wireless terminal

Abstract

To provide a radio terminal with higher antenna radiation efficiency.SOLUTION: A portable radio terminal includes a dielectric exterior case forming at least a plane portion and a side wall portion on the exterior of the radio terminal, a plate-shaped antenna ground that serves as the ground for a monopole antenna and is placed facing the back surface of the plane portion at a distance D (mm) inside the exterior case, and an antenna radiating element that is placed between the back surface of the side wall portion and the antenna ground inside the exterior case and is electrically connected to the antenna ground via a feeding point.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to wireless terminals. [Background technology]

[0002] Portable wireless terminals such as smartphones are provided with antennas for wireless communication inside the terminals (see Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-340887 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-40680 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-78333 Summary of the Invention [Problem to be solved by the invention]

[0004] When a monopole antenna is installed inside a portable wireless terminal, for example, the antenna ground and antenna radiating element may be formed on a dielectric substrate. When a high-frequency signal with a wavelength λ four times the length of the radiating element is input to such an antenna, if the length of the antenna ground is sufficiently longer than λ / 4, harmonic components will be generated in the antenna ground. Therefore, if a dielectric with a relatively large dielectric loss is adjacent to the antenna ground due to the housing design, heat loss due to harmonics may occur in the dielectric, which may reduce the antenna radiation efficiency.

[0005] One aspect of the disclosed technology aims to provide a wireless terminal with an antenna having higher radiation efficiency. [Means for solving the problem]

[0006] One aspect of the disclosed technology is exemplified by the following wireless device. A portable wireless terminal, a dielectric exterior case that forms at least a flat surface and a side wall on the exterior of the wireless terminal; A plate-shaped antenna ground that serves as the ground for the monopole antenna is placed opposite the rear surface of the flat part inside the exterior case at a distance D (mm), an antenna radiating element disposed within the exterior case between the rear surface of the side wall portion and the antenna ground, and electrically connected to the antenna ground via a feeding point; The antenna radiating element is a rod-shaped conductor with a length of l (mm) that operates at a predetermined frequency with a wavelength of λ (mm) and is arranged parallel to the rear surface of the side wall at a distance d (mm), When the length from the end of the antenna ground where the feed point is provided to the opposite end is L (mm), the length L and the distance D are expressed by the formulas (1) and (2) when the predetermined frequency is the 4 GHz band. D≧λ / 24 (1) D×L≧λ 2 / 12 (2) characterized in that Wireless terminal. [Effects of the Invention]

[0007] According to the disclosed technology, it is possible to provide a wireless terminal with an antenna having higher radiation efficiency. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the main parts of a wireless terminal. [Figure 2] FIG. 2 is a diagram showing an image of heat loss of an antenna in a wireless terminal according to the embodiment. [Figure 3] FIG. 3 is a diagram showing an image of the heat loss of the antenna in the wireless terminal according to the comparative example. [Figure 4] FIG. 4 is a first diagram showing the simulation results of the antenna efficiency. [Figure 5] FIG. 5 is a second diagram showing the simulation results of the antenna efficiency. [Figure 6] FIG. 6 is a third diagram showing the simulation results of the antenna efficiency. [Figure 7] FIG. 7 is a diagram illustrating an appearance of a smartphone according to an embodiment. [Figure 8] FIG. 8 is a diagram illustrating an example of an internal configuration of the smartphone according to the embodiment. [Figure 9] FIG. 9 is a diagram illustrating an example of dimensions of each part of the smartphone according to the embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of an internal configuration of the smartphone according to the embodiment. [Figure 11] FIG. 11 is a diagram showing an example of dimensions of each part of a smartphone according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Embodiment> The configurations of the embodiments described below are merely examples, and the disclosed technology is not limited to the configurations of the embodiments.

