Antenna apparatus

Abstract

An antenna apparatus according to the present disclosure comprises: a metal housing (10) that has an opening (10a) in one surface and that has disposed therein a liquid crystal display device (40) having a transparent conductive film facing the opening (10a); an antenna conductor (30) that transmits visible light, forms a gap serving as a slot line between the end surface and an edge surrounding the opening (10a) in the metal housing (10), constitutes a right-handed / left-handed composite transmission line in at least a part of the slot line, and causes the right-handed / left-handed composite transmission line in the slot line to function as a leakage wave antenna; and a power supply point (50) disposed in the gap.

Description

Antenna device

[0001] The present disclosure relates to an antenna device in which a liquid crystal display device having a transparent conductive film on substantially the entire surface of the liquid crystal screen is disposed inside a metal housing.

[0002] Transparent antennas using transparent conductive materials with high visible light transmittance are being developed, and an antenna device in which a liquid crystal display device using an indium tin oxide film as a transparent electrode is placed inside a metal housing is disclosed in Patent Document 1. The antenna device disclosed in Patent Document 1 operates as a slot antenna with a gap provided between the edge of the transparent antenna and the metal housing, with the gap acting as a slot.

[0003] Patent No. 7,221,450

[0004] Incidentally, in an antenna device that operates as a slot antenna, with the gap between the edge of the transparent antenna and the metal housing as a slot, the frequency at which the gain is high depends on the size of the metal housing. Therefore, there is a demand for an antenna device that has high gain not only at frequencies of 2.1 GHz, 2.7 GHz, and 3.3 GHz, but also in other frequency bands, such as the 2.4 GHz band used for Wi-Fi.

[0005] The present disclosure has been made in consideration of the above points, and has an object to provide an antenna device that can adjust the frequency at which the gain is high, regardless of the size of the metal housing.

[0006] The antenna device according to the present disclosure includes: a metal housing having an opening on one side and having a liquid crystal display device disposed therein, the liquid crystal display device having a transparent conductive film facing the opening; an antenna conductor that transmits visible light and forms a gap serving as a slot line between an end face of the metal housing and an edge surrounding the opening, the composite right-handed / left-handed transmission line being formed in at least a part of the slot line, causing the composite right-handed / left-handed transmission line in the slot line to function as a leaky wave antenna; and a feed point disposed in the gap.

[0007] According to the present disclosure, high gain can be obtained over a wide frequency band, regardless of the size of the metal housing.

[0008] 8 is a perspective view of an antenna device according to a first embodiment. FIG. 9 is a perspective view of a metal housing of the antenna device according to the first embodiment. FIG. 10 is a perspective view of the antenna device according to the first embodiment with a protective glass removed. FIG. 11 is a cross-sectional view taken along line A-A of FIG. 1. FIG. 12 is an equivalent circuit diagram of a minute section of a composite right-handed / left-handed line. FIG. 13 is an equivalent circuit diagram of a minute section of a right-handed transmission line. FIG. 14 is an equivalent circuit diagram of a minute section of a left-handed transmission line. FIG. 15 is a perspective view of a slot line model for designing a composite right-handed / left-handed line using unit cells. FIG. 16 is a cross-sectional view taken along line B-B of FIG. 1. FIG. 17 is a plan view of a unit cell configuration. FIG. 18 is a diagram showing dispersion characteristics of a unit cell (slit length S1 is 20 mm) showing the relationship between frequency and phase change. FIG. 19 is a diagram showing dispersion characteristics of a unit cell (slit length S1 is 16 mm) showing the relationship between frequency and phase change. FIG. 19 is a perspective view of a slot line model for designing a composite right-handed / left-handed line using 10 unit cells. 19A and 19B are diagrams showing electric field distribution when an electromagnetic wave of 4 GHz is propagated in a slot line model for designing a composite right-handed / left-handed line using 10 unit cells. 19B are diagrams showing electric field distribution when an electromagnetic wave of 2 GHz is propagated in a slot line model for designing a composite right-handed / left-handed line using 10 unit cells. 19C are diagrams showing frequency characteristics of absolute gain in the zenith direction in the antenna device according to the first embodiment. 19D are diagrams showing absolute gain radiation patterns in the Z-Y plane at 4 GHz in the antenna device according to the first embodiment. 19E are perspective views of an antenna device of a comparative example with a protective glass removed. 19F are plan views of an antenna device of a comparative example with a protective glass removed. 19G are cross-sectional views taken along CC in FIG. 19A and 19B. 19G are perspective views of an antenna device according to a second embodiment with a protective glass removed. 19H are perspective views of an antenna device according to a third embodiment with a protective glass removed. 19H are perspective views of an antenna device according to a fourth embodiment with a protective glass removed. 19H are perspective views of an antenna device according to another fifth embodiment with a protective glass removed. 19H are perspective views of an antenna device according to a sixth embodiment with a protective glass removed. FIG. 13 is an enlarged view of a main part showing an antenna device according to a sixth embodiment.

[0009] 1 to 20, an antenna device according to the first embodiment will be described. The antenna device according to the first embodiment comprises a metal housing 10, a protective glass 20, an antenna conductor 30, a feeding point 50, and a plurality of inductors. The liquid crystal display device comprises a liquid crystal display device 40, which is disposed inside the metal housing 10 of the antenna device.

[0010] As shown in Figures 3 and 4, the liquid crystal display device 40 has a transparent electrode 41 on almost the entire surface of the liquid crystal screen. Figure 3 is a perspective view with the protective glass 20 removed. The transparent electrode 41 has a rectangular planar shape. The transparent electrode 41 uses a transparent conductive film that is an indium tin oxide (ITO) film. In the following description, the transparent electrode 41 will be described as an ITO film 41.

[0011] Since the ITO film 41 has an extremely high sheet resistance of 50 Ω / sq or more, a lossy medium exists directly below the antenna conductor 30. In other words, if a current flows through the ITO film 41, it will result in a large loss and a decrease in gain. In the following explanation and illustrations, the liquid crystal display device 40 has various components such as a liquid crystal screen and a backlight, but only the ITO film 41, which is closely related to the antenna conductor 30, i.e., which greatly affects the radiation characteristics of the antenna, is modeled, and other components that make up the liquid crystal display device 40 are omitted.

