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.
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.
Further, at least one portion of portions of the conductor that circle the coil axis is contained in a plane inclined at an angle to the coil axis.
By adopting such a structure, the mutual interference between the axially-aligned adjacent antenna elements is reduced and the overall gain of the antenna is increased.
In the case of an antenna element having a coil section comprised by a conductor that circles a coil axis, there are several possible combinations of positioning each adjacent antenna element. Of the possible combinations, experiments have proven that higher gains are possible when the antenna elements are connected so that the axes of the coil sections are aligned on a straight line rather than connecting the antenna elements in parallel. In addition, the mutual interference is reduced when the adjacent antenna elements are arranged so that the coil axes are intersecting. In the present invention, priority is given to reducing the area required for mounting the antenna and also to increasing the ease of mounting.
The conductor is formed by linking the portion that circles the coil axis in the axial direction. If cylindrical coordinates are used to designate the coil axis as z-axis, and describe the position of each section of the conductor, a typical spiral exhibits monotonic changes in the z-coordinate as the angular coordinate xcex8 is varied. Then, consider a spiral conductor that circles the coil axis over an angular displacement of xcex8=360 degrees, and one plane intersecting the z-axis at right angles at the starting point and another plane intersecting the z-axis at the ending point of such a spiral, then this spiral does not intersect the planes except at the beginning point and at the ending point of the conductor spiral. If one supposes such a plane for each complete revolution (or turning portion) of the conductor spiral, then the conductor is divided by a series of such planes at right angles to the coil axis. When this argument is extended to a general spiral-like conductor or a conductor that can be approximated by a spiral, a group of such planes can be visualized to divide the conductor but the turning portions (loops) of the conductor do not intersect the planes except at the beginning points and the ending points of each loop. Then, each loop of the conductor can be associated with an adjacent imaginary plane using an expression xe2x80x9ca portion of the conductor that circles the coil axis is contained in a planexe2x80x9d (herein below imaginary planes that divide the conductor are referred to simply as planes).
In such a case, if at least one portion of the portions that circle the coil axis is contained in a plane that is inclined at an angle to the axis, then the direction of the magnetic field generated by the current flowing in this portion tends to be perpendicular to the plane. Looking at the whole antenna, the directions of the magnetic fields generated by the current flowing in the coil sections become asymmetrical about the coil axis, so that the magnetic field generated by the current flowing in one coil section is weakened at other coil section such that the mutual interference between the antenna elements is reduced.
Also, those portions of the conductor that circle the axis may be formed so as to be parallel to each other.
By adopting such a structure, the magnetic fields generated by the current flowing in the coil sections become even more asymmetric about the axis, so that the magnetic field generated by the current flowing in one coil section is weakened at other coil section such that the mutual interference of the antenna elements is reduced. Accordingly, the gain of the overall antenna can be increased even more effectively.
Also, it is preferable that the planes in two adjacent coil sections are inclined at different angles to the coil axis.
By adopting such a structure, in the adjacent coil sections whose axes are aligned substantially on a straight line, the directions of the magnetic fields generated by the current flowing in the coil section become asymmetrical about the axis, and the magnetic field generated by the current flowing in one coil section is weakened at other coil section, and the directions of the magnetic fields generated in the two coil sections intersect one another, so that the mutual interference of the antenna elements is reduced and the gain of the overall antenna is increased.
Another embodiment of the antenna in the present invention is comprised by not less than two antenna elements connected in series, wherein each antenna element has an inductance section and a capacitance section connected electrically in parallel, and wherein a conductor section is disposed between induction sections of at least two adjacent antenna elements.
By adopting such a structure, the conductor section so provided shields the electromagnetic waves generated by the antenna elements somewhat, so that the mutual interference between the adjacent antenna elements is reduced and the gain of the antenna is increased.
A fourth embodiment of the antenna in the present invention relates to the antenna in the third embodiment, wherein the coil section is provided with a first conductor pattern formed on a first plane, a second conductor pattern formed on a second plane oppositely disposed to the first plane, and a coil conductor section for electrically connecting the first conductor pattern to the second conductor pattern; and the capacitance section has a condenser section that has a third conductor pattern formed on a third plane and a fourth conductor pattern formed on a fourth plane oppositely disposed to the third plane; such that the first plane, the second plane, the third plane and the fourth plane are disposed so as to face each other.
By adopting such a structure, the coil section and the condenser section are assembled in three-dimensions so that the area required to construct the antenna is reduced, compared with the case of arranging the coil section and the condenser section on a single substrate plate, and the antenna can be miniaturized.
In the above antenna, it is preferable that the first plane and the second plane are constituted by two opposing planes of a first substrate plate; the third plane and the fourth planes are constituted by two opposing planes of a second substrate plate; and the first substrate plate and the second substrate plate are laminated with an intervening insulation layer into an integral unit.
By adopting such a structure, the antenna is comprised by two substrate plates with an intervening insulation layer so that the handling is facilitated.
Also, in the antenna in the first embodiment of the present invention, the plurality of antenna elements are connected in series to a frequency adjusting capacitance section.