[0010] A wireless device according to an embodiment has, for example, the following configuration: That is, a portable wireless terminal, comprising: a dielectric outer case that forms at least a flat portion and a side wall portion on the exterior of the wireless terminal; a plate-shaped antenna ground that serves as the ground of the monopole antenna and is disposed within the outer case facing the back surface of the flat portion at a distance D (mm) from the back surface of the side wall and is disposed within the outer case between the back surface of the side wall and the antenna ground and is electrically connected to the antenna ground via a feed point, wherein the antenna radiating element is a rod-shaped conductor with a length l (mm) that operates at a predetermined frequency with a wavelength λ (mm) and is disposed in parallel to the back surface of the side wall at a distance d (mm), and where L (mm) is the length from the end of the antenna ground where the feed point is provided to the opposite end, when the predetermined frequency is in the 4 GHz band, the length L and the distance D satisfy the following formulas (1) and (2): D≧λ / 24 (1) D×L≧λ 2 / 12 (2)

[0011] In the wireless device, the antenna ground of a predetermined length is disposed at a distance D from the dielectric, thereby suppressing loss in the dielectric when harmonic currents flow through the antenna ground, thereby improving the radiation efficiency of the antenna.

[0012] The wireless terminal will be described in detail below. Fig. 1 is a diagram showing the main parts of the wireless terminal. Fig. 1(A) shows a front view of the main parts of the wireless terminal 1, and Fig. 1(B) shows a side view of the main parts of the wireless terminal 1. The wireless terminal 1 includes an antenna ground 4, a dielectric 5 arranged parallel to the antenna ground 4, a feed point 3 arranged near the end of the antenna ground 4, and an antenna radiating element 2.

[0013] The antenna ground 4 serves as a ground that serves as a reference for the potential of the electronic circuits built into the wireless terminal. Antenna ground 4 can be used as an electrical ground for antenna radiating element 2 by combining such a printed circuit board with a plate-shaped conductor, for example.

[0014] As shown in Fig. 1, the antenna ground 4 has an appearance of a generally rectangular plate in overall view. A feed point 3 that feeds power to the antenna radiating element 2 is located at at least one of the ends of the antenna ground 4 in the longitudinal direction, i.e., on the short side of the rectangle. The antenna radiating element 2 is located slightly away from the short side of the antenna ground 4 and parallel to the short side. Therefore, the antenna radiating element 2 is not located directly above the main plane of the antenna ground 4.

[0015] The antenna radiating element 2 is a monopole antenna with one end connected to a feed point 3 and the other end open. The antenna radiating element 2 emits microwave radio waves fed from a transmitter / receiver circuit via the feed point 3, and receives radio waves transmitted from an external source. An appropriate matching circuit may be provided at the feed point 3. The antenna radiating element 2 has a length that resonates at a specific design frequency. Therefore, the length of the antenna radiating element 2, which is a monopole antenna, roughly corresponds to the length of a quarter wavelength at the design frequency. The antenna radiating element 2 is also arranged parallel to the short side of the antenna ground 4, which is formed in a plate shape. Therefore, the longitudinal direction of the antenna radiating element 2 corresponds to the short side of the antenna ground 4, which has a rectangular appearance.

[0016] The dielectric 5 is a thin plate-like member having a generally rectangular shape when viewed from above, with a main portion being flat. The dielectric 5 has a shape in which the edges are partially bent, and the bent portions form wall-like portions. Hereinafter, the main flat portion of the dielectric 5 will be referred to as the flat portion 5M, and the wall-like portion of the dielectric 5 will be referred to as the side wall portion 5S.

[0017] The dielectric 5 is made of a material that generates dielectric polarization when placed in an electric field, and specific examples include electrical insulators such as plastic and ceramic. In addition, in consideration of the design frequency of the antenna radiating element 2, the antenna ground 4 is required to have a certain size. Therefore, when the antenna ground 4 is incorporated into a portable wireless terminal, the main planar portion of the antenna ground 4 is inevitably positioned opposite the inner surface of the exterior material of the wireless terminal. Therefore, a typical example of what constitutes the dielectric 5 in the wireless terminal 1 of this embodiment is the exterior material of the wireless terminal 1.

