JP6860906B2 - Omnidirectional small flat antenna device - Google Patents

Description

The present invention relates to a small, planar structure antenna device having omnidirectionality.

Miniaturization of antennas is a desired theme for mobile wireless terminals and the like from the viewpoint of portability and the like. In addition, omnidirectionality is a characteristic that is also desired for mobile stations that change direction and base stations that communicate with terminals in all directions. As a compact and omnidirectional antenna device, a strip-shaped side conductor is vertically connected to the edge of the flat plate-shaped upper surface conductor and the lower surface conductor, and the lower surface conductor is connected from the upper surface conductor to the side conductor. An antenna device in which a communication slot composed of continuous slits leading to a portion is provided so that a part of a path in the longitudinal direction of the communication slot intersects a TEM wave traveling between the upper surface conductor portion and the lower surface conductor portion. Has been proposed (see, for example, Patent Document 1).

The antenna device described in Patent Document 1 can realize omnidirectionality with horizontally polarized waves. Further, the antenna device main body can be configured by a planar structure in which conductors are provided on both sides and side surfaces of the dielectric substrate, and the posture is ultra-low as compared with a monopole antenna or the like. Moreover, since the communication slot is configured by opening a slit from the upper surface conductor portion to the lower surface conductor portion via the side conductor portion, the diameter of the antenna device is reduced to about one wavelength of the matching frequency that can realize omnidirectionality. it can.

Japanese Unexamined Patent Publication No. 2009-55543

However, in the invention described in Patent Document 1, since the diameter of the substrate is about one wavelength, further miniaturization is desired in order to improve portability and mountability as a portable wireless terminal. In addition, in order to ensure stable communication even under the influence of multipath and changes in the orientation of mobile wireless terminals, omnidirectionality is provided not only by the horizontally polarized component but also by the vertically polarized component. It is desirable that it can be realized.

Therefore, an object of the present invention is to provide an omnidirectional compact planar antenna device capable of making the diameter smaller than one wavelength of the target matching frequency and realizing omnidirectionality not only in horizontally polarized waves but also in vertically polarized waves. To do.

In order to solve the above problems, the invention according to claim 1 is formed of a plate-shaped dielectric substrate having two opposing surfaces parallel to each other and a conductor having a required thickness on the first surface of the dielectric substrate. A first conductive layer provided with a first slit portion having a required shape, and a second conductive layer formed of a conductor having a required thickness on the second surface of the dielectric substrate and provided with a second slit portion having a required shape. A power supply port provided at a portion where a virtual central axis passing through the center of gravity of the dielectric substrate at right angles to the first and second surfaces of the dielectric substrate intersects the first conductive layer or the second conductive layer, and the dielectric. A conductive connecting portion formed on the outer surface or near the side surface of the substrate and electrically connecting the first conductive layer and the second conductive layer, and the side surface of the dielectric substrate continuous from the conductive connecting portion to the conductive connecting portion. The first slit portion is provided by providing a side slit portion that is exposed, one end of the side slit portion is connected to the first slit portion, and the other end of the side slit portion is connected to the second slit portion. It is characterized in that a long communication slot is formed from the side through the side slit portion to the second slit portion, and a signal is injected or taken out from the power feeding port.

Further, according to the second aspect of the present invention, in the omnidirectional small flat antenna device according to the first aspect, the first and second conductive layers and the dielectric substrate are divided into n equal parts through the virtual central axis, respectively. Each of the conductive connecting portions is provided at a portion where the equally divided surface (n is a natural number of 2 or more) intersects the side surface of the dielectric substrate, and the n slot antenna regions equally divided by the equally divided surface are provided with the conductive connecting portions, respectively. It is characterized in that communication slots having the same shape are formed.

The invention according to claim 3 is the omnidirectional small flat antenna device according to claim 1 or 2, wherein the first slit portion provided in the first conductive layer and the second conductive layer provided in the second conductive layer. The slit portions have the same shape, and are characterized in that they are arranged antisymmetrically with the dielectric substrate interposed therebetween.

Further, in the invention according to claim 4, in the omnidirectional small flat antenna device according to any one of claims 1 to 3, the first slit portion and / or the second slit portion is at least , The first end is connected to the side slit portion, and the other second end is bent-likely connected to the second end side of the base end slit with a base end slit having a required width extending in the central direction, and is a dielectric material. It is characterized by including a bending slit having a required width extending parallel to the side surface of the substrate.

The invention according to claim 5 is the shape of the first slit portion and the shape of the second slit portion in the omnidirectional small flat antenna device according to any one of claims 1 to 4. The matching frequency is changed by changing the thickness and / or the dielectric constant of the dielectric substrate without changing the slit length of the side slit portion.

According to the omnidirectional small flat antenna device according to the present invention, the diameter can be made smaller than one wavelength of the target matching frequency, and omnidirectionality can be realized not only in horizontally polarized light but also in vertically polarized light.

