Patent Application
20100045560
The embodiment invention relates to an antenna.
Recently, with expansion of demands of communication, small-sized radio devices such as cellular phone and so on are widely used. Many small-sized devices contain antennas in their casings. The internal antenna is required to be suitable for downsizing and light-weighting and have low cost and wide performance. Further, in daily life greatly, the influence when people directly touch the radio device or the influence by a conductor near the radio device affects the radiation characteristics of the internal antenna, so that its performance varies. Therefore, an antenna having a small change in characteristics due to the external influence is increasingly required.
In the conventional major kinds of antenna, the antenna could not be downsized because the antenna gain was not secured when the size of the antenna was reduced. Further, because of the narrow bandwidth of the resonant frequency of the antennas themselves, there was a phenomenon that the resonant frequency changes due to external influence, whereby the voltage standing wave ratio deteriorates to increase the consumption of battery, resulting in waste of the battery. Further, the antenna design was very difficult because the radiation pattern is affected by the influence of the casing in which the small-sized radio device is installed.
In addition, an antenna is required which is easily reduced in size and secure a state in which when the antenna is attached to the casing or the like of the radio device, the antenna radiation characteristics never change due to the casing to which the antenna is attached. Further, it is a challenge to realize an antenna which never causes change in the resonant frequency and change in the voltage standing wave ratio due to the influence of a human body or the influence of a conductor placed near the antenna.
Japanese Laid-open Patent Publication No. 2001-168637 discusses a print-type dipole antenna which has a small occupied space and is therefore suitable for downsizing. Japanese Laid-open Patent Publication No. 2003-209429 discusses an antenna device which is used for base station antenna device in mobile communication and attainable of two resonant characteristics as well as small in size and simple in structure and easy to manufacture. Japanese Laid-open Patent Publication No. 2000-278025 discusses a dipole antenna device which shares a plurality of frequency bands and is made to have a wider band for a first frequency band among them.
According to an aspect of the embodiment, An antenna includes a substrate made of a dielectric material, a first different dielectric constant region having a dielectric constant different from a dielectric constant of said substrate provided in said substrate, and a first antenna element provided on a front surface of said substrate.
The antenna of this embodiment is used for small-sized radio devices such as cellular phone, cordless phone, wireless radio communication PC (personal computer) card, USB data communication radio device, RF-ID and the like.
The substrate 100 is a substrate made of a dielectric material, for example, a glass epoxy substrate (FR4). The substrate 100 is preferably a substrate made of high-dielectric material. The substrate 100 has two through holes 102a and 102b. The via 102a and 102b each have a shape of a long hole.
Referring to
Next, referring to
The ground regions 103 on the front surface and the rear surface of the substrate 100 are mutually coupled via through holes in the ground regions 103. A through hole 102a is provided within the U-shape of the first antenna element 101a, and a though hole 102b is provided within the U-shape of the second antenna element 101b.
An end portion of the first antenna element 101a is coupled to a communication circuit 202 or 203 via a switch 201. The communication circuit 202 is a receiving circuit, and the communication circuit 203 is a transmission circuit. The first antenna element 101a is a feed antenna element to which power is fed from the transmission circuit 203. On the rear surface of the substrate 100, an end portion of the second antenna element 101b is coupled to the ground region 103. The second antenna element 101b is a parasitic antenna element.
The first antenna element 101a and the second antenna element 101b have regions projected via the substrate 100 including regions 403 mutually overlapping and other regions not mutually overlapping. The regions 403 are region which do not function as the antenna. By adjusting boundary positions between the regions 403 and the other regions, the frequency band in which the first antenna element 101a and the second antenna element 101b operate as the antenna may be adjusted.
The first antenna element 101a in the mutually overlapping region 403 is provided with a coupling point to the communication circuit 202 or 203 in
Similarly, the second antenna element 101b is provided with, at one end portion thereof, a coupling point to the ground region 103 in
The impedance matching antenna regions 402a and 402b are provided at end portions in the above-described not-mutually-overlapping regions.
