JP2011239094A - Broadband antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low profile broadband antenna device capable of covering a wide frequency band.SOLUTION: An electric power supply coaxial connector is provided in the central portion of the lower surface of a conductor plate 11. The coaxial connector connects an outer conductor to the conductor plate 11, and a central conductor 14 is led out upwardly from a hole 15 formed at the central portion of the conductor plate 11. An antenna element 21 is disposed at a predetermined height on the upper side of the conductor plate 11. The antenna element 21 has a ring-shaped groove 24 around a circular element 22 locating at the center of the antenna element to separate the circular element 22 from a cross-shaped element 23. Short-circuit elements 25a-25d are provided respectively at the outer ends of the cross-shaped element 23 so that the cross-shaped element 23 and the conductor plate 11 are short-circuited and connected. Below the circular element 22, a conductor element 26 is provided, which is formed in such a way that its semi-spherical outer circumferential surface has a semi-elliptic shape and the upper circular portion of the conductor element is connected to the circular element 22, and the lower end portion is connected to the central conductor 14 of the coaxial connector by the soldering or the like.

Description

  The present invention can be applied to, for example, UWB (Ultra Wide Band) or the like that requires broadband characteristics, or terrestrial digital broadcasting that can cover a large number of radio areas with a single antenna (terrestrial digital broadcasting for receiving portable devices: The present invention relates to a low-profile wideband antenna device used in one segment broadcasting), cellular phones, wireless LANs, Wimax, and the like.

  In recent years, dead zones in wireless communication such as terrestrial digital broadcasting (One Segment broadcasting), mobile phones, wireless LANs, Wimax, etc., which receive mobile devices, have become a problem in underground malls and buildings. As a countermeasure for this dead zone, a re-radiation method using a relay antenna is used. In this method, an antenna is installed on the indoor ceiling, so a low-profile and broadband antenna is required. In addition, as a relay antenna, a vertically polarized horizontal omnidirectional antenna is often used.

  Conventionally, a monopole antenna is generally used as a vertically polarized horizontal plane omnidirectional small and lightweight antenna. This monopole antenna has a configuration in which a coaxial plug is attached to one surface of a conductor plate, and the central conductor is insulated from the conductor plate and is extended by about 1/4 wavelength to the opposite surface.

  However, the above-mentioned conventional monopole antenna requires about 1/4 wavelength or more, and it is difficult to lower the position more than that, so it is not preferable as a relay antenna provided in an underground mall or the like. In addition, the monopole antenna can obtain good characteristics in a single frequency band, but basically has a narrow band, and the ratio band at a voltage standing wave ratio “VSWR ≦ 2” or less is generally sufficient. It is difficult to apply to a device that is about several percent and performs large-capacity transmission by broadband communication.

  For this reason, recently, a cross-shaped radiating element is arranged on a conductor plate at a predetermined height, a feeding path is provided below the radiating element, and power is fed to the center of the radiating element via the feeding path. Thus, an antenna that has a low profile and can obtain a wideband characteristic has been considered (see, for example, Patent Document 1).

JP 2008-219853 A

An antenna in which cross-shaped radiating elements are arranged at a predetermined height on the conductor plate can have a low profile and a usable frequency band of 470 to 2170 MHz (ratio band is 128%). Therefore, with one antenna,
(1) One Segment broadcasting (470 to 770 MHz) for receiving mobile devices
(2) 800 MHz mobile phone (810-958 MHz)
(3) 1500 MHz band mobile phone (1429 to 1501 MHz)
(4) 1800 MHz mobile phone (1710 to 1880 MHz)
(5) IMT2000 (International Mobile Telecommunications 2000) (1920-2170 MHz)
Can cover the bandwidth.

  However, the antenna using the cross-shaped radiating element cannot cover a frequency band higher than 2170 MHz, and the wireless LAN of 2400-2500 MHz band and WiMAX (Worldwide Interoperability for Microwave Access) of 2545-2625 MHz band I could not respond. For this reason, it is necessary to separately install an antenna for a wireless LAN of 2400-2500 MHz band and WiMAX of 2545-2625 MHz band.

  The present invention has been made to solve the above-described problems, and is suitable for a relay device installed in a small installation space such as an underground shopping center, broadband communication, and the like, and is intended for receiving terrestrial digital broadcasting (One Segment broadcasting) for portable devices. ) To a wide-band antenna device with a low attitude capable of covering a wide frequency band including WiMAX.

