Patent ID: 12212061

EXAMPLE EMBODIMENT

An example embodiment according to the present disclosure will be described hereinafter with reference to the drawings. The same reference numerals (or symbols) are assigned to the same or corresponding elements throughout the drawings, and duplicate descriptions thereof are omitted as appropriate for clarifying the explanation.

First Example Embodiment

<Configuration>

FIG.1is a schematic diagram showing an example of an antenna apparatus according to a first example embodiment.

As shown inFIG.1, an antenna apparatus10according to the first example embodiment includes a feeding antenna105(a radio device100t), and a passive element part110disposed in the Z-direction of the feeding antenna105(the radio device100t).

The radio device100tincludes a printed circuit board100and a housing (not shown) that covers the printed circuit board100. The printed circuit board100includes a dielectric layer101, a conductor layer102, a radio circuit (not shown), a feeding point103, a matching circuit104, and a feeding antenna105. The radio circuit is disposed (e.g., formed) on the printed circuit board100. The radio device100tmay be, for example, any of a mobile terminal, a tablet-type terminal, a smartphone, and the like. The printed circuit board may also be simply referred to as a substrate.

The dielectric layer101is formed of a dielectric and the conductor layer102is formed of a conductor. Each of the dielectric layer101and the conductor layer102is formed in a single layer or in multiple layers.

The feeding point103is a connection point between the radio circuit (not shown) that generates a radio signal and the feeding antenna105.

The feeding antenna105is disposed between the passive element part110and the feeding point103, and emits a radio signal into space (e.g., into the air). The feeding antenna105is an inverted L-shaped antenna that extends in the Z-direction from the feeding point103(or, when the matching circuit104is provided, from the matching circuit104), and then extends in the X-direction therefrom. Specifically, the feeding antenna105is an inverted L-shaped pattern antenna composed of a termination part105aextending in the Z-direction from the matching circuit104, and a tip part105bthat is bent at an angle of 90 degrees toward the X-direction and extends along the edge of the dielectric layer101. Further, the feeding antenna105is disposed in the conductor layer102.

The matching circuit104is disposed between the feeding antenna105and the feeding point103, and is used for impedance matching between the feeding antenna105and the radio circuit. Regarding the impedance matching, the impedance is typically adjusted to 50Ω (ohms).

The passive element part110includes a dielectric111and a passive element112. The passive element part110is disposed at a position including an XY-plane orthogonal to the printed circuit board100(a plane orthogonal to the Z-direction). In the example shown inFIG.1, the printed circuit board100is disposed on an XZ-plane, and the passive element part110is disposed on the XY-plane. Further, the passive element part110is disposed so that the tip part105bof the feeding antenna105is parallel to one side of the passive element112.

The reason for the above-described arrangement is to strengthen the spatial coupling between the feeding antenna105and the passive element112, and thereby to increase a high-frequency current induced in the passive element112. When the distance between the tip part105bof the feeding antenna105and the passive element112is increased, the spatial coupling therebetween becomes weak. Therefore, the passive element112is preferably disposed near the feeding antenna105. For example, the distance between them is preferably about one tenth of the wavelength at a desired frequency (a used frequency) or shorter. The distance between the passive element112and the feeding antenna105may be 0.11 times of the wavelength at the frequency used for the radio signal or shorter. Assuming that the used frequency is up to 5 GHz, one tenth of the wavelength is 6 mm. Therefore, the distance between the tip part105bof the feeding antenna105shown inFIG.1and the passive element112is 6 mm in the horizontal direction (the Z-axis direction).

Instead of being disposed in the Z-direction of the radio device100t, the passive element part110may be disposed on the inner surface of the housing of the radio device100tthat is opposed to the feeding antenna105.

Regarding the dielectric111and the passive element112of the passive element part110, the dielectric111may be formed of a housing and the passive element112may be formed of conductive tape. Alternatively, the dielectric111may be formed of a dielectric layer of a printed circuit board and the passive element112may be formed of a conductor layer of the printed circuit board. The passive element may also be referred to as a parasitic antenna (or a passive antenna).

The parasitic antenna (the passive element112) may be disposed inside a charger that also serves as a cradle for the mobile terminal (the radio device100t), and operated (i.e., used) as the passive element part110.

