WO2000077885A1

WO2000077885A1 - Antenna arrangement

Info

Publication number: WO2000077885A1
Application number: PCT/SE2000/001212
Authority: WO
Inventors: Tony BJÖRKMAN; Jari Paananen
Original assignee: Avantego Ab
Priority date: 1999-06-16
Filing date: 2000-06-09
Publication date: 2000-12-21
Also published as: AU5859600A

Abstract

The present invention relates to an antenna arrangement in a communication apparatus (8) for single, dual and/or multi-band frequency including at least two antenna elements (20, 30): a first antenna element (20) having a first (21) and a second end (22), and a second antenna element (30) having a first (31) and a second end (32). Said first and second elements (20, 30) are connected in series by connecting said first end (31) of the said second element (30) to said second end (22) of the said first element (20), which in at least some portion of its longitudinal direction is provided with a larger conductive material concentration (23) than the remaining parts.

Description

TITLE

ANTENNA ARRANGEMENT

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an antenna arrangement for transmission and/or reception of electromagnetic radiation, and specially to an antenna for single, dual and/or multi-band frequencies comprising at least two antenna elements.

BACKGROUND AND DESCRIPTION OF THE RELATED ART

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. A dual band antenna system is known through U.S. 5,812,097, which comprises an inner antenna element surrounded by an outer antenna element. In a first embodiment, the inner antenna element (102, 402) radiates and receives RF signals in a first RF band, and the outer antenna element (104, 404) arranged on an insulator (108, 408) radiates and receives RF signals in a second RF band. Optionally, the inner and outer antennas may be coupled together when operating in the first RF band in order to improve the antenna gain pattern of the dual band antenna. In a second embodiment, the inner antenna element radiates and receives RF signals in both the first and second RF bands. In this second embodiment, when operating in the second RF band, the outer antenna element is grounded, thus altering the signal length of the inner antenna element to resonate in the second RF band.

JP 10 322 122 describes a dual-band antenna which is applicable for a portable telephone set. A first and a second helical antenna element are formed integrally, so that a dual-band antenna is obtained. The dual-band antenna resonates with a first frequency band by the first and the second helical elements as a whole. The dual-band antenna resonates with a second frequency band which is higher than the first frequency band by the first helical element having shorter pitch distance.

WO98/58422 describes a dual band antenna including a rod -shaped radiating element having a first portion of a predetermined length connected to a coaxial feed line, and a second portion of specified length integrally extended from the first portion. The coaxial feed line connects to a ground plate and a first capacitive load connects to the first portion of the radiating element. A choke surrounds the second portion of the radiating element and has a shorting end connected to a distal end of the second portion and an open end at a proximal end of the choke. The input impedance of the choke differs for different bands.

The major drawback with the known antennas for different frequencies is that they have problems either with the bandwidth, size or efficiency. SUMMARY OF THE INVENTION

The main objective with the present invention is to overcome the drawbacks inherited from the known antennas, and to provide an antenna with an enhanced bandwidth(s) while the size and the efficiency are maintained or rather improved.

Another object is to achieve better network capacity and to make it possible to produce mobile phones for one, two or more different systems by providing antennas operating in one, two or more frequency bands.

There is also a need for a light and less costly single, dual and multi-band antenna system, which allows operation of a single communication device in multiple frequency bands.

For these reasons, in the initially described antenna arrangement said first and second antenna elements are connected in series by connecting said first end of the said second element to said second end of the said first element, which in at least some portion of its longitudinal direction is provided with a larger conductive material concentration than the remaining part.

Preferably, said conductive material concentration is variation in a cross-section of the first antenna element.

In one embodiment, the first antenna element is intended for high frequency wavelengths.

The second radiation element can be made of a conducting material and arranged as a low-pass filter so that higher frequencies are blocked while lower frequencies are passed through.

In one embodiment, the second element is formed as a helical or meander antenna.

The first and second elements in series form an antenna for low frequencies. The first and second elements can be connected galvanically or through capacitive or inductive connection. Moreover, the antenna can comprise at least a third antenna element connected in series or at least one antenna element arranged in parallel.

In one embodiment, the first antenna element is at least partly solid or hollow. The first antenna element can also be at least partly conical and/or at least partly cylindrical. In one embodiment, the first antenna element is substantially T-shaped.