The first embodiment of the omnidirectional small flat antenna device according to the present invention is shown, (a) is a perspective view showing the first surface (upper surface) side of the omnidirectional small flat antenna device, and (b) is omnidirectional. A perspective view showing the second surface (lower surface) side of the small flat antenna device, and (c) is an enlarged plan view showing the detailed shape of the first slit portion in the first slot antenna region of the omnidirectional small flat antenna device. It is explanatory drawing which showed each shape of the 1st to 4th communication slots by developing six surfaces of the omnidirectional small plane antenna device of the structure shown in FIG. It is explanatory drawing which shows the design dimension of the basic structure which formed the omnidirectional small plane antenna device of the structure shown in FIG. 1 so that the matching frequency fres = 117.6 MHz. (A) is a frequency characteristic diagram of a reflection coefficient | S11 | showing a case where the substrate thickness h is changed as a parameter in an omnidirectional small flat antenna device having a basic configuration. (B) is a frequency characteristic diagram of radiation efficiency ηrad showing a case where the substrate thickness h is changed as a parameter in an omnidirectional small flat antenna device having a basic configuration. It is a dependency characteristic diagram with respect to the substrate thickness h _{of the matching frequency fres, the maximum radiation efficiency frequency f η} , and the maximum radiation efficiency value η max in the omnidirectional small plane antenna device of the basic configuration. (A) is a vertical plane pattern characteristic diagram of the absolute gain Ga of horizontally polarized waves showing the case where the substrate thickness h is changed as a parameter in the omnidirectional small plane antenna device having a basic configuration. (B) is a vertical plane pattern characteristic diagram of an absolute gain Ga of vertically polarized light showing a case where the substrate thickness h is changed as a parameter in an omnidirectional small plane antenna device having a basic configuration. (A) is a frequency characteristic diagram of a reflectance coefficient | S11 | showing a case where the substrate relative permittivity εr is changed as a parameter in an omnidirectional small plane antenna device having a basic configuration. (B) is a frequency characteristic diagram of a radiation efficiency ηrad showing a case where the substrate relative permittivity εr is changed as a parameter in an omnidirectional small plane antenna device having a basic configuration. It is a dependency characteristic diagram with respect to the substrate relative permittivity εr _{of the matching frequency fres, the maximum radiation efficiency frequency f η} , and the maximum radiation efficiency value η max in the omnidirectional small plane antenna device of the basic configuration. (A) is a vertical plane pattern characteristic diagram of an absolute gain Ga of horizontally polarized light showing a case where the substrate relative permittivity εr is changed as a parameter in an omnidirectional small plane antenna device having a basic configuration. (B) is a vertical plane pattern characteristic diagram of an absolute gain Ga of vertically polarized light showing a case where the substrate relative permittivity εr is changed as a parameter in an omnidirectional small plane antenna device having a basic configuration. It is explanatory drawing which shows the design dimension of the prototype structure which formed the omnidirectional small plane antenna device of the structure shown in FIG. 1 so that the matching frequency fres = 169.7 MHz. It is an external view of the 1st surface (upper surface) side of the omnidirectional small plane antenna device prototyped based on the design dimension of the prototype configuration. It is a frequency characteristic diagram of the reflection coefficient | S11 | showing the actual measurement result and the simulation result actually obtained by the prototype omnidirectional small plane antenna device. It is explanatory drawing which shows the arrangement structure of the omnidirectional small plane antenna device of a basic structure, and a conductive plate. It is a frequency characteristic diagram of the reflection coefficient | S11 | which shows the case where the separation distance Hp with respect to the conductive plate of infinite size is changed as a parameter. It is a dependency characteristic diagram with respect to the separation distance Hp of the resonance frequency fres and the reflection coefficient | S11 | min at the time of resonance in the omnidirectional small plane antenna device of a basic configuration. It is a dependency characteristic diagram with respect to the separation distance Hp of the maximum radiation efficiency _{frequency f η} and the maximum radiation efficiency η max in the omnidirectional small plane antenna device of the basic configuration. It is a frequency characteristic diagram of the reflection coefficient | S11 | which shows the case where the width Wp of a conductive plate is changed as a parameter. It is a dependency characteristic diagram with respect to the width Wp of the conductive plate of the resonance frequency fres and the reflection coefficient | S11 | min at the time of resonance in the omnidirectional small plane antenna device of a basic configuration. It is a dependency characteristic diagram with respect to the width Wp of the conductive plate of the maximum radiation efficiency _{frequency f η} and the maximum radiation efficiency η max in the omnidirectional small plane antenna device of the basic configuration. (A) is an instantaneous current vector distribution diagram on the outer surface of the first conductive layer provided on the first surface (upper surface) of the omnidirectional small plane antenna device having a basic configuration. (B) is an instantaneous current vector distribution diagram on the inner surface of the first conductive layer provided on the first surface (upper surface) of the omnidirectional small plane antenna device having a basic configuration. (A) is a first modification example in which the communication slot in the omnidirectional small flat antenna device having the basic configuration is partially changed. (B) is a second modification example in which the communication slot in the omnidirectional small flat antenna device having the basic configuration is partially changed. It is a schematic plan view of the omnidirectional small plane antenna device which concerns on 2nd Embodiment. It is a schematic plan view of the omnidirectional small plane antenna device which concerns on 3rd Embodiment. It is a schematic plan view of the omnidirectional small plane antenna device which concerns on 4th Embodiment. (A) is a schematic plan view showing a first configuration example of the omnidirectional small plane antenna device according to the fifth embodiment. (B) is a schematic plan view showing a second configuration example of the omnidirectional small plane antenna device according to the fifth embodiment. (A) is a schematic plan view showing a first configuration example of the omnidirectional small plane antenna device according to the sixth embodiment. (B) is a schematic plan view showing a second configuration example of the omnidirectional small plane antenna device according to the sixth embodiment. It is a schematic plan view of the omnidirectional small plane antenna device which concerns on 7th Embodiment. It is a schematic plan view of the omnidirectional small plane antenna device which concerns on 8th Embodiment.

Next, an embodiment of the omnidirectional small planar antenna device according to the present invention will be described with reference to the accompanying drawings.

1 and 2 show the omnidirectional small planar antenna device 1A according to the first embodiment. The omnidirectional small flat antenna device 1A includes a dielectric substrate 2 having a substantially square side of W [mm] and a thickness of h [mm], and a first conductive layer formed on the first surface 21 of the dielectric substrate 2. 3 and a second conductive layer 4 formed on the second surface 22 of the dielectric substrate 2.

The dielectric substrate 2 is composed of a plate-shaped dielectric plate having two opposing surfaces parallel to each other. In the following description, if the first surface 21 side is referred to as an upper surface and the second surface 22 side is referred to as a lower surface. There is. Further, since the dielectric substrate 2 has a regular polygonal shape (square), the center of gravity always has a center of gravity along the axis passing through the center of the upper surface and the center of the lower surface. In the following description, the axis line orthogonal to the first surface 21 and the second surface 22 of the dielectric substrate 2 and passing through the center of gravity is referred to as a virtual center axis CA. A feeding port 5 is provided at a portion where the virtual central axis CA intersects the first conductive layer 3, and a signal is injected or taken out from the feeding port 5. When the coaxial cable is connected to the power feeding port 5, the outer conductor of the coaxial cable is made conductive to the first conductive layer 3, and the central conductor is made to conduct to the second conductive layer 4. Further, the communication port 5 may be provided on the second conductive layer 4 side.

The first conductive layer 3 is formed on the first surface 21 of the dielectric substrate 2 with a conductor having a required thickness, and has a required shape of an upper surface first slit portion 31, an upper surface second slit portion 32, and an upper surface third. A slit portion 33 and a fourth slit portion 34 on the upper surface are provided. The upper surface first to fourth slit portions 31 to 33 all have the same shape and are arranged point-symmetrically with respect to the center point (intersection with the virtual center axis CA) of the first conductive layer 3.

The second conductive layer 4 is formed on the second surface 22 of the dielectric substrate 2 with a conductor having a required thickness, and has a required shape of a lower surface first slit portion 41, a lower surface second slit portion 42, and a lower surface third. A slit portion 43 and a lower surface fourth slit portion 44 are provided. The upper surface first to fourth slit portions 31 to 33 all have the same shape and are arranged point-symmetrically with respect to the center point (intersection with the virtual center axis CA) of the first conductive layer 3.

The upper surface first to fourth slit portions 31 to 34 and the lower surface first to fourth slit portions 41 to 44 are formed by removing a part of the first and second conductive layers 3 and 4. This is a portion where the outer surface of the dielectric substrate 2 is exposed. Similarly, since the four side surfaces 23 of the dielectric substrate 2 are also exposed to the outside, each side surface has a first side surface slit portion 231 and a second side surface slit portion 232, a third side surface slit portion 233, and a fourth side surface slit portion 234. It becomes.