[0018] As can be seen from FIG. 1 , the flat portion 5M of the dielectric 5 is disposed parallel to the antenna ground 4 at a distance D from it. The side wall portion 5S of the dielectric 5 is disposed parallel to the antenna radiating element 2 at a distance d from it. The length L of the antenna ground 4 in the longitudinal direction is sufficiently longer than a quarter wavelength at the design frequency of the antenna radiating element 2, and the flat portion 5M is large enough to completely cover the main flat portion of the antenna ground 4 with such dimensions. The length l of the antenna radiating element 2 is determined taking into account the wavelength shortening due to the dielectric constant of the side wall portion 5S disposed at a distance d from it. The entire length l of the antenna radiating element 2 is also covered by the side wall portion 5S of the dielectric 5.

[0019] Usually, when designing a portable wireless terminal such as a smartphone, an attempt is made to make the housing as thin as possible. Therefore, when applying the design of a normal wireless terminal to the above-mentioned wireless terminal 1, the antenna ground 4 and the flat portion 5M are brought into almost intimate contact with each other, that is, the distance D is set to almost zero millimeters. However, in this embodiment, the distance D and the length L are designed to satisfy the following dimensional condition formulas (1) and (2), thereby reducing the antenna radiation. It is more efficient. <Dimensional conditions> D≧λ / 24 (1) D×L≧λ 2 / 12 (2)

[0020] Fig. 2 is a diagram showing an image of the heat loss of the antenna in the wireless terminal 1 according to the embodiment. Fig. 3 is a diagram showing an image of the heat loss of the antenna in the wireless terminal according to the comparative example. The thick lines shown in Figs. 2 and 3 are lines showing an image of the distribution of harmonic currents flowing through the antenna radiating element and the antenna ground. In Figs. 2 and 3, the longitudinal length of the antenna ground is assumed to be nine times the length of a quarter wavelength at the design frequency, and therefore a sine wave of nine-quarter wavelengths is shown in the antenna ground portion.

[0021] In the embodiment shown in FIG. 2, the antenna ground is spaced apart from the dielectric. In contrast, in the comparative example shown in FIG. 3, the antenna ground is in contact with the dielectric. Therefore, the embodiment has a smaller dielectric loss due to the dielectric than the comparative example. As a result, the wireless terminal 1 of the embodiment has a higher antenna radiation efficiency than the wireless terminal of the comparative example. The effects of the embodiment were verified by simulation, and the results are shown below.

[0022] Figure 4 is the first diagram showing the simulation results of antenna efficiency. This simulation was performed using an electromagnetic field simulator under the following calculation conditions: <Calculation conditions> Distance d=1mm Length l=13mm Length L = 200 mm Dielectric constant εr=3.5 Dielectric loss tanδ=0.2 Design frequency f=4.5GHz (λ=66.7mm)

[0023] To verify the relationship between the magnitude of the distance D and the antenna efficiency, we performed simulations under the above calculation conditions, setting the distance D to eight levels (1 / 3 / 5 / 7 / 15 / 20 / 50 / ∞mm) between 1mm and infinity as shown in Figure 4, as well as simulations where the dielectric was omitted.

[0024] As can be seen from comparing the antenna efficiency at the design frequency in the graph of simulation results shown in Figure 4, the antenna efficiency increases as the distance D becomes longer. Since there is no significant difference in antenna efficiency when the distance D is 15 mm, 20 mm, or 50 mm, we focused on the four cases where the distance D is 1 mm, 3 mm, 7 mm, and 15 mm, and calculated the difference in antenna efficiency at the design frequency as follows: Note that the following calculation results show values ​​where the loss in the antenna radiating element, antenna ground, and feed cable is assumed to be 2.1 dB, and the antenna efficiency is replaced with the loss of the entire device. <Calculation results> D= 1mm 3.8dB(=5.9dB-2.1dB) * D= 3mm 3.0dB (=5.1dB-2.1dB) *Difference of 0.8dB D= 7mm 2.3dB (=4.4dB-2.1dB) *Difference of 1.5dB D=15mm 1.9dB (=4.0dB-2.1dB) *Difference of 1.9dB

