JP2021069041A - Antenna device - Google Patents

Abstract

To provide an antenna device that can adjust the impedance and suppress an increase in the number of parts and cost.SOLUTION: An antenna device includes a ground plane, a first element that is arranged so as to face the ground plane at a predetermined distance, and has a feeding point with the ground plane, a second element that is arranged so as to face the ground plane at a predetermined distance and is grounded to the ground plane, and a third element in which a U-shaped folded monopole antenna having a folded portion for connecting the first element and the second element is formed, and that is arranged so as to face the ground plane at a predetermined distance, is connected to the ground plane via a first switch portion, is arranged along the second element with a space from the second element, and is connected to the second element via a second switch portion.SELECTED DRAWING: Figure 8

Description

The present invention relates to an antenna device in which the input impedance can be changed.

It is known that the impedance characteristics of an antenna are affected by an object such as a metal in the vicinity (Non-Patent Document 1). If the impedance characteristics of the antenna fluctuate, the desired characteristics may not be obtained from the antenna. Therefore, in order to reduce the influence when the metal plates are close to each other, a method of appropriately selecting the impedance of the antenna according to the shape of the antenna has been reported (Non-Patent Document 2). Further, in order to reduce the influence when the metal plates are close to each other, a method of adjusting the impedance characteristic of the antenna by providing an external matching circuit has been reported (Non-Patent Document 3).

M. Ohira, IEEE AP-S Int. Proc. pp.978-979, Jun.2013. Y. Nakagawa, et al. IEICE Commun. Express, vol. 6, no. 11, pp.621-626,2017 Koichi Ogawa, Theory of Credit (B), vol. J87-B, no. 9, pp.1287-1298, Sep. 2004

However, in the method of Non-Patent Document 2, since the impedance is adjusted according to the shape of the antenna, there is a problem that the impedance cannot be adjusted after the antenna is created. Further, in the method of Non-Patent Document 3, there is a problem that the number of parts increases and the cost increases because the impedance matching circuit is provided externally. Therefore, an object of the present invention is to provide a means for solving such a problem.

The antenna device according to the aspect of the present invention includes a ground plane, a first element which is arranged so as to face the ground plane at a predetermined distance and has a feeding point between the ground plane, and the ground plane. The first element is provided with a second element which is arranged so as to face each other at a predetermined distance and is grounded to the ground plane, and a folded portion for connecting the first element and the second element. The second element and the folded portion form a U-shaped folded monopole antenna, are arranged so as to face each other at a predetermined distance from the ground plane, and are connected to the ground plane via the first switch portion. It is preferable to further have a third element which is arranged along the second element with a space from the second element and is connected to the second element via a second switch portion.

The antenna device has a first mode in which the first switch unit and the second switch unit are in the OFF state, and a second mode in which the first switch unit and the second switch unit are in the ON state. It is preferable that the value of the input impedance of the second mode at the resonance frequency of the antenna device is larger than the value of the input impedance of the first mode at the resonance frequency.

The antenna device further has a third mode in which the first switch unit is in the ON state and the second switch unit is in the OFF state. In the third mode, the resonance frequency is included in the blocking band. It is preferable to have a resonance frequency different from the resonance frequency.

It is preferable that the second element and the third element have the same length in the longitudinal direction as the ground planes and the portions arranged so as to face each other at a predetermined distance.

The width of the third element, which indicates the length in the direction orthogonal to the longitudinal direction of the third element, is relative to the width of the second element, which indicates the length of the second element in the direction orthogonal to the longitudinal direction. It is preferable that they are the same or that the variation of the resonance frequency is long or short within 1%.

The width of the third element, which indicates the length of the third element in the direction orthogonal to the longitudinal direction, is relative to the width of the second element, which indicates the length of the second element in the direction orthogonal to the longitudinal direction. Therefore, it is preferable that the VSWR value can be varied within a practical range.

The separation distance between the second element and the third element is the same as the separation distance between the first element and the second element, or the fluctuation of the resonance frequency is long within 1%. Or it is preferably short.

Regarding the separation distance between the second element and the third element, it is preferable that the VSWR value can be changed within a practical range with respect to the separation distance between the first element and the second element. ..

Further including at least one or more elements arranged so as to face the ground plane at a predetermined distance and separated from each other, and arranged along the third element with a space from the third element, and at least one of the above. Each end of the above elements is connected to the ground plane via a switch, and the adjacent at least one or more elements are connected to each other at the other end opposite to the end connected to the switch. The element adjacent to the third element of the at least one element, which is connected to the switch portion by another switch portion, is the third element at the other end portion opposite to the end portion connected to the switch portion. Is preferably connected by a third switch unit.

When the first switch unit and the second switch unit are in the second mode in the ON state, when the third element and at least one or more elements are further electrically connected, the third element It is preferable that at least one or more elements connected to the ground plane are connected to the ground plane via the switch portion.

According to the present invention, it is possible to provide an antenna device capable of adjusting the impedance after producing the antenna and suppressing an increase in the number of parts and the cost.

It is a schematic diagram which shows an example of the structure of the antenna device which concerns on this embodiment. It is a schematic diagram which enlarged the main part of the antenna device of FIG. It is a schematic diagram of the Smith chart which shows an example of the impedance characteristic of the antenna device which concerns on this embodiment. It is a schematic diagram of the Smith chart which shows an example of the impedance characteristic with respect to the dimensional change of the 3rd element of the antenna device which concerns on this embodiment. It is a schematic diagram which shows an example of VSWR characteristic of the antenna device of FIG. It is a schematic diagram of the Smith chart which shows an example of the impedance characteristic with respect to the change of the gap dimension between the 2nd element and the 3rd element of the antenna device which concerns on this embodiment. It is a schematic diagram which shows an example of VSWR characteristic of the antenna device of FIG. It is a schematic diagram which shows another example of the structure of the antenna device which concerns on this embodiment. It is a schematic diagram which enlarged the main part of the antenna device of FIG. It is a schematic diagram of the Smith chart which shows an example of the impedance characteristic of the antenna device of FIG. It is a schematic diagram which shows an example of VSWR characteristic of the antenna device of FIG. It is a schematic diagram of the Smith chart including another example of the impedance characteristic of the antenna device of FIG.