Further, at each center position of the first to fourth side surface slit portions 231 to 234, a first conductive connecting portion 61 and a second conductive connecting portion for electrically connecting the first conductive layer 3 and the second conductive layer 4 are provided. 62, the third conductive connecting portion 63, and the fourth conductive connecting portion 64 are formed. Therefore, the first side surface slit portion 231 is divided into a first side surface A slit portion 231a and a first side surface B slit portion 231b with the first conductive connecting portion 61 as a boundary, and the second side surface slit portion 232 is a second conductive connecting portion. The second side surface A slit portion 232a and the second side surface B slit portion 232b are divided with the portion 62 as a boundary, and the third side surface slit portion 233 is divided into the third side surface A slit portion 233a and the third side surface A slit portion 233a with the third conductive connecting portion 63 as a boundary. It is divided into three side surface B slit portions 233b, and the fourth side surface slit portion 234 is divided into a fourth side surface A slit portion 234a and a fourth side surface B slit portion 234b with the fourth conductive connecting portion 64 as a boundary.

In the omnidirectional small flat antenna device 1A of the present embodiment, the first to fourth conductive connecting portions 61 to 64 each have a strip-shaped conductive layer having a width d [mm] on the four side surfaces 23 of the dielectric substrate 2. However, the structure of the conductive connecting portion is not limited to this, and the first conductive layer 3 and the second conductive layer 4 are connected by through holes formed in the vicinity of the four side surfaces 23 of the dielectric substrate 2. Such a conductive connecting portion may be used.

Further, the first to fourth conductive connecting portions 61 to 64 are provided at the center of the first to fourth side surface slit portions 231 to 234 of the dielectric substrate 2, and the omnidirectional small flat antenna device 1A is provided at the center. This is to divide the area into two equal parts. That is, an equally divided surface that divides the first and second conductive layers 3 and 4 and the dielectric substrate 2 into n equal parts (n is a natural number of 2 or more) passes through the virtual central axis CA, respectively, and intersects the side surface of the dielectric substrate 2. If conductive connecting portions are provided at each of the portions, n slot antenna regions equally divided by the equally divided surfaces can be formed.

In the omnidirectional small flat antenna device 1A according to the present embodiment, the equally divided surface that passes through the virtual central axis CA and is orthogonal to the first side surface slit portion 231 of the dielectric substrate 2 is outside the omnidirectional small flat antenna device 1A. The first dividing line PL1 intersecting the surface and the equally divided surface passing through the virtual central axis CA and orthogonal to the second side surface slit portion 232 of the dielectric substrate 2 intersect the outer surface of the omnidirectional small flat antenna device 1A. The dividing line PL2 and the third dividing line PL3 in which the equally divided surface that passes through the virtual central axis CA and is orthogonal to the third side slit portion 233 of the dielectric substrate 2 intersects the outer surface of the omnidirectional small flat antenna device 1A. Four slot antennas are provided by the fourth dividing line PL4 in which the equally divided surface orthogonal to the fourth side slit portion 234 of the dielectric substrate 2 passes through the virtual central axis CA and intersects the outer surface of the omnidirectional small flat antenna device 1A. Form a region.

Specifically, the first communication slot 11S is provided in the first slot antenna region 11 partitioned by the first equal dividing line PL1 and the second equal dividing line PL2, and the second equal dividing line PL2 and the third equal dividing line PL3 provide the first communication slot 11S. A second communication slot 12S is provided in the partitioned second slot antenna area 12, and a third communication slot 13S is provided in the third slot antenna area 13 partitioned by the third equal dividing line PL3 and the fourth equal dividing line PL4. The fourth communication slot 14S is provided in the fourth slot antenna region 14 partitioned by the equal dividing line PL4 and the first equal dividing line PL1, respectively.

The first communication slot 11S has each slit portion (upper surface first slit portion 31, first side surface A slit portion 231a, second side surface B slit portion 232b, lower surface first slit) provided in the first slot antenna region 11. It is composed of a part 41).

In the upper surface first slit portion 31, the first end 31a1 is connected to the split end side (formation side of the first conductive connecting portion 61) of the first side surface A slit portion 231a, and the other second end is the first equal dividing line. A width that extends in parallel with the first side surface A slit portion 231a and is flexibly connected to the base end slit 31a of the width SW1 extending in the central direction along PL1 and to the second end side of the base end slit 31a. The first bending slit 31b of the SW2 and the second bending slit 31c having a width SW3 that is flexedly connected to the extending end side of the first bending slit 31b and extends in parallel with the second side surface B slit portion 232b. It is composed of a tip slit 31d having a width SW4 that is flexedly connected to the extending end side of the second bending slit 31c and extends away from the center along the second equal dividing line PL2. Therefore, the upper surface first slit portion 31 has a slit length comparable to the width W of the dielectric substrate 2. As shown in FIG. 1C, the slit length of the base end slit 31a is SL1, the slit length of the first bending slit 31b is SL2, the slit length of the second bending slit 31c is SL3, and the slit length of the tip slit 31d. Is SL4.

In the lower surface first slit portion 41, the first end 41a1 is connected to the split end side (formation side of the second conductive connecting portion 62) of the second side surface B slit portion 232b, and the other second end is the fourth equal dividing line. The width of the base end slit 41a of the width SW1 extending in the central direction along the PL4 and the width extending in parallel with the fourth side surface B slit portion 232b by being flexibly connected to the second end side of the base end slit 41a. The first bending slit 41b of the SW2 and the second bending slit 41c having a width SW3 that is flexedly connected to the extending end side of the first bending slit 41b and extends in parallel with the first side surface A slit portion 231a. It is composed of a tip slit 41d having a width SW4 that is flexedly connected to the extending end side of the second bending slit 41c and extends away from the center along the first equal dividing line PL1. Therefore, the lower surface first slit portion 41 also has a slit length comparable to the width W of the dielectric substrate 2.

That is, as shown in FIG. 2, in the first slot antenna region 11, the first side surface from the upper surface first slit portion 31 (tip slit 31d → second bending slit 31c → first bending slit 31b → base end slit 31a). Long first communication from the A slit portion 231a and the second side surface B slit portion 232b to the lower surface first slit portion 41 (base end slit 41a → first bending slit 41b → second bending slit 41c → tip slit 41d). Slot 11S can be configured.

Similarly, in the second slot antenna region 12, the upper surface second slit portion 32 (tip slit 32d → second bending slit 32c → first bending slit 32b → base end slit 32a) to the second side surface A slit portion 232a and the second A long second communication slot 12S can be formed which reaches the lower surface second slit portion 42 (base end slit 42a → first bending slit 42b → second bending slit 42c → tip slit 42d) through the three side surface B slit portions 233b.

In the third slot antenna region 13, the upper surface third slit portion 33 (tip slit 33d → second bending slit 33c → first bending slit 33b → base end slit 33a) to the third side surface A slit portion 233a and the fourth side surface B. A long third communication slot 13S can be formed through the slit portion 234b to the lower surface third slit portion 43 (base end slit 43a → first bending slit 43b → second bending slit 43c → tip slit 43d).

In the fourth slot antenna region 14, the upper surface fourth slit portion 34 (tip slit 34d → second bending slit 34c → first bending slit 34b → base end slit 34a) to the fourth side surface A slit portion 234a and the first side surface B. A long fourth communication slot 14S can be formed through the slit portion 231b to the lower surface fourth slit portion 44 (base end slit 44a → first bending slit 44b → second bending slit 44c → tip slit 44d).