[0025] As is clear from the above calculation results, when the distance D is increased from 1 mm to 3 mm, the loss of the entire device is reduced significantly by 0.8 dB. Also, when the distance D is increased from 3 mm to 7 mm, the loss of the entire device is reduced by 1.5 dB. Also, when the distance D is increased from 7 mm to 15 mm, the loss of the entire device is reduced by 1.9 dB. If the difference is on the order of ±0.8 dB, the effect of this embodiment can be sufficiently confirmed even when the actual device is verified using a general measuring device with a measurement error of about ±0.8 dB.

[0026] Here, since the design frequency f in this simulation is 4.5 GHz (λ = 66.7 mm), a distance D of 3 mm is λ / 22.223. Therefore, when the design frequency is 4.5 GHz, if the condition D ≥ λ / 22.223 is satisfied, it can be said that increasing the distance D significantly reduces loss. Also, when the design frequency f is 4.2 GHz (λ = 71.4 mm), a distance D of 3 mm is λ / 23.8. Therefore, when the design frequency is 4.2 GHz, if the condition D ≥ λ / 23.8 is satisfied, it can be said that increasing the distance D significantly reduces loss. Also, when the design frequency f is 4.7 GHz (λ = 63.8 mm), a distance D of 3 mm is λ / 21.3. Therefore, when the design frequency is 4.7 GHz, if the condition D ≥ λ / 21.3 is satisfied, it can be said that increasing the distance D significantly reduces loss. Therefore, in view of these, when the design frequency is in the 4 GHz band, it can be said that there is an effect of reducing the loss of the antenna ground in the dielectric when the condition D≧λ / 24 is satisfied.

[0027] To confirm the relationship between the effect of increasing the distance D and the length L, we also simulated the overall device loss when the length L was changed under the above calculation conditions. Figure 5 is a second diagram showing the simulation results of antenna efficiency. Figure 5 shows the simulation results of the magnitude of the loss improvement effect when the distance D was set to 15 mm. The simulation results confirmed that, although the loss improvement effect of increasing the distance D is greater when the length L is somewhat longer, the loss improvement effect is also achieved when the length L is short. For example, when the length L is set to 13 mm (L = 1 × λ / 4), the simulation result showed that the loss improvement effect when the distance D was increased from 1 mm to 15 mm was 0.9 dB. Therefore, as mentioned above, although the loss improvement effect of increasing the distance D is inferior to the 1.9 dB improvement effect when the distance D was increased from 1 mm to 15 mm when the length L was 200 mm (L = 15 × λ / 4), it can be said that the loss improvement effect of increasing the distance D is still achieved even when the length L is 13 mm. Furthermore, the loss improvement effect is greater when the length L is 65 mm (L = 5 × λ / 4), and even greater when the length L is 120 mm (L = 5 × λ / 4). Furthermore, although the loss improvement effect is slightly inferior when the length L is 150 mm or more compared to when the length L is 120 mm, it can be said that an effective improvement effect is exerted. Such an improvement effect is considered to be basically the same even if the distance D changes. From the perspective of the loss improvement effect, the length L may be approximately 140 mm (L ≧ (λ / 4) × 8), which is the length at which harmonics are generated.