[0012] As shown in FIG. 2 , the metal housing 10 is a rectangular parallelepiped having an opening 10a on one side, a first side wall 11 to a fourth side wall 14, and a bottom plate 15. Although a rectangular parallelepiped is used as an example, the metal housing 10 does not have to be a rectangular parallelepiped. The first side wall 11 and the second side wall 12 are a pair of opposing long side walls, and the third side wall 13 and the fourth side wall 14 are a pair of opposing short side walls. The opening 10a is located on the top surface of the metal housing 10 facing the bottom plate 15 and is rectangular. In the first embodiment, the sides of the opening 10a corresponding to the first side wall 11 to the fourth side wall 14 are referred to as the first side to the fourth side.

[0013] For convenience of explanation, the direction along the third side wall 13 and the fourth side wall 14 is defined as the x-axis, the direction along the first side wall 11 and the second side wall 12 is defined as the y-axis, and the axis perpendicular to the plane of the bottom plate 15 is defined as the z-axis. As shown in Fig. 2, the metal casing 10 has dimensions Cx in the x-direction, Cy in the y-direction, and Cz in the z-direction. That is, the length of the outer surface of each of the third side wall 13 and the fourth side wall 14 is Cx, the length of the outer surface of each of the first side wall 11 and the second side wall 12 is Cy, and the height from the first side wall 11 to the fourth side wall 14 is Cz.

[0014] The metal casing 10 has a base 100 and a bezel 110 that forms an outer frame integrally bent inward at a right angle from the end faces (imaginary planes) of the side walls of the base 100. The metal casing 10 is made of metal, and the base 100 is a rectangular parallelepiped having a first side wall 11 to a fourth side wall 14 and a bottom plate 15. The bezel 110 forms a rectangular frame integrally bent inward at a right angle from the first side wall 11 to the fourth side wall 14 of the base 100. Note that, although the bezel 110 extends continuously from the base 100 in the metal casing 10, the metal casing 10 may be formed only by the base 100 without the bezel 110. Even in the case of a metal casing 10 that does not have the bezel 110 and is formed only by the base 100, the edges of the first side wall 11 to the fourth side wall 14 will be described as the bezel 110 in the first embodiment.

[0015] For convenience of explanation, in the following description, the bezels 110 will be referred to as the first bezel 111 to the fourth bezel 114, corresponding to the first side wall 11 to the fourth side wall 14. As shown in Figures 2 and 4, the width of the edges of the first bezel 111 to the fourth bezel 114, i.e., the edge surrounding the opening 10a in the metal casing 10, is denoted by Cb. The opening area of ​​the opening 10a in the metal casing 10 is {(Cx-2*Cb)*(Cy-2*Cb)}.

[0016] The protective glass 20 is disposed directly above the opening 10a of the metal housing 10. The protective glass 20 serves to protect the liquid crystal display device 40 when the liquid crystal display device 40 is disposed inside the metal housing 10. In addition, an antenna conductor 30, which is a transparent conductive film, is mounted on the back surface of the protective glass 20, i.e., on the surface of the liquid crystal display device 40.

[0017] 4, the protective glass 20 is attached to the metal housing 10 with a gap Dg provided between the rear surface of the protective glass 20 and the edge of the bezel 110 of the metal housing 10. As a result, there is also a gap Dg between the end of the antenna conductor 30 and the edge of the bezel 110 of the metal housing 10. A user of the liquid crystal display device views the liquid crystal screen of the liquid crystal display device 40 from the +Z direction toward the −Z direction with respect to the protective glass 20, with the protective glass 20 and the antenna conductor 30 interposed therebetween.

[0018] The antenna conductor 30 is a transparent conductive film that transmits visible light. In the first embodiment, as an example, a transparent conductive material having a relatively low sheet resistance of 1.5 Ω / sq is used. The end face of the antenna conductor 30 forms a gap that serves as a slot line between the end face and the edge of the bezel 110 that surrounds the opening 10a in the metal housing 10. The antenna conductor 30 serves as one ground plate, and the metal housing 10 serves as the other ground plate, and the gap Dm (see Figures 3 and 4) between the antenna conductor 30 and the metal housing 10 is used as the slot line.

[0019] The feed point 50 excites power to the antenna conductor 30. When power is excited from the feed point 50 to the antenna conductor 30, high-frequency current flows concentratedly at the edge of the antenna conductor 30. As shown in Figures 3 and 4 , the feed point 50 is disposed between the antenna conductor 30 and the first bezel 111 of the metal housing 10 at the center position of the first bezel 111 of the bezel 110 in the metal housing 10, that is, at a position on the first side of the opening 10a of the metal housing 10 that corresponds to the center of the first side.

[0020] The feed point 50 is located at the same z coordinate as the antenna conductor 30. In other words, the feed point 50 and the antenna conductor 30 are at the same height relative to the edge of the bezel 110 of the metal housing 10. The feed point 50 is electrically connected to the bezel 110 of the metal housing 10 by the metal sheet 80. Therefore, the antenna conductor 30 and the bezel 110 of the metal housing 10 are electrically connected via the feed point 50 and the metal sheet 80.

[0021] Power is excited from the feed point 50 to the antenna conductor 30 by, for example, an FPC (Flexible Printed Circuit) cable. As shown in Fig. 3 , the antenna conductor 30 has, on a first side of the opening 10a of the metal housing 10, a first slit group 31 and a second slit group 32 for respectively configuring a composite right / left-handed (CRLH) transmission line (hereinafter referred to as a CRLH transmission line) in the slot line, with the feed point 50 as the target.

[0022] The first slit group 31 is composed of a plurality of slits 31a to 31j, each of which is in contact with the slot line and has an open end face, and the plurality of slits 31a to 31j are arranged in parallel at equal intervals. The transparent conductive film portions of the antenna conductor 30 arranged on both sides of each of the slits 31a to 31j function as a pair of capacitor electrodes, and a plurality of capacitors connected in series are formed in the region of the antenna conductor 30 where the first slit group 31 is formed. As an example, the slit width Sw of each of the slits 31a to 31j is 3 mm, and the slit length Sl is 20 mm.