In the omnidirectional small flat antenna device 1A configured as described above, the first to fourth communication slots 11S to 114 having long slot lengths are equidistantly spaced in the first to fourth slot antenna regions 11 to 14, respectively. It will be placed in. The slot antenna requires a slot length of about half a wavelength of the matching frequency, but in the omnidirectional small flat antenna device 1A of the present embodiment, the four side surfaces 23 of the dielectric substrate 2 are used as slot openings and the upper surface is used. By appropriately bending the slits formed on the lower surface and increasing the slit length, the size can be reduced to about 0.1 wavelength of the substrate diameter.

In the omnidirectional small flat antenna device 1A according to the present embodiment, the upper surface first to fourth slit portions 31 to 34 provided in the first conductive layer 3 and the lower surface first to fourth provided in the second conductive layer 4 are provided. The slit portions 41 to 44 all have the same shape, and are arranged antisymmetrically with the dielectric substrate 2 interposed therebetween. In this way, as shown in FIG. 2, the first conductive layer 3 on which the upper surface first to fourth slit portions 31 to 34 are formed and the second conductive layer 3 on which the lower surface first to fourth slit portions 41 to 44 are formed are formed. Since the conductive layer 4 has the same shape, there is an advantage that the first conductive layer 3 and the second conductive layer 4 can be formed by the same etching mask. Of course, the shapes of the upper surface first to fourth slit portions 31 to 34 and the shapes of the lower surface first to fourth slit portions 41 to 44 do not necessarily have to be the same, and the slit width SW and the slit length SL are the upper surface and the lower surface. It does not matter if they are different.

FIG. 3 shows a dielectric substrate 2 having a substrate width W = 300 [mm], a substrate thickness h = 16 [mm], and a substrate relative permittivity εr = 2.17, with a number of divisions n = 4. This is an example of designing an omnidirectional small planar antenna device 1A having a matching frequency fres = 117.6 [MHz] using the finite element method simulation software HFSS (Ansys). The total length of the first to fourth communication slots 11S to 114 is about 870 mm, which is about 0.341 times the wavelength λres of the matching frequency. It can be seen that the substrate width W can be suppressed to 0.118 times the wavelength λres of the matching frequency. In the following description, the omnidirectional small planar antenna device 1A based on this design dimension is referred to as a basic configuration.

The influence of the thickness of the dielectric substrate 2 (substrate thickness h) in the omnidirectional small flat antenna device 1A having the basic configuration will be described with reference to FIGS. 4 to 6.

FIG. 4 shows the antenna characteristics when the substrate thickness h of the basic configuration is changed from 16 mm. FIG. 4A shows the frequency characteristics of the reflection coefficient | S11 |, and FIG. 4B shows the frequency characteristics of the radiation efficiency ηrad. When the substrate thickness h = 16 [mm] of the basic configuration, the frequency ratio band in which the reflectance coefficient | S11 | is −10 dB or less is a narrow band of about 0.42%. It can be seen that the thinner the substrate thickness h of the dielectric substrate 2, the narrower the matching frequency band. However, when the substrate thickness h is changed, the alignment may be improved by optimizing each dimension. Further, when the substrate thickness h = 16 [mm] of the basic configuration, the matching frequency fres = 117.6 [MHz], and the substrate width W = 300 [mm] of the dielectric substrate 2 is the wavelength λres of the matching frequency. = 0.118 times of 2551 [mm]. When the substrate thickness h is reduced to half, 8 mm, the matching frequency is reduced to 96.3 [MHz], which is 0.82 times lower, and the substrate width W of the dielectric substrate 2 is about 0.96 λres, but ηrad. Is found to deteriorate to -3.0 dB.

From FIG. 4, it can be seen that the matching frequency fres changes when the substrate thickness h of the dielectric substrate 2 is changed, but the state in which the matching frequency always exists is maintained. It can also be seen that the radiation efficiency ηrad also changes by changing the substrate thickness h. _{Therefore, FIG. 5 shows the dependence characteristics of the matching frequency fres, the maximum radiation efficiency frequency f η} , and the maximum radiation efficiency value η max on the substrate thickness h in the omnidirectional small flat antenna device 1A having the basic configuration.

From FIG. 5, _{it can be seen that the maximum radiation efficiency frequency f η at} which the radiation efficiency η rad is maximum changes while substantially matching the matching frequency fres. When the substrate thickness h is reduced, the matching frequency fres is lowered, which is effective in reducing the size of the antenna body. On the contrary, in order not to change the matching frequency fres even if the substrate thickness h of the dielectric substrate 2 is reduced, the antenna diameter (width W of the dielectric substrate 2) may be reduced, so that the omnidirectional compactness is small. The planar antenna device 1A is even smaller and lighter. However, the maximum radiation efficiency ηmax at the maximum radiation efficiency _{frequency f η decreases as the substrate thickness h decreases.}

FIG. 6A is a vertical plane pattern characteristic diagram of the absolute gain Ga of horizontally polarized light when the substrate thickness h of the dielectric substrate 2 is changed as a parameter in the omnidirectional small flat antenna device 1A having the basic configuration. FIG. 6B shows the vertical plane of the absolute gain Ga of vertically polarized light when the substrate thickness h of the dielectric substrate 2 is changed as a parameter in the omnidirectional small flat antenna device 1A having the basic configuration. It is a pattern characteristic diagram. The omnidirectional small plane antenna device 1A is substantially omnidirectional in both horizontally and vertically polarized waves in the horizontal plane. However, it can be seen that the horizontally polarized light is about 10 dB stronger than the vertically polarized light, and the thinner the substrate thickness h of the dielectric substrate 2, the larger the cross polarization discrimination degree and the smaller the ratio of the vertically polarized light.

Next, in the omnidirectional small flat antenna device 1A having the basic configuration, the influence of the relative permittivity εr of the dielectric constituting the dielectric substrate 2 will be described with reference to FIGS. 7 to 9.

FIG. 7 shows the antenna characteristics when the substrate relative permittivity εr of the basic configuration is changed from 2.17. FIG. 7A shows the frequency characteristics of the reflection coefficient | S11 |, and FIG. 7B shows the frequency characteristics of the radiation efficiency ηrad. From FIG. 7, it can be seen that the matching frequency fres changes by changing the substrate relative permittivity εr, but the frequency at which matching can be obtained always continues to exist.

_{Further, FIG. 8 shows the dependence characteristics of the matching frequency fres, the maximum radiation efficiency frequency f η} , and the maximum radiation efficiency value η max on the substrate relative permittivity εr in the omnidirectional small flat antenna device 1A having the basic configuration. From FIG. 8, _{it can be seen that the maximum radiation efficiency frequency f η} substantially coincides with the matching frequency fres and is lowered by increasing the substrate relative permittivity εr, but the radiation efficiency ηrad is also reduced. By using a high dielectric constant material with a substrate relative permittivity εr = 6, the matching frequency fres can be lowered from 117.6 [MHz] to 77.2 [MHz], but the radiation efficiency ηrad is also -5.9 [. It deteriorates to [dB].

