WO2003009418A1

WO2003009418A1 - Wire antenna for portable wireless communication terminal

Info

Publication number: WO2003009418A1
Application number: PCT/KR2002/000319
Authority: WO
Inventors: Hun-Joong Park
Original assignee: Actipass Co., Ltd.
Priority date: 2001-07-20
Filing date: 2002-02-26
Publication date: 2003-01-30

Abstract

Disclosed is a mobile station's wire antenna which comprises a flexible wire antenna coupled to a radio wave feeding line through a radio wave feeding path on the top of a bottom piece at a rear side of the mobile station, outwardly extended, and having a length of substantially 1/4 or 1/2 wavelenght, an insulated covered wire for wrapping the wire antenna and maintaining tension; and an ornamental weight coupled to an end of the insulated covered wire, for maintaining the wire antenna to be vertical, and maintaining a gap from the bottom piece for fluent radiation of radio waves. According to the above-noted configuration, the propagation loss generated by modification of the propagation angles of the antenna because of the carrying angles of the mobile station is reduced to thereby implement high-gain transmitting and receiving performance. Also, since the antenna is fixed and not protruded, and it is substituted with a mobile station's grip or an ornament, its outward appearance is attractive, and it is convenient to carry the mobile station.

Description

Wire Antenna for Portable Wireless Communication Terminal

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a mobile station antenna for a mobile phone or a portable terminal. More specifically, the present invention relates to a mobile station's wire monopole antenna for implementing high-gain transmitting and receiving performance without diversity receiving.

(b) Description of the Related Art

Conventional antennas used for mobile stations include a microstrip antenna disclosed by Korean Patent No. 1997-0077822, and a monopole antenna. The monopole antenna is arranged so that vertical polarized plane waves may be radiated in various directions with respect to a mobile station. As shown in FIG. 2, the angles of polarization are determined according to arrangement of the antenna with respect to the mobile station.

The above-described polarization of the mobile station antenna is variously changed depending on how a user carries the mobile phone, such as in a pocket, holding it with a right hand to call, and holding it with a left hand to call. In particular, since the positions of the user's shoulders and ears are on the same vertical line, the carrying angles with respect to the mobile station's extended vertical line from a state when the user extends the hand that holds the mobile station downward to another state when the user raises the phone to the user's ear position vary from -90 to 90 degrees, and if including the case of using the other hand, the variations of the carrying angles are anticipated to be changed from -180 to 180 degrees, totaling 360 degrees, as shown in Table 1. Table 1 shows the carrying angles with respect to the extended line of the mobile station. Table 1

The polarization angles of electromagnetic waves are changed because the carrying angles with respect to the extended line of the mobile station are changed, thereby reducing communication gains. FIG. 5 shows efficiency and loss caused by differences of the polarization angles. To compensate for efficiency deterioration caused by declination of the polarization of the antenna used for a conventional mobile station, Korean patent publication no. 1999-0068163 discloses a method for installing a monopole antenna as a default and adding a diversity antenna in various ways.