  A wideband antenna apparatus according to the present invention includes a conductor plate, a plate-like first radiating element provided at a predetermined height at a central portion on the conductor plate, and the outside of the first radiating element as a center. A plate-like second radiating element that is provided radially at a predetermined interval, a short-circuit element that short-circuits between the outer end of the second radiating element and the conductor plate, and a central portion of the conductor plate. A power supply terminal, and a conductor element provided on the lower side of the first radiating element, having an upper end connected to the first radiating element and a lower end connected to the power feeding terminal. The upper end is formed wider than the lower end.

  According to the present invention, it is possible to reliably cover a very wide frequency band including WiMAX from terrestrial digital broadcasting while maintaining a low attitude, and a low attitude suitable for a relay device installed in a narrow installation space such as an underground shopping center or broadband communication. It is possible to provide a wideband antenna apparatus.

It is a perspective view which shows the structure of the wideband antenna apparatus which concerns on Example 1 of this invention. It is a top view which shows the antenna element part of the wideband antenna apparatus which concerns on the Example 1. FIG. It is AA arrow sectional drawing of the wideband antenna apparatus shown in FIG. It is a VSWR characteristic view of the wideband antenna device according to the first embodiment. FIG. 5 is a VSWR characteristic diagram when a circular element and a cross-shaped element are omitted in the wideband antenna device according to the first embodiment. FIG. 6 is a VSWR characteristic diagram when a circular element and a cross-shaped element are integrally configured without providing a ring-shaped groove in the wideband antenna device according to the first embodiment. FIG. 6 is a gain characteristic diagram in the θ = 60 ° direction of the wideband antenna device according to the first embodiment. It is a characteristic view which shows the vertical polarization vertical plane directivity (ZX plane) in 470 MHz of the wideband antenna apparatus which concerns on the Example 1. FIG. FIG. 6 is a characteristic diagram showing vertical polarization horizontal plane directivity (θ = 60 °, XY plane) at 470 MHz of the wideband antenna device according to Example 1; It is a perspective view which shows the other structural example of the conductor element in the Example 1. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  1 is a perspective view showing a configuration of a wideband antenna apparatus according to an embodiment of the present invention, FIG. 2 is a top view showing an antenna element portion of the wideband antenna apparatus, and FIG. 3 is an A- of the wideband antenna apparatus shown in FIG. It is A line arrow sectional drawing.

1 to 3, reference numeral 11 denotes a conductor plate (ground plate) formed in a square shape, for example, having a side length W1 of about 0.96λ _L or more (λ _L is the wavelength of the lowest frequency in the used frequency band). Set to

  For example, an NJ type coaxial connector 12 is attached to the lower surface center portion of the conductor plate 11 as a power supply terminal. Although not shown, the coaxial connector 12 is connected with a power feeding coaxial cable from an antenna input circuit of the wireless device. The coaxial connector 12 includes an outer conductor 13 and a center conductor 14, and the outer conductor 13 is electrically connected to the conductor plate 11. Further, the center conductor 14 passes through a through hole 15 provided in the central portion of the conductor plate 11 and is provided so as to protrude upward by a predetermined length (0 to several mm) while being insulated from the conductor plate 11.

On the upper side of the conductor plate 11, an antenna element 21 formed in a cross shape by a metal plate (conductor plate) having a thickness of about 1 to 2 mm is provided at a predetermined height H. The height H of the antenna element 21 is set to about 0.055λ _L. In this case, the antenna element 21 is provided such that, for example, a portion formed to project in a cross shape coincides with the direction of each corner (four corners) of the conductor plate 11. The antenna element 21 includes a circular element 22 that constitutes a first radiating element located at the center, and a cross-shaped element 23 that constitutes a second radiating element located around the circular element 22 and located outside thereof. The circular element 22 and the cross-shaped element 23 are separated by providing a ring-shaped groove (gap) 24 between the circular element 22 and the cross-shaped element 23. By providing the ring-shaped groove 24, the circular element 22 and the cross-shaped element 23 are coupled by capacitive coupling. The outer diameter Dout of the ring-shaped groove 24 is set to about 0.09λ _L , and the inner diameter Din, that is, the outer diameter of the circular element 22 is set to about 0.08λ _L.

The cross-shaped element 23 is set to have a width W2 of about 0.18λ _L and a total length L of about 0.29λ _L. Further, short-circuit elements 25 a to 25 d having a height H are provided between the central portion of each outer end of the cross-shaped element 23 and the conductor plate 11. The short-circuit elements 25a to 25d are for electrically short-circuiting connection between the outer ends of the cross-shaped element 23 and the conductor plate 11, and, for example, means for bending the central portion of each outer end downward with a width Ws. It is formed by. The width Ws of the short-circuit elements 25a to 25d is set to about 6 mm.