FIG. 9A shows the vertical plane pattern characteristic of the absolute gain Ga of horizontally polarized light when the substrate relative permittivity εr of the dielectric substrate 2 is changed as a parameter in the omnidirectional small plane antenna device 1A having the basic configuration. FIG. 9B shows the absolute gain Ga of vertically polarized light when the substrate relative permittivity εr of the dielectric substrate 2 is changed as a parameter in the omnidirectional small planar antenna device 1A having the basic configuration. It is a vertical plane pattern characteristic diagram. The omnidirectional small plane antenna device 1A is substantially omnidirectional in both horizontally and vertically polarized waves in the horizontal plane. Further, it can be seen that when the substrate relative permittivity εr of the dielectric substrate 2 is increased, the degree of cross-polarization discrimination is increased as in the case where the substrate thickness h is reduced.

As described above, the matching frequency fres is lowered by reducing the substrate thickness h of the dielectric substrate 2 constituting the omnidirectional small planar antenna device 1A and increasing the substrate relative permittivity εr. Can be done. Equivalently, these design changes make it possible to reduce the size of the antenna body, but narrow the matching frequency band. If the number of divisions n of the slot antenna area in which the communication slot is provided is made smaller than 4, the slot length of each communication slot can be made relatively long with respect to the antenna size, so that the matching frequency fres can be lowered. Is considered possible. Therefore, if the number of divisions n of the slot antenna region is reduced, the antenna body can be miniaturized while maintaining the matching frequency fres.

FIG. 10 shows the number of divisions n = based on the dielectric substrate 2 having a substrate width W = 120 [mm], a substrate thickness h = 1.588 [mm], and a substrate relative permittivity εr = 2.17. This is an example of designing an omnidirectional small planar antenna device 1A having a matching frequency fres = 169.7 [MHz] in No. 4 using HFSS. The substrate width W is 0.068 times smaller than the wavelength λres of the matching frequency, which is smaller than the basic configuration, and the calculated value of the radiation efficiency ηrad is -4.3 [dB]. In the following description, the omnidirectional small planar antenna device 1A based on this design dimension is referred to as a prototype configuration.

FIG. 11 shows the appearance of the omnidirectional small planar antenna device 1A prototyped based on the design dimensions of the prototype configuration on the first surface (upper surface) side. The first to fourth conductive connecting portions 61 to 64 are configured by soldering a copper tape having a width of 3 [mm]. FIG. 12 is a frequency characteristic diagram of the reflectance coefficient | S11 | showing the actual measurement results actually obtained by this prototype antenna and the simulation results performed by the electromagnetic field analysis simulator HFSS (Ansys) by the finite element method. Although there was some deviation, matching was obtained at almost the design frequency even in the omnidirectional small planar antenna device 1A of the prototype configuration, and the matching operation was confirmed. Although better matching than the calculation is obtained, it is considered that the cause is that the symmetry of n = 4 is broken due to the low accuracy of the trial production.

As described above, the omnidirectional small flat antenna device 1A according to the present embodiment has a low profile, but has a communication slot that straddles both the upper surface and the lower surface, so that it comes into contact with a conductor such as an antenna accommodating housing. If the omnidirectional small flat antenna device 1A is installed in this state, the characteristics are considered to deteriorate. Therefore, the effect of being close to the conductor flat plate will be described on the assumption that it is installed close to the housing of a portable radio or the like. FIG. 13 shows a state in which the omnidirectional small flat antenna device 1A is arranged in parallel at a distance of Hp from the conductive plate 7 which is flat and has a width of Wp.

First, the width Wp of the conductive plate 7 is set to ∞, and the antenna characteristics (reflection coefficient | S11) when the separation distance Hp from the infinite conductive plate 7 to the omnidirectional small flat antenna device 1A having the basic configuration is changed. The change in (frequency characteristic of |) is shown in FIG. FIG. 15 shows a characteristic diagram of dependence of the resonance frequency fres and the reflection coefficient at resonance | S11 | min on the separation distance Hp in the omnidirectional small flat antenna device 1A having the basic configuration. FIG. 16 shows the dependence characteristics of the maximum radiation efficiency _{frequency f η} and the maximum radiation efficiency η max on the separation distance Hp in the omnidirectional small flat antenna device 1A having the basic configuration.

It can be seen that when the omnidirectional small flat antenna device 1A approaches the conductive plate 7, the reflectance coefficient | S11 | min at resonance first increases, and then the resonance frequency fres increases. Even if the separation distance Hp approaches 400 [mm] (about 0.16λres), the matching frequency of | S11 | <-6 dB is maintained at the frequency fres = 117.6 MHz that can be matched without the conductive plate 7. You can see that. Further, it can be seen that when the omnidirectional small flat antenna device 1A approaches the conductive plate 7, not only the matching is deteriorated but also the radiation efficiency ηrad is deteriorated. When the separation distance Hp is narrowed to 200 mm, the radiation efficiency ηrad deteriorates to -4.7 dB. Further, when the separation distance Hp is narrowed to 200 mm or less, the matching frequency fres and the maximum radiation efficiency frequency f _η suddenly change.

Next, the thickness of the conductive plate 7 is set to 1 mm, the separation distance Hp from the omnidirectional small flat antenna device 1A is fixed to 50 mm (about 0.02λres), and the plate width Wp of the square conductive plate 7 is set. FIG. 17 shows a change in the antenna characteristics (frequency characteristics of the reflection coefficient | S11 |) when the antenna characteristics are changed. FIG. 18 shows a characteristic diagram of dependence of the resonance frequency fres and the reflectance coefficient at resonance | S11 | min on the plate width Wp in the omnidirectional small flat antenna device 1A having the basic configuration. FIG. 19 shows the dependence characteristics of the maximum radiation efficiency _{frequency f η} and the maximum radiation efficiency η max on the plate width Wp in the omnidirectional small flat antenna device 1A having the basic configuration.

Even if the omnidirectional small flat antenna device 1A is close to the conductive plate 7 (separation distance Hp = 50 mm), there is no conductive plate 7 when the plate width Wp = 150 [mm] (about 0.059 λres). It can be seen that the matching of | S11 | <-8 dB can be maintained at the frequency fres = 117.6 [MHz] that can be matched in the state. When the plate width Wp increases to 200 [mm], it deteriorates to | S11 |> -3 dB at a frequency fres = 117.6 [MHz] that can be matched without the conductive plate 7. When the plate width Wp is further increased, the matching frequency fres is rapidly increased.

From FIGS. 17 to 19, it can be seen that the deterioration of the antenna characteristics due to the proximity of the conductor is more due to the deviation of the matching frequency fres than the deterioration of the reflection coefficient | S11 | and the radiation efficiency ηrad. Therefore, it is considered effective as a countermeasure against conductor proximity to design by shifting the matching frequency to the low frequency side in advance in consideration of the deviation of the matching frequency fres due to the proximity of the conductor.

Here, the current distribution in the omnidirectional small planar antenna device 1A (board thickness h = 16 [mm], matching frequency fres = 118 [MHz]) having the basic configuration is shown in vector representation in FIG. 20.