A monopole antenna, a conventional antenna that is most commonly used for mobile stations, has the best radiation directivity and is easy to implement, and it will be analyzed in detail to show an object of the present invention. FIG. 6 shows a conventional monopole antenna for a mobile station, and a total diagram of the mobile station itself will not be described because it is well-known in the art to which the present invention pertains. As shown, the conventional mobile station comprises a monopole antenna 1 and a bottom piece 2, and X, Y, and Z respectively show coordinates. FIGs. 7 through 9 show simulation results of the electromagnetic wave directivity at the frequency of 850MHz when the magnitude of the mobile station is 90mm x 45mm x 16mm, and the length of the monopole antenna is 90mm, an optimized design value at the frequency of 850MHz. FIGs. 10 through 12 show simulation results of the electromagnetic wave directivity at the frequency of 1 , 800MHz when the magnitude of the mobile station is 90mm x 45mm x 16mm, and the length of the monopole antenna is 40mm, an optimized design value at the frequency of 1,800MHz. FIGs. 7 and 10 show electromagnetic wave directivity on the horizontal surface (X-Y surface) in the free space when the user carries the mobile station in the vertical direction, FIGs. 8 and 11 show electromagnetic wave directivity on the horizontal surface (X-Y surface) in the free space when the user carries the mobile station at 60 degrees with respect to the vertical direction, and FIGs. 9 and 12 show electromagnetic wave directivity on the horizontal surface (X-Y surface) in the free space when the user carries the mobile station in the horizontal direction. The numbers provided on the respective circles of the drawings represent angles on the horizontal surface (X-Y surface) when the direction of the human body is set to be 0 degrees, that is, the direction of the X axis. Also, the solid lines represent vertical polarized plane wave components, and the dotted lines indicate horizontal polarized plane wave components. Among them, the vertical polarized plane wave components are the effective ones for the actual communication. The horizontal polarized plane wave components are illustrated to show that the total electromagnetic wave radiation is not reduced when the components of the vertical polarized plane waves are reduced according to the carrying angles. Table 2 shows distribution of the vertical polarized plane wave components according to the carrying angles. Table 2

As shown, the maximum gain and the minimum gain are reduced according to the terminal's angles. In the case of FIG. 8, it is known that the gain of the vertical polarized plane wave component is reduced up to -13dBi at the carrying angle of calling at the frequency of 850MHz, and the horizontal polarized plane wave component is increased on the contrary, and thereby effects to the human body are not reduced. In the case of FIG. 11 , it is known that the gain of the vertical polarized plane wave component is reduced by up to -1 OdBi at the carrying angle of calling at the frequency of 1 , 800MHz. In the case of FIG. 9, in particular, when the user calls with the antenna's angle horizontal, both gains are lowered to below -1 OdBi in all horizontal directions, thereby causing substantial lowering of communication performance.

The above-noted results show that the communication performance of the most commonly used monopole antenna is lowered according to the carrying angles, and since other conventional built-in antennas including a microstrip antenna, a planar type inverse-F antenna, a loop antenna, and a coil antenna require affixing the polarizations with respect to any directional arrangements, the vertical polarized plane wave components are problematically reduced depending on the variations of the carrying angle. Therefore, so as to solve the problem of using the conventional technique, it is required to install two antennas including a diversity antenna, and to additionally install a diversity circuit and an element in the mobile station's electrical circuit.

The vertical polarized plane wave components of the above- described conventional mobile station's antenna are reduced depending on the angles of the mobile station when the user carries it. SUMMARY OF THE INVENTION

It is an object of the present invention to use a single antenna without adding a diversity antenna to prevent lowering of performance caused by declination of polarized plane waves and to realize high-gain communication, on the basis that a method for adding a diversity antenna to the conventional mobile station so as to solve lowering of performance caused by declination of polarized plane waves increases cost and causes a complex configuration.

In one aspect of the present invention, there is provided a wire monopole antenna for maintaining the antenna's direction to be vertical with respect to the ground when the angle of carrying the mobile station is changed, and maintaining impedance matching to sustain radiation of radio waves, as shown in FIG. 13. The wire monopole antenna comprises: a string- type and flexible antenna cable 4; an insulated covered wire 5 for reinforcing tension of the antenna cable 4 and providing a good appearance; and a weight 6 for maintaining the antenna to be vertical, for maintaining a distance from the antenna 7 and a bottom piece 2 to maintain the impedance matching, and for displaying the antenna to be seen as an ornament. The antenna cable 4 is connected to a feeder or a feeding line on the top of the bottom piece of the rear side (a side in the direction opposite the human body at the time of calling) of the mobile station. The insulated covered wire 5 covers the antenna cable 4, and it is extended to be longer than the antenna cable; and the weight 6 is insulated and attached to the end of the insulated covered wire 5. When the weight is metallic, the distance relationship between the length of the antenna cable 4 and the weight 6 is determined according to a range where a capacitive coupling gives less influence to the antenna's impedance matching. The horizontal size of the weight 6 is set to be bigger by as much as possible so that the distance between the antenna cable 4 and the mobile station's bottom piece 2 may become the antenna's impedance matching. FIG. 14 shows an arrangement diagram of the wire monopole antenna. FIG. 15 shows that the wire monopole antenna 7 is always maintained to be^'vertical when the carrying angle of the mobile station is changed, Through various preferred embodiments and configurations according to given purposes and conditions, the present invention solves the problem of gain reduction according to changes of the carrying angle to implement high-gain radio communication, differing from the conventional radio mobile station antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, serve to explain the principles of the invention:

FIG. 1 shows a conventional mobile station's monopole antenna and a planar antenna;

FIG. 2 shows a polarization diagram of the conventional mobile station's monopole antenna; FIG. 3 shows a status when a user calls using a mobile station installed with the conventional monopole antenna;

FIG. 4 shows variations of carrying angles of the conventional monopole antenna when calling; FIG. 5 shows polarization efficiency and loss caused by differences of polarized angles between linear polarized waves;

FIG. 6 shows a conventional monopole antenna for a mobile station;

FIG. 7 shows the conventional mobile station's monopole antenna's horizontal free-space directivity when the monopole antenna is provided in the vertical direction;

FIG. 8 shows the conventional mobile station's monopole antenna's horizontal free-space directivity when the monopole antenna is slanted by 60 degrees;

FIG. 9 shows the conventional mobile station's monopole antenna's horizontal free-space directivity when the monopole antenna is provided in the horizontal direction;

FIG. 10 shows the conventional mobile station's monopole antenna's horizontal free-space directivity when the monopole antenna is provided in the vertical direction; FIG. 11 shows the conventional mobile station's monopole antenna's horizontal free-space directivity when the monopole antenna is slanted by 60 degrees;

FIG. 12 shows the conventional mobile station's monopole antenna's horizontal free-space directivity when the monopole antenna is provided in the horizontal direction;

FIG. 13 shows a configuration of a mobile station's wire monopole antenna according to a preferred embodiment of the present invention;

FIG. 14 shows an arrangement diagram of a mobile station's wire monopole antenna according to the preferred embodiment of the present invention;

FIG. 15 shows a diagram of the antenna's maintenance in the vertical direction according to variations of carrying angles of the mobile station's wire monopole antenna according to the preferred embodiment of the present invention;

FIG. 16 shows a mobile station's wire monopole antenna's horizontal free-space directivity when the monopole antenna is provided in the vertical direction according to the preferred embodiment of the present invention;

FIG. 17 shows a mobile station's wire monopole antenna's horizontal free-space directivity when the monopole antenna is slanted by 60 degrees according to the preferred embodiment of the present invention;

FIG. 18 shows a mobile station's wire monopole antenna's horizontal free-space directivity when the monopole antenna is provided in the horizontal direction according to the preferred embodiment of the present invention;

FIG. 19 shows a mobile station's wire monopole antenna's horizontal free-space directivity when the monopole antenna is provided in the vertical direction according to the preferred embodiment of the present invention;

FIG. 20 shows a mobile station's monopole antenna's horizontal free-space directivity when the monopole antenna is slanted by 60 degrees according to the preferred embodiment of the present invention;

FIG. 21 shows a mobile station's wire monopole antenna's horizontal free-space directivity when the monopole antenna is provided in the horizontal direction according to the preferred embodiment of the present invention;

FIG. 22 shows a diagram for comparing horizontal free-space directivity of vertical polarized plane waves of the mobile station's wire monopole antenna according to the preferred embodiment of the present invention and the conventional mobile station's monopole antenna;

FIG. 23 shows a diagram for comparing horizontal free-space directivity of vertical polarized plane waves of the mobile station's wire monopole antenna according to the preferred embodiment of the present invention and the conventional mobile station's monopole antenna; FIG. 24 shows a diagram for comparing horizontal free-space directivity of vertical polarized plane waves of the mobile station's wire monopole antenna according to the preferred embodiment of the present invention and the conventional mobile station's monopole antenna;

