Patent Grant
7071875
This invention relates to a multiple band antenna and in particular to an antenna suited for use with a radio communication device in a wireless LAN (local area network); a mobile telephone, Bluetooth, etc.
At present, in a wireless LAN, a communicating system using a 2.4-GHz band and a communicating system using a 5-GHz band are available and also in a mobile telephone, a communication system using a 0.8-GHz band and a communication system using a 1.5-GHz band are available.
Formerly, one communication device was able to communicate with another only in one frequency band system. In recent years, however, one communication device that can communicate in two frequency bands systems has also been developed.
Such a communication device that can communicate in a plurality of frequency bands needs to use a multi-band antenna capable of transmitting and receiving radio waves of a plurality of frequency bands.
Various types of multi-band antennas are available. For example, “Zukai idoutuushinyou antenna system” written by FUJIMOTO Kyouhei, YAMADA Yoshihide, and TUNEKAWA Kouichi, published by Sougou Denshi Shuppansha discloses an antenna shown in FIG. 6.
The antenna 100 shown in
On the other hand, to decrease such electromagnetic interaction, the distance between the two antenna elements 104 and 106 maybe set to a large distance. However, if the distance is thus set to a large distance, the dimension of the antenna 100 in the width direction (X direction) thereof becomes large; this is a problem.
Therefore, the invention is intended for solving the above-described problems in the related arts and it is an object of the invention to provide an antenna for making it possible to decrease electromagnetic interaction between antenna elements without upsizing the dimension of the antenna.
To the end, according to the invention, there is provided a multiple band antenna, including:
a dielectric substrate; and
a plurality of antenna elements being formed of each a conductor on the same face of the dielectric substrate and provided in a one-to-one correspondence with frequency bands to operate with the frequency bands, characterized in that
each of the antenna elements has an open end as one end and is connected at an opposite end to a feeder line and includes a narrow part being placed on the open end side and formed like a line with a comparatively narrow wide and a wide part being placed on the feeder line side and having a wider width than the narrow part, that
the narrow part is turned in order in substantially the same direction (preferably plus or minus 10°) as the width direction of the wide part, forming a meander shape, and that
the antenna elements have the wide parts joined in one piece forming a predetermined angle with each other so as to share a part of the wide parts.
Thus, in the antenna of the invention, the antenna elements share a part of the wide parts, so that the dimension of the antenna in the width direction thereof can be lessened accordingly. Since the antenna elements are placed forming the predetermined angle θ with each other, the electromagnetic interaction between the antenna elements can be decreased and the characteristics of the antenna elements are not impaired. The wide part is formed by line having wider width than that of line forming the narrow part, and is located between the narrow part and the feeder line. The narrow part is formed by line having narrower width than that of line forming the wide part, and has an open end as one end and is connected at an opposite end to the wide part.
In the antenna of the invention, the predetermined angle indicates 0° or more and 180° or less; preferably the predetermined angle is 0° or more and 130° or less, more preferably the predetermined angle is 0° or more and 90° or less, further more preferably the predetermined angle is 0° or more and 50° or less, and still further preferably the predetermined angle is 5° or more and 50° or less.
Thus, the angle between the antenna elements is set to a value in the range of 5° to 50°, so that a wide bandwidth can be achieved as the signal band of the high-frequency side, for example.
In the antenna of the invention, the dielectric substrate is a print circuit board for mounting parts.
The dielectric substrate on which the antenna elements are formed may be an antenna-dedicated substrate, but may be a print circuit board for mounting parts on which any other circuitry for communication is constructed, for example.
According to the invention, there is provided a radio frequency module for transmitting and receiving a signal, the radio frequency module including any of the antennas described above.
Thus, any of the antennas described above can be applied to the radio frequency module for transmitting and receiving a signal.
Referring now to the accompanying drawings, there are shown preferred embodiments of the invention.
An antenna 10 of the embodiment is used with a radio communication device in a wireless LAN, etc., for example, and operates with two frequency bands of a 2.4-GHz band and a 5-GHz band. The antenna adopts a monopole type in which the line length is one-quarter wavelength.
As shown in
The first antenna element 14 is able to operate with the 2.4-GHz band and the second antenna element 16 is able to operate with 5-GHz band. The first, second antenna element 14, 16 has an open end 14c, 16c as one end and a feeding end 18 as an opposite end. The open end 14c, 16c side is linear with a comparatively narrow width, forming a narrow part 14a, 16a. On the feeding end 18 side, a wide part 14b, 16b wider than the narrow part 14a, 16a is formed for impedance matching.