[0023] First inductor group 61, together with first slit group 31, constitutes a left-handed transmission line in the CRLH transmission line. As shown in Fig. 3, first inductor group 61 is constituted by a plurality of inductors 61a to 61j electrically connected between one side surface of each of a plurality of slits 31a to 31j in antenna conductor 30 and first bezel 111 of metal casing 10. A plurality of inductors 61a to 61j are connected in parallel to antenna conductor 30. The inductance of each of inductors 61a to 61j is set to 10 nH.

[0024] The plurality of slits 31a to 31j in the first slit group 31 and the plurality of inductors 61a to 61j in the first inductor group 61 are arranged alternately and closely to each other. The slits 31a to 31j and the inductors 61a to 61j connected to one side of the slits 31a to 31j form a unit cell, that is, one capacitor and one inductor form a unit cell, and the length of the unit cell including the width of the slit and the width of the inductor in the unit cell is called the periodic length p, and the periodic length p is set to 5 mm, for example.

[0025] The equivalent circuit in the infinitesimal section of the CRLH transmission line is a circuit in which inductors Ls are connected in series, capacitors Cp are connected in parallel, capacitors Cs are connected in series, and inductor Lp is connected in parallel, as shown in Fig. 5. That is, the equivalent circuit in the infinitesimal section of the CRLH transmission line is a circuit that combines the equivalent circuit in the infinitesimal section of the right-handed transmission line in which inductors Ls are connected in series and capacitors Cp are connected in parallel, as shown in Fig. 6, and the equivalent circuit in the infinitesimal section of the left-handed transmission line in which capacitors Cs are connected in series and inductor Lp are connected in parallel, as shown in Fig. 7.

[0026] In a slot line having antenna conductor 30 as one ground plane and metal casing 10 as the other ground plane, there is a minute section of a right-handed transmission line in which inductor Ls is connected in series and capacitor Cp is connected in parallel in a minute section of metal casing 10 and antenna conductor 30. Also, there is a left-handed transmission line made up of a plurality of capacitors connected in series present in the region of antenna conductor 30 where first slit group 31 is formed and a plurality of inductors 61 a to 61 j connected in parallel to antenna conductor 30.

[0027] Therefore, there exists first CRLH transmission line 71, which is constituted by a region of antenna conductor 30 where first slit group 31 consisting of a plurality of slits 31 a to 31 j is formed, first inductor group 61 consisting of a plurality of inductors 61 a to 61 j, and metal housing 10, and which is constituted by a left-handed transmission line formed by first slit group 31 and first inductor group 61, and a right-handed transmission line existing in the slot line in the region of antenna conductor 30 where first slit group 31 is formed. First CRLH transmission line 71 is a type of metamaterial, and is a transmission line that exhibits the properties of a right-handed transmission line or the properties of a left-handed transmission line depending on the frequency.

[0028] The presence of the first CRLH transmission line 71 allows the slot line to function as a leaky wave antenna that operates with the first CRLH transmission line 71. Although the number of slits 31a to 31j in the first slit group 31 and the number of inductors 61a to 61j are set to 10, they may be any number as long as they are 2 or more.

[0029] The second slit group 32 is composed of a plurality of slits 32a to 32j, each of which is in contact with the slot line and has an open end face, and the plurality of slits 32a to 32j are arranged in parallel at equal intervals. The transparent conductive film portions of the antenna conductor 30 arranged on both sides of each of the slits 32a to 32j function as a pair of capacitor electrodes, and a plurality of capacitors are formed in series in the region of the antenna conductor 30 where the second slit group 32 is formed. As an example, the slit width Sw of each of the slits 32a to 32j is 3 mm, and the slit length Sl is 20 mm.

[0030] Second inductor group 62, together with second slit group 32, constitutes a left-handed transmission line in the CRLH transmission line. As shown in Fig. 3, second inductor group 62 is composed of a plurality of inductors 62a to 62j electrically connected between one side surface of each of a plurality of slits 32a to 32j in antenna conductor 30 and first bezel 111 of metal casing 10. A plurality of inductors 62a to 62j are connected in parallel to antenna conductor 30. The inductance of each of inductors 62a to 62j is set to 10 nH.

[0031] The plurality of slits 32a to 32j in the second slit group 32 and the plurality of inductors 62a to 62j in the second inductor group 62 are arranged alternately and closely to each other. The slits 32a to 32j and the inductors 62a to 62j connected to one side of the slits 32a to 32j form a unit cell, that is, one capacitor and one inductor form a unit cell, and the periodic length p of the unit cell, including the width of the slit and the width of the inductor in the unit cell, is set to 5 mm, for example.

[0032] A second CRLH transmission line 72 is present, which is constituted by a region of antenna conductor 30 where second slit group 32 consisting of multiple slits 32 a to 32 j is formed, second inductor group 62 consisting of multiple inductors 62 a to 62 j, and metal housing 10, and which is constituted by a left-handed transmission line formed by second slit group 32 and second inductor group 62, and a right-handed transmission line present in the slot line in the region of antenna conductor 30 where second slit group 32 is formed. Second CRLH transmission line 72 is a type of metamaterial, and is a transmission line that exhibits the properties of a right-handed transmission line or the properties of a left-handed transmission line depending on the frequency.

[0033] The presence of the second CRLH transmission line 72 allows the slot line to function as a leaky wave antenna that operates with the second CRLH transmission line 72. Although the number of slits 32a to 32j in the second slit group 32 and the number of inductors 62a to 62j are set to 10, they may be any number other than 10, as long as they are 2 or more.

[0034] The planar shape of the antenna conductor 30 (hereinafter simply referred to as the planar shape) including the region where the first slit group 31 and the region where the second slit group 32 are formed is rectangular. When the liquid crystal display device 40 is mounted inside the metal housing 10, as shown in Figure 4, the antenna conductor 30 is disposed directly above the ITO film 41, and the planar shape of the antenna conductor 30 is a rectangle of the same size as the planar shape of the transparent electrode 41. In other words, the antenna conductor 30 covers the ITO film 41.

