WO2007083921A1

WO2007083921A1 - Small-sized antenna using materials with high dielectric constant

Info

Publication number: WO2007083921A1
Application number: PCT/KR2007/000281
Authority: WO
Inventors: Byung Hoon Ryou; Won Mo Sung; Gi Ho Kim
Original assignee: E.M.W. Antenna Co., Ltd.
Priority date: 2006-01-19
Filing date: 2007-01-17
Publication date: 2007-07-26
Also published as: KR100632692B1

Abstract

The present invention provides an antenna, including a substrate having a dielectric constant, a conductive radiator formed on the substrate, and one or more dielectric materials formed to cover a part or all of the substrate on which the radiator is formed and having a dielectric constant higher than that of the substrate, wherein the dielectric materials can be fabricated through injection molding without a sintering process. According to the present invention, there is provided a small-sized antenna, which has a size appropriate for a small-sized terminal while being capable of receiving a VHF band signal and tolerant to external shock, can be fabricated easily.

Description

SMALL-SIZED ANTENNA USING MATERIALS WITH HIGH

DIELECTRIC CONSTANT

Technical Field

[1] The present invention relates, in general, to an antenna capable of transmitting and receiving a VHF band signal, and more particularly, to a VHF band small-sized antenna employing a high dielectric material. Background Art

[2] A terrestrial Digital Multimedia Broadcasting (DMB) service begins in earnest, a user who moves at high speed can be provided with a variety of multimedia contents through a portable wireless communication terminal. The terrestrial DMB employs VHF band electromagnetic waves of 180 to 186 D and 204 to 210 D. Thus, in the case where a terrestrial DMB signal is received using a monopole antenna of a 1/4 wavelength length, the length of the antenna becomes about 37.5 D. However, this antenna is not suitable for a portable wireless communication terminal due to its very long length. It is therefore necessary to develop a small-sized antenna having a size suitable for a small-sized terminal while being capable of receiving the VHF band signal. The same problem also exists in a service method, such as Digital Video Broadcasting-Handheld (DVB-H) through which broadcasting can be seen and heard while moving, since it employs a VHF band and UHF band of a long wavelength.

[3] To overcome the problems, a helical antenna whose overall size is miniaturized without changing an electrical length by constructing a radiator in helix form has been known. However, the helix conductive radiator is problematic in that it is difficult to fabricate and maintain the gap between the turns constantly, and it is not constant in the performance of products upon mass-production.

[4] Further, an antenna employing ceramics as a substrate has also been known as the small-sized antenna. The ceramics is disadvantageous in that it can be easily broken by shock and has a high manufacturing cost since it has to be fabricated using sintering. Disclosure of Invention

Technical Problem

[5] Accordingly, the present invention has been made in an effort to solve the above- mentioned problems occurring in the prior art, and it is an object of the present invention to provide a small-sized antenna of a size suitable for a small-sized terminal while being capable of receiving a VHF band signal.

[6] Another object of the present invention is to provide a small-sized antenna that can be easily fabricated without a complicated process, such as sintering, and is tolerant to external shock. Technical Solution

[7] To achieve the above objects, according to an aspect of the present invention, there is provided an antenna, including a substrate having a dielectric constant, a conductive radiator formed on the substrate, and one or more dielectric materials formed to cover a part or all of the substrate on which the radiator is formed and having a dielectric constant higher than that of the substrate, wherein the dielectric materials can be fabricated through injection molding without a sintering process.

[8] At least one of the dielectric materials preferably has a dielectric constant of from

20 to 25, and is preferably formed from a material containing Polypheny lene Sulfide (PPS).

[9] Furthermore, the number of the dielectric materials may be 2, a first dielectric material can be formed to cover a part or all of a front surface of the substrate, and a second dielectric material can be formed to cover a part or all of a rear surface of the substrate.

[10] Further, the radiator can have a shape in which a segment of line and a meander are consecutively connected.