Hereinafter, the antenna device according to the present embodiment will be described in detail. The dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

FIG. 1 is an external perspective view of the antenna device 200 according to the embodiment.

The antenna device 200 includes a U-shaped folded monopole antenna (UFMA) including a first element E1 and a second element E2 formed on the ground plane GP, and a third element E3. The U-shaped folded monopole antenna is, for example, a conductor in which a conductor having a length close to 1/2 wavelength of radio waves transmitted and received is bent, and two monopole antenna elements having a length close to 1/4 wavelength are provided in parallel with each other. Is. In this embodiment, the case where the third element E3 functions as a short-circuit element of UFMA will also be described. The details of the antenna device will be described below. In FIG. 1, the X-axis, the Y-axis, and the Z-axis are shown to show the direction of each element.

The ground plane GP, the first element E1, the second element E2, and the third element E3 will be described with reference to FIG.

The ground plane GP is provided parallel to the plane composed of the X-axis and the Y-axis in FIG. The length of the ground plane GP in the X-axis direction is 0.64λ, and the length of the ground plane GP in the Y-axis direction is 0.4λ. λ is the wavelength of radio waves input to or output from the antenna device in free space. The first element E1 is provided at a position parallel to the X-axis direction at one end of the ground plane GP, and the second element E2 and the third element E3 are provided parallel to the first element E1. The first element E1, the second element E2, and the third element E3 do not have to be in a strictly parallel positional relationship, and are installed in a positional relationship in which desired characteristics can be obtained. The feeding point is provided between the first element E1 and the ground plane GP.

Further, the length of the ground plane GP in the X-axis direction and the length in the Y-axis direction are not limited to the above-mentioned dimensions. That is, the length of the ground plane GP in the X-axis direction is preferably longer than the length of the first element E1, the second element E2, and the third element E3 in the X-axis direction. Further, the length of the ground plane GP in the Y-axis direction is preferably longer than the total length of the first element E1, the second element E2, and the third element E3 in the Y-axis direction.

Next, the details of the first element E1, the second element E2, and the third element E3 will be described with reference to FIG.

The first element E1 receives power from a first element main body E11 arranged so as to face the ground plane GP at a predetermined distance h and a power supply circuit (not shown) grounded to the ground plane GP. Includes part E12. The first element power receiving unit E12 is arranged in the Z-axis direction with respect to the ground plane GP, and one end of the first element power receiving unit E12 on the opposite side to the feeding point is electrically connected to the first element main body unit E11. .. The power supply circuit may be formed on a substrate (not shown) forming the ground plane GP, but the formation position of the power supply circuit is not limited to this. The width of the first element main body E11 and the first element power receiving unit E12 in the Y-axis direction is w1, the length of the first element main body E11 in the X-axis direction is l1, and the Z of the first element power receiving unit E12. Let h be the length in the axial direction. Therefore, the length of the first element E1 is (l1 + h). Further, the first element main body portion E11 and the first element power receiving portion E12 may be integrally formed.

The second element E2 has a second element main body portion E21 which is arranged so as to face the ground plane GP at a predetermined distance h and a second element grounding portion E22 which is electrically connected to the ground plane GP and is grounded. including. The second element grounding portion E22 is arranged in the Z-axis direction with respect to the ground plane GP, and one end of the second element grounding portion E22 opposite to the grounding point is electrically connected to the second element main body portion E21. The width of the second element main body E21 and the second element grounding portion E22 in the Y-axis direction is w2, the length of the second element main body E21 in the X-axis direction is l2, and the Z of the second element grounding portion E22. Let h be the length in the axial direction. Therefore, the length of the second element E2 is (l2 + h). Further, the second element main body portion E21 and the second element grounding portion E22 may be integrally formed. Further, the separation distance between the first element E1 and the second element E2 is defined as s1.

The folded-back portion F12 has a side surface of the other end opposite to one end connected to the first element power receiving portion E12 of the first element main body E11, and a second element grounding portion E22 of the second element main body E21. Connect to the side surface of the other end on the opposite side to the one end connected to. That is, the folded-back portion F12 electrically connects the side surface of the other end portion of the first element main body portion E11 and the side surface of the other end portion of the second element main body portion E21 facing the side surface. The length of the folded portion F12 in the Y-axis direction is s1, and the width in the X-axis direction is w12. The width w12 of the folded-back portion F12 has the same dimensions as the width w1 of the first element E1 and the width w2 of the second element E2. In FIG. 1, the width w1 of the first element E1 and the width w2 of the second element E2 have the same dimensions, but the dimensions of the width w1 and the width w2 can be different. In this case, the width w12 of the folded-back portion F12 can also be changed by the dimension between the width w1 and the width w2. The first element E1 and the second element E2 are electrically connected by a folded-back portion F12, and the first element E1, the second element E2 and the folded-back portion F12 form an element included in the U-shaped folded monopole antenna FA1. .. Further, the first element E1, the second element E2, and the folded-back portion F12 may be integrally formed.

The third element E3 has a third element main body portion E31 arranged so as to face the ground plane GP at a predetermined distance h and a third element grounding portion E32 that is electrically connected to the ground plane GP and grounded. including. The third element grounding portion E32 is arranged in the Z-axis direction with respect to the ground plane GP. The third element main body portion E31 and the third element grounding portion E32 may be electrically connected and integrally formed. When the switch unit S31 is ON, the third element grounding unit E32 is electrically connected to the ground plane GP via the switch unit S31 and grounded. Further, when the switch portion S31 is OFF, the third element grounding portion E32 is electrically disconnected from the ground plane GP and is in an open state.

