WO2001011717A1

WO2001011717A1 - Antenna arrangement

Info

Publication number: WO2001011717A1
Application number: PCT/SE2000/001554
Authority: WO
Inventors: Tony BJÖRKMAN; Jari Paananen
Original assignee: Avantego Ab
Priority date: 1999-08-06
Filing date: 2000-08-07
Publication date: 2001-02-15
Also published as: AU6487300A

Abstract

The present invention relates to an antenna arrangement (10), comprising a first antenna element (12), a second antenna element (14), a third antenna element (15) being a socket and electrically connected to said second antenna element and connection means (13). Said first antenna element at one of said operative positions capacitively connects to said third antenna element (15) constituting an antenna for a certain frequency band whereby the second antenna element acts as a blocking element.

Description

TITLE

ANTENNA ARRANGEMENT

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an antenna arrangement, and specially a single, dual and/or multiband antenna arrangement, comprising a first antenna element being a whip, helical or meander antenna, a second antenna element, a third antenna element being a socket and connection means.

BACKGROUND OF THE INVENTION

The wireless forms of communications have become a standard way of communication. There are many types of means for conducting a wireless communication, such as cordless telephones, lap top computers with wireless modems, satellite and cellular telephones. The communication device, i.e. the mobile handsets rapidly become smaller and lighter and the globalization demand, multiple communication functions and standards being combined into a single unit, e.g. for communicates in multiple frequency bands. There are a variety of different radiotelephone systems in use today. These include different analogue or digital CDMA (Code Division Multiple Access) and TDMA (Time Division Multiple Access) based systems like GSM (Global System for Mobile telecommunication), AMPS (Advanced Mobile Phone System), DAMPS(Digital Advanced Mobile Phone System), PCS (Personal Communication Services), DCS (Digital Communication System) PCN (Personal Communication Networks ), PDC 800 and 1500 and different cordless telephone systems.

Different systems operate in different frequency bands, thus requiring different antennas for maximum efficiency.

US 5,717,409 discloses a dual frequency band antenna system where the two frequency bands are not harmonically related includes first and second antenna sections. The first antenna section comprises a straight rod, with the length of the rod being at least one quarter wavelength at the center frequency of the lower of the two frequency bands. The second antenna section includes a straight portion terminated by a helical wire portion, with the total electrical length of the second antenna section being substantially equal to the length of the straight rod. A conductive antenna base is connected to at least one of the first and second antenna sections. A matching circuit coupled to the base is arranged to substantially cancel the reactive portion of the impedance of the connected antenna section for both frequency bands and to substantially equalize the resistive portion of the impedance of the connected antenna section to the resistive portion of the output impedance of the radio transceiver to which the antenna system is coupled. The lengths of the straight rod and of the second antenna section are such that together with the matching circuit the resistive portion of the impedance of the connected antenna section is substantially the same for both frequency bands. The second antenna section may be permanently and directly coupled to the transceiver circuitry through the base and the matching circuit. Alternatively, the coupling of the base to the matching circuit may be either capacitive or inductive.

WO 9410720 discloses an antenna device intended for a portable equipment for transmitting and/or receiving radio signals. The antenna device comprises a helical antenna substantially having the characteristics of a half- wave antenna, a half-wave antenna, and an impedance transformer. The helical antenna, said half-wave antenna, and said impedance transformer are interconnected so that either said helical antenna alone is coupled to said impedance transformer or said helical antenna and said half-wave antenna are coupled in parallel to said impedance transformer in order to form two different working antenna functions.

In a radio frequency antenna according to EP 843 378 there is a connector for mechanical and electrical connection of the antenna to the radio set and a thick monopole radiator, which are essentially an integrated piece. In addition, the antenna comprises a second antenna element, which is movable in relation to the piece formed by the connector and the thick monopole radiator. The second antenna element should preferably be a whip component, for which there is an axial aperture in the connector and in the thick monopole radiator. The whip component may be locked in the upper position at different points in the aperture.

US 4,868,576 describes an antenna for a portable cellular telephone (100) includes a quarter- wavelength ground radiator (106) and a helical coil (104) capacitively coupled to an extendable half-wavelength radiator (102). The extendable half-wavelength radiator (102) includes a metallic coil (209) molded in plastic. The ground radiator (106) includes a serpentined transmission line (302) on a flexible circuit board (310). The helical coil (104) and ground radiator (106) are coupled by a transmission line (110) to a duplexer (112). The duplexer couples transmitter signals from a radio transmitter (114) to the antenna and receiver signals from the antenna to a radio receiver (116). The antenna may be advantageously utilized in any portable radio applications where small size and immunity to hand induced radiation losses are desired. An extendable half- wavelength radiating means (102) has a non-conductive top and bottom portions (206,210) and a conductive center portion (208) and extending through said helical winding, the conductive portion of said extendable half-wavelength radiating means being capacitively coupled to the second end of said helical winding when extended from the top portion of the housing means and being substantially decoupled therefrom when retracted into the bottom portion of the housing means.