FIG. 25 shows a configuration of a mobile station's wire monopole antenna according to a second preferred embodiment of the present invention;

FIG. 26 shows a configuration of a mobile station's wire monopole antenna according to the second preferred embodiment of the present invention; FIG. 27 shows a configuration of a mobile station's wire monopole antenna according to the second preferred embodiment of the present invention;

FIG. 28 shows a configuration of a mobile station's wire monopole antenna according to a third preferred embodiment of the present invention;

FIG. 29 shows a configuration of a mobile station's wire monopole antenna according to a fourth preferred embodiment of the present invention;

FIG. 30 shows a configuration of a mobile station's wire monopole antenna according to a fifth preferred embodiment of the present invention; FIG. 31 shows a configuration of a mobile station's wire monopole antenna according to a sixth preferred embodiment of the present invention; and

FIG. 32 shows simulation results of VSWR (standing wave ratio) and efficiency of the wire monopole antenna depending on the bending radius according to the sixth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description, only the preferred embodiment of the invention has been shown and described, simply by way of illustration of the best mode contemplated by the inventor(s) of carrying out the invention. As will be realized, the invention is capable of modification in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not restrictive.

(First preferred embodiment) FIGs. 16 through 18 show simulation results of the electromagnetic wave directivity at the frequency of 850MHz when the magnitude of the mobile station is 90mm x 45mm x 16mm, and the length of the wire monopole antenna is 90mm. FIGs. 19 through 21 show simulation results of the electromagnetic wave directivity at the frequency of 1 , 800MHz when the magnitude of the mobile station is 90mm x 45mm x 16mm, and the length of the wire monopole antenna is 40mm.

FIGs. 16 and 19 show electromagnetic wave directivity on the horizontal surface (X-Y surface) in the free space when the user carries the mobile station in the vertical direction, FIGs. 17 and 20 show electromagnetic wave directivity on the horizontal surface (X-Y surface) in the free space when the user carries the mobile station at 60 degrees with respect to the vertical direction, and FIGs. 18 and 21 show electromagnetic wave directivity on the horizontal surface (X-Y surface) in the free space when the user carries the mobile station in the horizontal direction. The numbers provided on the respective circles of the drawings represent angles on the horizontal surface (X-Y surface) when the direction of the human body is set to be 0 degrees, that is, the direction of the X axis. Also, the solid lines represent vertical polarized plane wave components, and the dotted lines indicate horizontal polarized plane wave components. Among them, the vertical polarized plane wave components are the effective ones for actual communication. Table 3 shows distribution of the vertical polarized plane wave components according to the carrying angles. Table 3

Referring to Table 3, regarding the directivity of the vertical polarized plane waves of the wire monopole antenna for the frequency of 850MHz and of the length of 90mm, the minimum gain of the vertical polarized plane waves at the time when the user carries the mobile station in the vertical direction is -5dBi, which represents the carrying angle of the mobile station when the user is not using the mobile station; and referring to FIG. 16, a horizontal directional angle for the minimum gain is not matched with communication since the mobile station is inevitably covered by the human body in the human body's direction when the user carries it, and the horizontal direction angle in the opposite direction of the human body has the maximum gain of 5dBi, thereby indicating good communication quality. Also, when the carrying angle of the mobile station is a calling angle (i.e., 60 degrees), the vertical polarized plane wave's minimum gain is -1dBi, and it is higher by 12dB than the vertical polarized plane wave's minimum gain at the same terminal angle in the identical frequency band, as shown in Table 2. When converged into the power unit, it is 15 times greater than the minimum gain. Further, the case when the user calls with the mobile station's angle being horizontal generates a difference of 13dB compared to the same condition of the conventional monopole antenna, and when converted into the power unit, it has 20 times the difference.