Further, the third element main body E31 is electrically connected to the second element E2 via the switch S32 when the switch S32 is ON. Further, when the switch portion S32 is OFF, the third element main body portion E31 is electrically disconnected from the second element E2 and is in an open state. Examples of the switch unit S31 and the switch unit S32 include, but are not limited to, a PIN diode.

The length obtained by combining the length of the third element grounding portion E32 in the Z-axis direction and the length of the switch portion S31 in the Z-axis direction may be referred to as h.

Further, the width of the third element E3 in the Y-axis direction is w3, the length of the third element main body E31 in the X-axis direction is l3, and the separation distance between the second element E2 and the third element E3 is s2. It may be called.

Table 1 shows the width w1 of the first element E1, the width w2 of the second element E2, the width w3 of the third element E3, the length l1 of the first element E1 in the longitudinal direction, and the length of the second element E2 in the longitudinal direction. An example of dimensions such as length l3 in the longitudinal direction of l2 and the third element E3 is shown. Further, in Table 1, the separation distance s1 between the first element E1 and the second element E2, the separation distance s2 between the second element E2 and the third element E3, and the predetermined distance h from the ground plane GP are shown. An example of dimensions is also included. λ is the wavelength of the free space of the radio wave input to the antenna device or output from the antenna device. In this embodiment, the frequency of the radio wave is 2.4 GHz, the dimensions of each component are determined, and the characteristics such as impedance are measured. doing.

The length (l1 + l2 + 2h + w12) of the U-shaped folded monopole antenna FA1 is slightly shorter (0.478λ) from 1/2 wavelength (however, w12 = 0.008λ). The length of the U-shaped folded monopole antenna FA1 is slightly shorter than 1/2 wavelength because the thickness of the portion that functions as the antenna is taken into consideration. When the frequency is 2.4 GHz, w1, w2, w3, s1 and s2 are about 1 mm, h is about 3 mm, and l1, l2 and l3 are about 26.4 mm.

FIG. 3 shows a Smith chart (impedance plane) of simulation results when the antenna device 200 having the above dimensions described in FIG. 2 is arranged in a free space. In FIG. 3, the horizontal axis shows the value of the real part of the input impedance of the antenna device 200, and the circumferential value shows the value of the imaginary part of the input impedance of the antenna device 200. The upper half region of the circle in FIG. 3 shows the region where the imaginary part is inductive, and the lower half region of the circle in FIG. 3 shows the region where the imaginary part is capacitive. The solid line L1 in FIG. 3 shows that the frequency applied to the feeding point of the first element E1 changes from about 2.0 GHz to about 2.8 GHz when the switch portions S31 and the switch portions S32 at both ends of the third element E3 are in the OFF state. The change of the input impedance when it is made is shown. The frequency applied to the feeding point is about 2.4 GHz and the solid line L1 intersects the horizontal axis of the Smith chart, indicating that the antenna device resonates at about 2.4 GHz. The value of the input impedance at the intersection C1 between the solid line L1 and the horizontal axis is about 44.6Ω. That is, when the switch portions S31 and the switch portions S32 at both ends of the third element E3 are in the OFF state, they resonate at about 2.4 GHz, and the input impedance of the antenna device at about 2.4 GHz is about 44.6 Ω. The mode in which the switch portions S31 and the switch portions S32 at both ends of the third element E3 are in the OFF state may be referred to as mode 1.

The end of the capacitive region of the solid line L1 shows a point at a frequency of about 2.0 GHz, and the end of the inductive region of the solid line L1 shows a point at a frequency of about 2.8 GHz.

In the solid line L2 of FIG. 3, the frequency applied to the feeding point of the first element E1 is changed from about 2.0 GHz to about 2.8 GHz when the switch portions S31 and the switch portions S32 at both ends of the third element E3 are in the ON state. The change of the input impedance when it is made is shown. The frequency applied to the feeding point is about 2.4 GHz and the solid line L2 intersects the horizontal axis of the Smith chart, indicating that the antenna device resonates at about 2.4 GHz. The value of the input impedance at the intersection C2 between the solid line L2 and the horizontal axis is about 71.4Ω. That is, when the switch portions S31 and the switch portions S32 at both ends of the third element E3 are in the ON state, they resonate at about 2.4 GHz, and the input impedance of the antenna device at about 2.4 GHz is about 71.4 Ω. The mode in which the switch portions S31 and the switch portions S32 at both ends of the third element E3 are in the ON state may be referred to as mode 2.

The end of the capacitive region of the solid line L2 shows a point at a frequency of about 2.0 GHz, and the end of the inductive region of the solid line L2 shows a point at a frequency of about 2.8 GHz.

The solid line L1 and the solid line L2 in FIG. 3 resonate with each other without changing the resonance frequency depending on whether the switch portions S31 and the switch portions S32 at both ends of the third element E3 are both in the OFF state or the ON state. It shows that the input impedance at the frequency changes. In the present embodiment, when the third element E3, which is a non-feeding element, is connected in parallel with the second element E2, which is a non-feeding element, the resonance frequency does not change and the input impedance at the resonance frequency becomes high impedance. To do. When the conductive infinite ground plate approaches the ground plane GP from the Z-axis direction parallel to the ground plane GP, the input impedance of the antenna device decreases. Therefore, when the infinite ground plate or the conductive plate such as metal approaches the ground plane GP from the Z-axis direction, the switch portions S31 and the switch portions S32 at both ends of the third element E3 of the antenna device are turned on. This makes it possible to prevent the input impedance of the antenna device from decreasing. That is, by turning on the switches at both ends of the third element E3 of the antenna device, it is possible to prevent the value of VSWR (Voltage Standing Wave Ratio) of the antenna device from becoming large. In this case, the mode in which the input impedance of the antenna device can be changed by changing the width dimension of the third element E3 or the distance between the second element E2 and the third element E3 will be described in detail below.