The invention also relates to a method for receiving or transmitting in single, dual and/or multi- band frequencies in a communication apparatus having an antenna arrangement including at least two antenna elements: a first antenna element having a first and a second end, and a second antenna element having a first and a second end. The method comprises the steps of: connecting said first and second elements in series, providing said first element at least partly with a conductive material concentration, arranging said second element as a low-pass filter for blocking high frequencies while allowing through lower frequencies, and forming said antenna for low frequencies with said first and second elements in series.

The invention also relates to an antenna arrangement in a communication apparatus for single band frequency including an antenna element, comprising, in at least some portion of its longitudinal direction, a larger conductive material concentration than the remaining parts.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Fig. 1 is a schematic perspective illustration of a communication device, and

Figs. 2-8 illustrate in a schematic way enlarged views from one side of embodiments of antenna arrangements according to the invention, which can be arranged on the device according to fig. 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS In the following description, the same parts of each embodiment are denoted with the same reference signs. The communication device 8 according to fig. 1, e.g. a mobile station in a cellular communications system such as GSM, is known per se. However, it is arranged with an antenna system 10 according to the invention, preferably inside a casing 9. The antenna system 10 is connected to the transmitting and receiving parts of the station in accordance with known technique.

The antenna system according to a first embodiment is shown in fig. 2 and denoted with reference sign 10. The antenna system comprises a first radiation element 20 and a second radiation element 30.

The first radiation element 20 is made of a conductive material, e.g. brass or gold-plated material etc., and comprises a first end 21 and a second end 22. The first end 21 is smaller or has a smaller longitudinal cross-section than the second end 22 (with respect to the plane of the drawing), resulting in a larger section 23 or concentration of the amount of the conducting material at the second end 22. In this case the cross-section tapers towards the first end forming a substantially conical configuration, with a disk-shaped based at the second end. However, the cross-section enlargement 23 may be arranged in any part of the first element 20 along the longitudinal axis of the first element.

On the communication device 8, the first end 21 of the first antenna element 20 is connected to the appropriate electronic. The thickness of the second end 22 is so chosen that it is larger than the intended frequency, resulting in that the first element, in spite of its short physical length with respect to the intended radiating frequency, is able to radiate high frequency wavelengths. At the same time the first element 20 will operate as a part of a radiator for low frequencies, which provides for a space-saving antenna system.

Similarly, the second radiation element 30 is made of a conducting material and comprises a first end 31 and a second end 32. The second element is arranged as, e.g. a coil, a helical antenna etc. The second element 30 is in series with the first element by connecting the first end 31 of the second element 30 to the second end 22 of the first element 20. Suitably, the second end 32 of the second element 30 is free.

Preferably, the second element is arranged as a low-pass filter, e.g. formed as a coil with such a pitch that higher frequencies are blocked while the lower frequencies are transferred with minimum loss. Accordingly, the first and second elements 20 and 30 in series form a radiator for the low frequencies. This radiator will then have such a bandwidth that it can be used as a multi-band antenna.

The first end 21 can be provided with threads or formed as a screw cap to be used as a mechanical and electrical interface, e.g. specially in mobile telephones.

The embodiment according to fig. 3 is similar to the embodiment according to fig. 2. The antenna system 10 comprises two antenna elements 20 and 30, respectively, in same way as previously described embodiment. However, the first element 20 is not entirely made of a conductive material and it has a substantially uniform cross-section. The concentration 20 of the conductive material is arranged by having more conductive material particles at one end.

In the antenna system 10 according to fig. 4, the entire first antenna element 20 has a large diameter comprising the higher conductive material concentration. In the antenna system 10 according to fig. 5 the first element 20 is substantially T-shaped with a larger base section 23 at the second end connected to the second antenna element.

According to fig. 6 the first element 20 of the antenna system 10 comprises a main section having a larger diameter or cross-section than a second holder section 40. In this case the conductive material concentration is collected at the opposite end of the end being connected to the second antenna element 30 through a narrowing section 50 arranged as threads. The same configuration is provided in the embodiment of fig. 7, which comprises a first antenna element 20 according to the embodiment shown in fig. 2 provided with a holder section 40 receiving the narrowing part 50 of the second antenna element 30. Also, the holder section acts as part of the antenna. As mentioned above, the shape or design of the second antenna element can be varied. Fig. 8 shows an antenna system 10 similar to the one shown in fig. 7. In this case the helical second antenna element is substituted by a meander antenna 60 of known type.

The fist antenna element 20 may be substantially cylindrica, cubic or the like. It may also be provided solid or hollow.