When comparing the vertical polarized plane wave gains of the antennas at the frequency of substantially 1 ,800MHz in the like manners, since the vertical polarized plane wave's minimum gain is -1 OdB from FIG. 11 for showing the horizontal directivity at the carrying angle of 60 degrees of the mobile station of the conventional monopole antenna, and the minimum vertical polarized plane wave's minimum gain is -5dBi from FIG. 12 for showing the horizontal directivity at the carrying angle of 60 degrees of the mobile station of the wire monopole antenna according to the preferred embodiment of the present invention, the gain of the wire monopole antenna according to the preferred embodiment is better by 5dB than that of the conventional monopole antenna. When converted into the power ratio, it has 3 times the improvement.

FIG. 22 shows a diagram for comparing the wire monopole antenna according to the preferred embodiment with the conventional antenna under the same condition by setting the maximum gain of the vertical polarized plane wave components of the wire monopole antenna as 100% at the carrying angle of 60 degrees of the mobile station, when the user calls at the frequency of 850MHz according to the preferred embodiment. Therefore, FIG. 22 shows a percentage diagram with respect to the vertical polarized plane wave's maximum gain of FIG. 17 obtained by converting the directivity degrees of the vertical polarized plane waves of FIGs. 8 and 17. The solid line represents directivity degrees of the vertical polarized plane waves of the mobile station's wire monopole antenna according to the preferred embodiment of the present invention, and the dotted line represents directivity degrees of the vertical polarized plane wave components of the conventional monopole antenna. As shown by FIG. 22, the performance of the wire monopole antenna according to the preferred embodiment is better than that of the conventional monopole antenna by from 2 to several dozen times depending on the horizontal directional angles.

FIG. 23 shows a diagram for comparing the wire monopole antenna according to the preferred embodiment with the conventional antenna under the same condition by setting the maximum gain of the vertical polarized plane wave components as 100% at the carrying angle of 60 degrees of the mobile station when the user calls at the frequency of 1 , 800MHz, according to the preferred embodiment. Therefore, FIG. 23 shows a percentage diagram with respect to the vertical polarized plane wave's maximum gain of FIG. 20 obtained by converting the directivity degrees of the vertical polarized plane waves of FIGs. 11 and 20. The solid line represents directivity degrees of the vertical polarized plane waves of the mobile station's wire monopole antenna according to the preferred embodiment of the present invention, and the dotted line represents directivity degrees of the vertical polarized plane wave components of the conventional monopole antenna. From the directivity comparison of the horizontal polarized plane waves, it is found that the performance of the wire monopole antenna according to the preferred embodiment of the present invention is excellent compared to the conventional monopole antenna except in several directions. Improvements of performance in the several directions are possible by extending the length of the wire monopole antenna up to 50mm. Referring to FIG. 24, the relative performance becomes better when extending the length of the wire monopole antenna to 50mm.

(Second preferred embodiment) FIG. 25 shows a configuration for connecting a loading coil to an end of the wire monopole antenna wherein an electrical length of an antenna with a frequency having a very long length of 1/4 wavelength is compensated, a reactance component is removed from an impedance of an antenna having a length of shorter than the 1/4 wavelength, and impedance matching is performed to thereby fluently transmit and receive electromagnetic waves. Since the antenna's directivity is varied according to the length of the antenna, the loading coil is used to perform matching with a resonance impedance of about 1/2 wavelength when the length of the antenna is required to be longer than the 1/4 wavelength and shorter than the 1/2 wavelength so as to obtain desired directivity. A configuration of FIG. 26 for providing a loading coil in the middle of the wire monopole antenna, and another configuration of FIG. 27 for inserting a loading coil into an end of the antenna are used for the identical purpose, and corresponding arrangements may be modified as needed according to features of delaying the current distribution.

(Third preferred embodiment)

Since the mobile station's wire monopole antenna according to the preferred embodiment of the present invention functions as a fashionable antenna, a configuration for easily attaching the antenna to the mobile station is required. FIG. 28 shows a configuration in which an extension line 9 of a feeding line 8 is extended and fixed from an inner wall of an attachable groove 10 provided on the bottom piece 2 to a facing wall of the attachable groove 10, thereby enabling easy attaching or removing of the wire monopole antenna 7 to/from the mobile station.