On the other hand, a conductor element 26 is provided below the circular element 22. The conductor element 26 has a hemispherical outer peripheral surface formed so as to form an exponential function curve, and is formed with the upper end wider than the lower end. The conductor element 26 is soldered to the central conductor 14 of the coaxial connector 12 whose upper circular portion is connected to the lower surface of the circular element 22 and the top of the exponential function curve located on the lower side is led to the upper part of the conductor plate 11. Connected by The circular element 22 and the conductor element 26 are electrically connected by being fixed by screws or the like at several places. The conductor element 26 holds the circular element 22 at the same height H as the cross-shaped element 23. The diameter D1 of the upper circular portion of the conductor element 26 is set to a value smaller than the outer diameter Din (about 0.08λ _L ) of the circular element 22, for example, about 0.05λ _L.

  For example, when the broadband antenna apparatus configured as described above is installed on the ceiling of an underground shopping mall, a plurality of broadband antenna apparatuses are installed at predetermined intervals with the antenna element 21 on the lower side and the coaxial connector 12 on the upper side. The broadband antenna device is provided with a protective cover (radome) for protecting the antenna element 21 as necessary.

  For example, an outdoor antenna for receiving terrestrial (TV, mobile phone), for example, is installed on the ground, and the terrestrial wave received by the outdoor antenna is received and amplified by the relay receiver, and the coaxial connector 12 of the antenna is connected by a coaxial cable. Power to In the wideband antenna device, when power is supplied to the coaxial connector 12, a feeding current flows from the conductor element 26 to the short-circuit elements 25 a to 25 d via the circular element 22 and the cross-shaped element 23, and the circular element 22 and the cross-shaped element 23. Vertically polarized radio waves are radiated from the bottom.

  Therefore, even in an underground shopping center where direct terrestrial waves do not reach, radio waves retransmitted from the antenna device installed in the underground shopping center can be received by a mobile phone, a television receiver, or a mobile device having a television reception function. It becomes possible.

  FIG. 4 shows the VSWR characteristics of the wideband antenna apparatus configured as described above. The horizontal axis represents frequency [GHz] and the vertical axis represents VSWR. 4 shows the length W1 of one side of the conductor plate 11, the outer diameter Dout and inner diameter Din of the ring-shaped groove 24 provided between the circular element 22 and the cross-shaped element 23, and the total length L of the cross-shaped element 23. The VSWR characteristics are shown when the width W2, the height H of the cross element 23, the width Ws of the short-circuit elements 25a to 25d, and the diameter D1 of the upper circular portion of the conductor element 26 are set as follows.

W1: 0.96λ _L
Dout: 0.09λ _L
Din: 0.08λ _L
L: 0.29λ _L
W2: 0.18λ _L
H: 0.055λ _L
Ws: 6mmλ _L
D1: 0.05λ _L
According to the wideband antenna device shown in the first embodiment, as is clear from FIG. 4, a wide frequency band of 470 to 3150 MHz can be covered below VSWR2, and a specific band of about 148% is obtained. Further, the height H of the antenna element 21 is about 0.055λ _L (about 35 mm), and the antenna element 21 can be in a low posture.

  FIG. 5 shows, for comparison, the VSWR characteristics when the circular element 22 and the cross-shaped element 23 are omitted in the first embodiment, and a radio wave is radiated from the conductor element 26 provided on the conductor plate 11. Is. When radio waves are radiated from the conductor element 26, the VSWR is 2 or less in a high frequency band of about 1.6 GHz or higher, but the VSWR rapidly deteriorates in a frequency band lower than about 1.6 GHz. Therefore, it can be seen that the conductor element 26 has an effect of improving the VSWR characteristic in the high frequency band portion.

  FIG. 6 shows, for comparison and reference, the VSWR characteristics when the circular element 22 and the cross-shaped element 23 are integrally formed without providing the ring-shaped groove 24 in the first embodiment. is there. When the circular element 22 and the cross-shaped element 23 are integrally formed, the VSWR is 2 or more in a high frequency band of about 2.3 GHz or more, but the VSWR is 2 in a low frequency band of about 0.4 to 0.7 GHz. It becomes as follows. Therefore, it can be seen that the cross-shaped element 23 has an effect of improving the VSWR characteristics in a low frequency band.