FIG. 20A shows the current distribution flowing on the outer surface of the first conductive layer 3 provided on the first surface (upper surface) of the omnidirectional small flat antenna device 1A, and FIG. 20B shows omnidirectionality. The current distribution flowing on the inner surface (the surface in contact with the first surface of the dielectric substrate 2) of the first conductive layer 3 provided on the first surface (upper surface) of the small flat antenna device 1A is shown. A strong current flows through the edges of the upper surface first to fourth slits 31 to 34 and the outer edge of the first conductive layer 3 on both the outer surface and the inner surface of the first conductive layer 3. On the other hand, a current flows radially in the central portion of the inner surface, and a current flows in the rotational direction in the central portion of the outer surface, and it is considered that the current in the rotational direction is involved in the horizontally polarized radiation. Due to the anti-symmetry of the antenna structure, a current flows on the surface side and the inner surface side of the second conductive layer 4 in an antisymmetric manner with respect to FIGS. 20A and 20B.

As described above, the omnidirectional small planar antenna device 1A according to the present embodiment can be configured with an antenna width of about 0.1 times the wavelength λres of the target matching frequency fres, and has a low attitude and is omnidirectional. Has sex. Therefore, by reducing the thickness of the dielectric substrate 2, the antenna body can be made smaller and lighter, although the radiation efficiency is deteriorated and the band is narrowed. Although the matching frequency band is as narrow as about 1% or less, the narrow band can be utilized in a communication application in which there is a high need to suppress interference with an adjacent system.

In addition, the main polarization of the omnidirectional small plane antenna device 1A is horizontal polarization, but has a vertical polarization of about -10 dB. Therefore, the omnidirectional small plane antenna device 1A having a certain sensitivity to both polarizations is not limited to one polarization plane unlike a normal loop antenna, and therefore, there is a communication application suitable for this characteristic. Conceivable.

Further, the omnidirectional small flat antenna device 1A can maintain the matching of | S11 | <-6 dB even if it approaches the conductive plate 7 up to a separation distance of about 0.16 times the wavelength λres of the matching frequency fres. .. Further, since the deviation of the matching frequency fres is the main cause of the matching deterioration, it is possible to design the omnidirectional small planar antenna device 1A by shifting the matching frequency low so as to cancel the increase in the matching frequency due to the nearby installation. It is considered to be effective.

Further, the shape of the communication slot provided in the omnidirectional small flat antenna device 1A may be appropriately changed according to the required characteristics. For example, the omnidirectional small flat antenna device 1A'shown in FIG. 21A is a first modification of the omnidirectional small flat antenna device 1A according to the first embodiment, and is the tip of the upper surface first slit 31'. Slit 31d', tip slit 32d'of the upper surface second slit 32', tip slit 33d' of the upper surface third slit 33', tip slit 34d' of the upper surface fourth slit 34', tip slit 41d of the lower surface first slit 41' ′, The tip slit 42d ′ of the lower surface second slit 42 ′, the tip slit 43d ′ of the lower surface third slit 43 ′, and the tip slit 44d ′ of the lower surface fourth slit 44 ′ are all extended toward the center. .. Further, the omnidirectional small flat antenna device 1A "shown in FIG. 21B is a second modification of the omnidirectional small flat antenna device 1A according to the first embodiment, and is a second modification of the upper surface first slit 31'. 2 Bending slit 31c ′, 2nd bending slit 32c ′ of upper surface 2nd slit 32 ′, 2nd bending slit 33c ′ of upper surface 3rd slit 33 ′, 2nd bending slit 34c ′ of upper surface 4th slit 34 ′, lower surface first The second bending slit 41c'of the 1 slit 41', the second bending slit 42c' of the lower surface second slit 42', the second bending slit 43c' of the lower surface third slit 43', and the second bending of the lower surface fourth slit 44'. The structure is such that the slits 44c'are all at the tip, and the tip slit provided substantially parallel to the equidistant line is not provided.

FIG. 22 shows the omnidirectional small planar antenna device 1B according to the second embodiment. Also in the omnidirectional small flat antenna device 1B of the present embodiment, the first to fourth communication slots 11S to 114 having long slot lengths are arranged at equal intervals in the first to fourth slot antenna regions 11 to 14, respectively. It is a structure. In addition to this, in the first slot antenna region 11, an upper edge first slit portion 351 connected to the upper edge of the second side surface B slit portion 232b is provided on the first conductive layer 3, and the first side surface A slit portion 231a is provided. A lower edge first slit portion 451 connected to the lower edge is provided. Similarly, in the second slot antenna region 12, an upper edge second slit portion 352 that is connected to the upper edge of the third side surface B slit portion 233b is provided on the first conductive layer 3, and is below the second side surface A slit portion 232a. A lower edge second slit portion 452 that is continuous with the edge is provided. In the third slot antenna region 13, an upper edge third slit portion 353 connected to the upper edge of the fourth side surface B slit portion 234b is provided in the first conductive layer 3, and is connected to the lower edge of the third side surface A slit portion 233a. A lower edge third slit portion 453 is provided. In the fourth slot antenna region 14, an upper edge fourth slit portion 354 connected to the upper edge of the first side surface B slit portion 231b is provided in the first conductive layer 3, and is connected to the lower edge of the fourth side surface A slit portion 234a. A lower edge fourth slit portion 454 is provided.

FIG. 23 shows the omnidirectional small planar antenna device 1C according to the third embodiment. In the omnidirectional small flat antenna device 1C of the present embodiment, by providing the first to fourth conductive connecting portions 61 to 64 at the four corners of the dielectric substrate 2, a substantially triangular first to fourth slot antenna region is provided. 11 to 14 are formed. In the first slot antenna region 11, the first slit portion 31 provided on the first conductive layer 3 is connected to the lower surface first slit portion 41 provided on the second conductive layer 4 via the first side slit portion 231. The communication slot 11S is formed. Similarly, in the second slot antenna region 12, the upper surface second slit portion 32 provided in the first conductive layer 3 passes through the second side surface slit portion 232 to the lower surface second slit portion 42 provided in the second conductive layer 4. A series of second communication slots 12S are formed. In the second slot antenna region 12, the second slit portion 32 provided on the first conductive layer 3 is connected to the lower surface second slit portion 42 provided on the second conductive layer 4 via the second side slit portion 232. The communication slot 12S is formed. In the third slot antenna region 13, a third slit portion 33 provided on the first conductive layer 3 is connected to a third slit portion 43 on the lower surface provided in the second conductive layer 4 through the third slit portion 33 on the upper surface and the slit portion 233 on the third side surface. The communication slot 13S is formed. In the fourth slot antenna region 14, the fourth slit portion 34 provided on the first conductive layer 3 is connected to the lower surface fourth slit portion 44 provided on the second conductive layer 4 via the fourth slit portion 34 on the upper surface and the slit portion 234 on the fourth side surface. The communication slot 14S is formed. Since the first to fourth slot antenna regions 11 to 14 of the omnidirectional small flat antenna device 1C have a triangular shape with the four side edges of the dielectric substrate 2 as long sides, the upper surfaces of the first to fourth slots are first to fourth. The slit portions 31 to 34 and the lower surface first to fourth slit portions 41 to 44 have a shape extending from the base end slit to the tip end slit through the bending slit. Further, the bent slits of the upper surface first to fourth slit portions 31 to 34 and the lower surface first to fourth slit portions 41 to 44 may have a stepped structure having different slit widths in the middle.