[0028] Here, as mentioned above, the effect of reducing the loss of the antenna ground in the dielectric is remarkable when the distance D is 3 mm or more when the design frequency f is 4.5 GHz (λ = 66.7 mm). Therefore, when the condition where the length L is 150 mm and the distance D is 3 mm is expressed in terms of wavelength λ (mm), D × L ≥ λ 2 Therefore, if the design frequency is 4.5GHz, D×L≧λ 2When the condition of / 9.89 is satisfied, it can be said that the loss is significantly reduced by increasing the distance D. Also, when the design frequency f is 4.2 GHz (λ=71.4 mm), the condition of length L being 150 mm and distance D being 3 mm expressed in terms of wavelength λ (mm) is D×L≧λ 2 Therefore, when the design frequency is 4.2GHz, D×L≧λ 2 When the condition of / 11.33 is satisfied, it can be said that the loss is significantly reduced by increasing the distance D. Also, when the design frequency f is 4.7 GHz (λ=63.8 mm), the condition of the length L being 150 mm and the distance D being 3 mm, expressed in wavelength λ (mm), is D×L≧λ 2 Therefore, when the design frequency is 4.7GHz, D×L≧λ 2 When the condition of / 9.05 is satisfied, it can be said that the loss is significantly reduced by increasing the distance D. When the frequency is in the 4 GHz band, D×L≧λ 2 When the condition of / 12 is satisfied, it can be said that there is an effect of reducing the loss of the antenna ground in the dielectric.

[0029] The reason why the loss improvement effect of increasing the distance D weakens as the length L shortens is thought to be because the area of ​​the portion of the dielectric facing the antenna ground decreases in proportion to the length L, thereby reducing the proportion of dielectric loss in the overall device loss. For example, when the length L is 13 mm, the overall device loss is 0.9 dB, which is smaller than the 1.9 dB of the overall device loss when the length L is 200 mm. When the proportion of dielectric loss in the overall device loss decreases, the overall device loss itself decreases, and the loss improvement effect of increasing the distance D weakens relatively. Therefore, considering this result, it can be said that practical effects of this embodiment can be expected when the length L is at least sufficiently longer than a quarter wavelength at the design frequency.

[0030] Next, to confirm the relationship between distance d and antenna efficiency, we also performed a simulation of the antenna efficiency when distance d was changed under the above calculation conditions. Figure 6 is the third diagram showing the simulation results of antenna efficiency. This simulation was performed using the electromagnetic field simulator with the following calculation conditions set: <Calculation conditions> Length l = 13 mm Length L = 200 mm Distance D=∞ Dielectric constant εr=3.5 Dielectric loss tanδ=0.2 Design frequency f=4.5GHz (λ=66.7mm)

[0031] To verify the relationship between the magnitude of the distance d and the antenna efficiency, we performed simulations under the above calculation conditions, setting the distance d to six levels (1.0 / 1.5 / 2.0 / 3.0 / 5.0 / 10.0 mm) between 1.0 mm and 10.0 mm as shown in Figure 6, as well as simulations where the dielectric was omitted.

[0032] As can be seen from the simulation results graph shown in Figure 6, which compares antenna efficiency at the design frequency, it can be seen that antenna efficiency increases as distance d increases. However, extending distance d from 1.0 mm to 5.0 mm only improves antenna efficiency by about 0.4 dB. Considering the difficulty of extending distance d due to the structural constraints of the housing of a mobile device, it can be said that the improvement in antenna efficiency commensurate with the increase in distance d is small. Furthermore, changing distance d changes the effect of wavelength shortening due to the dielectric constant of sidewall 5S on antenna radiating element 2 of length l, and therefore, as shown by the circle in the graph of Figure 6, the resonant frequency of antenna radiating element 2 also changes as follows: <Resonance frequency> When d = 1.0 mm, the resonance frequency f = approximately 4.5 GHz When d=1.5mm, the resonance frequency f=approximately 4.6GHz When d = 2.0 mm, the resonance frequency f = approximately 4.6 GHz When d=3.0 mm, the resonance frequency f=approximately 4.7 GHz When d = 5.0 mm, the resonance frequency f = approximately 4.7 GHz When d = 10.0 mm, the resonance frequency f = approximately 4.8 GHz When d = ∞ mm, the resonance frequency f = approximately 5.1 GHz

[0033] From the above, it can be said that it is reasonable to set the distance d within the following range. 0 mm < d ≤ λ / 33 mm (approximately 2 mm)

[0034] <Example> An example in the case where the above-described wireless terminal 1 is a smartphone will be described. FIG. 7 is a diagram showing the appearance of the smartphone according to the example. The smartphone 101 is a portable wireless terminal. The smartphone 101 is provided with a display 6 and an exterior case 7. The display 6 is a display with a touch panel that receives various image displays and input operations. The exterior case 7 is a housing that forms the exterior portion of the edge and the back of the wireless terminal 1, and is formed of, for example, an electrical insulator such as resin.

