JP2004260582A - Patch antenna - Google Patents

Abstract

A patch antenna having a wide band and a low profile is provided.
The patch antenna includes a planar ground conductor, a plate-shaped dielectric disposed on the ground conductor, and a patch-shaped radiation conductor disposed on an upper surface of the dielectric. The length of the ground conductor 32 is less than half the free space wavelength of the frequency used, and the length of the dielectric 11 and the radiation conductor 21 is shorter than that of the ground conductor 32. Since the length of the ground conductor 32 is set to be equal to or less than a half wavelength and the radio wave can be radiated in all directions, the frequency band of the antenna can be widened even if the thickness of the dielectric 11 is not large. it can.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a microstrip type patch antenna used in wireless communication devices such as mobile phones and wireless LANs, and various other communication devices.
[0002]
[Prior art]
FIG. 4 shows an example of a conventional microstrip patch antenna used in a wireless communication device such as a mobile phone and a wireless LAN, and various other communication devices.
[0003]
In FIG. 4, an antenna 101 includes a dielectric 111, a radiation conductor 121 disposed on an upper surface of the dielectric 111, and a first ground conductor 131 (not shown) disposed on a lower surface of the dielectric 111. The substrate 132 is a second ground conductor connected to the first ground conductor 131 and having a side length L132 longer than the free space wavelength of the frequency used.
[0004]
In this conventional microstrip patch antenna, since the length of one side of the second ground conductor 132 is longer than the free space wavelength of the used frequency, radio waves are transmitted from the radiation conductor 121 to the respective ground conductors 131 and 132 ( In FIG. 4, the light is not radiated in the negative direction of the Z axis, but is radiated in the opposite direction (the positive direction of the Z axis in FIG. 4), and the radiation characteristic becomes unidirectional.
[0005]
Further, in the conventional microstrip type patch antenna, the radiation conductor 121, the dielectric 111, and the second ground conductor 132 disposed on the upper surface of the dielectric 111 sandwich the radiation conductor 121 and the second ground conductor 132 with the dielectric 111 interposed therebetween. An electric field is generated between the ground conductors 132, and the electric field spreads in space, so that radio waves are emitted. Here, as the distance between the radiating conductor 121 and the second ground conductor 132, that is, the thickness of the dielectric 111 increases, the electric field spreads more easily in the space. As a result, the frequency band increases, and conversely, the electric field spreads in the space. And the frequency band becomes narrower. For this reason, the frequency band of the conventional antenna has been adjusted by adjusting the thickness of the dielectric 111.
[0006]
[Patent Document 1]
JP-A-1997-148840
[Problems to be solved by the invention]
However, in such a conventional microstrip type patch antenna, it is necessary to increase the thickness of the dielectric 111 in order to widen the frequency bandwidth, and it is difficult to achieve both a wide band and a low profile. there were.
[0008]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a microstrip type patch antenna having a low height and a wide band.
[0009]
[Means for Solving the Problems]
The patch antenna of the present invention is a patch antenna including a planar ground conductor, a plate-shaped dielectric disposed on the ground conductor, and a patch-shaped radiating conductor disposed on an upper surface of the dielectric. Wherein the length of the ground conductor is less than half the free space wavelength of the frequency used, and the length of the dielectric and the radiation conductor is shorter than that of the ground conductor. It is.
[0010]
According to the patch antenna of the present invention, since the length of the ground conductor is longer than the length of the radiation conductor, an end effect occurs, an electric field is generated between the radiation conductor and the ground conductor, and the electric field radiates radio waves into space. Patch antenna can be provided.
[0011]
According to the patch antenna of the present invention, since the length of the ground conductor is equal to or shorter than one half of the free space wavelength of the frequency used, the radio wave is transmitted to the side where the radiation conductor is located when viewed from the ground conductor. Not only that, it is also emitted in the opposite direction. Therefore, radio waves are radiated in all directions without bias in the radiation direction, compared to the case where the radiation characteristics of a conventional antenna are unidirectional. In this case, radio waves can be radiated even in frequency bands that are difficult to radiate, so it is possible to broaden the frequency band of radio waves radiated from the antenna and provide a low-profile patch antenna with a thick dielectric material can do.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a patch antenna of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is a perspective view showing an example of an embodiment of a patch antenna according to the present invention. In FIG. 1, reference numeral 1 denotes a plate-shaped dielectric 11 and a conductor disposed on the upper surface of the dielectric 11 and having a side length of L21 adheres to the dielectric 11 with a substantially uniform thickness of several microns to several tens of microns. The antenna substrate 32 composed of the patch-shaped radiation conductor 21 has a length L32 of one side longer than the length L21 of one side of the radiation conductor 21 and is a half of a free space wavelength of a used frequency. The following is the second ground conductor. The dielectric 11 is disposed on the ground conductor 32.
