GB2360393A

GB2360393A - Aerial coupler

Info

Publication number: GB2360393A
Application number: GB0006328A
Authority: GB
Inventors: Gadi Shirazi; Moshe Einat; Moshe Bitran
Original assignee: Motorola Israel Ltd
Current assignee: Motorola Solutions Israel Ltd
Priority date: 2000-03-16
Filing date: 2000-03-16
Publication date: 2001-09-19
Anticipated expiration: 2020-03-16
Also published as: GB0006328D0; GB2360393B

Abstract

An antenna 17 of a mobile telephone 10 has a helical element with an exposed conductive ring 21, 23 at either end of the helix. A connector 40, enabling the mobile unit to be connected to the exterior antenna of a vehicle, includes a metal conductor 41 with protrusions 42, 43 which contact respective rings 23, 21. This de-tunes the antenna 17 and substantially eliminates the radiation from it.

Description

2360393 12- ANTENNA COUPLER FOR A RADIO DEVICE

FIELD OF THE INVENTION

This invention is in the general field of electromagnetic energy coupling, and in particular it concerns radio antenna applications such as cellular telephones, which require coupling of Radio Frequency (RF) energy from the internal antenna of the telephone to an external device.

BACKGROUND OF THE INVENTION

In many applications, it is required to couple electromagnetic energy from an internal antenna of a radio to an external device. A specific known application of electromagnetic coupling is a vehicle adapter for a cellular telephone. As is well known, receiving and transmitting RF energy through the internal antenna of a cellular telephone in a vehicle introduces relatively high losses of the R-F signal due to shielding by the metallic body of the vehicle.

It is therefore customary to couple the RF energy to an external device (normally the vehicle's adapter) instead of the antenna, which in turn transfers the energy to an external antenna that is fitted, say, on the vehicle's roof. In contrast to the telephone's internal antenna located in the vehicle, the external antenna can be relatively large, grounded and capable of receiving and transmitting energy to and from the environment. Consequently, by using an external antenna, the R-F signal quality (e.g. RF power) is substantially improved as compared to the alternative of using the internal antenna.

In order to route the RF energy to the external antenna, it must first be coupled to the vehicle adapter. There are known in the literature several ways to achieve this task. Thus, an R-F switch, of known type may be used in order to couple the energy to the adapter instead of the internal antenna.

The RF switch has inherent limitations. For example, the actual switching involves loss of energy, which naturally reduces the RF signal quality. Moreover, since the switch has relatively large physical dimensions, its incorporation into the telephone 5 enlarges the unit, contrary to the present trend of compacting it.

Another known approach for coupling the energy to an external device is by electromagnetic coupling of the antenna radiation. By way of example, U.S. patent no. 5,668,561 Assigned to Motorola Inc., U.S.A. discloses one form of coupling, i.e. the socalled "capacitance couplinj for accomplishing the specified energy routing.

The electromagnetic coupling solution has some clear advantages over the R-F switch. For one, it does not involve physical contact with the antenna so that when the telephone unit is not fitted to the vehicle adapter energy losses are reduced. The electromagnetic coupling solution is more reliable and extends the product life span. Lastly, since the electromagnetic coupling device resides externally to the telephone unit (unlike the RF switch), it does not affect the unit's dimensions.

This notwithstanding, the electromagnetic coupling has some inherent limitations and in particular it involves losses of at least 2.5 - 5 dB which, in some applications, may be intolerable.

There is accordingly a need in the art to provide for a method and device which facilitate electromagnetic energy coupling with relatively low losses of energy.

SUMMARY OF THE INVENTION

The invention provides an apparatus for coupling electromagnetic radiation from a radio device to an external device; the radio device includes a hot section coupled to a radio antenna for conveying the electromagnetic radiation to the antenna; the system comprising:

(a) an electrically conductive exposed section, associated with said antenna; at least a portion of said section is coupled to said hot section and to said external device, for coupling the electromagnetic radiation from said hot section to the external device, and The invention further provides for an apparatus for coupling electromagnetic radiation from a telephone radio device to a vehicle adapter; the telephone radio device includes a hot section that is coupled to a radio antenna for conveying the electromagnetic radiation to the antenna; the hot section includes a hot line connected to a printed circuit board of the telephone radio and to an antenna receiving socket; the antenna receiving socket is capable of snuggly receiving the radio antenna, the system comprising:

(a) an electrically conductive exposed section, associated with said antenna; at least a portion of said section is coupled to said hot section and to said vehicle adapter, for coupling the electromagnetic radiation from said hot section to the external device, and (b) de-tuning the antenna to thereby at least in part neutralize it as a radiactive element.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carnied out in practice, a preferred embodiment will now be descriffied, by way of non- limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 illustrates generally a radio telephone unit fitted with antenna; Fig. 2 is a perspective view of a helix antenna with an electrically conductive exposed section, in accordance with one embodiment of the invention; Fig. 3 is a schematic side view of the antenna shown in Fig. 2; Fig. 4 is a schematic side cross-section view of a vehicle adapter fitted with an antenna neutralizer in accordance with one embodiment of the invention; Fig. 5 is a schematic illustration of an antenna fitted in a vehicle adapter, in accordance with one embodiment of the invention; Fig. 6 is a graph illustrating response of tuned and off-tuned antennas, respectively; Fig. 7 illustrates schematically a generalized tuning net circuitry for matching impedance between the telephone ufflit and the vehicle adapter; Fig. 8 is a perspective view of a helix antenna with an electrically conductive exposed section, in accordance with another embodiment of the invention; and Fig. 9 illustrates schematically an antenna neutralizer associated with radiation shield member, in accordance with one embodiment of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

For convenience of explanation, the invention is described for the specific embodiment of a cellular telephone unit, having a particular configuration of vehicle adapter, and operating at a particular RF range. Those versed in the art will readily appreciate that the invention is, likewise, applicable to other radio devices and/or other io external devices, and/or other ranges of electromagnetic radiation.

Bearing this in mind, attention is first directed to Fig. 1 illustrating schematically a radio antenna (17) fitted to a cellular telephone unit (10) operating at, say, about 400 MHz. The invention is not bound to this operational range. The cellular telephone unit (10) includes a case (11) accommodatmig a printed circuit board (PCB) (12), bearing the electronic circuitry of the unit, and a battery (13) serving as the power source of the unit.

The telephone umit (10) further accommodates a so-called hot section (14) that conducts the electromagnetic radiation from the PCB to the antenna. By the specific embodiment of Fig. 1 the hot section includes a hot line (15) connected at the one end thereof to the PCB (12) and at the second end thereof to an antenna receiving socket (16), which by this embodiment is capable of snuggly receiving the antenna (17). By the specific example of Fig. 1 the antenna is threaded to the receiving socket (16).

Turning now to Fig. 2 there is shown the helix antenna (17) with the plastic cover thereof removed. Also shown, two spaced apart conductive rings (21) and (22) having slightly larger diameter than that of the helix antenna's turns, and being electrically coupled to the antenna. By the specific embodiment of Fig. 2, the rings are disposed at the respective two ends of the helix antenna. As shown in Fig. 3 a conventional RF plastic cover (30) covers the helix antenna leaving the rings exposed. The rings arrangement stand for one out of many possible variants of the electrically conductive exposed section.

In normal operation, i.e. when the telephone unit is not fitted to the vehicle. adapter, the antenna (30 in Fig. 3) functions normally and the rings (21 and 22) have no function whatsoever. Any interference caused by the rings can be compensated for by altering the operational parameters of the helix antenna, such as turns' pitch rate, turns' 5 diameter, antenna length, wire width, all as known per se.

Turning now to Fig. 4, there is shown a schematic side cross-section view of a vehicle adapter (40) fitted with an antenna neutralizer (41) in accordance with one embodiment of the invention. By this particular embodiment the antenna neutralizer includes a longitudinal metal conductor and two spaced-part protruding sections (42 and lo 43). The longitudinal extent of the metal conductor is preferably less than J4, where 2, stands for wavelength that corresponds to the operational frequency of the cellular telephone say, about 400 Nffiz.

In operation, and as shown in Fig. 5, when the cellular telephone unit (10) is fitted into the vehicle adapter (40) the rings (21 and 23) contact the respective protruding sections (43 and 42) of the longitudinal metal conductor (41). Now, a portion of the antenna is short-circuited and is rendered out of tuning and accordingly its functionality is significantly reduced (as will be explained in greater detail below). The invention is not bound by short-circuit of the part of the antenna, but rather other electrical activity may be applied in order to neutralize the antenna and render it out-of- tuning.

Some of the energy that would otherwise be conveyed from the hot section to the antenna (17) is now coupled to the adapter through the rings and the metal conductor. This connection by itself would have incapable of directing most of the energy to the external device, had the antenna (17) being operative, however, due to the short-circuit, the antenna is rendered off-tuned, facilitating appropriate coupling of the electromagnetic energy to the external device (and therefrom to the external antenna in a known per se manner).