[11] The antenna can further include a conductive member formed in the substrate and serving as a parasitic element of the radiator without being electrically connected to the radiator, and an impedance matching circuit formed in the substrate.

[12] Meanwhile, the number of the dielectric materials can be 2 or more, and at least two of the dielectric materials can be different from one another in at least one of dielectric constant, shape, size and location.

[13] To achieve the above objects, according to another aspect of the present invention, there is also provided a wireless communication apparatus including an antenna, wherein the antenna comprises a substrate having a dielectric constant, a conductive radiator formed on the substrate, and one or more dielectric materials formed to cover a part or all of the substrate on which the radiator is formed and having a dielectric constant higher than that of the substrate, wherein the dielectric materials can be fabricated through injection molding without a sintering process.

Advantageous Effects

[14] According to the present invention, there is provided a small-sized antenna of a size suitable for a small-sized terminal while being capable of receiving a VHF band signal. [15] Furthermore, according to the present invention, there is provided a small-sized antenna that can be easily fabricated without a complicated process, such as sintering, and is tolerant to external shock.

Brief Description of the Drawings [16] FIG. 1 is a plan view of an antenna according to an embodiment of the present invention.

[17] FIG. 2 is a circuit diagram of an impedance matching circuit included in the antenna according to an embodiment of the present invention.

[18] FIG. 3 is a perspective view of an antenna according to an embodiment of the present invention. Mode for the Invention

[19] The present invention will now be described in detail in connection with embodiments with reference to the accompanying drawings.

[20] FIG. 1 is a plan view of an antenna according to an embodiment of the present invention.

[21] As shown in FIG. 1, the antenna according to the present embodiment includes a substrate 100 having a dielectric constant, a conductive radiator 200 formed on the substrate 100, and at least one dielectric material (not shown) formed to cover a part or all of the substrate 100 on which the radiator 200 is formed, and having a dielectric constant higher than that of the substrate 100. FIG. l(a) illustrates a front surface of the substrate 100, and FIG. l(b) illustrates a rear surface of the substrate 100.

[22] A Printed Circuit Board (PCB) can be used as the substrate 100 having a dielectric constant. In this case, the substrate 100 and the radiator 200 can be fabricated simply through etching or printing.

[23] The radiator 200 can be formed on the front surface and the rear surface of the substrate 100. The radiator 200 formed on the front surface of the substrate 100 and the radiator 200 formed on the rear surface thereof can be connected through a via hole 120 formed in the substrate 100. Alternatively, the radiator 200 can be formed on the front surface, the rear surface or the side of the substrate 100, or can be interposed within the substrate 100. The radiator 200 can have one end 220 electrically connected to a feed unit (not shown) of a RF circuit. The conductive radiator 200 transmits and receives information while resonating along with electromagnetic waves of a specific frequency, and can also resonate at a multi-band depending on its shape.

[24] As shown in FIG. 1, the radiator 200 has a shape in which a straight line and a meander are repeated twice from the one end 220, and can thus resonate at a multi- band. In this case, the length of the first straight- line section from the one end 220 of the radiator 200 decides a first resonant characteristic, and the shape and length of the radiator 200, ranging from the one end 220 of the radiator 200 to a point at which the first meander section is ended, decides a second resonant characteristic. Further, the shape and length of the radiator 200, ranging from the one end 220 of the radiator 200 to the via hole 120 where the second straight-line section is ended, decides a third resonant characteristic, and the shape and length of the whole section of the radiator 200, including the second meander section formed on the rear surface of the substrate 100, decides a fourth resonant characteristic.

[25] A conductive member 300 can be formed on the substrate 100 without being electrically connected to the radiator 200. The conductive member 300, which is also not electrically connected to the feed unit (not shown) of the RF circuit, serves as a parasitic element by electromagnetic coupling with the radiator 200 that transmits and receives electromagnetic waves. Therefore, the resonant frequency of the radiator 200 can be lowered and a wideband characteristic can be accomplished.