[0035] FIG. 8 is a diagram showing an example of the internal configuration of the smartphone 101 according to the example. FIG. 8 shows a state where the exterior case 7 of the smartphone 101 is removed from the back side. The smartphone 101 is provided with an exterior frame 8 for enhancing structural rigidity. The exterior frame 8 has a frame-like form into which the exterior case 7 fits, and is formed of, for example, a metal such as aluminum. The antenna radiation element 2 is formed in a form incorporated in a part of the exterior frame 8. Inside the exterior frame 8, an aluminum chassis ground 11 is arranged. The aluminum chassis ground 11 is a plate-like member arranged on the back side of the display 6, and various electronic components such as a substrate ground 9 and a battery 10 are mounted thereon. The substrate ground 9 has, for example, a high-frequency circuit responsible for wireless communication, an image processing circuit responsible for display control of the display 6, a CPU (Central Processing Unit) responsible for various information processing, etc. Also The battery 10 is a rechargeable secondary battery that stores the power to be supplied to the board ground 9 .

[0036] The board ground 9 is attached to the aluminum chassis ground 11 using metal screws, metal gaskets, etc. Therefore, the board ground 9 is electrically connected to the aluminum chassis ground 11 and can be regarded as an integrated antenna ground corresponding to the antenna ground 4 in the above embodiment.

[0037] FIG. 9 is a diagram showing an example of the dimensions of each part of a smartphone 101 according to an embodiment. FIG. 9(A) shows the positional relationship of the internal configuration of smartphone 101 when viewed from the rear side, and FIG. 9(B) shows the positional relationship of the internal configuration of smartphone 101 when viewed from the side. As described above, antenna radiating element 2 is incorporated into a part of exterior frame 8. Antenna radiating element 2 is fed power from the high-frequency circuit of board ground 9 via feed point 3. This board ground 9 is mounted on aluminum chassis ground 11, and the entire aluminum chassis ground 11, including board ground 9, serves as the antenna ground for antenna radiating element 2. Therefore, when exterior case 7 is fitted to exterior frame 8 with board ground 9 and aluminum chassis ground 11 arranged inside, resin exterior case 7, which is a substantially plate-shaped member, is positioned so as to face board ground 9 and aluminum chassis ground 11. The board ground 9 and aluminum chassis ground 11, which serve as antenna grounds for antenna radiating element 2, correspond to antenna ground 4 in wireless terminal 1 described above. Therefore, the resin exterior case 7 arranged in a position facing the board ground 9 and the aluminum chassis ground 11 corresponds to the dielectric 5 in the wireless terminal 1 described above.

[0038] 9, the dimensional symbols D, d, L, and l used in the wireless terminal 1 described above are shown on the equivalent parts of smartphone 101. That is, in Fig. 9, the distance between board ground 9 and exterior case 7 is represented by D, the longitudinal length of aluminum chassis ground 11 is represented by L, the length of antenna radiating element 2 is represented by l, and the distance between antenna radiating element 2 and exterior case 7 is represented by d.

[0039] In the smartphone 101 according to this embodiment, if the distance D and the length L are designed to be the values ​​indicated in the dimensional conditions of the wireless terminal 1 in the above embodiment, even if a high-loss material such as a material with a relative dielectric constant εr of 0.2 is used as the material of the exterior case 7, This can maximize the antenna efficiency of the radiating element 2. This broadens the options for materials for the exterior case 7, making it possible to accommodate a wide variety of designs and concepts. For example, in the case of a smartphone designed around the concept of protecting the global environment, it is conceivable to use an environmentally friendly material for the exterior case 7, even though it has a high relative dielectric constant εr.