[0014]
According to the patch antenna of the present invention configured as shown in FIG. 1, since the length L32 of the ground conductor 32 is longer than the length L21 of the radiation conductor 21, an end effect occurs, and the distance between the radiation conductor and the ground conductor is increased. An electric field is generated, and the electric field radiates radio waves into space. The length L32 of the ground conductor 32 is larger than the length L21 of the radiation conductor 21 in consideration of the swelling of lines of electric force formed between the end of the radiation conductor 21 and the ground conductor 32, that is, the end effect of the electric field. It is preferable to make the thickness of the dielectric 11 approximately twice as long. At this time, the length of the side adjacent to one side of the radiation conductor 21 and the ground conductor 32 may be approximately the same as each side. The radiation conductor 21 and the ground conductor 32 are generally formed in a rectangular shape such as a rectangle or a square, but may be formed in any shape as long as the shape acts as a patch antenna. In addition, the length L21 of one side of the radiation conductor 21 may be set to about one half of the effective wavelength in the dielectric 11 at the frequency to be used.
[0015]
Further, according to the patch antenna of the present invention configured as shown in FIG. 1, since the length L32 of the ground conductor 32 is equal to or shorter than one half of the free space wavelength of the used frequency, Since the ground conductor 32 is not long enough to obstruct the emission of radio waves as in the unidirectional antenna of FIG. 1, the radio waves are viewed only from the side of the radiation conductor 21 as viewed from the ground conductor 32 (the positive direction of the Z axis in FIG. 1). Instead, it is also radiated in the opposite direction (the negative direction of the Z axis in FIG. 1). Therefore, compared with the case of the conventional patch antenna shown in FIG. 4 in which the radiation characteristics are unidirectional, radio waves are radiated in all directions since there is no bias in the radiation direction, and radio waves are easily radiated. In the unidirectional antenna described above, radio waves can be radiated even in a frequency band that is difficult to radiate, so that the frequency band can be widened, and the frequency band of the antenna can be widened even if the dielectric 11 is not thick. be able to.
[0016]
Here, the dielectric 11 functions to maintain the interval between the radiation conductor 21 and the ground conductor 32 and to reduce the size of the radiation conductor 21 by the dielectric constant of the dielectric 11 in the patch antenna of the present invention. The length L21 of one side of the radiation conductor 21 and the length of the side adjacent to the one side should be larger than the length L21 of the side of the radiation conductor 21 so that the required size reduction effect can be obtained. I just need.
[0017]
In forming the patch antenna of the present invention, the dielectric 11, the radiation conductor 21, and the ground conductor 32 may be the same as those of various materials and forms used for known high-frequency wiring boards. it can.
[0018]
Examples of the dielectric 11 include ceramic materials such as alumina ceramics and mullite ceramics, inorganic materials such as glass ceramics, and ethylene tetrafluoride-ethylene resin (polytetrafluoroethylene; PTFE) / tetrafluoroethylene-ethylene copolymer. Fluororesin such as resin (tetrafluoroethylene-ethylene copolymer resin; ETFE), ethylene tetrafluoride-perfluoroalkoxyethylene copolymer resin (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin; PFA), glass epoxy resin, etc. A resin material such as polyimide is used. The shape and dimensions (thickness, width, length) of the dielectric 11 made of these materials are set according to the frequency used, the application, and the like.
[0019]
The radiating conductor 21 and the grounding conductor 32 are formed by applying a Ni plating layer and an Au plating layer on a conductor layer of a metal material for transmitting a high-frequency signal, for example, a Cu layer / Mo-Mn metallization layer. A Ni-plated layer and an Au-plated layer adhered thereon; a Cr-Cu alloy layer; a Ni-plated layer and an Au-plated layer adhered on a Cr-Cu alloy layer; and Ni over a Ta ₂ N layer. -A Cr alloy layer and an Au plating layer are applied.-A Pt layer and an Au plating layer are applied on a Ti layer, or a Pt layer and an Au plating layer are applied on a Ni-Cr alloy layer. It is formed by a thick film printing method, various thin film forming methods, a plating method, or the like. The thickness, width, and the like are also set according to the frequency, use, and the like of the transmitted high-frequency signal.
