JP2008113336A - Wide-band omnidirectional antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna element having a wide-band omnidirectional radiation pattern. <P>SOLUTION: The antenna has two radiation elements of plate type conductors. One radiation element is in a key-like shape and the inside of a bent portion forming the key-like shape is formed with arbitrary straight lines or curved lines. The other radiation element is in an L shape, and the inside of a bent portion forming the L shape is formed with arbitrary straight lines or curved lines. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an antenna formed of a printed circuit board.

  In recent years, antennas using WiMAX technology scheduled to start in the 2.5 GHz band and 3.5 GHz band are expected to introduce advanced diversity technologies such as MIMO, and are not capable of receiving reflected waves from all directions. A directional antenna is required. Furthermore, the frequency used in WiMAX varies around the world, and in order to cover all, it is necessary to cover a wide band. For example, 2.5 GHz band and 3.5 GHz band (the frequency band used in each country is expected to be slightly different, and it is necessary to cover a wide band of about 600 MHz from 3.2 GHz to 3.8 GHz in order to use it in common. To cover both), it is necessary to cover 2.5 GHz to 3.8 GHz.

  Devices having similar needs include wireless LAN and UWB. In the wireless LAN, if the frequency of the 5 GHz band is expanded in recent years and it can cover about 4.9 GHz to 5.9 GHz, the world 5 GHz band can be covered. In UWB, 3.1 GHz to 4.8 GHz is scheduled to be used mainly.

  From such a background, it can be said that an antenna having a wide-band omnidirectional radiation pattern such as this antenna is very important.

  The invention described in Patent Document 1 relates to a monopole antenna. Further, Patent Document 1 does not have a description regarding directivity and bandwidth.

Further, the invention described in Patent Document 2 has a narrow relative bandwidth of 30%.
JP 2006-005816 A Japanese Patent Laid-Open No. 11-097915 "Antenna Engineering Handbook" Author: IEICE, Release Date: October 1980, ISBN: 4-274-02677-9, 42P

  As shown in FIG. 20, the prior art antenna is an antenna called a printed dipole formed by etching a dipole antenna on a printed board.

FIG. 20 shows an antenna using a conventional printed circuit board. A radiating element 101 and a radiating element 102 made of a strip-shaped conductor are disposed on the front and back surfaces of the printed circuit board 100 so as to extend in opposite directions to constitute an equivalent dipole antenna. The radiating elements 101 and 102 are connected to and supplied with power from the microstrip line 103, and the lower microstrip line is connected to the ground 104.
This antenna is described, for example, on page 42 of "Antenna Engineering Handbook (Ohm)". This type of antenna cannot obtain a wide band characteristic unlike the present antenna, and can obtain a specific band of about 10% at most. Further, in FIG. 20, a non-directional radiation pattern cannot be configured on a horizontal plane. In particular, the directivity on the horizontal plane has a drawback that there is a null point at which the gain drops extremely in the left and right lateral directions of the printed circuit board (shown in FIG. 20), leading to deterioration of communication characteristics.

  Therefore, an object of the present invention is to provide an antenna element having a broadband and non-directional radiation pattern.

  The broadband omnidirectional antenna of the present invention is connected to the surface of a printed circuit board on a pentagonal surface having a single obtuse angle exceeding 180 degrees composed of a conductor and to the end of the radiating element. In order to supply power, a microstrip line composed of a strip-shaped conductor, a triangular radiating element composed of a conductor on the back surface of the printed circuit board, and an end of the triangular radiating element connected to supply power Further, it is composed of a strip-shaped conductor, and a tapered conductor whose opposite end portion is tapered, and a conductor ground plate to which the tapered conductor is connected. At this time, the microstrip line and the tapered conductor extend in the same direction on the front and back of the printed circuit board, and overlap each other on the front and back of the printed circuit board. Further, the pentagonal radiating element and the triangular radiating element are arranged in a positional relationship such that they do not overlap each other on the front and back sides.