[0035] Therefore, the ITO film 41 is not present directly below the magnetic current O, which serves as a radiation source generated in the slot line formed between the end face of the antenna conductor 30 and the edge of the bezel 110 of the metal housing 10. As a result, the capacitive coupling between the antenna conductor 30 and the ITO film 41 is suppressed, the current flowing through the ITO film 41 due to the capacitive coupling is reduced, and a decrease in gain can be prevented.

[0036] The planar shape of the antenna conductor 30 does not have to be the same size as the planar shape of the transparent electrode 41, and may be larger or smaller than the planar shape of the transparent electrode 41, provided that a gap Dm formed between the end face of the antenna conductor 30 and the edge of the bezel 110 of the metal housing 10 allows a slot line to exist. In short, the planar shape of the antenna conductor 30 only needs to have a planar area large enough to allow a slot line to exist within the gap Dm, which functions as a leaky wave antenna, relative to the opening area of ​​the opening 10a of the metal housing 10.

[0037] Next, the design concept of the antenna device according to embodiment 1 will be described. First, a unit cell 700, which is made up of one capacitor connected in series and one inductor connected in parallel, is configured by a transparent conductive film 300 corresponding to the antenna conductor 30 having one slit 310 formed therein, and an inductor 610. A slot line model using a simple CRLH transmission line based on the unit cell 700 will be described with reference to FIGS.

[0038] The transparent conductive film 300 is mounted on the surface of glass 200, which corresponds to the protective glass 20. The metal film 120, which corresponds to the metal housing 10, is mounted on the surface of the glass 200 with one end face provided with a gap Dm between it and the end face of the transparent conductive film 300. The gap Dm forms a slot line, and the unit cell 700 is disposed at the center of the slot line in the transmission direction. The slit 310 is rectangular, with its end face opening in contact with the slot line.

[0039] The transparent conductive film portions of the transparent conductive film 300 arranged on both sides of the slit 310 serve as a pair of electrodes that are connected in series as a capacitor. The ITO film 410 corresponding to the ITO film 41 has the same size as the transparent conductive film 300, and the inductor 610 arranged directly above it is connected between the transparent conductive film 300 and the metal film 120, and serves as an inductor connected in parallel.

[0040] The slit width Sw was 3 mm, the slit length Sl was 20 mm, the inductance of the inductor 610 was 10 nH, and the periodic length p of the unit cell 700 was 5 mm. The unit cell 700 configured in this manner yielded the dispersion characteristics shown in Fig. 11. In Fig. 11, the horizontal axis represents frequency, and the vertical axis represents the phase change βp before and after the electromagnetic wave passes through the unit cell 710, which is the value obtained by multiplying the phase constant β by the periodic length p. The solid line DC1 represents the dispersion characteristics of the unit cell 700, showing the relationship between frequency and phase change, and the dashed line AL is called the AirLine.

[0041] AirLine has a phase velocity of the speed of light (ω = βc, where ω is the angular frequency [rad / s], β is the phase constant [rad / m], and c is the speed of light (≒ 3 × 10 ８ The region where the phase constant is smaller than that of AirLine (AL) is the fast wave region FWR, and the region where the phase constant is larger than that of AirLine (AL) is the slow wave region SWR. In the band where the dispersion characteristic DC1 is in the fast wave region FWR, the transmission line in which the slot line unit cell 700 exists operates as a leaky wave antenna. In the band where the dispersion characteristic DC1 is in the slow wave region SWR, no leaky wave is generated from the transmission line in which the slot line unit cell 700 exists.

[0042] As can be seen from the dispersion characteristics of the unit cell 700 shown in Fig. 11, the band BR1 around 1.8 GHz and the band BR2 between 3.2 GHz and 4.2 GHz are located in the fast wave region FWR, and the slotline transmission line operates as a leaky wave antenna. Furthermore, the band BR3 where the phase shift βp is 0, and the band between bands BR1 and BR2 in Fig. 11, are band gap regions where electromagnetic waves do not propagate through the slotline transmission line where the unit cell 700 is located.

[0043] Next, the slit length Sl of the unit cell 700 was changed from 20 mm to 16 mm, and the dispersion characteristics of the unit cell 700 were investigated, resulting in the results shown in Fig. 12. The slit width Sw was 3 mm, the inductance of the inductor 610 was 10 nH, and the periodic length p of the unit cell 700 was 5 mm, which are the same as those of the unit cell 700 with a slit length Sl of 20 mm. In Fig. 12, the solid line DC1 indicates the dispersion characteristics of the unit cell 700 with a slit length Sl of 20 mm, and the dashed-dotted line DC2 indicates the dispersion characteristics of the unit cell 700 with a slit length Sl of 16 mm.

[0044] 12, the frequency band BR4 of 4.3 GHz to 5 GHz is located in the fast wave region FWR, and the transmission line in which the slot line unit cell 700 is located operates as a leaky wave antenna. Therefore, the slit length S1 should be set to 20 mm for the electromagnetic wave frequency band BR1 around 1.8 GHz and the band BR2 of 3.2 GHz to 4.2 GHz, and the slit length S1 should be set to 16 mm for the band BR4 of 4.3 GHz to 5 GHz.

[0045] Although the slit length S1 is shown as 20 mm and 16 mm, by changing the slit length S1, the frequency band in which it operates as a leaky wave antenna can be changed, and the transmission line made of a slot line can be used as a leaky wave antenna for various frequency bands. In other words, by changing the slit length S1, an antenna device that matches the frequency band of electromagnetic waves can be obtained.

[0046] Although it has been described above that the frequency band in which the leaky wave antenna operates can be changed by changing the slit length Sl, the capacitance value of the unit cell 700 can also be changed by changing the slit width Sw, so that an antenna device that matches the frequency band of electromagnetic waves can be obtained by changing the length of the slit width Sw. Similarly, an antenna device that matches the frequency band of electromagnetic waves can be obtained by changing the inductance of the inductor 610 of the unit cell 700.