For a better understanding of the foregoing, attention is now directed to Fig. 6 showing a graph of the response of tuned and out-of-tuned antennas, respectively.

The antenna normally operates at frequency fo and responds as depicted in graph (60). The most efficient operation is brought about in the resonant frequency f,, (see peak 62). When the neutralizer is connected, the resonance frequency of the antenna f. is changed downwards. Put differently, the antenna responds as depicted in graph (61) and therefore the antenna return loss is significantly increased and the antenna returns almost all the RF energy instead of radiating it (see 64).

The actual routing of the electromagnetic radiation to the external antenna is illustrated by way of example in Fig. 7. Thus, the electromagnetic radiation from the 5 longitudinal metal conductor (41) is routed to a tuning net (designated generally as 71 in Fig. 7) which matches the impedance of the telephone unit to that of the vehicle adapter, all as known per se. The coupled energy is now directed (72) to the designated destination, e.g. an antenna fitted on the vehicle's roof (not shown).

Fig. 8 illustrates a perspective view of a helix antenna (80) with an electrically conductive exposed section, in accordance with another embodiment of the invention. By this particular example the electrically conductive exposed section consists of two spaced apart turns (81 and 82) having larger diameter than the rest of the turns of the helix antenna such that when said telephone radio device is fitted to said vehicle adapter the exposed turns (81 and 82) being 'm electrical registration with the longitudinal metal conductor (e.g., with the corresponding protruding sections of the longitudinal metal conductor), operative to neutralize the antenna e.g., by short circuit thereby rendering the antenna out-of-tuning.

An additional element can be added to improve both the coupling and the out-oftuning. Thus, a shield member (90), preferably although not necessary, grounded, covers the antenna neutralizer (41). In the case where the length of the antenna neutralizer (41) is short in comparison to the wavelength (e.g., up to V4), the shield member is not necessary, and a tuning net can be sufficient. If the antenna neutralizer (41) length becomes a significant part of the radiated wavelength, the shield member can be designed to be an RF transmission line structure together with the antenna neutralizer, as is known per se.

Of course the present invention is not bound by the specific examples of exposed sections illustrated in Figs. 2 and 8, and likewise not by the specific antenna neutralizer described with reference to Fig. 4.

In one embodiment, the signal loss in the presence of a shield in accordance with the invention was determined experimentally better than 1 dB over a 60 MHz bandwidth at operating frequency of 420 MHz, so it is superior to prior art coupling devices.

The present invention has been descriffied with a certain degree of particularity, but those versed in the ail will readily appreciate that various alterations and modifications may be camied out without departing ftom. the scope of the following claims:

Claims

CLAIMS:

1. A method for coupling electromagnetic radiation from a radio device to an external device; the radio device includes a hot section operative to be coupled to a radio antenna for conveying the electromagnetic radiation to the antenna; the method 5 comprising the steps of.

(a) coupling the electromagnetic radiation from the hot section to the external device and; (b) de-tuning the antenna to thereby at least in part neutralize it as a radiactive element io

2. The method according to Claim 1, wherein said electromagnetic radiation is in the radio-frequency (RF) range.

3. The method according to Claim 1 or 2, wherein said radio device is a cellular telephone.

4. The method according to claim 3, wherein said external device is an adaptor for coupling the radio device to a further antenna.

5. Apparatus for coupling electromagnetic radiation ftom a radio device to an external device; the radio device includes a hot section coupled to a radio antenna for conveying the electromagnetic radiation to the antenna; the system comprising:

(a) an electrically conductive exposed section, associated with said antenna; at 20 least a portion of said section is coupled to said hot section and to said external device, for coupling the electromagnetic radiation from said hot section to the external device, and (b) an antenna neutralizer associated with said external device, operative to detune the antenna thereby at least in part neutralizing it as a radiactive 25 element.

6. The apparatus according to Claim 5, wherein said electromagnetic radiation is in the radio-frequency (RF) range.

7. The apparatus according to Claims 5 or 6, wherein said radio device is a cellular telephone.

8. The apparatus according to anyone of Claims 5 to 7, wherein said external device is a vehicle adapter.

9. An antenna and an electrically conductive exposed section associated therewith, for use in apparatus according to anyone of claims 5 to 8.