US 5,952,974 describes a mono-pole antenna is composed of a first element and a second element. An insulator spacer is disposed between the first element and the second element so as to capacitively couple them. In the state that the antenna is retracted, the helical antenna operates. In the state that the antenna is extended, the mono-pole antenna composed of the first element and the second element operates. Since the mono-pole antenna is composed of the first element and the second element that are capacitively coupled, even if the electrical length of the helical antenna is different from the electrical length of the mono-pole antenna, the impedances can be properly matched with a common matching circuit.

SUMMARY OF THE INVENTION

The main object of the present invention is to overcome the drawbacks of the prior art by means of a simple but yet an efficient antenna, which is easy to manufacture and assemble. Another object of the invention is to provide an antenna enhancement wherein some of the drawbacks of galvanic coupling between the antenna elements are avoided and which provides extra means for enhancing frequency bands, preferably low frequency band.

Therefore, in the initially mentioned antenna arrangement said first antenna element is arranged to assume at least a first and a second operative position, and said first antenna element at one of said operative positions capacitively connects to said third antenna element constituting an antenna for a certain frequency band, whereby the second antenna element acts as a blocking element.

Preferably, said first antenna element is a whip antenna, a helical or meander antenna. Moreover, the first antenna element is provided with a conducting member at some portion of it. The second antenna element is provided with said third antenna element as a conducting member. The first and second antenna elements capacitively contact when said conducting members face each other. Moreover, a dielectric material is arranged between said conducting members. Advantageously, it is an antenna for high frequency bands in one of said operative positions. In one embodiment, said connection means comprises a snap-in connection but it may also be a screw-join or the like.

In a most preferred embodiment the antenna arrangement concerns an antenna for a communication device, comprising a whip antenna element, a helical antenna element, a straight antenna element and connection means. The whip antenna element is arranged to assume at least a first and a second operative position. The whip antenna element at one of said operative positions capacitively connects to said straight antenna element constituting an antenna for a certain frequency band. Preferably, the straight antenna element is a substantially cylindrical socket and the whip antenna element is arranged coaxially to said helical and substantially cylindrical socket. The helical antenna element and said straight antenna element constitute a dual band antenna. BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be further described in a non- limiting way under reference to the accompanying drawings in which:

Fig.l is a schematic elevation view of an antenna arrangement according to the present invention, and Fig. 2 is a cross-section along the line II-II showing some part of the antenna according to fig. 1.

DETAILED DESCRIPTION OF THE EMBODIMENT

A preferred embodiment of the antenna arrangement 10, shown in figs. 1 and 2, consists of three essentially main parts: an antenna housing 11, housing an antenna element 14, a whip component 12 and a connector part 13. The whip component 12 is shown in extracted position. The antenna is intended to be arranged on a communication unit, such as a mobile or cellular telephone handset (not shown).

The whip 12 comprises a substantially flexible conductor 121 coated with a protective and insulating layer 122, such as rubber or plastic. The whip 12 has a first end provided with an end socket 123 of a conducting material and a second end having a stop boss 124, both ends of the whip may be provided with reinforcements 125 of a thicker plastic layer.

The housing 11, preferably made of an insulating material, is hollow and comprises a first open end and a second end having an opening for the whip antenna 12, through which the whip can be retraced or extracted.

Inside the housing is arranged a second antenna element 14, formed as a coil constituting a helical antenna having a first free end 141 and a second end 142 connected (galvanically) to a conducting socket 15. The second end 142 of the helical antenna 14 has partially narrow pitches and connected to the conducting socket 15, e.g. through press fitting, screwing or the like.

The connector part 13 comprises a substantially cylindrical carrier 131 (or other shaped carrier) of insulating material (or conducting depending on the connection to the communications unit) having a first end 132 wedged inside a corresponding compartment in the housing 11 and a second end 133 provided with snap connection 134 in form of a hook, which is arranged to cooperate with a corresponding receiver in the communication unit to attach the antenna arrangement to the same. The cylinder 131 is also provided with a slit 135 to expose a conducting, resilient connector member 136.

The connector member 136 has a first end 1361 in contact with the conducting socket 15 and a second, substantially protuberance end 1362 arranged for making contact with the receiver/transmitter parts of the communications unit and thus galvanically connecting the conducting socket 15 and the helical antenna element to 14 to the receiver/transmitter parts of the communications unit. However, the galvanic connection may be substituted with capacitive or inductive connections.

The conducting socket 123 at the second end of the whip 12 has a first end 1231 connected to the conductor 121 of the whip and a second end 1232 provided with a knob acting as a stop element.