[26] The antenna according to the present embodiment can include a matching circuit for impedance matching. To this end, a ground surface 140, a feed terminal 160 and devices (not shown) for an impedance matching circuit can be formed in the substrate 100. A circuit diagram of a case where a serial matching circuit for impedance matching is constructed is shown in FIG. 2. The device 180 for the serial matching circuit can include an inductor and/or a capacitor. In the case where the serial matching circuit is included, the feed terminal 160 is electrically connected to the feed unit (not shown) of the RF circuit, and the radiator 200 is fed from the one end 220 connected to the feed terminal 160 through the serial matching circuit. Since impedance matching is carried out as above, the RF circuit within the terminal does not need to include an additional matching circuit. Accordingly, a construction can be simplified and the degree of freedom of design can be secured. Furthermore, the characteristics of the antenna can be adjusted by changing only the matching circuit without changing the shape or location of the radiator 200.

[27] FIG. 3 is a perspective view of the antenna according to an embodiment of the present invention.

[28] As shown in FIG. 3, the antenna according to the present embodiment includes a substrate 100 having a dielectric constant, a conductive radiator 200 formed on the substrate 100, and at least one dielectric material 420 and 440 formed to cover a part or all of the substrate 100 on which the radiator 200 is formed and having a dielectric constant higher than that of the substrate 100. In particular, the first dielectric material 420 can be formed to cover a part of the front surface of the substrate 100, and the second dielectric material 440 can be formed to cover a part of the rear surface of the substrate 100.

[29] The wavelength of electromagnetic waves in the dielectric material is shorter than that in the free space. The wavelength of electromagnetic waves in the dielectric material can be expressed in the following equation.

[30] ^dielectric ^{~ Λ}ai,-

[31] where

T

ULelectric is the wavelength within the dielectric material,

is the wavelength in the air, and

is a relative dielectric constant of the dielectric material.

[32] The electrical length of the radiator is decided in proportion to the wavelength of transmitted and received electromagnetic waves. Thus, the dielectric materials 420 and 440 having a dielectric constant higher than that of the substrate 100 are formed to cover a part or all of the substrate 100 having the radiator 200 formed thereon. Accordingly, an effective electric length of the radiator 200 can be extended significantly, and the radiator 200 can be formed as a small size. In particular, in order to transmit and receive a VHF band signal, a high dielectric material having a relative dielectric constant of 15 or higher, preferably 20 to 25 can be used to form a small-sized antenna appropriate for a small-sized terminal. The a high dielectric material can include polymer material, such as material in which an additive for enhancing the dielectric constant is mixed with Polypheny lene Sulfide (PPS), that is, polymer where benzene rings and S atoms are repeatedly combined. The polymer material can be easily fabricated through injection molding, etc., is tolerant to shock, and has less dielectric loss at the VHF band. Thus, the polymer material is appropriate for an antenna for transmitting and receiving the VHF band signal.

[33] As one of the polymer material, PPS having the dielectric constant listed in the following table can be used. The following values are ones measured with respect to the lots of 1 to 200 kg.

[34] Table 1

[35] As described above, the polymer material has a very high dielectric constant of 20 to 25 compared with a general engineering plastic having a dielectric constant of about 3 to 4. Thus, the length of the radiator 200 can be reduced significantly.

[36] Further, polymer material has a density of 2.86 g/D, tensile strength of 467 Pa-s, and bending strength of 87 Mpa, and thus has characteristics that it is lighter in weight than ceramics and is tolerant to shock.

[37] The first dielectric material 420 and the second dielectric material 440 can have different dielectric constants, shapes, sizes or locations. Thus, the resonant frequency and the Q factor of the antenna can be controlled. Alternatively, the dielectric material can be formed to cover all of one surface of the substrate 100, or can be formed to cover all of the substrate 100, so that it covers the whole surface of the substrate 100.