[0047] Since a single unit cell 700 results in a small amount of leakage of electromagnetic waves even when the slot line is operated as a leaky wave antenna, it is preferable to arrange multiple unit cells 700 to increase the amount of leakage of electromagnetic waves propagating through the slot line. Fig. 13 shows a slot line model using a CRLH transmission line with ten unit cells arranged. The slot line model shown in Fig. 13 is a slot line model using a CRLH transmission line with ten unit cells shown in Figs. 8 to 10 arranged in parallel along the slot line.

[0048] The transparent conductive film 300 has a slit group 310 consisting of ten slits 310a to 310j, each of which is in contact with a slot line and has an open end face. A first inductor group 61 is configured by ten inductors 610a to 610j electrically connected between one side of each of the ten slits 310a to 310j in the transparent conductive film 300 and the metal film 120.

[0049] The ten slits 310a to 310j and the ten inductors 610a to 610j in the slit group 310 are arranged alternately and closely to each other. Therefore, a CRLH transmission line 710 having ten unit cells 700 exists due to the region of the transparent conductive film 300 where the slit group 310 is formed and the ten inductors 610a to 610j.

[0050] In the CRLH transmission line 710 having ten unit cells 700 configured in this manner, similar to the dispersion characteristics of one unit cell 700 (see FIG. 11), the frequency band BR1 around 1.8 GHz and the frequency band BR2 of 3.2 GHz to 4.2 GHz are located in the fast wave region FWR, the transmission line made of a slot line operates as a leaky wave antenna, and the band between bands BR1 and BR2 is a bandgap region.

[0051] In the CRLH transmission line 710 having ten unit cells 700 configured in this manner, the electric field distribution when a 4 GHz electromagnetic wave is propagated from the + direction to the - direction of the x-axis shown in Fig. 13 through the transmission line having ten unit cells 700 in a slot line, operating as a leaky wave antenna, is shown in Fig. 15. Also, the electric field distribution when a 2 GHz electromagnetic wave, which is in the bandgap region, is propagated is shown in Fig. 14.

[0052] As can be seen from Fig. 14, it can be confirmed that electromagnetic waves leak into space in the CRLH transmission line 710 having ten unit cells 700. Furthermore, as can be seen from Fig. 15, it can be confirmed that electromagnetic waves do not leak in the CRLH transmission line 710 having ten unit cells 700, and that the electromagnetic waves do not propagate beyond the CRLH transmission line 710.

[0053] Next, a description will be given of the results of verification of the gain versus frequency in the antenna apparatus according to the first embodiment. In the antenna apparatus according to the first embodiment, the first CRLH transmission line 71 and the second CRLH transmission line 72 each have the same design as the CRLH transmission line 710 having ten unit cells 700 shown in Fig. 13. In the antenna apparatus according to the first embodiment, the absolute gain versus frequency in the zenith direction (+z direction), which are verification results, is shown by a solid line G in Fig. 16, and the absolute gain radiation pattern in the vertical plane (zy plane) is shown by a solid line G in Fig. 17.

[0054] For reference, the absolute gain in the zenith direction (+z direction) versus frequency, which is the verification result for the comparative example shown in Figures 18 to 20, is shown by the dashed line R in Figure 16, and the absolute gain radiation pattern in the vertical plane (zy plane) is shown by the dashed line R in Figure 17. The antenna device of the comparative example is shaped so that the antenna conductor 30R covers the ITO film 41R, and is an antenna device that utilizes a magnetic current O generated in a gap Dm between the bezel 110R (111R to 114R) of the metal casing 10R and the antenna conductor 30R.

[0055] That is, the antenna device of the comparative example has the following configuration. The metal housing 10R has an opening 10a on one side, is a rectangular parallelepiped having first to fourth side walls 11 to 14, and a bottom plate 15, and has a bezel 110R (111R to 114R) that forms the outer frame. The antenna conductor 30R is a rectangular transparent conductive film mounted on the back surface of the protective glass 20R. The antenna conductor 30R is located directly above a rectangular ITO film 41R provided on the liquid crystal screen of the liquid crystal display device.

[0056] The antenna conductor 30R and the ITO film 41R have the same shape and size. The antenna device of the comparative example does not have the first CRLH transmission line 71 and the second CRLH transmission line 72 in the first embodiment, that is, the antenna conductor 30R has the same shape as the ITO film 41R except that it does not have the first slit group 31 and the second slit group 32 and the first inductor group 61 and the second inductor group 62.

[0057] 16, the antenna device according to embodiment 1 has a higher absolute gain in the zenith direction than the antenna device of the comparative example (dashed line R) in the band BR2 of 3.2 GHz to 4.2 GHz. The reason for the higher absolute gain in the zenith direction is that the first CRLH transmission line 71 and the second CRLH transmission line 72 operate as leaky wave antennas, increasing the gain.

[0058] 17, the antenna device according to the first embodiment has an increased absolute gain in the front direction at a frequency of 4 GHz compared to the antenna device of the comparative example (dashed line R). Thus, the antenna device according to the first embodiment has a high absolute gain in the zenith direction in the wide frequency band BR2 of 3.2 GHz to 4.2 GHz, without changing the size of the metal housing, and can be used in a wide range of applications.

[0059] In addition, in the antenna device of embodiment 1, if the slit length Sl is set to 16 mm, it is possible to obtain a high absolute gain in the zenith direction in the band BR4 of 4.3 GHz to 5 GHz, which operates as a leaky wave antenna as described using Figure 12.

[0060] As described above, the antenna device according to the first embodiment has a composite right-handed / left-handed transmission line formed in at least a part of the slot line in antenna conductor 30, which forms gap Dm serving as a slot line between itself and the edge surrounding opening 10 a in metal housing 10, and causes the composite right-handed / left-handed transmission line in the slot line to function as a leaky wave antenna. Therefore, a high gain can be obtained over a wide frequency band regardless of the size of metal housing 10, and the range of applications is expanded.