According to this embodiment, the antenna elements 101a and 101b are arranged on the front surface and the rear surface of the dielectric material substrate 100, so that the electric length of a signal is shortened due to the dielectric constant of the dielectric material substrate 100. Thus, the antenna elements 101a and 101b may be shortened to downsize the antenna. Further, by bending the antenna elements 101a and 101b into a U-shaped form, the resonant frequency band of the antenna itself may be widened.
Further, the antenna elements 101a and 101b are bent inward at their open end sides to provide the impedance matching antenna regions 402a and 402b. The impedance matching antenna regions 402a and 402b will be regions contributing to impedance matching. The antenna elements 101a and 101b may be separated into the regions 402a and 402b contributing to the impedance matching and the regions 401a and 401b contributing to the radio wave radiation.
Further, the via 102a and 102b in the long-hole shape are provided adjacent to the antenna elements 101a and 101b, thereby causing discontinuity of the dielectric constant. The dielectric constant ∈r of the glass epoxy substrate 101 is 4.8, whereas the dielectric constant ∈r of air existing in the via 102a and 102b is 1. Due to the discontinuity of the dielectric constant, the antenna elements 101a and 101b may exist as elemental units independent in terms of high frequency to widen the bandwidth of the resonant frequency of the antenna. This may make the antenna insusceptible to the influence of the casing of a radio device in which the antenna is installed, the influence of a conductor placed near the antenna, or the influence of radio wave radiation characteristics caused by the influence when a human body touches the antenna.
In the measurement test, the voltage standing wave ratio in
f=(2.71−1.84)/{1.84+(2.71−1.84)/2}×100≈38%
Note that, as a result of a similar measurement performed on a first comparative example of the antenna having no through holes 102a and 102b and antenna elements 101a and 101b in a linear shape in
Further, as a result of a similar measurement performed on a second comparative example of the antenna having no through holes 102a and 102b and antenna elements 101a and 101b in a U-shaped form in
Further, as a result of measurement performed on the antenna having the via 102a and 102b and the antenna elements 101a and 101b in a U-shaped form as in the above-described present embodiment, the discontinuitywidth was 38%. By providing the via 102a and 102b, the discontinuitywidth may be further widened as compared to the second comparative example. In the present embodiment, the discontinuitywidth may be widened by 13% or more as compared to the first comparative example.
Note that the via 102a and 102b are for causing the discontinuity of the dielectric constant of the substrate 100, so that a material having a dielectric constant different from that of the substrate 100 may be provided in the via 102a and 102b.
For example, the regions 102a and 102b may be different dielectric constant regions having a dielectric constant different from that of the dielectric constant of the substrate 100 provided within the substrate 100. The different dielectric constant regions 102a and 102b may be through holes in the substrate 100 as in the above-described embodiment. Further, the different dielectric constant regions 102a and 102b may be the regions through the substrate 100 in which are a material having the above-described different dielectric constant is provided. The above-described material having a different dielectric constant is, for example, polytetrafluoroethylene (the dielectric constant ∈r=18.6 to 68.4), ABS (acrylonitrile butadiene styrene) resin (the dielectric constant ∈r≈3.0), or vinyl (the dielectric constant ∈r≈2.0) or the like.
Though the case where the different dielectric constant regions 102a and 102b are in the U-shaped form has been explained, they are not limited to such a shape but may be in an L-shaped form or the like. The first different dielectric constant region 102a is provided adjacent to the first antenna element 101a, and the second different dielectric constant region 102b is provided adjacent to the second antenna element 101b.
According to this embodiment, by providing the different dielectric constant regions 102a and 102b and/or making the antenna elements 101a and 101b in the U-shaped form, the resonant frequency band may be widened to reduce the change in the radio wave radiation characteristics due to external influence.
Note that the present embodiment is to be considered in all respects as illustrative and no restrictive, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.
The resonant frequency band is widened to reduce the change in the radio wave radiation characteristics due to external influence.
This application is a Continuation of International Application No. PCT/JP2007/051677, with an international filing date of Feb. 1, 2007, which designating the United States of America, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2007/051677 | Feb 2007 | US |
| Child | 12512755 | US |
