which is each feeding pattern of the first antenna element 3 and the second antenna element 4 may be formed linearly with respect to each other. desirable.

Further, the distance between the intermediate element 5 and the ground plane GND differs depending on the antenna occupation area, the antenna distance (distance between the first antenna element 3 and the second antenna element 4), and the desired resonance frequency, Should be set to be loosely coupled. However, if the intermediate element 5 is too close to the antenna element AT, it is not preferable because the impedance is high, and it is desirable to provide a certain distance to the antenna element AT. For example, although different depending on the length of the base end side extending portion E1 and the distance between the intermediate element 5 and the ground plane GND, the intermediate element 5 is positioned closer to the feeding point FP than the intermediate point between the antenna element AT and the ground plane GND. It is desirable to provide
In addition, it is desirable that the capacitance value of the capacitor 5C in the parallel resonance portion be a high impedance with respect to a desired resonance frequency.

  As described above, in the antenna device 1 of the present embodiment, the intermediate element 5 is arranged so as to be separated from the ground plane GND, and extends to the proximal end side extension portion E1 of the first antenna element 3 and the proximal end side extension of the second antenna element 4. A pair of both end extending parts 5a having an inductance component is connected to the existing part E1, and an inductor 5L and a capacitor 5C are connected in parallel between the pair of both end extending parts 5a to constitute a mutual coupling suppressing part. Therefore, the mutual coupling between the antenna constituted by the first antenna element 3 and the antenna constituted by the second antenna element 4 can be reduced, and high-performance antenna characteristics can be obtained.

  That is, as shown in FIG. 2, the inductance component L obtained by the pair of both end extending portions 5a of the intermediate element 5, the stray capacitance C between the pair of both end extending portions 5a and the ground plane GND, and the inductor 5L The parallel resonance between the capacitor 5C and the capacitor 5C suppresses the flow of high-frequency current to the ground plane GND, and the impedance between the antennas can be made high, thereby suppressing the mutual coupling level. Further, by appropriately setting the inductance of the inductor 5L of the parallel resonance portion and the capacitance of the capacitor 5C provided in the center of the first antenna element 3 and the second antenna element 4, the mutual coupling suppression level and the mutual coupling band are set. The width and the mutual coupling frequency to be suppressed can be adjusted flexibly.

  In addition, the first antenna element 3 and the second antenna element 4 are each connected to the ground plane GND at one end connected in the middle of the base end side extending portion E1 and the other end separated from the feeding point FP. Since the high-impedance passive elements P1 and P3 are connected to the ground connection extending part E3, the antenna elements 3 and 4 constitute an inverted F-type antenna and the high-impedance passive elements. The flow of high-frequency current to the ground plane GND is suppressed by P1 and P3. Thereby, the space | interval of the 1st antenna element 3 and the 2nd antenna element 4 can be narrowed more, and it becomes possible to achieve size reduction further.

Furthermore, since the antenna element AT of the dielectric antenna is provided at the distal end portion of the distal end extending portion E2, the distal end extending portion E2 can be shortened and reduced in size by selecting the antenna element AT that is a dielectric antenna. And high performance.
Further, since the adjustment passive elements P2 and P4 are connected to the base end side extending portion E1, the first antenna element 3 and the second antenna element 4 are set by setting (changing constants, etc.) of the adjustment passive elements P2 and P4. It is possible to adjust the resonance frequency of the.

  Next, for Example 1 in which the antenna device of this embodiment was actually manufactured, the antenna A composed of the first antenna element 3, the antenna B composed of the second antenna element 4, and their mutual coupling (isolation) ) Return loss was measured. The measurement results are shown in FIG.

An inductor 5L having an inductance L of 3.3 nH and a capacitor 5C having a capacitance C of 0.3 pF were used. The size of the substrate body 2 was 50 mm × 50 mm, and the distance between the first antenna element 3 and the second antenna element 4 (the distance between the pair of proximal end extending portions E1) was 10 mm. Further, 5.6 nH was used for the high-impedance passive elements P1 and P3, 11 nH was used for the adjustment passive element P2, and 12 nH was used for the adjustment passive element P4.
As can be seen from this measurement result, the mutual coupling between the antenna A configured by the first antenna element 3 and the antenna B configured by the second antenna element 4 is −28.3 dB (2500 MHz), which is desired. Mutual coupling is greatly suppressed at the frequency of.