By adopting such a structure, the resonant frequency (it may also be referred to sometimes as the center frequency in the description) at which the antenna resonates with a maximum gain can be altered.
It is preferable that the plurality of antenna elements are contained in an antenna main body, and the frequency adjusting capacitance section is provided as a separate body from the antenna main body such that the antenna main body and the frequency adjusting capacitance section comprise an antenna module.
By adopting such a structure, the capacitance of the frequency adjusting capacitance section is provided in another component body so that the resonant frequency can be adjusted independently of the antenna main body. That is, once the antenna main body is formed to suit a particular frequency, subsequent adjusting of frequency is carried out by adjusting the capacitance of the frequency adjusting capacitance section provided as a separate body from the antenna main body. Such an antenna module comprised by an antenna main body and a separate frequency adjusting capacitance section, enables flexible frequency adjustment.
Also, in the antenna according to the first embodiment, the plurality of antenna elements and an electrode one connected electrically to the antenna elements are provided in the antenna main body; and the antenna main body is mounted on a substrate plate having an electrode two so as to form a frequency adjusting capacitance section between the electrode one and the electrode two.
In the present invention, an electrode one provided on the antenna main body operates in conjunction with an electrode two provided on a substrate plate mounted with the antenna, for example, the grounding plate for the printed board mounted with the antenna, to form the frequency adjusting capacitance section. By adopting such a structure, it is possible to adjust the capacitance of the frequency adjusting capacitance section by altering the area of the electrode two provided on the substrate plate, for example, or by adjusting the position of the substrate plate on which the antenna is mounted. More specifically, the capacitance value of the frequency adjusting capacitance section can be adjusted when mounting the antenna on the substrate plate, by adjusting the size of the area opposing the grounding plate on the printed board, for example. When assembling the antenna into a product, a shift in the antenna frequency caused by the effect of casing and the like can be corrected by adjusting the mounting position of the antenna so as to change the capacitance of the frequency adjusting capacitance section. Or, it is also possible to deliberately change the frequency of the antenna by a large amount.
Also, in the antenna in the fourth embodiment, the plurality of antenna elements and an electrode one formed on a fifth plane that opposes the first to fourth planes inclusively are contained in an antenna main body; and the antenna main body is mounted on a substrate plate having an electrode two so as to form a frequency adjusting capacitance section between the electrode one and the electrode two.
In the present invention, the electrode one provided on the antenna main body operates in conjunction with the electrode two provided on a substrate plate mounted with the antenna, for example, the grounding plate of the printed board mounted with the antenna, to form the frequency adjusting capacitance section. By adopting such a structure, it is possible to adjust the capacitance of the frequency adjusting capacitance section by altering the area of the electrode two provided on the substrate plate, for example, or by adjusting the position of the substrate plate on which the antenna is mounted. More specifically, the capacitance value of the frequency adjusting capacitance section can be adjusted when mounting the antenna on the substrate plate, for example, by adjusting the size of the area opposing the grounding plate of the printed board. When assembling the antenna into a product, a shift in the antenna frequency caused by the effect of casing and the like can be corrected by adjusting the mounting position of the antenna so as to change the capacitance of the frequency adjusting capacitance section. Or, it is also possible to deliberately change the frequency of the antenna by a large amount.
Also, the plurality of antenna elements and the frequency adjusting capacitance section are connected in three-dimensions so that the antenna does not occupy a large space when it is incorporated into a device to enable to miniaturize the device.
It is preferable in the above case that the first plane and the second plane are constituted by two opposing planes of a first substrate plate; the third plane and the fourth planes are constituted by two opposing planes of a second substrate plate; the fifth plane is constituted by a plane of a frequency adjusting substrate plate; and the first substrate plate, the second substrate plate and the frequency adjusting substrate plate are laminated with respective intervening insulation layers into an integral unit.
By adopting such a structure, the antenna may be mounted as an integral unit on a substrate plate to facilitate handling.
Also, the present invention relates to the antenna in the first 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 a 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.
Further, at least one portion of portions of the conductor that circle the coil axis is contained in a plane inclined at an angle to the coil axis.
By adopting such a structure, the mutual interference between the axially-aligned adjacent antenna elements is reduced and the overall gain of the antenna is increased.
Also, it is preferable that the planes in two adjacent coil sections are inclined at different angles to the coil axis.
By adopting such a structure, the mutual interference of the antenna elements is reduced more effectively and the gain of the overall antenna is increased.
The overall effect of the antenna according to the present invention are summarized below.
According to the present invention, because a inductance section and a capacitance section are connected in parallel in each antenna element, and plurality of such antenna elements are connected in series, the gain is increased, and also, unlike the monopole antennas or helical antennas, the size of the antenna can be reduced because the antenna is constructed of solid-state circuit elements. Accordingly because the antenna can be incorporated into various devices for processing radio signals, there is no need for antenna to be extended manually so that the danger of breaking is eliminated and the overall appearance of the device is enhanced.