[38] The antenna according to the present embodiment includes one or more a high dielectric materials 420 and 440 formed to cover a part or all of the substrate 100 on which the radiator 200 is formed, so that the length of the radiator 200 can be shortened significantly. In particular, since a high dielectric material having a relative dielectric constant of 15 or higher, such as PPS, is used, a small- sized antenna having a size appropriate for a small-sized terminal, while being capable of receiving a VHF band signal, can be implemented.

[39] Further, the antenna according to the present embodiment can transmit and receive electromagnetic waves of a multi-band since it includes the radiator 200 having a shape in which the straight lines and the meanders are repeated. Furthermore, the antenna according to the present embodiment can represent a wideband characteristic since it includes the conductive member 300 that operates as a parasitic element by electromagnetic coupling with the radiator 200.

[40] Although the specific embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Industrial Applicability

[41] According to the present invention, there is provided a small-sized antenna of a size suitable for a small-sized terminal while being capable of receiving a VHF band signal.

[42] Furthermore, according to the present invention, there is provided a small-sized antenna that can be easily fabricated without a complicated process, such as sintering, and is tolerant to external shock.

[43]

Claims

[1] An antenna, comprising: a substrate having a dielectric constant; a conductive radiator formed on the substrate; and one or more dielectric materials formed to cover a part or all of the substrate on which the radiator is formed and having a dielectric constant higher than that of the substrate, wherein the dielectric materials can be fabricated through injection molding without a sintering process.

[2] The antenna of claim 1, wherein at least one of the dielectric materials has a dielectric constant of 20 to 25.

[3] The antenna of claim 1, wherein at least one of the dielectric materials is formed from a material containing Polypheny lene Sulfide (PPS).

[4] The antenna of any one of claims 1 to 3, wherein the number of the dielectric materials is 2, a first dielectric material is formed to cover a part or all of a front surface of the substrate, and a second dielectric material is formed to cover a part or all of a rear surface of the substrate.

[5] The antenna of any one of claims 1 to 3, wherein the radiator has a shape in which a segment of line and a meander are consecutively connected.

[6] The antenna of any one of claims 1 to 3, further comprising a conductive member formed in the substrate and serving as a parasitic element of the radiator without being electrically connected to the radiator.

[7] The antenna of any one of claims 1 to 3, further comprising an impedance matching circuit formed in the substrate.

[8] The antenna of any one of claims 1 to 3, wherein the number of the dielectric materials is 2 or more, and at least two or more of the dielectric materials are different from one another in at least one of dielectric constant, shape, size and location.

[9] A wireless communication apparatus including an antenna, the antenna comprising: a substrate having a dielectric constant; a conductive radiator formed on the substrate; and one or more dielectric materials formed to cover a part or all of the substrate on which the radiator is formed and having a dielectric constant higher than that of the substrate, wherein the dielectric materials can be fabricated through injection molding without a sintering process.

[10] The wireless communication apparatus of claim 9, wherein at least one of the dielectric materials has a dielectric constant of from 20 to 25.

[11] The wireless communication apparatus of claim 9, wherein at least one of the dielectric materials is formed from a material containing Polyphenylene Sulfide (PPS).

[12] The wireless communication apparatus of any one of claims 9 to 11, wherein the number of the dielectric materials is 2, a first dielectric material is formed to cover a part or all of a front surface of the substrate, and a second dielectric material is formed to cover a part or all of a rear surface of the substrate.

[13] The wireless communication apparatus of any one of claims 9 to 11, wherein the radiator has a shape in which a segment of line and a meander are consecutively connected.

[14] The wireless communication apparatus of any one of claims 9 to 11, wherein the antenna further comprises a conductive member formed in the substrate and serving as a parasitic element of the radiator without being electrically connected to the radiator.

[15] The wireless communication apparatus of any one of claims 9 to 11, wherein the antenna further comprises an impedance matching circuit formed in the substrate.

[16] The wireless communication apparatus of any one of claims 9 to 11, wherein the number of the dielectric materials is 2 or more, and at least two of the dielectric materials are different from one another in at least one of dielectric constant, shape, size and location.