  A comparative example 1 without the intermediate element 5 which is a mutual coupling suppression part was produced under the same conditions as in the first example. FIG. 5 shows the result of measuring the return loss of mutual coupling between the antenna A and the antenna B for the comparative example 1. Here, the high-impedance passive elements P1 and P3 use 4.7 nH, the adjustment passive element P2 uses 8.2 nH, and the adjustment passive element P4 uses 12 nH. As can be seen from the measurement results, in Comparative Example 1, the mutual coupling between the antennas is as large as −8.7 dB (2500 MHz), and the performance of each antenna has deteriorated.

  Next, as Comparative Example 2, a case in which the distance between the antenna A and the antenna B was as large as 20 mm when there was no mutual coupling suppression portion was produced. FIG. 6 shows the measurement results of the return loss of the mutual coupling between the comparative example 2 and the comparative example 1 in which the distance between the antennas is 10 mm and the above example 1 (in FIG. 6, the comparative example 1 is “the distance between the antennas: 10 mm / The present invention: None ”, Comparative Example 2 is described as“ Distance between antennas: 20 mm / Invention: None ”, and Example 1 is described as“ Distance between antennas: 10 mm / Invention: Present ”). As can be seen from these measurement results, in Comparative Example 2 in which the distance between the antennas is doubled compared to Comparative Example 1 in which the distance between the antennas is 10 mm, the suppression of mutual coupling can be improved only by about 3 dB. In the first embodiment of the present invention in which the intermediate element 5 serving as the suppressing portion is provided, the mutual coupling is greatly suppressed.

  Next, FIG. 7 shows the return loss measurement result of the mutual coupling of each antenna in Example 2 in which the capacitance value of the capacitor C was changed from 0.3 pF to 1.0 pF in the example of the present invention. Note that Comparative Example 1 and Example 1 are also shown in FIG. 7 (in FIG. 7, Comparative Example 1 is “distance between antennas: 10 mm / present invention: none”, and Example 1 is “inter-antenna Distance: 10 mm / present invention: present (C = 0.3 pF) ”and Example 2 is described as“ distance between antennas: 10 mm / present invention: present (C = 1.0 pF) ”. As can be seen from these measurement results, in Example 2 in which the capacitance value was changed, the mutual coupling suppression level was changed as compared to Example 1.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, the first antenna element and the second antenna element constitute an antenna using the same frequency band, but may be antennas using different frequency bands.

  DESCRIPTION OF SYMBOLS 1 ... Antenna apparatus, 2 ... Board | substrate main body, 3 ... 1st antenna element, 4 ... 2nd antenna element, 5 ... Intermediate element, 5a ... End extension part, 5L ... Inductor, 5C ... Capacitor, AT ... Antenna element, E1 ... proximal end extension part, E2 ... distal end side extension part, E3 ... ground connection extension part, GND ... ground plane, P1, P3 ... passive element for high impedance, P2, P4 ... passive element for adjustment, FP ... Feeding point

Claims (4)

An insulating substrate body;
A ground plane patterned with a metal foil on the surface of the substrate body, a first antenna element, a second antenna element, and an intermediate element,
The first antenna element and the second antenna element are arranged apart from each other, and separate feeding points are provided at base ends arranged on the ground plane side, respectively, in a direction away from the ground plane. Having at least a proximal-side extension extending from the feed point;
A pair of both ends in which the intermediate element is arranged apart from the ground surface and has an inductance component in the base end side extension portion of the first antenna element and the base end side extension portion of the second antenna element An extension part is connected and an inductor and a capacitor are connected in parallel between the pair of both end extension parts to constitute a mutual coupling suppression part ,
Each of the first antenna element and the second antenna element is in a direction perpendicular to the proximal end extending portion from the distal end of the proximal end extending portion, and the first antenna element and the second antenna element And a ground connection extension in which one end is connected in the middle of each of the proximal end extension portions and the other end is connected to the ground plane at a position away from the feeding point. antenna apparatus characterized by having a part. The antenna device according to claim 1,
A high impedance passive element is connected to the ground connection extending portion. The antenna device according to claim 1 or 2,
An antenna device, wherein an antenna element of a dielectric antenna is provided at a distal end portion of the distal end side extending portion. In the antenna device according to any one of claims 1 to 3,
An antenna device, wherein an adjustment passive element is connected to the base end side extending portion.