  Alternatively, on the surface of the printed circuit board, a radiating element on a rectangular surface composed of a conductor, a microstrip line composed of a strip-shaped conductor connected to an end of the radiating element and supplied with power, and a print A triangular radiating element composed of a conductor on the back surface of the substrate, and a taper that is connected to the end of the triangular radiating element and is composed of a strip-shaped conductor for feeding power, with the opposite end extending in a taper shape And a conductor ground plate to which the tapered conductor is connected. At this time, the microstrip line and the tapered conductor extend in the same direction on the front and back of the printed circuit board, and overlap each other on the front and back of the printed circuit board. Furthermore, the rectangular radiating element and the triangular radiating element are arranged in a positional relationship such that they do not overlap each other on the front and back sides.

  (1) The printed circuit board can be easily and inexpensively configured by etching, (2) has a wide band characteristic, and (3) is almost non-directional in a horizontal plane (surface formed by etching the antenna into a flat shape). It has the radiation pattern of.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  The wide-band omnidirectional antenna of the present invention is an antenna that can be easily formed by etching at the tip of a PCMCIA card type used for a personal computer or the like, and has a wide-band characteristic. It has a generally omnidirectional radiation pattern in terms of construction.

  Since it has a wide band characteristic, it can be used for various terminals using various recent communication technologies. For example, a communication service using WiMAX technology is currently scheduled to start in the 2.5 GHz band and the 3.5 GHz band. In particular, in the 3.5 GHz band, the frequency band used in each country in the world is expected to be slightly different, and in order to use in common, it is necessary to cover a wide band of about 600 MHz from 3.2 GHz to 3.8 GHz.

  It is possible to configure the front end of a PCMCIA card or a CompactFlash (registered trademark) card, which is expected to be used for a terminal device that can be commonly used for communication services using the WiMAX technology, by etching.

  In addition, in the wireless LAN 5 GHz band service, various frequencies are used all over the world, and in order to be able to use all of them, it is necessary to be able to use in a wide band of about 4.9 GHz to 5.9 GHz. Etching can also be applied to the edge of a PDA terminal equipped with a wireless LAN function or the motherboard substrate of a personal computer. Similarly, an indoor wireless LAN access point can be formed by etching at the end of a built-in printed circuit board.

  In addition, devices and terminals for WPAN (wireless personal area network) using UWB (ultra-wide band) technology must be usable in the band of 3.4 GHz to 4.8 GHz in Japan. Is possible.

  As described above, the broadband omnidirectional antenna according to the present invention can be (1) simply and inexpensively configured by etching a printed circuit board, (2) has broadband characteristics, and (3) is in a horizontal plane (the antenna is planar). The surface is formed by etching into a substantially non-directional radiation pattern.

  FIG. 1 shows a configuration diagram of a first embodiment of a broadband omnidirectional antenna of the present invention. Further, FIG. 2 shows a front surface, a back surface, and a perspective view of the printed circuit board 1 of FIG. In FIG. 1, this antenna is an antenna formed by etching on a printed circuit board 1 having a dielectric, a front surface, and a thin conductor layer such as a copper foil on the back surface. A radiating element 2 and a microstrip line 4 are formed on the surface. The radiating element 3, the taper line 6, and the ground 7 are formed on the back surface.

  A stub 5 is formed in the middle of the microstrip line 4 on the surface in order to obtain electrical impedance matching. The taper line 6 on the back surface is also provided for impedance matching similarly to the stub 5. The slope of the taper line 6 is linear, but is often formed by a curve. Generally, an exponential curve, a trigonometric curve, a circle or an ellipse curve, or the like is used.

  The radiating element 2 has a shape in which the acute vertices of two right-angled triangles are connected to each other, and the other acute-angled vertices of one right-angled triangle are connected to the tip of the microstrip line 4 to be fed.

  The microstrip line 4 is provided with a stub 5 in the middle for impedance matching. In this case, it is not necessary when impedance matching can be obtained without the stub 5. Further, the shape of the stub 5 is not limited to a rectangle, and may be an arbitrary shape such as a triangle or a semicircle in order to obtain impedance matching.

  The radiating element 3 has a right triangle shape, and a vertex portion of one acute angle is connected to the tip of the taper line 6 to be fed. The taper line 6 has a thin tip and gradually becomes wider and is connected to the ground 7. The microstrip line 4 and the taper line 6 form a microstrip line on the front and back of the printed circuit board 1. As can be seen from the perspective view of FIG. 2 (3), the microstrip line 4 changes in width at a portion overlapping the ground 7, and thereafter has a constant width. The microphone strip line 4 forms a ground strip 7 and a microstrip line of about 50 ohms.