FIG. 24 shows the omnidirectional small planar antenna device 1D according to the fourth embodiment. In the omnidirectional small flat antenna device 1D of the present embodiment, a circular dielectric substrate 2D is used, a circular first conductive layer 3D is provided on the upper surface thereof, and a circular second conductive layer 4D is provided on the lower surface thereof. The first to fourth slot antenna regions 11 to 14 are formed. Like the regular polygonal substrate, the circular dielectric substrate 2D always has a center of gravity along the axis passing through the center of the upper surface and the center of the lower surface, so that it can be equally divided so as to pass through the virtual central axis. Although an elliptical substrate having two focal points also has a virtual central axis, it cannot be equally divided into the same shape, which is considered to be an obstacle in realizing horizontal omnidirectionality. However, if the omnidirectional small flat antenna device 1D using a perfect circular dielectric substrate cannot be accommodated due to the size of the terminal case, etc., an elliptical dielectric substrate with a small difference between the major axis and the minor axis is used. If the directional small flat antenna device 1D is made, there is a possibility that characteristics close to omnidirectional can be obtained.

In the first slot antenna region 11 of the omnidirectional small flat antenna device 1D, the second conductive layer 4D passes through the arc-shaped first side slit portion 231 from the upper surface first slit portion 31 provided in the first conductive layer 3D. The first communication slot 11S connected to the lower surface first slit portion 41 provided in the above is formed. Similarly, in the second slot antenna region 12, the lower surface second slit provided in the second conductive layer 4D via the arc-shaped second side surface slit portion 232 from the upper surface second slit portion 32 provided in the first conductive layer 3D. A second communication slot 12S connected to the unit 42 is formed. In the second slot antenna region 12, the upper surface second slit portion 32 provided in the first conductive layer 3D passes through the arc-shaped second side surface slit portion 232 to the lower surface second slit portion 42 provided in the second conductive layer 4D. A series of second communication slots 12S are formed. In the third slot antenna region 13, the upper surface third slit portion 33 provided in the first conductive layer 3D passes through the arc-shaped third side surface slit portion 233 to the lower surface third slit portion 43 provided in the second conductive layer 4D. A series of third communication slots 13S are formed. In the fourth slot antenna region 14, the upper surface fourth slit portion 34 provided in the first conductive layer 3D passes through the arc-shaped fourth side surface slit portion 234 to the lower surface fourth slit portion 44 provided in the second conductive layer 4D. A series of fourth communication slots 14S are formed. Since the first to fourth slot antenna regions 11 to 14 of the omnidirectional small flat antenna device 1C are fan-shaped, respectively, the upper surface first to fourth slit portions 31 to 34 and the lower surface first to fourth slits are The portions 41 to 44 have a shape extending from the base end slit through the bending slit to the tip slit, and each bending slit has an arc shape along the first to fourth side surface slit portions 231 to 234. Further, a step structure having a different slit width in the middle of each bending slit may be used.

FIG. 25A shows the omnidirectional small planar antenna device 1E according to the fifth embodiment, in which the number of divisions n is 6. In the omnidirectional small flat antenna device 1E of the present embodiment, a hexagonal dielectric substrate 2E is used, a hexagonal first conductive layer 3E is provided on the upper surface thereof, and a hexagonal second conductive layer 4E is provided on the lower surface thereof. By providing the first to sixth conductive connecting portions 61 to 66 in the central portion of each side, the antenna regions 11 to 16 are equally divided into the first to sixth slot antenna regions. The first to sixth slot antenna regions 11 to 16 are provided with the first to sixth communication slots 11S to 16S, respectively, but the slit length of each communication slot cannot be made so long with respect to the antenna diameter. The omnidirectional small flat antenna device 1E'shown in FIG. 25B is a modified example of the omnidirectional small flat antenna device 1E according to the fifth embodiment, and the first to sixth conductive connecting portions 61 are connected to each corner. By providing ~ 66, the antenna regions 11 to 16 are equally divided into the first to sixth slot antenna regions. Even in this omnidirectional small flat antenna device 1E', the slit length of each communication slot cannot be made very long with respect to the antenna diameter. Therefore, in the omnidirectional small flat antenna devices 1E and 1E'in which the number of divisions n is larger than 4, the antenna body can be made smaller and lighter than the omnidirectional small flat antenna device 1A according to the first embodiment. It is considered to be disadvantageous.

On the other hand, FIG. 26 shows the omnidirectional small flat antenna device 1F according to the sixth embodiment, in which the number of divisions n is 3. In the omnidirectional small flat antenna device 1F of the present embodiment, a triangular dielectric substrate 2F is used, a triangular first conductive layer 3F is provided on the upper surface thereof, and a triangular second conductive layer 4F is provided on the lower surface thereof. By providing the first to third conductive connecting portions 61 to 63 in the central portion, the antenna regions are equally divided into the first to third slot antenna regions 11 to 13. The first to third slot antenna regions 11 to 13 are provided with the first to third communication slots 11S to 13S, respectively, and the slit length of each communication slot can be made longer than the antenna diameter. The omnidirectional small flat antenna device 1F'shown in FIG. 26B is a modified example of the omnidirectional small flat antenna device 1F according to the sixth embodiment, and the first to third conductive connecting portions 61 are connected to each corner. By providing ~ 63, the antenna regions 1 to 3 are equally divided into the first to third slot antenna regions 11 to 13. Even in this omnidirectional small flat antenna device 1F', the slit length of each communication slot can be made longer than the antenna diameter. Therefore, in the omnidirectional small flat antenna devices 1F and 1F'in which the number of divisions n is smaller than 4, the antenna body can be made smaller and lighter than the omnidirectional small flat antenna device 1A according to the first embodiment. It is considered to be advantageous.

FIG. 27 shows the omnidirectional small planar antenna device 1G according to the seventh embodiment, in which the number of divisions n is 2. In the omnidirectional small flat antenna device 1G of the present embodiment, a quadrangular dielectric substrate 2 is used, and first and second conductive connecting portions 61 and 62 are provided at the central portions of the two opposing sides. , The second slot antenna area 11 and 12 are equally divided. The first communication slot 11S provided in the first slot antenna region has the upper surface first slit portion 31 provided in the first conductive layer 3 to the first side surface A slit portion 231a, the second side surface slit portion 232, and the third side surface B slit. It is connected to the lower surface first slit portion 41 provided in the second conductive layer 4 via the portion 233b. The second communication slot 12S provided in the second slot antenna region has the upper surface second slit portion 32 provided in the first conductive layer 3 to the third side surface A slit portion 233a, the fourth side surface slit portion 234, and the first side surface B slit. It is connected to the lower surface second slit portion 42 provided in the second conductive layer 4 via the portion 231b.