Note that although the above description has been given on the assumption that the passive element part110is located outside the radio device100tand is located, for example, inside the cradle, the configuration of the antenna apparatus is not limited to this example. The passive element part110may be disposed inside the radio device100t.

The dielectric111is a dielectric disposed parallel to the XY-plane orthogonal to the Z-direction. Although the dielectric111is disposed between the passive element112and the feeding antenna105inFIG.1, the configuration of the antenna apparatus is not limited to this example. That is, the dielectric111may be disposed in the Z-direction of the passive element112. The dielectric111is disposed between the passive element112and the feeding antenna105, or disposed in the Z-direction of the passive element112.

The passive element112is disposed parallel to the XY-plane orthogonal to the Z-direction, is made of a conductor, and includes a plurality of slots. The plurality of slots include a first slot113and a second slot114(i.e., the first and second slot113and114are provided (i.e., formed) in the passive element112). The material of the passive element112is preferably a material containing a conductor having a low surface resistivity, for example, a material containing at least one of gold, silver, copper, and aluminum.

The first and second slot113and114, among the plurality of slots, are parts in which there is no conductor. Each of the first and second slot113and114has such a shape that the slot is bent at or near the center so that a tip (one end) thereof gets closer to (i.e., extends toward) one of the sides of the passive element112. That is, the first slot113extends in the X-direction orthogonal to the Z-direction, and then extends in the Y direction orthogonal to the X- and Z-directions therefrom. The second slot114extends in the X-direction and then extends in the Y-direction therefrom. The length of the first slot113is longer than the length of the second slot114. The sizes of the passive element112shown inFIG.1are, for example, as follows: a=b=29.5 mm (millimeters); c=d=20 mm; e=f=12 mm; and the slot width w=4 mm.

The length of the first slot113in the X-direction is longer than the length of the second slot114in the X-direction. The length of the first slot113in the Y-direction is longer than the length of the second slot114in the Y-direction.

The length of the first slot113is equal to a half-wavelength length at a first frequency used for the radio signal. The length of the second slot114is equal to a half-wavelength length at a second frequency used for the radio signal.

FIG.2is a graph showing an example of return losses in a printed circuit board.

InFIG.2, the horizontal axis indicates frequencies, and the vertical axis indicates return losses.

FIG.2shows return losses of the feeding antenna105as being observed from the feeding point103in the case where only the radio device100t(the printed circuit board100) is provided in the antenna apparatus10shown inFIG.1, i.e., in the case where the passive element part110is not provided in the antenna apparatus10. The return loss is also referred to as a return loss (RL: Return Loss) or a reflectivity.

The return loss is one of the indices indicating the characteristics of an antenna, and is obtained by a calculation formula “10×Log10(Returned Power/Incident Power)”. Since the returned power is equal to or smaller than the input power, the sign of the returned loss is negative and the unit thereof is dB (decibel). The smaller the value of the return loss is, the less the incident power is returned, and hence the more the incident power is emitted into the air. In general, when the return loss is −5 dB or smaller, the feeding antenna satisfactorily functions as an antenna.

As shown inFIG.2, the return loss is −10 dB or smaller in a frequency band of 2.5 GHz to 5 GHz. Therefore, it can be said that the feeding antenna105satisfactorily functions over a range of 2.5 GHz to 5 GHz.

<Operation>

FIG.3Ais a schematic diagram showing an example of, when a high-frequency current is fed to the feeding antenna according to the first example embodiment, the high-frequency current flowing through the feeding antenna, a conductor layer, and a passive element.

FIG.3Bis a schematic diagram showing an example of, when a high-frequency current is fed to the feeding antenna according to the first example embodiment, the high-frequency current flowing through the feeding antenna, the conductor layer, and the passive element.

As shown inFIGS.3A and3B, when a high-frequency current is fed to the feeding antenna105, the high-frequency current flows through the feeding antenna105and a part of the conductor layer102located therearound (indicated by solid arrows), and a high-frequency current is also induced in the passive element112disposed near the feeding antenna105.