The embodiment is first characterized by the fact that the first antenna element 14 is placed almost along the length direction (Y direction) of the dielectric substrate 12, that the second antenna element 16 is inclined at a predetermined angle θ with respect to the first antenna element 14, and that the first antenna element 14 and the second antenna element 16 have the wide parts 14b and 16b joined in one piece so as to share a part of the wide parts 14b and 16b.
Thus, the first and second antenna elements 14 and 16 share a part of the wide parts 14b and 16b, so that the wide part occupation area can be lessened accordingly and thus dimension W of the antenna 10 in the width direction (X direction) thereof can be lessened.
As the wide parts 14b and 16b are joined in one piece, the feeding end 18 is also made common to the first and second antenna elements 14 and 16 and a feeder line (not shown) is connected to the common feeding line 18. That is, power is supplied from a signal source (not shown) via the feeder line (not shown) through the feeding end 18 to the first and second antenna elements 14 and 16. Thus, the feeding end 18 is also made common, thereby eliminating the need for branching the feeding line connected to the feeding end 18 and circumventing complication of the configuration of the feeding line.
The second antenna element 16 is inclined at the predetermined angle θ with respect to the first antenna element 14, so that the electromagnetic interaction between the first and second antenna elements 14 and 16 can be decreased and the characteristics of the first and second antenna elements 14 and 16 are not impaired.
As seen in
Generally, in the 5-GHz band of the high-frequency side, particularly a wide band is required as the bandwidth; specifically an about 20% of relative bandwidth (bandwidth/center frequency) is required.
Then, in the embodiment, the angle θ between the first and second antenna elements 14 and 16 is set to a value in the range of 5° to 50°. Accordingly, 1000 MHz or more can be provided as the bandwidth in the 5-GHz band of the high-frequency side. What value in the range of 5° to 50° to set is determined by making a comparison between the degree of decrease in the electromagnetic interaction between the first and second antenna elements 14 and 16 and the degree of shortening the dimension of the antenna 10.
The embodiment is second characterized by the fact that each of the narrow parts 14a and 16a of the first and second antenna elements 14 and 16 forms a meander shape. Specifically, the narrow part 14a, 16a starts at the corresponding wide part 14b, 16b and projects along the length direction of the wide part from the wide part and is bent toward the width direction of the wide part. Then, the narrow part 14a, 16a is turned in the opposite direction in the width direction and likewise is turned in the opposite direction in the width direction in order and the whole of the narrow part 14a, 16a extends along the length direction. Finally, the narrow part 14a, 16a arrives at the corresponding open end 14c, 16c as the end point. The meander shape may be formed by a curbed line, a straight line or a jagged line, or a combination thereof.
Thus, the narrow parts 14a and 16a of the first and second antenna elements 14 and 16 are made each such a meander shape, whereby the lengths of the antenna elements 14 and 16 in the length directions thereof can be shortened. The narrow part 14a, 16a is turned in the width direction of the wide part 14b, 16b in order, thereby forming the meander shape, so that the wide part 14b, 16b can function sufficiently as the impedance matching part, as mentioned above.
Further, the embodiment is third characterized by the fact that the first and second antenna elements 14 and 16 are formed on the same face of the dielectric substrate 12.
The first and second antenna elements 14 and 16 are thus formed on the same face of the dielectric substrate 12, whereby the manufacturing process can be simplified as compared with the case where the first and second antenna elements 14 and 16 are formed on different planes such as the surface and a side or the back of the dielectric substrate or are formed in the dielectric substrate, for example.
To form the first and second antenna elements 14 and 16 on one surface of the dielectric substrate 12, for example, a method of performing screen printing of silver paste as the shapes of the antenna elements 14 and 16 on the surface of the dielectric substrate 12 and then baking at a predetermined temperature can be used.
As described above, according to the invention, the first and second antenna elements 14 and 16 share a part of the wide parts 14b and 16b, so that the dimension W of the antenna 10 in the width direction thereof can be lessened. Since the second antenna element 16 is inclined at the predetermined angle θ with respect to the first antenna element 14, the electromagnetic interaction between the first and second antenna elements 14 and 16 can be decreased and the characteristics of the antenna elements 14 and 16 are not impaired. Particularly, the angle θ is set to a value in the range of 5° to 50°, so that 1000 MHz or more can be provided as the bandwidth in the 5-GHz band of the high-frequency side.
Next,
In the second embodiment, as the antenna elements 14′ and 16′ are placed on the dielectric substrate 12′ as described above, functions similar to those of the antenna of the first embodiment can be accomplished and similar advantages to those in the first embodiment can be provided.