The antenna system is not limited to two antenna elements, but three or more elements of different types, i.e. a solid part or helical/meander part, can be arranged in series. Also, a combination of antennas in series arranged in parallel may occur which also may include a whip antenna. Moreover, in some embodiments the pitch distance of the helical part or meander configuration of the second element can vary.

It is also appreciated that the antenna elements in all disclosed embodiments can be coupled galvanically, e.g. through soldering, milling or using conductive adhesives etc., or through capacitive or inductive connection.

Moreover, the antenna system is connected to the communications device through screw cap or snap-in arrangement. In the latter, for example one end of the first element is arranged with snap-in notch arranged to co-operate with a corresponding receiving part on the communication device and fix the antenna onto the device. The galvanic connection of the antenna to the communication device may be obtained through a spring loaded tongue, which extends from the snap-in end of the antenna and contacts a signal conductor in the device.

Further, the arrangement allows designing radiators which can be implemented as antennas for only one frequency band if an extra large bandwidth is needed, for example in Wide band CDMA (UMTS), which allows the high and low frequencies pass through one another.

In one special embodiment the antenna system may only include the first antenna element 20 having said conductive material concentration on at least some part of its longitudinal direction. The antenna element is also arranged with a fitting (screw cap, snap-in) for connecting the element to the communication device. The antenna according to this embodiment is suitable for single band application, with the advantages of being simple, easy to manufacture and cheap. Clearly, all relevant features mentioned above may also apply to this embodiment.

The invention is not limited to the disclosed embodiments but can be varied in a number of ways 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.

Claims

1. In a communication apparatus (8) an antenna arrangement for single, dual and/or multi-band frequency including at least two antenna elements (20, 30): a first antenna element (20) having a first (21) and a second end (22), and a second antenna element (30) having a first (31) and a second end (32), characterised in, that said first and second elements (20, 30) are connected in series by connecting said first end

(31) of the said second element (30) to said second end (22) of the said first element (20), which in at least some portion of its longitudinal direction is provided with a larger conductive material concentration (23) than the remaining parts.

2. An antenna arrangement according to claim 1, characterised in, that said conductive material concentration (23) is variation in a cross-section of the first antenna element.

3. An antenna arrangement according to claim 1, characterised in, that said first antenna element is intended for high frequency wavelengths.

4. An antenna arrangement according to any of the preceding claims, characterised in, that the second radiation element (30) is made of a conducting material and arranged as a low- pass filter so that higher frequencies are blocked while lower frequencies are passed through.

5. An antenna arrangement according to any of the preceding claims, characterised in, that said second element is formed as a helical or meander (60) antenna.

6. An antenna arrangement according to any of the preceding claims, characterised in, that said first and second elements (20, 30) in series form an antenna for low frequencies.

7. An antenna arrangement according to any of the preceding claims, characterised in, that said first and second elements (20, 30) are connected galvanically.

8. An antenna arrangement according to any of the claims 1-6, characterised in, that said first and second elements (20, 30) are connected through capacitive or inductive connection.

9. An antenna arrangement according to any of the preceding claims, characterised in, that the arrangement comprises at least a third antenna element connected in series.

10. An antenna aπangement according to any of the preceding claims, characterised in, that the arrangement comprises at least one antenna element arranged in parallel.

11. An antenna arrangement according to any of the preceding claims, characterised in, that said first antenna element is at least partly solid or hollow.

12. An antenna arrangement according to any of the preceding claims, characterised in, that said first antenna element is at least partly conical.

13. An antenna arrangement according to any of the preceding claims, characterised in, that said first antenna element is at least partly cylindrical.

14. An antenna arrangement according to any of the preceding claims, characterised in, that said first antenna element is substantially T-shaped.

15. A method for receiving or transmitting in single, dual and/or multi-band frequencies in a communication apparatus (8) having an antenna arrangement including at least two antenna elements (20, 30): a first antenna element (20) having a first (21) and a second end (22), and a second antenna element (30) having a first (31) and a second end (32), characterised by, - connecting said first and second elements in series,

- providing said first element at least partly with a conductive material concentration,

- arranging said second element as a low-pass filter for blocking high frequencies while allowing through lower frequencies, and

- forming said antenna for low frequencies with said first and second elements in series.

16. In a communication apparatus (8) an antenna arrangement for at least single band frequency comprising an antenna element (20), characterised in, that said first element (20) in at least some portion of its longitudinal direction is provided with a larger conductive material concentration (23) than the remaining parts.