Also, according to the present invention, because the plurality of antenna elements are arranged so that the directions of the magnetic fields generated by the current flowing in the inductance sections are intersecting, directivity of signal radiation becomes more homogeneous when processing radio signals, compared with the case of simply arranging the antenna elements in series, and the gain can be increased.
Also, according to the present invention, because the inductance section has a coil section, the value of inductance can be increased, and, because the plurality of antenna elements are arranged so that the magnetic fields generated by the coil sections are intersecting, directivity for signal radiation can be reduced when processing radio signals comperd with the case of simply arranging the antenna elements in series, and the gain can be increased.
Also, according to the present invention, because the inductance section has a coil section, the value of inductance can be significantly increased compared with the case of having simple line conductors and the like, and because the adjacent antenna elements are arranged so that the coil axes of the coil sections are aligned in a straight line, the overall size of the antenna can be made smaller and directivity for signal reception can become more homogeneous and the gain can be increased.
Also, according to the present invention, because the coil sections in the adjacent antenna elements are aligned substantially on a straight line, and the portions (turning section) that circle the coil axis are contained in associated planes that are oriented at an angle to the coil axis, the mutual interference between the antenna elements is reduced to enable to construct a high gain compact antenna.
Also, according to the present invention, because the portions that circle the coil axis are contained in associated planes that are oriented at an angle to the coil axis and are arranged in parallel to each other, the mutual interference between the antenna elements are further reduced to enable to construct a high gain compact antenna.
Also, according to the present invention, because the planes that substantially contain the portions that circle the coil axis of the conductor are oriented at different angles in the coil sections of adjacent coil sections, the mutual interference between the antenna elements is reduced to enable to construct a high gain compact antenna.
Also, according to the present invention, because a conductor section is disposed between the adjacent antenna elements, the mutual interference between the antenna elements is reduced to enable to construct a high gain compact antenna.
Also, according to the present invention, because the coil section and the condenser section are constructed of a lamination in which the first to fourth conductor patterns inclusively oppose respective planes in a three-dimensional structure so that, compared with the case of arranging the coil section and the condenser section on a single piece of substrate plate, the antenna is contained in a smaller space. Thus, the antenna is miniaturized to facilitate its incorporation inside the device for processing radio signals.
Also, according to the present invention, a unitized antenna can be assembled into a device for processing radio signals so that its handling is facilitated.
Also, according to the present invention, because a frequency adjusting capacitance section is connected to the antenna, a frequency at which a maximum gain is achieved can be varied and altered.
Also, according to the present invention, because the plurality of antenna elements are contained in an antenna main body, and the frequency adjusting capacitance section is provided as a separate body from the antenna main body such that the antenna main body and the frequency adjusting capacitance section comprise an antenna module, so that after the antenna main body is formed to suit a particular frequency, subsequent adjusting of frequency can be carried out by adjusting the capacitance of the frequency adjusting capacitance section provided as a separate body from the antenna main body to enable to perform frequency adjustment operation flexibly.
Also, according to the present invention, because the plurality of antenna elements and an electrode one connected electrically to the antenna elements are provided in the antenna main body; and the antenna main body is mounted on a substrate plate having an electrode two so as to form a frequency adjusting capacitance section between the electrode one and the electrode two, it is possible to adjust the capacitance of the frequency adjusting capacitance section by altering the area of the electrode two provided on the substrate plate, or by adjusting the position of the antenna to the substrate plate by mounting. When assembling the antenna into a product, a shift in the antenna frequency caused by the effect of casing and the like can be corrected by adjusting the mounting position of the antenna so as to change the capacitance of the frequency adjusting capacitance section. Or, it is also possible to deliberately change the frequency of the antenna by a large amount.
Also, according to the present invention, because the plurality of antenna elements and an electrode one formed on a fifth plane that opposes the first to fourth planes inclusively are contained in an antenna main body; and the antenna main body is mounted on a substrate plate having an electrode two in such a way to form a frequency adjusting capacitance section between the electrode one and the electrode two, it is possible to adjust the capacitance of the frequency adjusting capacitance section by altering the area of the electrode two provided on the substrate plate, or by adjusting the position of the antenna to the substrate plate by mounting. When assembling the antenna into a product, a shift in the antenna frequency caused by the effect of casing and the like can be corrected by adjusting the mounting position of the antenna so as to change the capacitance of the frequency adjusting capacitance section. Or, it is also possible to deliberately change the frequency of the antenna by a large amount. Further, the plurality of antenna elements and the frequency adjusting capacitance section are connected in three-dimensions so that the antenna does not occupy a large space when it is incorporated into a device to enable to miniaturize the device.
Also, according to the present invention, because the first plane and the second plane are constituted by two opposing planes of a first substrate plate; and the third plane and the fourth planes are constituted by two opposing planes of a second substrate plate; and the fifth plane is constituted by a plane of a frequency adjusting substrate plate; and the first substrate plate, the second substrate plate and the frequency adjusting substrate plate are laminated with respective intervening insulation layers into an integral unit, the antenna is made as one unit and handling is facilitated when mounting the antenna on a substrate plate.