[0020]
The ground conductor 32 may be a well-known high-frequency wiring board, a printed wiring board often used for electronic equipment, or the like, in which a conductor is provided in a predetermined shape on the surface, a plate-shaped metal plate, or the like.
[0021]
As a method of manufacturing the patch antenna of the present invention, first, when the dielectric substrate 11 is made of glass ceramic, for example, a green sheet of glass ceramic to be the dielectric 11 is first prepared, and a predetermined After a punching process is performed to form a through hole in which a through conductor serving as a power supply conductor (not shown in FIG. 1) for supplying power to the radiation conductor 21 is formed, a conductor paste such as Cu is penetrated by screen printing. In addition to filling the holes, a pattern of a conductor layer to be the radiation conductor 21 and other predetermined transmission line patterns as necessary are printed and applied. Next, baking is performed at 850 to 1000 ° C., and finally, the surface of each conductor layer is subjected to Ni plating and Au plating.
[0022]
Next, the antenna substrate 1 is attached to a ground conductor 32 formed on the surface of a mounting board such as a printed wiring board by active brazing or the like. The antenna substrate 1 may be attached to the ground conductor 32 by brazing a metal layer formed on the lower surface of the antenna substrate 1. In this case, when forming the radiation conductor 21 and the like of the antenna substrate 1, A metal layer may also be formed on the lower surface, a solder paste or the like may be applied to the metal layer, and the metal layer may be heated to about 200 ° C. in a reflow furnace, a heater block, or the like, and attached to the ground conductor 32.
[0023]
FIGS. 2 and 5 respectively show an example of the embodiment of the patch antenna of the present invention shown in FIG. 1 and the example of the conventional patch antenna shown in FIG. FIG. 2 and 5, the numbers on the outer circumference of the circle are angles (unit: °) indicating an azimuth with the vertex direction of the patch antenna (the direction indicated by the positive direction of the Z axis in FIGS. 1 and 4) being 0 °, The radial direction of the circle indicates the gain (unit: dBi), and the characteristic curve indicates the radiation characteristic, that is, the azimuth characteristic of the gain. The radiation characteristics shown in this diagram are obtained by using an electromagnetic field simulation.
[0024]
The thickness of the dielectric 11 (111) is 1.6 mm, the length of one side is 11 mm, the dielectric constant is 8.8, the length of one side of the radiation conductor 21 (121): L21 (L121) is 9.2 mm, In the patch antenna of the present invention having the radiation characteristics shown in FIG. 2, the length L32 of one side of the ground conductor 32 is longer than the length L21 of the radiation conductor 21 = 9.2 mm, and the frequency 5.15 GHz used is used. In a conventional patch antenna having a radiation characteristic shown in FIG. 5 which is 20 mm shorter than a half of the free space wavelength of about 60 mm and which has the radiation characteristic shown in FIG. It was 50 mm, which is close to about 60 mm, which is a free space wavelength of 5.15 GHz.
[0025]
The radiation characteristic of the conventional patch antenna shown in FIG. 5 is unidirectional with a high gain in the direction of 0 °, whereas the radiation characteristic of the patch antenna of the present invention shown in FIG. The gain in other directions is also higher.
[0026]
3 and 6 are diagrams showing reflection characteristics of the example of the embodiment of the patch antenna of the present invention shown in FIG. 1 and the example of the conventional patch antenna shown in FIG. 4, respectively. 3 and 6, the horizontal axis represents frequency (unit: GHz), and the vertical axis connects a feed conductor (not shown) to the radiating conductor 21 (121) through the dielectric 11, and applies an electromagnetic wave to the feed conductor. This is a VSWR measured by supplying power, and the characteristic curve indicates a reflection characteristic, that is, a frequency characteristic of the VSWR. The reflection characteristics shown in this diagram were obtained using the same electromagnetic field simulation used to obtain the radiation characteristics, and the dimensions and materials of each patch antenna were used to obtain the reflection characteristics. It was the same as the one. From this result, while the bandwidth of the example of the conventional patch antenna shown in FIG. 6 where the VSWR is 2 or less is 72 MHz, the VSWR of the example of the embodiment of the patch antenna of the present invention shown in FIG. It can be seen that the following bandwidth is as wide as 106 MHz.