  In FIG. 1, the length of “a” is often 0.05 to 0.1 wavelength of the lowest usable frequency, and the length of “b” is often 0.1 to 0.15 wavelength. As a result of the experiment, when the minimum use frequency is 2.2 GHz, a = 10 mm, about 0.07 wavelength, b = 17 mm, about 0.125 wavelength, 2.2 GHz to 5 GHz and VSWR is 2.0 or less. Become. An example of this is shown in FIG.

  FIG. 3 shows a block diagram of a second embodiment of the broadband omnidirectional antenna of the present invention. 4 shows a front surface, a back surface, and a perspective view of the printed circuit board 10 of FIG. In FIG. 3, the difference from the structure in FIG. 1 is that the microstrip line 11 is not tapered like the taper line 6, but is formed in a linear strip having a constant width. . The difference between FIG. 1 and FIG. 3 is mainly the difference between the alignment by the taper line 6 and the alignment by the microstrip line 11.

  In FIG. 3, the length of c is often 0.1 to 0.13 wavelength, which is the lowest usable frequency, and the length of d is often 0.18 to 0.23 wavelength. As a result of the experiment, when the minimum use frequency is 3.4 GHz, a = 10 mm, about 0.11 wavelength, b = 17 mm, about 0.19 wavelength, 3.4 GHz to 6.4 GHz, and VSWR is 2.0. It becomes as follows. An example of this is shown in FIG.

  FIG. 5 shows a configuration diagram of a third embodiment of the broadband omnidirectional antenna of the present invention. 6 shows a front surface, a back surface, and a perspective view of the printed circuit board 20 of FIG. In FIG. 5, the difference from the structure in FIG. 3 is that a rectangular radiating element 21 is used instead of the radiating element 2.

  In FIG. 5, the length of e is often 0.7 to 0.1 wavelength of the lowest usable frequency, and the length of f is often 0.12 to 0.16 wavelength. As a result of the experiment, when the minimum use frequency is 2.5 GHz, a = 10 mm, about 0.08 wavelength, b = 17 mm, about 0.14 wavelength, 2.5 GHz to 6.2 GHz, and VSWR is 2.0. It becomes as follows. An example of this is shown in FIG.

  FIG. 7 shows a configuration diagram of a fourth embodiment of the broadband omnidirectional antenna of the present invention. Further, FIG. 8 shows a front surface, a back surface, and a perspective view of the printed circuit board 30 of FIG. FIG. 7 shows an example in which two broadband omnidirectional antennas having the structure of FIG. 1 are used. Normally, a PCMCIA card type communication unit that is inserted into a notebook computer is used for communication by forming two antennas as shown in FIG. 7 at the end of the card and using diversity technology or the like. There are many.

  FIG. 9 shows a configuration diagram of a fifth embodiment of the broadband omnidirectional antenna of the present invention. FIG. 10 shows a front surface, a back surface, and a perspective view of the printed circuit board 40 of FIG. FIG. 9 shows an example in which two broadband omnidirectional antennas having the structure of FIG. 3 are used.

  FIG. 11 shows a configuration diagram of a sixth embodiment of the broadband omnidirectional antenna of the present invention. FIG. 12 shows a front surface, a back surface, and a perspective view of the printed circuit board 50 of FIG. FIG. 11 shows an example in which two broadband omnidirectional antennas having the structure of FIG. 5 are used.

  FIG. 13 shows the shape of the radiating element 2 in FIGS. 1 to 4 and FIGS. 7 to 10, and modifications as shown in FIGS. 13 (1) to (7) are conceivable. (1) is the same shape as FIGS. In (2), the tip is a band with a constant width. (3) is a shape in which the tip portion is a band shape and is bent inward. (4) is a band-shaped conductor on a U-shape. (5) is a shape in which one side of the tip of the L-shaped strip-shaped conductor is widened in a tapered shape. (6) is a shape obtained by hollowing out the inside of a rectangular conductor with a semi-ellipse. In (7), a rectangular conductor is hollowed out by a semi-ellipse, and a right-angle portion of the outer periphery is formed into an arc shape.