FIG. 4 is a Smith chart showing a change in input impedance when the width w3 of the third element E3 is changed in an antenna device including the first element E1 and the second element E2. The dimensions of the first element E1 and the second element E2 are as shown in Table 1, and the separation distance s2 between the second element E2 and the third element E3 is fixed at 0.008λ. That is, the dimensions of the first element E1 and the second element E2 in the measurement of FIG. 4 are the same as the dimensions of the first element E1 and the second element E2 in the measurement of FIG. Referring to FIG. 4, the resonance frequency at w3 = 0.002λ is about 2.4 GHz, and the input impedance at the resonance frequency is 56.7 Ω. The resonance frequency at w3 = 0.004λ is about 2.4 GHz, and the input impedance at the resonance frequency is 61.1 Ω. The resonance frequency at w3 = 0.016λ is about 2.4 GHz, and the input impedance at the resonance frequency is 83.1 Ω. The resonance frequency at w3 = 0.024λ is about 2.4 GHz, and the input impedance at the resonance frequency is 96.7 Ω. The resonance frequency at w3 = 0.032λ is about 2.4 GHz, and the input impedance at the resonance frequency is 110 Ω. That is, the resonance frequency hardly changes with respect to the width w2 of the second element E2 in both the case where the width w3 of the third element E3 is narrow and the case where the width w3 is thick. Therefore, it is possible to change the input impedance of the antenna device 200 by changing the width w3 of the third element E3. Further, the narrower the width w3 of the third element E3, the smaller the value of the input impedance of the antenna device 200, and the thicker the width w3 of the third element E3, the larger the value of the input impedance of the antenna device 200. In FIG. 3, even if the width w3 of the third element E3 is changed from 1/4 to 4 times the width of the first element E1 and the second element E2, the resonance frequency is substantially changed. Without doing so, the input impedance changes significantly. Further, in FIG. 4, the change between the resonance frequency at w3 = 0.002λ and the resonance frequency at w3 = 0.032λ can be kept within 0.4% with respect to 2.4 GHz. ing.

In FIG. 4, the end of the capacitive region of each line shows a point at a frequency of about 2.0 GHz, and the end of the inductive region of each line shows a point at a frequency of about 2.8 GHz.

FIG. 5 is a diagram showing a change in VSWR when the width w3 of the third element E3 is changed in the antenna device 200 including the first element E1 and the second element E2 in FIG. The separation distance s2 between the second element E2 and the third element E3 is fixed at 0.008λ. At VSWR = 1, all power is input to the antenna without loss. Generally, VSWR = 3 is said to be the practical limit of the antenna. The resonance frequency at w3 = 0.002λ of the present embodiment is about 2.4 GHz, and the VSWR value at the resonance frequency is 1.14. The resonance frequency at w3 = 0.004λ is about 2.4 GHz, and the VSWR value at the resonance frequency is 1.22. The resonance frequency at w3 = 0.008λ is about 2.4 GHz, and the VSWR value at the resonance frequency is 1.38. The resonance frequency at w3 = 0.016λ is about 2.4 GHz, and the VSWR value at the resonance frequency is 1.66. The resonance frequency at w3 = 0.024λ is about 2.4 GHz, and the VSWR value at the resonance frequency is 1.94. The resonance frequency at w3 = 0.032λ is about 2.4 GHz, and the VSWR value at the resonance frequency is 2.20. Therefore, it is shown that the antenna device 200 of the present embodiment can be practically used in the dimension of w3 = 0.032λ or less.

As shown in FIGS. 4 and 5, when the width w3 of the third element E3 is changed, the actual part of the input impedance of the antenna device 200 can be adjusted without substantially changing the resonance frequency. It will be possible. Further, the input impedance of the antenna device 200 is determined by (width w2 of the second element E2) + (width w3 of the third element E3) + (distance s2 between the second element E2 and the third element E3). Therefore, with respect to the width w2 (= 0.008λ) of the second element E2, the resonance frequency hardly changes regardless of whether the third element E3 is thin or thick, and the input of the antenna device 200 is input. It becomes possible to adjust the impedance.

FIG. 6 shows the input impedance when the separation distance s2 between the second element E2 and the third element E3 is changed in the antenna device 200 including the first element E1 and the second element E2 in FIGS. 4 and 5. It is a Smith chart showing the change of. The width w3 of the third element E3 is 0.008λ, which is the same as the width w2 of the second element E2. The resonance frequency at s2 = 0.004λ is about 2.4 GHz, and the input impedance at the resonance frequency is 65.0 Ω. The resonance frequency at s2 = 0.008λ is about 2.4 GHz, and the input impedance at the resonance frequency is 69.1 Ω. The resonance frequency at s2 = 0.012λ is about 2.4 GHz, and the input impedance at the resonance frequency is 71.3 Ω. The resonance frequency at s2 = 0.016λ is about 2.4 GHz, and the input impedance at the resonance frequency is 72.8 Ω. As described above, when the separation distance s2 between the second element E2 and the third element E3 increases, the actual part of the input impedance slightly increases. Further, in FIG. 6, the change between the resonance frequency at s2 = 0.004λ and the resonance frequency at s2 = 0.016λ can be kept within 0.6% with respect to 2.4 GHz. ing.

In FIG. 6, the end of the capacitive region of each line shows a point at a frequency of about 2.0 GHz, and the end of the inductive region of each line shows a point at a frequency of about 2.8 GHz.