  In the present invention, as shown in the first embodiment, a ring-shaped groove 24 is provided between the circular element 22 and the cruciform element 23, and the circular element 22 and the cruciform element 23 are capacitively coupled. By combining the good actions of the cross-shaped element 23 and the conductor element 26, it is possible to reduce the attitude of the antenna and cover a wide frequency band of 470 to 3150 MHz below VSWR2. That is, by providing a conductor element 26 between the conductor plate 11 and the circular element 22, connecting the outer conductor 13 of the coaxial connector 12 to the conductor plate 11, and connecting the center conductor 14 of the coaxial connector 12 to the conductor element 26. Further, the characteristics of the high frequency band are improved, and the circular element 22 connected to the conductor element 26 is connected to the cruciform element 23 by capacitive coupling, and the conductor plate is further connected to the cruciform element 23 via the short-circuit elements 25a to 25d. By connecting to 11, the characteristics of the low frequency band are improved.

The antenna device according to the first embodiment has a wideband characteristic of 470 to 3150 MHz, and with one antenna,
(1) One Segment broadcasting (470 to 770 MHz) for receiving mobile devices
(2) 800 MHz mobile phone (810-958 MHz)
(3) 1500 MHz band mobile phone (1429 to 1501 MHz)
(4) 1800 MHz mobile phone (1710 to 1880 MHz)
(5) IMT2000 (International Mobile Telecommunications 2000) (1920-2170 MHz)
(6) 2400-2500MHz wireless LAN
(7) WiMAX (Worldwide Interoperability for Microwave Access) in the 2545-2625 MHz band
Can cover all the bands.

  FIG. 7 shows the gain characteristic in the θ = 60 ° direction of the wideband antenna apparatus according to the first embodiment. The gain characteristic is approximately over a wide band including terrestrial digital broadcasting (470 to 770 MHz) to WiMAX (2545 to 2625 MHz). The gain is high around 4 [dBi].

  FIG. 8 shows the vertical polarization vertical plane directivity (ZX plane) at 470 MHz of the wideband antenna device according to the first embodiment, which shows good directivity characteristics.

  FIG. 9 is a diagram illustrating the vertical polarization horizontal plane directivity (θ = 60 °, XY plane) at 470 MHz of the antenna device according to the first embodiment. The horizontal plane directivity of the antenna device according to the first embodiment is omnidirectional with a deviation of 2 dB or less.

  In the first embodiment, the conductor element 26 is described as having a hemispherical outer peripheral surface formed so as to form an exponential curve. However, the hemispherical outer peripheral surface may be formed in a substantially semi-elliptical shape. .

  In addition, the conductor element 26 has a shape in which a plurality of circular metal plates 31a, 31b, 31c,... Having different diameters, for example, as shown in FIG. That is, you may form in the shape which expanded the upper end rather than the lower end.

  Furthermore, the conductor element 26 can be formed in any shape such as a conical shape, a triangular pyramid shape, a quadrangular pyramid shape, a hemispherical shape, and a trapezoidal shape as long as the upper end is wider than the lower end. .

  In the first embodiment, the case where the circular element 22 is used at the center of the antenna element 21 has been described. However, the antenna element 21 is not limited to a circular shape, and may be formed in a polygonal shape such as a square.

  In the first embodiment, the case where the cruciform element 23 is provided outside the circular element 22 as the antenna element 21 is shown, but the cruciform element 23 is provided with, for example, a plurality of elements in a radial pattern other than the cruciform. May be.

  Moreover, in the said Example 1, although it showed about the case where the outer side edge part of the cross-shaped element 23 was bent and provided the short circuit elements 25a-25d, short circuit elements 25a-25d were provided separately from the cross-shaped element 23, You may make it attach this short circuit element 25a-25d to the outer front-end | tip part of the cross-shaped element 23 by screwing etc. FIG.

  In the first embodiment, the case where the cruciform element 23 is arranged on the diagonal line of the conductor plate 11 has been described. However, the cruciform element 23 is provided corresponding to other positions, for example, each side portion of the conductor plate 11. May be.

  Furthermore, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.

  DESCRIPTION OF SYMBOLS 11 ... Conductor plate, 12 ... Coaxial connector, 13 ... Outer conductor, 14 ... Center conductor, 15 ... Through-hole, 21 ... Antenna element, 22 ... Circular element, 23 ... Cross-shaped element, 24 ... Ring-shaped groove, 25a- 25d: short-circuit element, 26: conductor element, 31a, 31b, 31c, ..., metal plate.

Claims (1)

  A conductor plate, a plate-like first radiating element provided at a predetermined height in the center of the conductor plate, and the first radiating element as a center, with a predetermined distance outside and radially A plate-like second radiating element provided, a short-circuit element that short-circuits between the outer end of the second radiating element and the conductor plate, a power supply terminal provided in a central portion of the conductor plate, and the first A conductive element provided on the lower side of the radiating element, having an upper end connected to the first radiating element and a lower end connected to the power supply terminal, and the conductive element is formed with the upper end wider than the lower end. Wideband omnidirectional antenna characterized by

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