Between the whip 12 and the socket 15, a sleeve 16 of a dielectric or plastic material is arranged, which at its one end is fixed to the socket 15.

The whip is arranged substantially coaxially in the center of the helical antenna. The whip is so arranged that there is no galvanic connection between it and the rest of the antenna, neither at the retracted position nor at the pulled out position. When the whip is pulled out, preferably in its entire length so that the end socket 123 is placed inside the socket 15, it makes a capacitive contact with the socket 15, preferably using the sleeve 16 as the dielectric member of the capacitor. Moreover, the sleeve functions as a fixing element which sustains the whip at pulled out position (or retracted position in corporation with the reinforcement 125 at the other end of the whip) when the end socket bears on the sleeve.

The antenna arrangement operates in following way. The helical antenna 14 and the socket 15 constitute the dual band antenna, thereby as resonators for two different frequency bands. The helical antenna acts as a blocking element whereby the helical antenna 14 and socket 15 compose the low frequency band antenna and the socket 15 the high frequency band antenna. The whip 12 is used for enhancement of the antenna characteristics, and therefore it is important that a balanced capacitive connection is obtained to avoid to much coupling of high frequency to the whip, which would be the case if a galvanic connection was used.

Accordingly, when the whip is retracted it is not operative and only the helical antenna 14 and the socket 15 are operative as antennas, and the helical antenna blocks the high frequencies and functions as an antenna for low frequency band.

The characteristics of the capacitive connection can be changed by changing the lengths of the end socket 123, socket 15 or sleeve 16 or the material it is made of. It is also possible to form antenna elements with different electrical length by arranging several conducting sleeves in different positions along the length of the whip. Moreover, the helical antenna can be substituted with any other antenna elements such as an additional whip, a meander antenna etc.

Furthermore, the sleeve 16 can be arranged displacable on the end socket 123; or both the end socket 123 and the sleeve 16 can be arranged fixed inside the socket 15 and the end of the whip can be arranged to contact the socket.

The antenna arrangement according to the invention can be used in any device with a need for receiving and/or transmitting electro-magnetical waves, and because of its small size it is most suitable for use in cellular phones or the like.

The invention is not limited to the shown embodiment but can be varied in a number of ways, e.g. through combination of two or more embodiments shown, without departing from the scope of the appended claims and the arrangement and the method can be implemented in various ways depending on application, functional units, needs and requirements etc. REFERENCE SIGNS

10 Antenna

11 Housing

12 Whip

121 Conductor

122 Protective layer

123 End socket

1231 First end

1232 First end

124 Boss

125 Reinforcement

13 Connection means

131 Carrier

132 First end

133 Second end

134 Snap connection

135 Slit

136 Connector member

1361 First end

1362 Second end

14 Helical antenna

141 First end

142 Second end

15 Sockel

16 Sleeve

Claims

1. An antenna arrangement (10), comprising a first antenna element (12), a second antenna element (14), a third antenna element (15) being a socket electrically connected to said second antenna element and connection means (13), characterised in, that said first antenna element (12) is arranged to assume at least a first and a second operative position, and that said first antenna element at one of said operative positions capacitively connects to said third antenna element (15) constituting an antenna for a certain frequency band whereby the second antenna element acts as a blocking element.

2. The antenna arrangement of claim 1, characterised in, that said first antenna element (12) is one of a helical, meander or whip antennas.

3. The antenna arrangement of claim 1 or 2 characterised in, that said first antenna element (12) is provided with a conducting member (123) at some portion of it, that said second antenna element (14) is provided with said third antenna element (15) as a conducting member, and that said first and second antenna elements (12, 14) capacitively contact when said conducting members (123, 15) face each other.

4. The antenna arrangement according to claim 3, characterised in, that a dielectric material (16) is arranged between said conducting members (123, 15).

5. The antenna arrangement according to any of preceding claims, characterised in, that it is an antenna for high frequency bands in one of said operative positions.

6. The antenna arrangement according to claim 1, characterised in, that said connection means (13) comprises a snap-in connection.

7. In a communication device an antenna arrangement (10), comprising a whip antenna element (12), a helical antenna element (14), a straight antenna element (15) and connection means (13), characterised in, that said whip antenna element (12) is arranged to assume at least a first and a second operative position, and that said whip antenna element at one of said operative positions capacitively connects to said straight antenna element (15) constituting an antenna for a certain frequency band.

8. The antenna arrangement according to claim 7, characterised in, that said straight antenna element is a substantially cylindrical socket (15).

9. The antenna arrangement according to claim 7 and 8, characterised in, that said whip antenna element is arranged coaxially to said helical and substantially cylindrical socket.

10. The antenna arrangement according to any one of claims 7 -9, characterised in, that said helical antenna element and said straight antenna element constitute a dual band antenna.