[0061] Furthermore, the antenna device according to the first embodiment has a plurality of slits 31a to 31j, 32a to 32j arranged in parallel, with their end faces opening in contact with the gap Dm, in the antenna conductor 30, which forms a gap Dm between itself and the edge surrounding the opening 10a in the metal casing 10 and which form a slot line, and a plurality of inductors 61a to 61j electrically connected between one side of each of the plurality of slits 31a to 31j, 32a to 32j in the antenna conductor 30 and the metal casing 10. Therefore, a high gain can be obtained over a wide frequency band without depending on the size of the metal casing 10, and moreover, by changing at least one of the slit length Sl and slit width Sw of each of the slits 31a to 31j, 32a to 32j, or the inductance of the inductors 61a to 61j, the frequency band with high gain can be changed without depending on the size of the metal casing 10, thereby further expanding the range of applications.

[0062] Second Embodiment An antenna device according to a second embodiment will be described with reference to Fig. 21. In the antenna device according to the first embodiment, the first CRLH transmission line 71 and the second CRLH transmission line 72 are arranged on the same side of the opening 10a of the metal housing 10 as the side of the opening 10a on which the feed point 50 is arranged, that is, on the side of the first side wall 11 of the metal housing 10.

[0063] In contrast, in the antenna device according to the second embodiment, the third CRLH transmission line 73 and the fourth CRLH transmission line 74 are arranged on the side of the opening 10a of the metal housing 10 that faces the side of the opening 10a on which the feed point 50 is arranged, that is, on the side of the second side wall 12 of the metal housing 10. The other points of the antenna device according to the second embodiment are the same as those of the antenna device according to the first embodiment. Note that in Fig. 21, the same reference numerals as those in Figs. 1 to 4 indicate the same or corresponding parts.

[0064] The following description will focus on the differences from the antenna device according to embodiment 1. The third CRLH transmission line 73 is arranged on the third bezel 113 side of the metal housing 10. The third CRLH transmission line 73 is composed of the region of the antenna conductor 30 where the third slit group 33 is formed and multiple inductors 63a to 63j.

[0065] The third slit group 33 is made up of a plurality of slits 33a to 33j, each of which has an open end face in contact with the slot line on the second bezel 112 side of the metal casing 10, and the plurality of slits 33a to 33j are arranged in parallel at equal intervals. The number of the plurality of slits 33a to 33j is, for example, 10, and the slit width Sw and slit length Sl of each of the slits 33a to 33j are, for example, 3 mm and 20 mm, respectively.

[0066] The third inductor group 63 is composed of a plurality of inductors 63a to 63j that are electrically connected between one side surface of each of the plurality of slits 33a to 33j in the antenna conductor 30 and the second bezel 112 of the metal housing 10. The plurality of inductors 63a to 63j are connected in parallel to the antenna conductor 30. The number of the plurality of inductors 63a to 63j is, for example, 10, and the inductance of each of the inductors 63a to 63j is set to 10 nH.

[0067] The fourth CRLH transmission line 74 is arranged on the fourth bezel 114 side of the metal housing 10. The third CRLH transmission line 73 and the fourth CRLH transmission line 74 are arranged symmetrically with respect to the longitudinal direction of the second bezel 112 of the metal housing 10, i.e., the center point in the y-axis direction. The fourth CRLH transmission line 74 is composed of a region of the antenna conductor 30 where the fourth slit group 34 is formed and multiple inductors 64a to 64j.

[0068] The fourth slit group 34 is made up of a plurality of slits 34a to 34j, each of which has an open end face that contacts the slot line on the second bezel 112 side of the metal housing 10, and the plurality of slits 34a to 34j are arranged in parallel at equal intervals. The number of the plurality of slits 34a to 34j is, for example, 10, and the slit width Sw and slit length Sl of each of the slits 34a to 34j are, for example, 3 mm and 20 mm, respectively.

[0069] The fourth inductor group 64 is composed of a plurality of inductors 64a to 64j that are electrically connected between one side surface of each of the plurality of slits 34a to 34j in the antenna conductor 30 and the second bezel 112 of the metal housing 10. The plurality of inductors 64a to 64j are connected in parallel to the antenna conductor 30. The number of the plurality of inductors 64a to 64j is, for example, 10, and the inductance of each of the inductors 64a to 64j is 10 nH. The antenna device according to the second embodiment has the same effects as the antenna device according to the first embodiment.

[0070] Third Embodiment An antenna device according to a third embodiment will be described with reference to Fig. 22. In the antenna device according to the first embodiment, the first CRLH transmission line 71 and the second CRLH transmission line 72 are arranged on the same side of the opening 10a of the metal housing 10 as the side of the opening 10a on which the feed point 50 is arranged, that is, on the side of the first side wall 11 of the metal housing 10.

[0071] In contrast, in the antenna device according to the third embodiment, the fifth CRLH transmission line 75 and the sixth CRLH transmission line 76 are respectively arranged on the sides of the opening 10a of the metal housing 10 that are perpendicular to the side of the opening 10a on which the feed point 50 is arranged, that is, on the third side wall 13 side and the fourth side wall 14 side of the metal housing 10. The other points of the antenna device according to the third embodiment are the same as those of the antenna device according to the first embodiment. In Fig. 22, the same reference numerals as those in Figs. 1 to 4 indicate the same or corresponding parts.

[0072] The following description will focus on the differences from the antenna device according to embodiment 1. The fifth CRLH transmission line 75 is disposed in the center in the longitudinal direction of the third bezel 113 of the metal housing 10. The fifth CRLH transmission line 75 is composed of the region of the antenna conductor 30 where the fifth slit group 35 is formed and multiple inductors 65a to 65j.

[0073] The fifth slit group 35 is made up of a plurality of slits 35a to 35j, each of which has an open end face in contact with the slot line on the third bezel 113 side of the metal casing 10, and the plurality of slits 35a to 35j are arranged in parallel at equal intervals. The number of the plurality of slits 35a to 35j is, for example, 10, and the slit width Sw and slit length Sl of each of the slits 35a to 35j are, for example, 3 mm and 20 mm, respectively.