[0040] <Modification> Note that the smartphone 101 according to the above-described embodiment may be modified, for example, as follows. FIG. 10 is a diagram showing an example of the internal configuration of the smartphone 101 according to the embodiment. FIG. 11 is a diagram showing an example of the dimensions of each part of the smartphone 101 according to a modified example. This modified example has basically the same configuration as the above-described embodiment, but the shape of the exterior frame 8 is slightly different. That is, while the cross-sectional shapes of the antenna radiating element 2 and the exterior frame 8 in the above-described embodiment are L-shaped as shown in FIG. 9 , in this modified example, the cross-sectional shapes are not L-shaped. Therefore, in this modified example, the antenna radiating element 2 is almost completely covered by the exterior case 7. However, even in the smartphone 101 according to this modified example, if the distance D and the length L are designed to satisfy the values ​​shown in the dimensional conditions of the wireless terminal 1 in the above-described embodiment, the radiation efficiency of the antenna radiating element 2 can be maximized. Therefore, good antenna efficiency can be ensured even for an antenna radiating element 2 that is almost completely covered by the exterior case 7.

[0041] <Other variations> The wireless terminal 1 of the above embodiment and the smartphone 101 according to the examples and modifications may be modified as appropriate. For example, in the smartphone 101 according to the above example and modifications, two board grounds 9 are provided on the aluminum chassis ground 11, but one or three or more board grounds 9 may be provided on the aluminum chassis ground 11. Furthermore, in the smartphone 101 according to the above example and modifications, two antenna radiating elements 2 are provided for a MIMO (Multi-Input Multi-Output) configuration to improve the stability of communication quality, but the number of antenna radiating elements 2 may be one or three or more. The wireless terminal 1 of the above embodiment and the smartphone 101 according to the examples and modifications may be combined as appropriate, or may be modified in various other ways. [Explanation of symbols]

[0042] 1. Wireless terminal 2. Antenna radiating element 3. Power supply point 4. Antenna ground 5. Dielectric 5M··Plane part 5S...Side wall part 6. Display 7. Outer case 8. Exterior frame 9. Board ground 10...battery 11 Aluminum chassis ground 101··Smartphone

Claims

1. A portable wireless terminal, a dielectric exterior case that forms at least a flat portion and a side wall portion on the exterior of the wireless terminal; a plate-shaped antenna ground that serves as a ground for the monopole antenna and is disposed within the exterior case opposite the rear surface of the flat portion at a distance D (mm); an antenna radiating element disposed within the exterior case between a rear surface of the side wall portion and the antenna ground, and electrically connected to the antenna ground via a feeding point; The antenna radiating element is a rod-shaped conductor having a length of 1 (mm) and operating at a predetermined frequency with a wavelength of λ (mm), and is arranged in parallel to the rear surface of the side wall portion at a distance d (mm), When the length of the antenna ground from the end where the feeding point is provided to the opposite end is L (mm), the length L and the distance D are expressed by the following equations (1) and (2) when the predetermined frequency is in the 4 GHz band. D≧λ / 24 (1) D×L≧λ ２ / 12 (2) characterized in that Wireless terminal.

2. The outer case is a dielectric material having a dielectric loss (tan σ) of 0.2 or more. The wireless terminal of claim 1 .

3. The outer case has a side wall portion integrally covering the entire length 1 (mm) of the antenna radiating element, and a flat portion integrally covering the entire length L (mm) of the antenna ground.

3. The wireless terminal according to claim 1 or 2.

4. The distance d is expressed by the formula (3). 0<d≦λ / 33 (3) characterized in that A wireless terminal according to any one of claims 1 to 3.

5. The length L is given by equation (4). L≧(λ / 4)×8 (4) characterized in that A wireless terminal according to any one of claims 1 to 4.

6. The antenna ground is a plate-shaped metal material including a substrate connected to the feed point. A wireless terminal according to any one of claims 1 to 5.

7. the antenna radiating element is part of a frame forming a housing of the wireless terminal; A wireless terminal according to any one of claims 1 to 6.

8. The wireless terminal is a smartphone. A wireless terminal according to any one of claims 1 to 7.

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