FIG. 7 shows a change in VSWR when the separation distance s2 between the second element E2 and the third element E3 is changed in the antenna device 200 including the first element E1 and the second element E2 in FIG. It is a figure. The width w3 of the third element E3 is 0.008λ, which is the same as the width w2 of the second element E2. As described above, at VSWR = 1, all power is input to the antenna without loss. Generally, VSWR = 3 is said to be the practical limit of the antenna. The resonance frequency at s2 = 0.004λ of this embodiment is about 2.4 GHz, and the VSWR value at the resonance frequency is 1.30. The resonance frequency at s2 = 0.008λ is about 2.4 GHz, and the VSWR value at the resonance frequency is 1.38. The resonance frequency at s2 = 0.012λ is about 2.4 GHz, and the VSWR value at the resonance frequency is 1.44. The resonance frequency at s2 = 0.016λ is about 2.4 GHz, and the VSWR value at the resonance frequency is 1.49. Therefore, it is shown that the antenna device 200 of the present embodiment can be practically used at a dimension of the separation distance s2 = 0.016λ or less between the second element E2 and the third element E3.

As shown in FIGS. 6 and 7, when the separation distance s2 between the second element E2 and the third element E3 is changed, the actual input impedance of the antenna device 200 is not changed without changing the resonance frequency. It becomes possible to adjust the part. Further, the input impedance of the antenna device 200 is determined by (width w2 of the second element E2) + (width w3 of the third element E3) + (distance s2 between the second element E2 and the third element E3). At a dimension of the separation distance s2 = 0.016λ or less between the second element E2 and the third element E3, the input impedance of the antenna device 200 can be adjusted with almost no change in the resonance frequency.

FIG. 8 shows an antenna device when a fourth element and a fifth element are further added to the first element E1, the second element E2, and the third element E3 in FIG. 2 to increase the step-up ratio. It is a figure which shows the whole structure of 200.

FIG. 9 is a diagram showing a configuration of an antenna device 200 in which the first element E1, the second element E2, the third element E3, the fourth element, and the fifth element portion in FIG. 8 are enlarged.

The fourth element E4 in FIG. 9 has a fourth element main body E41 arranged so as to face the ground plane GP at a predetermined distance h, and a fourth element that is electrically connected to the ground plane GP and grounded. Includes grounding section E42. The fourth element grounding portion E42 is arranged in the Z-axis direction with respect to the ground plane GP. The fourth element main body portion E41 and the fourth element grounding portion E42 may be electrically connected and integrally formed. When the switch unit S41 is ON, the fourth element grounding unit E42 is electrically connected to the ground plane GP via the switch unit S41 and grounded. Further, when the switch portion S41 is OFF, the fourth element grounding portion E42 is electrically disconnected from the ground plane GP and is in an open state.

Further, the fourth element main body E41 is electrically connected to the third element E3 via the switch S42 when the switch S42 is ON. Further, when the switch portion S42 is OFF, the fourth element main body portion E41 is electrically disconnected from the third element E3 and is in an open state. An example of the switch unit S41 and the switch unit S42 includes, but is not limited to, a PIN diode.

The length obtained by combining the length of the fourth element grounding portion E42 in the Z-axis direction and the length of the switch portion S41 in the Z-axis direction may be referred to as h.

Further, the width of the fourth element E4 in the Y-axis direction is w4, the length of the fourth element main body E41 in the X-axis direction is l4, and the separation distance between the third element E3 and the fourth element E4 is s3. It may be called.

The fifth element E5 in FIG. 9 will be described below in the same manner as the fourth element E4.

The fifth element E5 in FIG. 9 is a fifth element main body E51 that is arranged so as to face the ground plane GP at a predetermined distance h, and a fifth element that is electrically connected to the ground plane GP and grounded. Includes grounding section E52. The fifth element grounding portion E52 is arranged in the Z-axis direction with respect to the ground plane GP. The fifth element main body portion E51 and the fifth element grounding portion E52 may be electrically connected and integrally formed. When the switch unit S51 is ON, the fifth element grounding unit E52 is electrically connected to the ground plane GP via the switch unit S51 and grounded. Further, when the switch portion S51 is OFF, the fifth element grounding portion E52 is electrically disconnected from the ground plane GP and is in an open state.

Further, the fifth element main body E51 is electrically connected to the fourth element E4 via the switch S52 when the switch S52 is ON. Further, the fifth element main body E51 is electrically disconnected from the fourth element E4 when the switch S52 is OFF, and is in an open state. An example of the switch unit S51 and the switch unit S52 includes, but is not limited to, a PIN diode.

The length obtained by combining the length of the fifth element grounding portion E52 in the Z-axis direction and the length of the switch portion S51 in the Z-axis direction may be referred to as h.

Further, the width of the fifth element E5 in the Y-axis direction is w5, the length of the fifth element main body E51 in the X-axis direction is l5, and the separation distance between the fourth element E4 and the fifth element E5 is s4. It may be called.

In the present embodiment, the length and width of the first element E1, the second element E2, the third element E3, the fourth element E4, and the fifth element E5 are the same, and the distance from the ground plane GP is also the same. .. Further, between the first element E1 and the second element E2, between the second element E2 and the third element E3, between the third element E3 and the fourth element E4, the fourth element E4 and the fifth element E5. The distance between and is the same. That is, l1, l2, l3, l4 and l5 are 0.211λ, w1, w2, w3, w4 and w5 are 0.008λ, s1, s2, s3 and s3 are 0.008λ and h is. It is 0.024λ.