[0027]
As described above, according to the patch antenna of the present invention configured as shown in FIG. 1, since the length L32 of the ground conductor 32 is longer than the length L11 of the radiation conductor 11, the reflection characteristics and the radiation shown in FIGS. As the characteristics are obtained, the ground conductor 32 can be used as the ground conductor of the patch antenna with respect to the radiation conductor 21.
[0028]
Further, according to the patch antenna of the present invention configured as shown in FIG. 1, since the length L32 of the ground conductor 32 is equal to or less than half the free space wavelength of the frequency used, the radiation characteristic of FIG. As shown in FIG. 1, the radio wave is transmitted not only from the direction from the radiation conductor 21 to the surface on which the radiation conductor 21 of the ground conductor 32 is arranged (the positive direction of the Z axis in FIG. 1 and the direction of 0 ° in FIG. 2), but also Are also radiated in the direction opposite to the surface on which the is disposed (the negative direction of the Z-axis in FIG. 1 and the direction of 180 ° in FIG. 2). Therefore, compared to the case where the radiation characteristic of the conventional patch antenna shown in FIG. 4 is unidirectional, radio waves are more likely to be radiated in all directions, and the frequency band is increased to 106 MHz compared to 72 MHz of the conventional patch antenna. Spread. At this time, since the thickness of the dielectric 11 (111) is constant at 1.6 mm, it can be seen that the band could be widened without increasing the thickness of the dielectric.
[0029]
It should be noted that the present invention is not limited to the above-described embodiments, and various changes can be made without departing from the gist of the present invention. For example, in the above description, the dielectric 11, the radiation conductor 21, and the ground conductor 32 are square, but may be circular. With such a configuration, the housing of the device incorporating the patch antenna has a circular shape. It is preferable if there is. When the dielectric 11, the radiation conductor 21, and the ground conductor 32 are circular, the diameter of the radiation conductor 21 may be shorter than the diameter of the ground conductor 32, and the diameter of the ground conductor 32 is two minutes of the free space wavelength of the frequency used. It is sufficient if it is 1 or less.
[0030]
The radiating conductor 21 and the ground conductor 32 are usually formed on a plane, but may be formed on a flat or plate-like surface having a curved surface of about several millimeters or irregularities of about several millimeters.
[0031]
【The invention's effect】
According to the patch antenna of the present invention, a patch including a planar ground conductor, a plate-shaped dielectric disposed on the ground conductor, and a patch-shaped radiating conductor disposed on the upper surface of the dielectric In the antenna, the length of the ground conductor is less than half the free space wavelength of the frequency used, and the length of the dielectric and the radiation conductor is shorter than that of the ground conductor. Since the length is longer than the length of the radiating conductor, an end effect occurs, an electric field is generated between the radiating conductor and the ground conductor, and the patch electric field radiates radio waves into space by the electric field.
[0032]
According to the patch antenna of the present invention, since the length of the ground conductor is equal to or shorter than one half of the free space wavelength of the frequency used, the radio wave is transmitted to the side where the radiation conductor is located when viewed from the ground conductor. Not only that, it is also emitted in the opposite direction. Therefore, compared to the case where the radiation characteristics are unidirectional as in a conventional patch antenna, radio waves are easily radiated, the frequency band radiated from the antenna can be widened, and the thickness of the dielectric is not thick A low-profile patch antenna can be provided.
[0033]
As described above, according to the present invention, a low-profile and wide-band patch antenna can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view illustrating an example of an embodiment of a patch antenna of the present invention.
FIG. 2 is a diagram showing radiation characteristics of the patch antenna of the present invention.
FIG. 3 is a diagram showing reflection characteristics of the patch antenna of the present invention.
FIG. 4 is a perspective view showing an example of a conventional patch antenna.
FIG. 5 is a diagram showing radiation characteristics of a conventional patch antenna.
FIG. 6 is a diagram showing reflection characteristics of a conventional patch antenna.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Antenna board 11 ... Dielectric 21 ... Radiation conductor 32 ... Ground conductor

Claims (1)

A patch antenna comprising: a planar ground conductor, a plate-shaped dielectric disposed on the ground conductor, and a patch-shaped radiation conductor disposed on an upper surface of the dielectric; A patch antenna, wherein the length is less than half the free space wavelength of the frequency used, and the length of the dielectric and the radiation conductor is shorter than the ground conductor.

Images