The high-frequency current induced in the passive element112resonates at a frequency at which the slot length becomes equal to one half wavelength (a half wavelength), and flows in the slot part in a concentrated manner (indicated by dotted arrows). The length of the first slot113is 40 mm (=c+d), and the length of the second slot114is 24 mm (=e+f). Therefore, the resonance frequency of the slot under normal conditions is about 3.8 GHz and 6 GHz. However, since the passive element112is in contact with the dielectric111, the resonance frequency is affected by wavelength shortening. Therefore, when the relative dielectric constant of the dielectric111is 3, the first slot113resonates at about 2.8 GHz and the second slot114resonates at about 4.2 GHz.

FIG.3Ais a schematic diagram (a simplified image) showing an example of the high-frequency current at 2.8 GHz. At the frequency of 2.8 GHz, the high-frequency current is concentrated in the first slot113. In this state, two one-half wavelength current distributions in each of which the current at the tip part of the first slot113is large occur. Further, by disposing the tip part in which the high-frequency current is large on the edge of the passive element112, a high-frequency current of which the direction is the same as (i.e., parallel to) that of the current flowing at the tip of the first slot113is induced on the edge of the passive element112. As a result, a one-half wavelength high-frequency current indicated by solid lines in which the current at or near the tip part of the first slot113is large is generated on each of the upper, the left, the right, and the lower sides of the passive element112as viewed from a position on the opposite side in the Z-direction. Since this high-frequency current includes currents flowing in the Y-direction, it contributes to the vertical polarization on the XZ-plane.

FIG.3Bis a schematic diagram (a simplified image) showing an example of the high-frequency current at 4.2 GHz. At the frequency of 4.2 GHz, the high-frequency current is concentrated in the second slot114. In this state, similarly to the frequency of 2.8 GHz, two one-half wavelength current distributions in each of which the current at the tip part of the second slot114is large occur. Further, by the high-frequency current at the tip part of the second slot114, a one-half wavelength current distribution indicated by solid lines occurs on each of the left and lower sides of the passive element112as viewed from a position on the opposite side in the Z-direction. However, in the case of 4.2 GHz, in contrast to 2.8 GHz, a one-half wavelength high-frequency current indicated by chain lines is also generated on each of the upper and right sides of the passive element112. Although the phase of the high-frequency current indicated by the solid lines and that of the high-frequency current indicated by the chain lines are opposite to each other, the current indicated by the solid lines at or near the tip of the second slot114is larger and hence is not canceled out. Therefore, the high-frequency current indicated by the solid lines contributes to the emission, thus making it possible to obtain the vertical polarization on the XZ-plane.

<Effect>

FIG.4shows graphs showing examples of emission patterns in a printed circuit board.

FIG.4shows emission patterns on three planes (XZ-plane/YZ-plane/XY-plane) of the feeding antenna105at 2.8 GHz in the case where only the radio device100t(the printed circuit board100) is provided in the antenna apparatus10shown inFIG.1, i.e., in the case where the passive element part110is not provided in the antenna apparatus10.

As shown inFIG.4, horizontal polarization is obtained on each of the XZ-, YZ-, and XY-planes, but vertical polarization is not obtained on the XZ-plane.

FIG.5is a graph showing an example of average gains in a printed circuit board.

FIG.5is a graph showing an example of average gains of vertical polarization on the XZ-plane shown inFIG.4. InFIG.5, the horizontal axis indicates frequencies, and the vertical axis indicates average gains. The unit of the average gain is dBi (decibels per isotropic) in order to show the absolute gain of the antenna.

As shown inFIG.5, the average gain of the printed circuit board is very low, i.e., about −40 dBi in a frequency range of 2.5 GHz to 5 GHz.

FIG.6shows graphs showing examples of emission patterns in the antenna apparatus according to the first example embodiment.

FIG.6shows emission patterns on three planes (XZ-plane/YZ-plane/XY-plane) at 2.8 GHz in the antenna apparatus10shown inFIG.1.

As shown inFIG.6, unlike the emission patterns in the printed circuit board shown inFIG.4, vertical polarization occurs on the XZ-plane in the emission patterns in the antenna apparatus10.

FIG.7is a graph showing an example of average gains of the antenna apparatus according to the first example embodiment.