Next,
Like the first, second antenna element 14, 16, the added third antenna element 20 has an open end 20c as one end and a feeding end 18 as an opposite end. On the open end 20c side, a narrow part 20a is formed and on the feeding end 18 side, a wide part 20b is formed.
Like the second antenna element 16, the third antenna element 20 is inclined at a predetermined angle θ″ with respect to the first antenna element 14 and in addition, the first, second, and third antenna elements 14, 16, and 20 have wide parts 14b, 16b, and 20b joined in one piece so as to share a part of the wide parts 14b, 16b, and 20b.
Like a narrow part 14a, 16a of the first, second antenna element 14, 16, the narrow part 20a of the third antenna element 20 forms a meander shape. Further, the third antenna element 20 is also formed on the same face of a dielectric substrate 12″ as the first and second antenna elements 14 and 16 are formed.
Since the third antenna element 20 is thus configured, the antenna 10″ of the embodiment basically can accomplish functions similar to those of the antenna of the first embodiment and can provide similar advantages to those in the first embodiment and further operates with three frequency bands systems.
The antenna 10, 10′, 10″ in the first to third embodiments described above is installed in a radio communication device in a wireless LAN, etc., as one component of a radio frequency module, for example.
Then, such a radio frequency module incorporating the antenna 10, 10′ of the embodiment will be discussed briefly.
As shown in
The base band IC 52 controls the RFIC 54 and transfers a low-frequency signal to and from the RFIC 54. The RFIC 54 converts a low-frequency transmission signal received from the base band IC 52 into a radio frequency signal and converts a radio frequency reception signal into a low-frequency signal and passes the low-frequency signal to the base band IC 52.
The diplexer 76 performs band switching between 2.4-GHz and 5-GHz bands. Specifically, to communicate in the 2.4-GHz band, the diplexer 76 connects the antenna 10 and the circuit for the 2.4-GHz band; to communicate in the 5-GHz band, the diplexer 76 connects the antenna 10 and the circuit for the 5-GHz band.
Each of the switches 72 and 74 switches the signal path in response to transmission or reception. Specifically, to receive a signal, the signal path on the BPF side is selected; to transmit a signal, the signal path on the LPF side is selected.
Therefore, for example, if communications are conducted in the 2.4-GHz band and the antenna 10 receives a signal, the reception signal is input through the diplexer 76 and the switch 72 to the BPF 64 and is subjected to band limitation through the BPF 64 and then the signal is amplified by the low-noise amplifier 56 and is output to the RFIC 54. The RFIC 54 converts the reception signal from the 2.4-GHz band to a low-frequency band and passes the conversion result to the base band IC 52.
In contrast, to transmit a signal through the antenna 10, a low-frequency transmission signal is passed from the base band IC 52 to the RFIC 54, which then converts the transmission signal from a low-frequency band to the 2.4-GHz band. The transmission signal is amplified by the power amplifier 58 and then the low-frequency band is cut through the LPF 66 and then the signal is transmitted from the antenna 10 through the switch 72 and the diplexer 76.
On the other hand, to communicate in the 5-GHz band, using the circuit for the 5-GHz band, processing involved in transmission and reception is performed according to a similar procedure to that of communications in the 2.4-GHz band, and a signal is transmitted and received using the same antenna 10 as used in the 2.4-GHz band.
It is to be understood that the invention is not limited to the specific embodiments thereof and various embodiments of the invention may be made without departing from the spirit and scope thereof. For example, at least part of each antenna element may be covered with an insulation layer. The insulation layer preferably comprises a ceramic which may be same as that of the dielectric substrate or a resin such as an epoxy resin and a phenol resin. The thickness of the insulation layer is not limited, but, preferably from 10 to 100 μm.
In the above-described embodiments, antenna-dedicated boards are used as the dielectric substrates 12, 12′, and 12″, but print circuit boards for mounting parts may be used in place of the dedicated boards. For example, to apply the antenna of the invention to a radio frequency module as shown in
In the embodiments, the case where the antenna is used with a radio communication device in a wireless LAN, etc., is described, but the antenna maybe used with a radio communication device in a mobile telephone, Bluetooth, etc.
In the embodiments, the antennas for operating with two or three frequency bands systems are described, but if the number of antenna elements is increased to four, five, or more, the antenna can operate with as many frequency bands systems as the number of antenna elements. In this case, the angle between one pair of the antenna elements may be the same as or different from the angle between another pair of the antenna elements.
This application is based on Japanese Patent application JP 2002-153733, filed May 28, 2002, the entire content of which is hereby incorporated by reference, the same as if set forth at length.
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|---|---|---|---|
| 2002-153733 | May 2002 | JP | national |
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