[0074] The fifth inductor group 65 is composed of a plurality of inductors 65a to 65j that are electrically connected between one side surface of each of the plurality of slits 35a to 35j in the antenna conductor 30 and the third bezel 113 of the metal casing 10. The plurality of inductors 65a to 65j are connected in parallel to the antenna conductor 30. The number of the plurality of inductors 65a to 65j is, for example, 10, and the inductance of each of the inductors 65a to 65j is set to 10 nH.

[0075] The sixth CRLH transmission line 76 is disposed in the center in the longitudinal direction on the fourth bezel 114 side of the metal housing 10. The sixth CRLH transmission line 76 is composed of the region of the antenna conductor 30 where the sixth slit group 36 is formed and the multiple inductors 66a to 66j.

[0076] The sixth slit group 36 is made up of a plurality of slits 36a to 36j, each of which has an open end face in contact with the slot line on the fourth bezel 114 side of the metal casing 10, and the plurality of slits 36a to 36j are arranged in parallel at equal intervals. The number of the plurality of slits 36a to 36j is, for example, 10, and the slit width Sw and slit length Sl of each of the slits 36a to 36j are, for example, 3 mm and 20 mm, respectively.

[0077] The sixth inductor group 66 is composed of a plurality of inductors 66a to 66j that are electrically connected between one side surface of each of the plurality of slits 36a to 36j in the antenna conductor 30 and the fourth bezel 114 of the metal housing 10. The plurality of inductors 66a to 66j are connected in parallel to the antenna conductor 30. The number of the plurality of inductors 66a to 66j is, for example, 10, and the inductance of each of the inductors 66a to 66j is 10 nH. The antenna device according to the third embodiment has the same effects as the antenna device according to the first embodiment.

[0078] Fourth Embodiment An antenna device according to a fourth embodiment will be described with reference to Fig. 23. In the antenna device according to the first embodiment, the first CRLH transmission line 71 and the second CRLH transmission line 72 are arranged on the same side of the opening 10a of the metal housing 10 as the side of the opening 10a on which the feed point 50 is arranged, that is, on the side of the first side wall 11 of the metal housing 10.

[0079] In contrast to this, in the antenna device according to the fourth embodiment, in addition to the first CRLH transmission line 71 and the second CRLH transmission line 72, a fifth CRLH transmission line 75 and a sixth CRLH transmission line 76 are each arranged on the sides of the opening 10 a of the metal housing 10 that are perpendicular to the side of the opening 10 a on which the feed point 50 is arranged, that is, on the third side wall 13 side and the fourth side wall 14 side of the metal housing 10.

[0080] That is, the antenna device according to embodiment 4 has a first CRLH transmission line 71, a second CRLH transmission line, a fifth CRLH transmission line 75, and a sixth CRLH transmission line 76. Other points in the antenna device according to embodiment 4 are the same as those in embodiment 1. Note that in Fig. 23, the same reference numerals as those in Figs. 1 to 4 indicate the same or corresponding parts.

[0081] The fifth CRLH transmission line 75 and the sixth CRLH transmission line 76 are the same as the fifth CRLH transmission line 75 and the sixth CRLH transmission line 76 in the antenna device according to embodiment 3. The antenna device according to embodiment 4 has the same effects as the antenna device according to embodiment 1.

[0082] Fifth Embodiment An antenna device according to a fifth embodiment will be described with reference to Fig. 24. In the antenna device according to the first embodiment, the first CRLH transmission line 71 and the second CRLH transmission line 72 are arranged on the same side of the opening 10a of the metal housing 10 as the side of the opening 10a on which the feed point 50 is arranged, that is, on the side of the first side wall 11 of the metal housing 10.

[0083] In contrast to this, in the antenna device according to the fifth embodiment, in addition to the first CRLH transmission line 71 and the second CRLH transmission line 72, a third CRLH transmission line 73 and a fourth CRLH transmission line 74 are arranged on the side of the opening 10 a of the metal housing 10 that faces the side of the opening 10 a where the feed point 50 is arranged, that is, on the side of the second side wall 12 of the metal housing 10, and a fifth CRLH transmission line 75 and a sixth CRLH transmission line 76 are arranged on the side of the opening 10 a that is perpendicular to the side of the opening 10 a of the metal housing 10 where the feed point 50 is arranged, that is, on the side of the third side wall 13 and the side of the fourth side wall 14 of the metal housing 10.

[0084] That is, the antenna device according to the fifth embodiment has a first CRLH transmission line 71 and a second CRLH transmission line, a third CRLH transmission line 73 and a fourth CRLH transmission line 74, and a fifth CRLH transmission line 75 and a sixth CRLH transmission line 76. In the antenna device according to the fifth embodiment, the CRLH transmission lines 71 to 74 are arranged on all four sides of the opening 10a of the metal housing 10. In other respects, the antenna device according to the fifth embodiment is the same as the antenna device according to the first embodiment. Note that in Fig. 24, the same reference numerals as those in Figs. 1 to 4 indicate the same or corresponding parts.

[0085] The third CRLH transmission line 73 and the fourth CRLH transmission line 74 are the same as the third CRLH transmission line 73 and the fourth CRLH transmission line 74 in the antenna device according to embodiment 2. The fifth CRLH transmission line 75 and the sixth CRLH transmission line 76 are the same as the fifth CRLH transmission line 75 and the sixth CRLH transmission line 76 in the antenna device according to embodiment 3. The antenna device according to embodiment 5 has the same effects as the antenna device according to embodiment 1.

[0086] Sixth Embodiment An antenna device according to a sixth embodiment will be described with reference to Figures 25 and 26. The antenna device according to the sixth embodiment differs from the antenna device according to the first embodiment in that it uses a meander element as an inductor, but is otherwise the same as the antenna device according to the first embodiment. Note that in Figures 25 and 26, the same reference numerals as those in Figures 1 to 4 indicate the same or corresponding parts.

