Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2001-08-03
2003-07-22
Nguyen, Hoang (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S895000
Reexamination Certificate
active
06597315
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an antenna, suitable for inclusion in various devices having capabilities for processing radio signals, such as electrical home appliances, office equipment, wireless LAN, telemetric systems, including mobile communication devices that can transmit and receive radio signals.
2. Description of the Related Art
In recent years, there have been increasing uses for antennas that can be used in frequency bands in a range of several hundreds of MHz to several tens of GHz due to increasing demand for various devices having capabilities for transmitting and receiving radio signals, including various communication devices for processing radio signals. Obvious uses for such antennas include mobile communications, next generation traffic management systems, non-contacting type cards for automatic toll collection systems, but in addition, because of the trend toward the use of wireless data handling systems that enable to handle data without using cumbersome lengthy cables such as cordless operation of household appliances through the Internet, Intranet radio LAN, Bluetooth and the like, it is anticipated that the use of such antennas will also be widespread in similar fields. Furthermore, such antennas are used in various systems for wireless data handling from various terminals, and the demand is also increasing for applications in telemetering for monitoring information on water pipes, natural gas pipelines and other safety management systems and POS (point-of-sale) terminals in financial systems. Other applications are beginning to emerge over a wide field of commerce including household appliances such as TV that can be made portable by satellite broadcasting as well as vending machines.
To date, such antennas described above used in various devices having capabilities for receiving and transmitting radio signals are mainly monopole antennas attached to the casing of a device. Also known are helical antennas that protrude slightly to the exterior of the casing.
However, in the case of monopole antennas, it is necessary to extend the structure for each use of the device to make the operation cumbersome, and, there is a further problem that the extended portion is susceptible to breaking. Also, in the case of the helical antennas, because a hollow coil that serves as the antenna main body is embedded in a covering material such as polymer resin for protection, the size of device tends to increase if it is mounted on the outside the casing and it is difficult to avoid the problem that the aesthetics suffers. Nevertheless, reducing the size of the antenna leads only to lowering of signal gain, which inevitably leads to increasing the circuit size for processing radio signals to result in significantly higher power consumption and a need for increasing the size of the battery, and ultimately leading back to the problem that the overall size of the device cannot be reduced.
Particularly, in an attempt to increase the gain, if the antenna is constructed of a plurality of compact antenna elements grouped in a small area, it presents a problem that, when the antenna elements are placed in close proximity with one another, the overall gain cannot be raised effectively due to mutual interference of electromagnetic waves emitted from one antenna element upon its neighboring antenna elements.
To avoid mutual interference among antenna elements, it is necessary to separate the antenna elements, as in conventional arrayed antennas, ideally at a distance of more than a half wavelength of the operational frequency, or more preferably, at a distance of about several wavelengths. However, such an approach does not achieve the original objective of reducing the antenna size, at least in the MHz range of frequency bands. For this reason, there has been a need to develop a new technology for increasing the signal gain by reducing mutual interference of closely spaced antenna elements.
SUMMARY OF THE INVENTION
The present invention is provided in view of the background information described above, and an object is to provide a high gain compact antenna that reduces the overall size of a device by reducing the size of the exterior dimensions of the antenna so as to permit the antenna to be assembled into devices that process radio signals; to provide pleasing aesthetics; to eliminate the need to extend the antenna to prevent breaking, and to eliminate the need for a large sized circuit structure and battery.
Also, the present invention is provided in view of the information described above, and another object is to provide a high gain compact antenna that enables high gain to be attained by reducing the mutual interference caused by a plurality of antenna elements.
Further, the present invention is provided in view of the information described above, and another object is to provide a high gain compact antenna that enables to improve gain through a structure in which more than one antenna element are connected each other.
A first embodiment of the present invention relates to an antenna having not less than two antenna elements, wherein a plurality of antenna elements are connected in series, and each antenna element is comprised by an inductance section connected in parallel to a capacitance section.
In the present invention, an antenna element is comprised by a resonance system constituted by the inductance section and the capacitance section connected in parallel, and when more than two such antenna elements are connected in series, the assembly functions as an antenna. Compared with a case of having a singular antenna element, gain of the antenna and bandwidth can be adjusted more readily by arranging a plurality of such antenna elements. Further, the antenna is constructed by circuits having the inductance section and the capacitance section in such a way to effectively capture varying electrical and magnetic field components, so that the antenna size can be reduced by optimizing the values of the capacitance and inductance.
Also, the second embodiment of the present invention relates to the antenna in the first embodiment, wherein the plurality of antenna elements connected in series are arranged in such a way that directions of magnetic fields generated by a current flowing in each inductance section are intersecting with one another.
By adopting such a structure, the mutual interference between the antenna elements is optimized so that, compared with the case of only connecting the antenna elements in series without any care for directions of magnetic fields generated by a current flowing in each inductance section, directivity for signal reception and transmission is reduced and the gain is increased.
The present invention relates to the antenna in the first embodiment, wherein the inductance section has a coil section and a plurality of antenna elements connected in series are arranged in such a way that directions of magnetic fields generated by a current flowing in each coil section are intersecting with one another.
By adopting such a structure, the mutual interference between the antenna elements is optimized so that, compared with the case of only connecting the antenna elements in series without any care for directions of magnetic fields generated by a current flowing in each inductance section, directivity for signal reception and transmission is reduced and the gain is increased.
Also, third embodiment of the present invention relates to the antenna in the second embodiment, wherein the inductance section has a coil section comprised by a conductor formed in a spiral shape or an angular shape that can be approximated by a spiral circling a coil axis; and the plurality of antenna elements are arranged so that respective axes of adjacent coil sections are aligned on a straight line.
By adopting such a structure, the axes of the coil sections are aligned so that the size of the overall antenna is reduced, and directivity for transmitting and receiving radio waves is reduced and the gain is increased.
Furthe
Chiba Toshiyuki
Kobayashi Hideki
Sugimura Shiro
Ueoka Yasushige
Yokoshima Takao
Mitsubishi Materials Corporation
Nguyen Hoang
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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