The upper surface first slit portion 31 of the first communication slot 11S has a base end slit 31 having a required width in which the first end is connected to the first side surface A slit portion 231a and the other second end extends in the central direction. A first bent slit 31b having a required width that is bent and connected to the second end side of the base end slit 31 and extends in parallel with the first side surface A slit portion 231a, and bent to the extending end of the first bent slit 31b. The second bent slit 31c which is connected in a shape and extends parallel to the second side surface slit portion 232 and the second bent slit 31c which is bent and connected to the extending end of the second bent slit 31c and is parallel to the third side surface B slit portion 233b. It is composed of a third bending slit 31d that extends and a tip slit 31e that is flexibly connected to the extending end side of the third bending slit 31d and extends away from the center. Therefore, the upper surface first slit portion 31 has a slit length of nearly 1/2 of the entire circumference of the substrate. The second bending slit 31c has a stepped structure including a second bending front slit 31c1 and a second bending rear slit 31c2 having different slit widths and separation distances from the second side surface slit portion 232.

Since the upper surface second slit portion 32 and the lower surface first and second slit portions 41 and 42, which are not described, all have the same shape as the upper surface first slit portion 31, each has a slit length close to 1/2 of the entire circumference of the substrate. Since each of the first and second communication slots 11S and 12S is provided, each of the first to fourth communication slots 11S to 14S in the omnidirectional small flat antenna device 1A having a basic configuration in which the number of divisions n = 4 is provided. It is very long compared to the slot length. Therefore, it is considered that the omnidirectional small flat antenna device 1G having the number of divisions n of 2 can realize lower frequency without changing the antenna dimensions as compared with the omnidirectional small flat antenna device 1A having the basic configuration. ..

Therefore, when we simulated a design change from the omnidirectional small flat antenna device 1A with n = 4 to the omnidirectional small flat antenna device 1G with n = 2 without changing the antenna dimensions, we simulated the omnidirectional small flat surface. From the matching frequency fres = 128 MHz in the antenna device 1A, the matching frequency fres = 69 MHz was obtained in the omnidirectional small flat antenna device 1G. When the number of divisions n is halved from 4 to 2, the matching frequency fres can also be reduced to about half.

Further, if the omnidirectional small flat antenna device 1G is designed so that the same matching frequency as the omnidirectional small flat antenna device 1A can be obtained, the size is about half the size of the substrate used in the omnidirectional small flat antenna device 1A. Since it is considered that the omnidirectional compact flat antenna device 1G can be configured by the dielectric substrate 2 having a substrate width of W / 2, the area, volume, and weight can be reduced to about 1/4.

From the above, it is considered that designing with a small n is effective for miniaturization. FIG. 28 shows the omnidirectional small planar antenna device 1H according to the eighth embodiment in which the number of divisions n = 1. When n = 1, since the antenna area is not equally divided into two or more, only the first slot antenna area 11 in which the first communication slot 11S is formed is formed. However, by providing the conductive connecting portion 6 that electrically connects the first conductive layer 3 and the second conductive layer 4, the side surface of the dielectric substrate 2 is divided, and the upper surface first slit portion 31 is the conductive connecting portion 6. It is connected to the first side surface A slit portion 231a in the vicinity of one side, and the lower surface first slit portion 41 is connected to the first side surface B slit portion 231b in the vicinity of the other side of the conductive connecting portion 6. That is, the first communication slot 11S of the omnidirectional small flat antenna device 1H has the upper surface first slit portion 31 to the first side surface A slit portion 231a, the second side surface slit portion 232, the third side surface slit portion 233, and the fourth side surface. A long slot length can be obtained from the slit portion 234 and the first side surface B slit portion 231b to the lower surface first slit portion 41.

It is generally known that the radiation efficiency decreases when the antenna is miniaturized. That is, if the number of divisions n is reduced, the size of the antenna body can be reduced, but practical radiation efficiency may not be obtained. Therefore, it is appropriate to obtain the target matching frequency and sufficient radiation efficiency. It is desirable to select a number of divisions n.

The omnidirectional small planar antenna device according to the present invention has been described above based on the embodiments, but the present invention is not limited to these embodiments, and the present invention is not limited to these embodiments, unless the configuration described in the claims is changed. All omnidirectional small plane antenna devices that can be realized in the above are included in the scope of rights.

1A omnidirectional small flat antenna device (first embodiment)
11-14 1st to 4th slot antenna area 11S-14S 1st to 4th communication slots 2 Dielectric substrate 21 1st surface (upper surface)
22 Second surface (lower surface)
23 Four side surfaces 3 First conductive layer 31 to 34 Upper surface first to fourth slits 4 Fourth conductive layer 41 to 44 Lower surfaces first to fourth slits 5 Power supply ports 61 to 64 First to fourth conductive connecting parts

Claims (5)

A plate-shaped dielectric substrate with two parallel surfaces facing each other,
A first conductive layer formed of a conductor having a required thickness on the first surface of the dielectric substrate and provided with a first slit portion having a required shape.
A second conductive layer formed of a conductor having a required thickness on the second surface of the dielectric substrate and provided with a second slit portion having a required shape.
A power supply port provided at a portion where the virtual center axis passing through the center of gravity of the dielectric substrate orthogonal to the first surface and the second surface of the dielectric substrate intersects the first conductive layer or the second conductive layer.
A conductive connecting portion formed near the outer surface or the side surface of the dielectric substrate and electrically connecting the first conductive layer and the second conductive layer.
A side slit portion in which the side surface of the dielectric substrate is continuously exposed from the conductive connecting portion to the conductive connecting portion,
With
By connecting one end of the side slit portion to the first slit portion and connecting the other end of the side slit portion to the second slit portion, the first slit portion passes through the side slit portion to the second slit portion. An omnidirectional small flat antenna device characterized in that a long communication slot is formed so as to inject or take out a signal from the power feeding port. The conductive connecting portion is located at a portion where an equally divided surface that divides the first and second conductive layers and the dielectric substrate into n equal parts (n is a natural number of 2 or more) passing through the virtual central axis and intersects the side surface of the dielectric substrate. Each
The omnidirectional small planar antenna device according to claim 1, wherein communication slots having the same shape are formed in each of the n slot antenna regions equally divided by the equally divided surfaces. The claim is characterized in that the first slit portion provided in the first conductive layer and the second slit portion provided in the second conductive layer have the same shape and are arranged antisymmetrically with the dielectric substrate interposed therebetween. 1 or the omnidirectional small planar antenna device according to claim 2. The first slit portion and / or the second slit portion is at least
A base end slit having a required width in which the first end is connected to the side slit portion and the other second end extends in the central direction,
A bending slit having a required width that is bent and connected to the second end side of the base end slit and extends parallel to the side surface of the dielectric substrate.
The omnidirectional small planar antenna device according to any one of claims 1 to 3, wherein the omnidirectional small planar antenna device is provided. By changing the thickness and / or the dielectric constant of the dielectric substrate without changing the shape of the first slit portion, the shape of the second slit portion, and the slit length of the side slit portion, the matching frequency can be adjusted. The omnidirectional small planar antenna device according to any one of claims 1 to 4, wherein the device is changed.

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