  FIG. 14 shows the shape of the radiating element 3 in FIGS. 1 to 12, and modifications such as FIGS. 14 (1) to (7) are conceivable. (1) is the same shape as FIGS. (2) is a cut of the lower tip. (3) is an example using a normal triangle instead of a right triangle. (4) uses an L-shaped strip-shaped conductor. (5) is a semi-elliptical tip of (4). (6) is a shape obtained by hollowing out the inside of a rectangular conductor with a semi-ellipse. In (7), a rectangular conductor is hollowed out by a semi-ellipse, and a right-angle portion of the outer periphery is formed into an arc shape.

  FIG. 15 shows the shape of the radiating element 21 in FIGS. 5 to 6 and FIGS. 11 to 12, and modifications such as FIGS. 15 (1) to (7) are conceivable. (1) is the same shape as FIGS. 5-6 and FIGS. (2) is a semi-elliptical shape. (3) is a shape in which the left side of the rectangle is cut out with a triangle. (4) is a shape in which the left side of the rectangle is cut out with a rectangle. (5) is a shape obtained by hollowing out the center of the rectangle with a rectangle. It is a shape in which one side of a triangle is lined with a microstrip line. (7) is a shape obtained by horizontally inverting the triangular portion of (6).

  FIG. 16 shows measured values of the return loss characteristics of the antenna of the first embodiment. As the printed board, a glass epoxy board (FR-4) having a thickness of 1 mm is used. The dimensions are a = 10 mm and b = 17 mm in FIG. At 2.2 to 5 GHz, the return loss is −9.5 dB or less and the VSWR is 2 or less, which is a practical band.

  FIG. 17 is an actual measurement value of the return loss characteristic of the antenna of the second embodiment. The printed circuit board is the same as in FIG. The dimensions are c = 10 mm and d = 17 mm in FIG. In 3.4 to 6.4 GHz, the return loss is −9.5 dB or less and the VSWR is 2 or less, which is a practical band.

  FIG. 18 is an actual measurement value of the return loss characteristic of the antenna of the third embodiment. The printed circuit board is the same as in FIG. The dimensions are e = 10 mm and f = 17 mm in FIG. At 2.5 to 6.2 GHz, the return loss is −9.5 dB or less and the VSWR is 2 or less, which is a practical band.

  FIG. 19 shows measured values of radiation pattern characteristics in the horizontal plane of the antenna of the fourth embodiment. FIG. 7 shows the radiation patterns on the horizontal plane of 3.1 GHz and 4.8 GHz when a = 10 mm and b = 17 mm in the configuration of FIG. The measured values are fed to the antenna on the right front side in FIG. 7, and the feeding point of the left far side antenna is terminated at 50 ohms. In FIG. 19, the 0 degree direction indicates the Z-axis direction. The radiation pattern shows an omnidirectional radiation pattern that is substantially uniform at 0 ° ± 100 °, that is, a radiation pattern with little level fluctuation. In this case, omnidirectionality is not obtained at 360 degrees because the ground 31 (FIG. 7) exists on the same plane as the polarization, and the rear is blocked and radiation is suppressed, or disturbance due to scattering occurs. It is.

  The broadband omnidirectional antenna of the present invention is used as a communication service terminal or base station antenna using WiMAX technology, as a wireless LAN terminal or base station antenna, and further as a UWB terminal antenna. It is possible.

  An antenna using WiMAX wireless technology. An antenna using MIMO technology. An antenna using UWB wireless technology. Wireless LAN antenna. Other small antennas that require wide bandwidth and non-directional radiation characteristics.

Configuration diagram of a first embodiment of a broadband omnidirectional antenna of the present invention Front view and back view of printed circuit board 1 The block diagram of the 2nd Example of the broadband omnidirectional antenna of this invention Front view and back view of printed circuit board 10 The block diagram of the 3rd Example of the wideband omnidirectional antenna of this invention Front view and back view of printed circuit board 20 The block diagram of the 4th Example of the wideband omnidirectional antenna of this invention Front view and back view of printed circuit board 30 The block diagram of the 5th Example of the wideband omnidirectional antenna of this invention Front view and back view of printed circuit board 40 The block diagram of the 6th Example of the wideband omnidirectional antenna of this invention Front view and back view of printed circuit board 50 Shape of radiating element 2 Shape of radiating element 3 Radiation element 21 shape Return loss characteristics of the antenna of the first embodiment Return loss characteristics of the antenna of the second embodiment Return loss characteristics of the antenna of the third embodiment Radiation pattern characteristics of the antenna of the fourth embodiment Antenna using printed circuit board of the prior art