A contact unit of the antenna and the extension line 9 of the feeding line 8 adopts a conductive covered wire or an exposed antenna cable 4 to easily conduct electricity with the extension line 9, the length of the antenna is controlled to increase an inductive component, and an original insulated covered wire 5 is provided in the extension line 9 of the feeding line 8 so that the antenna cable 4 may function as a capacitive reactance and a compensator.

(Fourth preferred embodiment)

The fourth embodiment has a configuration that appears to have no antenna but achieves high-gain per ormance. That is, it combines an end of the wire antenna with a mobile station's carrying string. FIG. 29 shows an arrangement diagram of a string wire antenna. In this case, when the user holds the string to carry the mobile station the wire monopole antenna stays vertical because of the string's weight, thereby providing excellent receiving performance for receiving signals.

(Fifth preferred embodiment)

Referring to FIG. 30, so as to have high-gain performance identical with those of the above-described embodiments and substitute the conventional antenna with an ornament, the conventional antenna is separated, and a bolt that fits to an assembly hole is formed to provide a mobile station's wire monopole antenna having a configuration for combining a wire antenna. In this case, the conventional mobile station's monopole antenna is substituted with a fashionable ornament, and the wire monopole antenna stays vertical, thereby generating excellent receiving performance for receiving signals.

(Sixth preferred embodiment)

In the sixth embodiment, a radio wave receiver of the mobile station's wire monopole antenna is made of an elastic metallic cable, or the radio wave receiver is covered or injected with elastic insulation material to thereby control the wire antenna's elasticity so that the antenna may not be completely bent because of the ornament's weight.

FIG. 31 shows a configuration of the wire monopole antenna.

As shown, since the wire monopole antenna according to the sixth preferred embodiment of the present invention has a predetermined bending radius R and is distant from the antenna's ground, it prevents the increase of the VSWR that is generated when the antenna approaches the ground, with corresponding performance-lowering. FIG. 32 shows simulation results of the VSWR (standing wave ratio) and efficiency of the wire monopole antenna depending on the bending radius according to the sixth preferred embodiment of the present invention.

As shown, the more the bending radius increases, the more the SNR reduces and the efficiency increases. When the bending radius is greater than 10mm, the VSWR becomes lower than 3 and the efficiency in this case becomes greater than 80%.

In general, the VSWR of an industrial antenna is 1.2, or below 1.5, the VSWR of the antenna for receiving low power in the case of the mobile station is 2, and the VSWR for consumers' goods includes 3. As described, compared to the conventional case for complementing the polarization performance by adding a diversity antenna, the mobile station's antenna is a single wire monopole antenna designed to maintain the polarization angles, and accordingly, the polarization efficiency caused by the declination of the polarized waves according to the declined angles of the mobile station at the time of the user's carrying the mobile station is increased to implement a high-gain antenna, and since the antenna is positioned on the rear side of the mobile station, radiation of electromagnetic waves in the direction of the human body when the user carries the mobile station in the clothes is reduced. Also, since the mobile station's wire antenna according to the present invention may additionally use various ornaments, a fashionable product functions as an antenna.

While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A wire antenna for a mobile station, comprising: an antenna connector connected and coupled to an output end of the antenna in the mobile station; a radio wave receiver coupled to the antenna connector and being made of elastic cable; and a weight insulated from the radio wave receiver and positioned on an end of the radio wave receiver.

2. The antenna of claim 1 , wherein the radio wave receiver is covered with elastic insulation material.

3. The antenna of claim 1 , wherein a reactance element is installed in the radio wave receiver.

4. The antenna of claim 1 , further comprising a carrying string at the end of the wire antenna.

5. The antenna of one of claims 1 through 4, wherein the antenna is applied to another device.

6. The antenna of claim 5, further comprising: an attachable groove provided on the external surface of the mobile station, and performing a function for attaching the wire antenna; and an extension line of a feeding line penetrating the inner portion of the attachable groove.