[0087] The following description will focus on the differences from the antenna device according to embodiment 1. In the antenna device according to embodiment 6, a seventh CRLH transmission line 77 and an eighth CRLH transmission line 78 are arranged on the same side of the opening 10a of the metal housing 10 as the side of the opening 10a on which the feed point 50 is arranged, that is, on the first side wall 11 side of the metal housing 10. The seventh CRLH transmission line 77 is arranged on the third bezel 113 side of the metal housing 10. The seventh CRLH transmission line 77 is composed of a region of the antenna conductor 30 in which the seventh slit group 37 is formed and a plurality of inductors 67a to 67e.

[0088] The seventh slit group 37 is made up of a plurality of slits 37a to 37e, each of which has an open end face in contact with the slot line on the first bezel 111 side of the metal housing 10. The plurality of slits 37a to 37e are arranged in parallel at equal intervals. The number of the plurality of slits 37a to 37e is, for example, five.

[0089] The seventh inductor group 67 is composed of a plurality of inductors 67a to 67e that are electrically connected between one side surface of each of the plurality of slits 37a to 37e in the antenna conductor 30 and the first bezel 111 of the metal housing 10. The plurality of inductors 67a to 67e are connected in parallel to the antenna conductor 30. Each of the inductors 67a to 67e is a meander element. The number of the plurality of inductors 67a to 67e is, for example, five.

[0090] The eighth CRLH transmission line 78 is disposed on the fourth bezel 114 side of the metal housing 10. The seventh CRLH transmission line 77 and the eighth CRLH transmission line 78 are disposed symmetrically with respect to the longitudinal direction of the first bezel 111 of the metal housing 10, i.e., the center point in the y-axis direction. The eighth CRLH transmission line 78 is composed of the region of the antenna conductor 30 where the eighth slit group 38 is formed and multiple inductors 68a to 68e.

[0091] The eighth slit group 38 is made up of a plurality of slits 38a to 38e, each of which has an open end face in contact with the slot line on the first bezel 111 side of the metal housing 10. The plurality of slits 38a to 38e are arranged in parallel at equal intervals. The number of the plurality of slits 38a to 38e is, for example, five.

[0092] The eighth inductor group 68 is composed of a plurality of inductors 68a to 68e that are electrically connected between one side surface of each of the plurality of slits 38a to 38e in the antenna conductor 30 and the first bezel 111 of the metal housing 10. The plurality of inductors 68a to 68e are connected in parallel to the antenna conductor 30. Each of the inductors 68a to 68e is a meander element. The number of the plurality of inductors 68a to 68e is, for example, five.

[0093] The antenna device according to the sixth embodiment has the same effects as the antenna device according to the first embodiment, and in addition, since meander elements are used as inductors, the number of elements used as inductors can be reduced.

[0094] It should be noted that the embodiments may be freely combined, or any of the components in each embodiment may be modified, or any of the components in each embodiment may be omitted.

[0095] The antenna device according to the present disclosure is applied to an antenna device that uses an antenna conductor that transmits visible light, and is applied to a liquid crystal display device in which a liquid crystal display device is disposed inside a metal housing.

[0096] 10 Metal housing, 10a Opening, 20 Protective glass, 30 Antenna conductor, 31 to 37 Slit group, 31a to 31j, 32a to 32j, 33a to 33j, 34a to 34j, 35a to 35j, 36a to 36j, 37a to 37e, 38a to 38e Slit, 40 Liquid crystal display device, 41 Transparent electrode (ITO film), 50 Power supply point, 61 to 68 Inductor group, 61a to 61j, 62a to 62j, 63a to 63j, 64a to 64j, 65a to 65j, 66a to 66j, 67a to 67e, 68a to 68e Inductor, 71 to 78 CRLH transmission line.

Claims

1. An antenna device comprising: a metal casing having an opening on one side and in which a liquid crystal display device having a transparent conductive film facing the opening is placed; an antenna conductor transparent to visible light, the antenna conductor having an end face that forms a gap serving as a slot line between an edge surrounding the opening in the metal casing and at least a part of the slot line that constitutes a composite right / left handed transmission line, and causing the composite right / left handed transmission line in the slot line to function as a leaky wave antenna; and a feed point placed in the gap.

2. The antenna device according to claim 1, wherein the antenna conductor has a slit group consisting of a plurality of slits arranged in parallel and whose end faces open in contact with the slot line, the plurality of slits form a left-handed transmission line in the composite right-handed / left-handed transmission line together with a plurality of inductors electrically connected between one side of each of the plurality of slits and the metal casing, and the right-handed transmission line in the composite right-handed / left-handed transmission line exists in the slot line in the region of the antenna conductor where the slit group is formed.

3. The antenna device according to claim 2, wherein the feed point is disposed at the center of one side of the opening of the metal housing.

4. The antenna device according to claim 2, wherein said metal housing has a wide bezel around its edge surrounding said opening.

5. The antenna device according to claim 2, wherein each of said plurality of inductors is a meander-shaped element.

6. An antenna device as described in any one of claims 2 to 5, wherein the opening of the metal housing is rectangular, and the multiple slits and the multiple inductors are arranged on the same side of the opening of the metal housing as the side of the opening on which the power supply point is arranged.

7. The antenna device according to claim 6, wherein the plurality of slits and the plurality of inductors are each divided into two groups, and the divided groups are arranged symmetrically with respect to the feed point.

8. An antenna device described in any one of claims 2 to 5, wherein the opening of the metal housing is rectangular, and the multiple slits and the multiple inductors are arranged on a side of the opening that faces the side of the opening of the metal housing on which the feed point is located.

9. An antenna device described in any one of claims 2 to 5, wherein the opening of the metal housing is rectangular, and the multiple slits and the multiple inductors are arranged on a side of the opening that is perpendicular to the side of the opening of the metal housing on which the feed point is located.

10. An antenna device comprising: a metal casing having an opening on one side and in which a liquid crystal display device having a transparent conductive film facing the opening is disposed; an antenna conductor transparent to visible light, the end face of which is disposed with a gap between it and the edge surrounding the opening in the metal casing and the end face has a plurality of slits arranged in parallel and the end face opens in contact with the gap; a plurality of inductors electrically connected between one side of each of the plurality of slits in the antenna conductor and the metal casing; and a power supply point disposed in the gap.

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