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printed circuit board 2 Radiation element 3 Radiation element 4 Microstrip line 5 Stub 6 Tapered line 7 Ground

Claims (16)

  An antenna having two plate-shaped radiating elements, one of the radiating elements is shaped like a key, and the inside of the bent portion forming the shape like the key is an arbitrary straight line or curved line The antenna is characterized in that the shape of the other radiating element is L-shaped, and the inside of the bent portion constituting the L-shape is formed by an arbitrary straight line or curve. The antenna according to claim 1, wherein
An antenna configured by etching a printed circuit board, which is fed by a microstrip line configured on the printed circuit board,
The tip of the radiating element and the microstrip includes a “B” -shaped portion in which a gap between the tip of the radiating element and the root of the tip of the microstrip is missing. antenna. The antenna according to claim 2, wherein
The radiating element includes at least one of a portion having a triangular shape, a portion having a quadrangular shape, and a portion having a trapezoidal shape. The antenna according to claim 3,
The antenna is characterized in that the radiating element includes a portion removed in a curved shape. The antenna according to claim 2, wherein
The antenna is characterized in that the radiating element has a quadrangular shape with a part removed by a triangle, a quadrangle, a trapezoid, or a semi-ellipse. The antenna according to claim 2, wherein
An angle in a plane parallel to the surface of the printed circuit board of a tangent line on the outer periphery of the radiating element is distributed in at least two directions. The antenna according to claim 2, wherein
The antenna is characterized in that the radiating element is asymmetrical about a center line parallel to the microstrip line. The antenna according to any one of claims 2 to 6,
The antenna according to claim 1, wherein the radiating element is provided on a front surface and a back surface. The antenna according to claim 8, wherein
The radiating element provided on the front surface and the radiating element provided on the back surface are asymmetrical with respect to the microstrip line. The antenna according to claim 8 or 9,
One of the radiating elements is coupled to a ground. The antenna according to claim 2, wherein
The first radiating element includes a first trapezoidal portion on the distal end side and a second trapezoidal portion on the root side so that the lower base of the first trapezoid and the upper base of the second trapezoid coincide with each other. A first trapezoidal portion on the tip side and a second trapezoidal portion on the root side,
The first trapezoid has an upper base on the tip side, a lower base that is the opposite side, a first side that is adjacent to the microstrip line, and a second side that is the opposite side,
The upper and lower bases of the first trapezoid are orthogonal to the microstrip line;
A second side of the first trapezoid is parallel to the microstrip line;
The lower base of the first trapezoid is shorter than the upper base of the first trapezoid,
The second trapezoid has an upper base on the tip side, a lower base that is the opposite side, a first side that is adjacent to the microstrip line, and a second side that is the opposite side,
The upper base of the second trapezoid coincides with the lower base of the first trapezoid,
The bottom of the second trapezoid is perpendicular to the microstrip line;
A second side of the second trapezoid is parallel to the microstrip line;
The antenna according to claim 2, wherein the lower base of the second trapezoid is longer than the upper base of the second trapezoid. The antenna according to claim 11,
The second radiating element is composed of a right triangle, and of the two sides sandwiching the right angle of the right triangle, one side is orthogonal to the microstrip line, and the other side is parallel to the microstrip line. An antenna characterized by. The antenna according to claim 12,
Further comprising a taper line on a microstrip coplanar with the second radiating element;
The taper line is a taper line whose width gradually increases in a stepped shape, a curved shape, or a linear shape as the distance from the second radiating element increases. The antenna according to claim 2, wherein
The first radiating element has a rectangular portion, and is a wide-band omnidirectional antenna. The antenna according to claim 14, wherein
The second radiating element is formed of a right triangle, and one of the two sides sandwiching the right angle of the right triangle is orthogonal to the microstrip line, and the other side is parallel to the microstrip line. An antenna characterized by. The antenna according to claim 12 or 13,
An antenna comprising a plurality of sets of the first radiating element and the second radiating element.

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