FIG. 10 shows a Smith chart (impedance plane) of simulation results when the antenna device 200 having the above dimensions shown in FIGS. 8 and 9 is arranged in free space. In FIG. 10, the horizontal axis shows the value of the real part of the input impedance of the antenna device 200, and the circumferential value shows the value of the imaginary part of the input impedance of the antenna device 200. The upper half region of the circle in FIG. 10 shows the region where the imaginary part is inductive, and the lower half region of the circle in FIG. 10 shows the region where the imaginary part is capacitive. The solid line shown without the additional element connection in FIG. 10 shows the impedance characteristics of the antenna device 200 when the third element E3, the fourth element E4, and the fifth element E5 are open. That is, when no additional element is connected, the antenna device 200 is a case where the switches at both ends of the third element E3 are in the OFF state, the switches at both ends of the fourth element E4 are in the OFF state, and the switches at both ends of the fifth element E5 are in the OFF state. It is the impedance characteristic of. When the switches at both ends of the third element E3 are in the OFF state, it means that the switch unit S31 and the switch unit S32 are in the OFF state. Further, the OFF state of the switches at both ends of the fourth element E4 indicates that the switch unit S41 and the switch unit S42 are in the OFF state. Further, the OFF state of the switches at both ends of the fifth element E5 indicates that the switch unit S51 and the switch unit S52 are in the OFF state.

In such a state, the solid line shown without the additional element connection in FIG. 10 shows the input impedance when the frequency applied to the feeding point of the first element E1 is changed from about 2.0 GHz to about 2.8 GHz. Show change. The frequency applied to the feeding point is about 2.4 GHz and the solid line shown without additional element connection intersects the horizontal axis of the Smith chart, indicating that the antenna device 200 resonates at about 2.4 GHz. Further, the value of the input impedance at the intersection of the solid line and the horizontal axis shown without the additional element connection is about 44.5Ω. That is, when the switches at both ends of the third element E3, the fourth element E4, and the fifth element E5 are in the OFF state, resonance occurs at about 2.4 GHz, and the input impedance of the antenna device 200 at about 2.4 GHz is about 44. It becomes .5Ω. Therefore, as compared with FIG. 3, it can be seen that there is almost no difference in input impedance between the presence and absence of the unconnected fourth element E4 and fifth element E5.

The solid line shown by E3 in FIG. 10 shows the frequency applied to the feeding point of the first element E1 from about 2.0 GHz to about 2. The change in the input impedance when changed to 8 GHz is shown. The solid line indicated by E3 indicates that the fourth element E4 and the fifth element E5 are in the open state. The solid line indicated by E3 at a frequency applied to the feeding point of about 2.4 GHz indicates that the antenna device 200 resonates at about 2.4 GHz, intersecting the horizontal axis of the Smith chart. The value of the input impedance at the intersection of the solid line and the horizontal axis indicated by E3 is about 71.1Ω. That is, when the switches at both ends of the third element E3 are in the ON state and the fourth element E4 and the fifth element E5 are in the open state, the antenna device 200 resonates at about 2.4 GHz and is at about 2.4 GHz. The input impedance of is about 71.1Ω.

The solid line shown by E3 + E4 in FIG. 10 shows the frequency applied to the feeding point of the first element E1 from about 2.0 GHz to about 2.8 GHz with the switches at both ends of the third element E3 and the fourth element E4 turned on. The change in input impedance when changed to is shown. In the solid line indicated by E3 + E4, the fifth element E5 is in the open state. The frequency applied to the feeding point is about 2.4 GHz and the solid line indicated by E3 + E4 intersects the horizontal axis of the Smith chart, indicating that the antenna device 200 resonates at about 2.4 GHz. The value of the input impedance at the intersection of the solid line represented by E3 + E4 and the horizontal axis is about 96.4 Ω. That is, when the switches at both ends of the third element E3 and the fourth element E4 are in the ON state and the fifth element E5 is in the open state, the antenna device 200 resonates at about 2.4 GHz and is at about 2.4 GHz. The input impedance of is about 96.4Ω.

The solid line indicated by E3 + E4 + E5 in FIG. 10 indicates that the switches at both ends of the third element E3, the fourth element E4, and the fifth element E5 are in the ON state. The solid line indicated by E3 + E4 + E5 indicates the change in input impedance when the frequency applied to the feeding point of the first element E1 is changed from about 2.0 GHz to about 2.8 GHz. The frequency applied to the feeding point is about 2.4 GHz and the solid line indicated by E3 + E4 + E5 intersects the horizontal axis of the Smith chart, indicating that the antenna device 200 resonates at about 2.4 GHz. Further, the value of the input impedance at the intersection of the solid line represented by E3 + E4 + E5 and the horizontal axis is about 122Ω. That is, when the switches at both ends of the third element E3, the fourth element E4, and the fifth element E5 are in the ON state, they resonate at about 2.4 GHz, and the input impedance of the antenna device 200 at about 2.4 GHz is about 122 Ω. It becomes.

As described above, the value of the input impedance can be controlled by making the total width of the short-circuit elements of the FMA including the first element E1 and the second element E2 variable. In particular, when the total width of the short-circuit elements is increased, the value of the input impedance increases, so that the input impedance of the antenna device 200 can be appropriately controlled when the metal plate approaches the antenna device 200. That is, by increasing the number of additional elements connected to the second element E2, which is a non-feeding element, it is possible to increase the amount of change in the input impedance of the antenna device 200.

FIG. 11 shows a change in VSWR with respect to a change in frequency applied to the feeding point of the antenna device 200 including the first element E1, the second element E2, the third element E3, the fourth element E4, and the fifth element E5 in FIG. It is a figure which shows.