FIG.7shows the average gains of the vertical polarization on the XZ-plane in a range of 2.5 GHz to 5 GHz in the antenna apparatus10shown inFIG.1. InFIG.7, the horizontal axis indicates frequencies, and the vertical axis indicates average gains.

As shown inFIG.7, the average gains of the vertical polarization on the XZ-plane in the antenna apparatus10are increased over all the frequencies as compared to the average gains in the case where only the printed circuit board100is provided as shown inFIG.5.

FIG.8is a graph showing an example of average gains of the antenna apparatus in the case where the passive element includes no slot.

FIG.8shows average gains of vertical polarization on the XZ-plane in a range of 2.5 GHz to 5 GHz in the antenna apparatus10shown inFIG.1in which the passive element112does not include the first and second slot113and114.

As shown inFIG.8, the average gains of the antenna apparatus on the XZ-plane in the case where the passive element includes no slot are increased over all the frequencies as compared to the average gains in the case where only the printed circuit board100is provided as shown inFIG.5. However, as compared to the average gains in the case of the antenna apparatus10shown inFIG.7, there is a difference of 6 dB or larger at or near 2.8 GHz. When this difference converted into a difference, it is about twice the distance in the case of the antenna apparatus10shown inFIG.7.

When the passive element112is simply disposed near the feeding antenna105, it was impossible to obtain the required characteristics (an omni-directional emission pattern and an average gain equal to or higher than a predetermined gain). However, as shown inFIGS.6and7, by adopting the configuration of the antenna apparatus10according to the first example embodiment, it becomes possible to obtain the emission pattern and the average gain required for the horizontal polarization and the vertical polarization on all the planes (XZ-plane/YZ-plane/XY-plane) over a wide frequency band.

As a result, according to the first example embodiment, it is possible to provide an antenna apparatus including an antenna capable of having both a wide-band characteristic and an omni-directional characteristic. Therefore, the antenna apparatus10according to the first example embodiment can be used as an antenna of a communication apparatus such as those in conformity with a 3G/4G/5G/Wireless LAN (Local Area Network).

Note that the length of the outer shape of the passive element112may be made longer than one wavelength of the lower-limit frequency of the used frequency band.

Further, the length of the first slot113or the second slot114may be made equal to one half of the wavelength at a predetermined frequency selected from a plurality of frequency bands to be used.

Further, the feeding antenna105may be disposed so that its tip part105bis parallel to one of the sides of the passive element112.

Features of the antenna apparatus10according to the first example embodiment will be described hereinafter.

The antenna apparatus10includes a thin radio device100tin which a feeding antenna105is provided, and a passive element112including a first slot113and a second slot114disposed near the feeding antenna105and perpendicular to the feeding antenna105. Further, by spatially coupling the feeding antenna105with the passive element112, a radio wave generated by a high-frequency current flowing in the Y-direction (the thickness direction of the radio device100t), which would otherwise be weak by the feeding antenna105alone, is strengthened in a plurality of frequency bands, so that the frequency band is widened.

Further, features of the antenna apparatus10according to the first example embodiment from other viewpoints will be described hereinafter.In the antenna apparatus10, a passive element112of which the length of the outer shape is adjusted to one wavelength at a frequency F0 or larger is disposed near an omni-directional feeding antenna105of which the used frequency is in a rage of F0 [GHz] to F1 [GHz] in such a manner that the passive element112has a plane (i.e., a surface) different from that of the feeding antenna105.One or a plurality of bending slots are provided (i.e., formed) in the passive element112.The length of the slot(s) (the slot length(s)) is made equal to one half of the wavelength at a frequency in a range of F0 to F1.

In this way, when a high-frequency current is fed to the feeding antenna105, the high-frequency current flows to the slot(s) of the passive element112, and a high-frequency current is induced on the edge of the passive element112by the aforementioned high-frequency current, so that a radio wave is emitted into space (i.e., into the air). Further, by the emission from the feeding antenna105and the passive element112, it is possible to obtain horizontal polarization and vertical polarization in a multi-plane manner over a wide frequency band.

Note that the slot(s) is bent in order to reduce the length of the outer shape of the passive element112, and in order to dispose the tip part where the current is large near the edge of the passive element112and thereby to induct a current on the edge of the passive element112.