The horizontal axis of FIG. 11 shows the change in the frequency applied to the feeding point, and the vertical axis of FIG. 11 shows the change in VSWR. The solid line shown without the additional element connection in FIG. 11 corresponds to the configuration of the solid line shown without the additional element connection in FIG. That is, the solid line shown without the additional element connection in FIG. 11 shows the VSWR characteristics of the antenna device 200 in which the third element E3, the fourth element E4, and the fifth element E5 are in the open state. Further, the solid line shown by E3 in FIG. 11 corresponds to the configuration of the solid line shown by E3 in FIG. That is, the solid line shown by E3 in FIG. 11 shows VSWR characteristics in which the switch portions S31 and the switch portions S32 at both ends of the third element E3 are in the ON state, and the fourth element E4 and the fifth element E5 are in the open state. Shown. Further, the solid line shown by E3 + E4 in FIG. 11 corresponds to the configuration of the solid line shown by E3 + E4 in FIG. That is, the solid line shown by E3 + E4 in FIG. 11 shows the VSWR characteristic in which the switches at both ends of the third element E3 and the fourth element E4 are in the ON state and the fifth element E5 is in the open state. Further, the solid line shown by E3 + E4 + E5 in FIG. 11 corresponds to the configuration of the solid line shown by E3 + E4 + E5 in FIG. That is, the solid line shown by E3 + E4 + E5 in FIG. 11 shows the VSWR characteristics when the switches at both ends of the third element E3, the fourth element E4, and the fifth element E5 are in the ON state.

The value of VSWR in the case of the solid line indicated by E3 + E4 + E5 in FIG. 11 is larger than the value of VSWR in the case of the solid line indicated by E3 and E3 + E4. However, at 2.4 GHz, which is the resonance frequency of the antenna device 200, the solid VSWR value indicated by E3 + E4 + E5 is 3 or less, indicating that there is no practical problem.

As described above, the results of the VSWR characteristics indicate that the input impedance can be controlled with almost no influence on the resonance frequency according to the present embodiment.

The features of the antenna device 200 of this embodiment will be described below.

The antenna device 200 according to the first aspect of the present invention is a first element which is arranged so as to face the ground plane GP at a predetermined distance from the ground plane GP and has a feeding point SP between the ground plane GP and the ground plane GP. Including E1. Further, the antenna device 200 is arranged so as to face the ground plane GP at a predetermined distance at a distance from each other, and is folded back to connect the second element E2 grounded to the ground plane GP and the first element E1 and the second element E2. Includes part F12. The first element E1, the second element E2, and the folded portion F12 form a U-shaped folded monopole antenna. Further, the antenna device 200 includes a third element E3. The third element E3 is arranged so as to face the ground plane GP at a predetermined distance at a distance from each other, and is connected to the ground plane GP via the switch unit S31. Further, the third element E3 is arranged along the second element E2 with a space from the second element E2, and is connected to the second element E2 via the switch portion S32. The switch unit S31 may be referred to as a first switch unit, and the switch unit S32 may be referred to as a second switch unit.

According to the above configuration, it is possible to provide an antenna device capable of adjusting the impedance after producing the antenna and suppressing an increase in the number of parts and the cost.

The antenna device 200 according to the second aspect of the present invention includes a first mode in which the switch unit S31 and the switch unit S32 are in the OFF state, and a second mode in which the switch unit S31 and the switch unit S32 are in the ON state. The value of the input impedance of the second mode at the resonance frequency of the antenna device 200 is larger than the value of the input impedance of the first mode at the resonance frequency.

According to the above configuration, by connecting the third element E3 along the second element E2, which is a non-feeding element, with reference to the input impedance of the U-shaped folded monopole antenna, the resonance frequency fluctuates practically. The input impedance can be increased without it. Therefore, when the metal plate approaches the antenna device 200, the input impedance of the antenna device 200 can be controlled by setting the antenna device 200 to the second mode.

The antenna device 200 according to the third aspect of the present invention further includes a third mode in which the switch unit S31 is in the ON state and the switch unit S32 is in the OFF state. In the third mode, the resonance frequency is included in the blocking band and has a resonance frequency different from the resonance frequency.

The antenna device 200 according to the fourth aspect of the present invention has the same length in the longitudinal direction as the portions of the second element E2 and the third element E3 that are arranged so as to face each other at a predetermined distance from the ground plane GP. It is preferable to have.

According to the above configuration, the third element E3 operates as a short-circuit element of the U-shaped folded monopole antenna, and the short-circuit element width is equivalently increased, so that the input impedance can be increased.

In the antenna device 200 according to the fifth aspect of the present invention, the width of the third element E3 indicating the length in the direction orthogonal to the longitudinal direction of the third element E3 is in the direction orthogonal to the longitudinal direction of the second element E2. It is preferably the same as the width of the second element E2 indicating the length. Alternatively, it is preferable that the fluctuation of the resonance frequency is within 1% and the width of the third element E3 is longer or shorter than the width of the second element E2.

According to the above configuration, not only when the width of the third element E3 is the same as the width of the second element E2, but also whether it is wider or narrower than the width of the second element E2, the fluctuation of the resonance frequency is a problem in practical use. It is possible to adjust the input impedance within a range that does not exist. As an example, the width of the third element E3 can be adjusted in the range of 4 times to more than 1/4 times the width of the second element E2.

In the antenna device 200 according to the sixth aspect of the present invention, it is preferable that the width of the third element E3 has a VSWR value that can vary within a practical range with respect to the width of the second element E2.

According to the above configuration, not only when the width of the third element E3 is the same as the width of the second element E2, but also whether it is wider or narrower than the width of the second element E2, the fluctuation of the resonance frequency and the VSWR value It is possible to adjust the fluctuation within a range where there is no problem in practical use. As an example, the width of the third element E3 can be adjusted in the range of 4 times to more than 1/4 times the width of the second element E2. The input impedance can be changed within the adjustable range.

In the antenna device 200 according to the seventh aspect of the present invention, the separation distance between the second element E2 and the third element E3 is the same as the separation distance between the first element E1 and the second element E2. It is preferable that the fluctuation of the resonance frequency is long or short within 1%.

According to the above configuration, the separation distance between the second element E2 and the third element E3 is the same as the separation distance between the first element E1 and the second element E2, and the resonance frequency fluctuates regardless of whether it is wide or narrow. It is possible to make adjustments within a range that does not cause any problems in practical use. As an example, the separation distance between the second element E2 and the third element E3 can be adjusted in the range of 2 to more than 1/2 times the separation distance between the 1st element E1 and the 2nd element E2. is there. The input impedance can be changed within the adjustable range.

In the antenna device 200 according to the eighth aspect of the present invention, the separation distance between the second element E2 and the third element E3 is relative to the separation distance between the first element E1 and the second element E2. It is preferable that the VSWR value can be varied within a practical range.

According to the above configuration, the separation distance between the second element E2 and the third element E3 can be adjusted within a range in which fluctuations in the resonance frequency and fluctuations in the VSWR value are not problematic in practical use. That is, not only when the separation distance between the second element E2 and the third element E3 is the same as the separation distance between the first element E1 and the second element E2, but also when it is larger than the width of the second element E2. It can be adjusted widely or narrowly. As an example, the separation distance between the second element E2 and the third element E3 can be adjusted in the range of 2 to more than 1/2 times the separation distance between the 1st element E1 and the 2nd element E2. is there. The input impedance can be changed within the adjustable range.

The antenna device 200 according to the ninth aspect of the present invention is arranged so as to face the ground plane GP at a predetermined distance at a predetermined distance, and is arranged along the third element E3 with a space from the third element E3. It further contains one or more elements. Each end of at least one or more elements is connected to the ground plane GP via the switch portions S41 and S51. At least one or more adjacent elements are connected to each other by another switch portion S52 at the other end on the opposite side to the end connected to the switch portions S41 and S51. The elements adjacent to the third element E3 of at least one or more elements are connected to the third element E3 by the switch portion S42 at the other end opposite to the end portion connected to the switch portions S41 and S51. The switch unit S42 may be referred to as a third switch unit.

According to the above configuration, it is possible to increase the amount of change in the input impedance of the antenna device 200 by increasing the number of additional elements.

In the antenna device 200 according to the tenth aspect of the present invention, at least one or more elements may be further electrically connected to the third element E3 in the second mode. In this case, at least one or more elements connected to the third element E3 are connected to the ground plane via the switch portions S41 and S51.

According to the above configuration, it is possible to increase the amount of change in the input impedance of the antenna device 200 by increasing the number of additional elements connected to the second element E2, which is a non-feeding element.

Although the embodiments have been described in detail with reference to the drawings, the present invention is not limited to the contents described in the above embodiments. In addition, the components described above include those that can be easily assumed by those skilled in the art and those that are substantially the same. Further, the configurations described above can be combined as appropriate. In addition, various omissions, substitutions or changes of the configuration can be made without departing from the gist of the present invention.

E1 1st element E2 2nd element E3 3rd element E4 4th element E5 5th element F12 Folded part GP ground plane SP Feeding point S31, S32, S41, S42, S51, S52 Switch part 200 Antenna device

Claims (10)

With the ground plane
A first element which is arranged so as to face the ground plane at a predetermined distance and has a feeding point between the ground plane and the ground plane.
A second element, which is arranged so as to face the ground plane at a predetermined distance and is grounded to the ground plane,
A folded portion for connecting the first element and the second element is provided, and the first element, the second element, and the folded portion form a U-shaped folded monopole antenna.
It is arranged so as to face the ground plane at a predetermined distance and separated from each other, connected to the ground plane via the first switch portion, and arranged along the second element with a space from the second element. An antenna device further comprising the second element and a third element connected via a second switch portion. The antenna device has a first mode in which the first switch unit and the second switch unit are in the OFF state, and a second mode in which the first switch unit and the second switch unit are in the ON state. The antenna device according to claim 1, wherein the value of the input impedance of the second mode at the resonance frequency of the antenna device is larger than the value of the input impedance of the first mode at the resonance frequency. The antenna device further has a third mode in which the first switch unit is in the ON state and the second switch unit is in the OFF state. In the third mode, the resonance frequency is included in the blocking band. The antenna device according to claim 2, which has a resonance frequency different from the resonance frequency. The invention according to any one of claims 1 to 3, wherein the second element and the third element have the same length in the longitudinal direction as the ground plane and the portions arranged so as to face each other at a predetermined distance. Antenna device. The width of the third element, which indicates the length in the direction orthogonal to the longitudinal direction of the third element, is relative to the width of the second element, which indicates the length of the second element in the direction orthogonal to the longitudinal direction. The antenna device according to any one of claims 2 to 4, which is the same or has a long or short resonance frequency variation within 1%. The width of the third element, which indicates the length of the third element in the direction orthogonal to the longitudinal direction, is relative to the width of the second element, which indicates the length of the second element in the direction orthogonal to the longitudinal direction. The antenna device according to claim 5, wherein the VSWR value is variable within a practical range. The separation distance between the second element and the third element is the same as the separation distance between the first element and the second element, or the variation of the resonance frequency is long within 1%. Alternatively, the antenna device according to any one of claims 2 to 4, which is short. 7. The distance between the second element and the third element is such that the VSWR value can be varied within a practical range with respect to the distance between the first element and the second element. The antenna device described in. Further including at least one or more elements arranged so as to face the ground plane at a predetermined distance and separated from each other, and arranged along the third element with a space from the third element, and at least one of the above. Each end of the above elements is connected to the ground plane via a switch, and the adjacent at least one or more elements are connected to each other at the other end opposite to the end connected to the switch. The element adjacent to the third element of the at least one element, which is connected to the switch portion by another switch portion, is the third element at the other end portion opposite to the end portion connected to the switch portion. The antenna device according to any one of claims 1 to 8, which is connected to the antenna device by the third switch unit. When the first switch unit and the second switch unit are in the second mode in the ON state, when the third element and the at least one or more elements are further electrically connected, the third element The antenna device according to claim 9, wherein the at least one or more elements connected to the ground plane are connected to the ground plane via the switch unit.

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