Second Example Embodiment

<Configuration>

FIG.9is a schematic diagram showing an example of a passive element part of an antenna apparatus according to a second example embodiment.

As shown inFIG.9, in a passive element part210according to the second example embodiment, the orientation of slots is different from that of the slots of the passive element part110according to the first example embodiment.

The passive element part210includes a dielectric211, and a passive element212made of a conductor. The passive element212has such a shape that one of the four corners of a square (or a rectangle) is cut out. The passive element212includes a first slot213and a second slot214. Each of the first and second slots213and214has such a shape that a tip of the slot is bent so as to get closer to (i.e., extend toward) the edge of a different side of the passive element212. That is, the passive element212has a cut-out in a part thereof on the opposite side in the X-direction and on the opposite side in the Y-direction as viewed in the Z-direction. The first slot213extends in the X-direction orthogonal to the Z-direction, and then extends in the direction opposite to the Y-direction (i.e., toward the negative side in the Y-direction) orthogonal to the X- and Z-directions therefrom. The second slot214extends in the X-direction and then extends in the direction opposite to the Y-direction therefrom. The length of the first slot213is longer than the length of the second slot214. The sizes of the passive element212shown inFIG.9are as follows: a=b=29 mm; c=d=23 mm; e=f=17 mm; and g=h=14 mm. Further, the distance between the feeding antenna205and the passive element212is 6 mm in the Z-direction.

FIG.10Ais a schematic diagram showing an example of, when a high-frequency current is fed to the feeding antenna according to the second example embodiment, the high-frequency current flowing through the feeding antenna, a conductor layer, and a passive element.

FIG.10Ashows a case of 2.8 GHz.

FIG.10Bis a schematic diagram showing an example of, when a high-frequency current is fed to the feeding antenna according to the second example embodiment, the high-frequency current flowing through the feeding antenna, the conductor layer, and the passive element.FIG.10Bshows a case of 3.8 GHz.

As shown inFIG.10A, the operation (i.e., the behavior) of the passive element212is similar to the operation of the passive element112shown inFIG.3A. As shown inFIG.10B, the operation (i.e., the behavior) of the passive element212is similar to the operation of the passive element112shown inFIG.3B. The resonance frequency is determined according to the length of the first slot213, and the high-frequency current is concentrated in the first slot213at the resonance frequency. The resonance frequency is determined according to the length of the second slot214, and the high-frequency current is concentrated in the second slot214at the resonance frequency. A one-half wavelength (half-wavelength) high-frequency current is induced on the edge of the passive element212by large currents flowing in the tip parts of the first and second slots213and214, respectively.

FIG.11is a graph showing an example of average gains of the antenna apparatus according to the second example embodiment.

FIG.11shows an average gain of vertical polarization on the XZ-plane in a range of 2.5 GHz to 5 GHz in the passive element212shown inFIG.9.

As shown inFIG.11, the vertical polarization on the XZ-plane is obtained over a wide frequency band. As described above, in the antenna apparatus20according to the second example embodiment, it is possible to adjust the frequency band at which the effect is obtained by changing each of the sizes (i.e., each of the lengths) of the passive element212and/or by the cut-out thereof.

Although the present disclosure is described above with reference to example embodiments, the present disclosure is not limited to the above-described example embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the disclosure.

Note that the present disclosure is not limited to the above-described example embodiments, and they may be modified as appropriate without departing from the scope and spirit of the invention.

The first and second embodiments can be combined as desirable by one of ordinary skill in the art.

While the disclosure has been particularly shown and described with reference to embodiments thereof, the disclosure is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the claims.

According to the present disclosure, it is possible to provide an antenna apparatus including an antenna capable of having both a wide-band characteristic and an omni-directional characteristic.10,20ANTENNA APPARATUS100tRADIO DEVICE100PRINTED CIRCUIT BOARD101DIELECTRIC LAYER102,202CONDUCTOR LAYERS103FEEDING POINT104MATCHING CIRCUIT105,205FEEDING ANTENNAS105aTERMINATION PART105bTIP PART110,210PASSIVE ELEMENT PART111,211DIELECTRIC112,212PASSIVE ELEMENT113,213FIRST SLOT114,214SECOND SLOT