10. Apparatus system for coupling electromagnetic radiation from a telephone radio device to a vehicle adapter; the telephone radio device includes a hot section that is coupled to a radio antenna for conveying the electromagnetic radiation to the antenna; the hot section includes a hot line connected to a printed circuit board of the telephone radio and to an antenna receiving socket; the antenna receiving socket is capable of snuggly receiving the radio antenna, the system comprising:

(a) an electrically conductiven exposed section, associated with said antenna; at least a portion of said section is coupled to said hot section and to said vehicle adapter, for coupling the electromagnectic radiation from said hot section to the external device, and (b) an antenna neutralizer associated with said vehicle adapter, operative to neutralize the antenna by de-tuning the antenna.

11. The system according to Claim 10, wherein said electrically conductive exposed section is constituted by spaced apart electrically conductive rings, each surrounding at least one turn of the helix antenna, and wherein said antenna neutralizer being a longitudinal metal conductor mounted to said vehicle adapter; the longitudinal metal conductor having spaced apart protruding sections, such that when said telephone radio device is fitted to said vehicle adapter the conductive rings being in electrical registration with the protruding sections operative to shorten major portion of the antenna thereby de- tuning the antenna.

12. The system according to Claim 10, wherein said electrically conductive exposed section is constituted by spaced apart exposed turns of said helix antenna, and wherein said antenna neutralizer being a longitudinal metal conductor mounted to said vehicle adapter; when said telephone radio device is fitted to said vehicle adapter the exposed turns being in electrical registration with longitudinal metal conductor, operative to shorten major portion of the antenna thereby rendering the antenna detuned.

13. The apparatus according to Claim 12, wherein said exposed turns having larger diameter than the diameter of the remaining turns of said helix antenna.

14. The apparatus according to Claim 12 or 13 wherein the longitudinal metal conductor spaced apart protruding sections for engaging turns of the helix antenna when the radio device is fitted to the vehicle adapter such that antenna is de- tuned.

15. The apparatus according to anyone of Claims 10 to 14, wherein the longitudinal extent of said antenna neutralizer being smaller than about 2A, wherein, being the wavelength that corresponds to the operational frequency of said telephone radio device. 16. The appartus according to anyone of Claims 10 to 15, wherein said neutralizer is 5 associated with a shield member.

11 Amendments to the claims have been filed as follows 1. A method for coupling electrical energy to be emitted as electromagnetic radiation from a radio device including a radio antenna to an external device, the radio device including a section which in use is a hot section operative to be coupled to the radio antenna for conveying to the antenna the electrical energy to be emitted as electromagnetic radiation by the antenna; the method comprising the steps of connecting a conductor to the antenna at electrically conducting exposed protruding portions of the antenna adapted to make contact with the conductor which thereby provides a short circuit which de-tunes the antenna and galvanically couples the electrical energy to be emitted as electromagnetic radiation from the said section to the external device via the exposed protruding portions of the antenna and the conductor.

2. A method according to claim 1, wherein said electromagnetic radiation is in the radio-frequency (RF) range.

3. A method according to claim 1 or 2, wherein said radio device is a cellular telephone.

4. A method according to claim 1, 2 or 3, wherein said external device is an adaptor for coupling the radio device to a further antenna.

5. Apparatus for coupling electrical energy to be emitted as electromagnetic radiation 20 from a radio device including an antenna to an external device; the radio device including a section which in use is a hot section and which is coupled to the radio antenna for conveying to the antenna the electrical energy to be emitted as electromagnetic radiation by the antenna; the apparatus comprising electrically conducting exposed protruding portions on the antenna which are adapted to make contact with a conductor connected to the external device, the exposed protruding portions when connected to the conductor being capable of providing a galvanic contact to the conductor thereby to short circuit at least part of the antenna and de- tune the antenna, the exposed protruding portions and the conductor providing a galvanic connection for electrical energy to be emitted as electromagnetic radiation from the said section to the external device.

6. Apparatus according to claim 5, wherein said electromagnetic radiation is in the radio-frequency (RF) range.

7. Apparatus according to claims 5 or 6, wherein said radio device is a cellular 12- telephone.

8. Apparatus according to any one of claims 5 to 7, wherein said external device comprises a vehicle adapter.

9. Apparatus according to claim 8 and wherein the vehicle adapter is connected to a 5 further antenna.

10. Apparatus according to any one of claims 5 to 9, the apparatus including a radio device which includes a printed circuit board, an antenna receiving socket for receiving the antenna which has the exposed portions and a conductor which in use is a hot line and is connected to the printed circuit board and to the antenna receiving socket.

io 11. Apparatus according to any one of claims 5 to 10 and wherein the antenna having the exposed portions comprises a helix antenna and the electrically conductive exposed portions are constituted by spaced apart electrically conductive rings, each surrounding at least one turn of the antenna helix, and wherein said conductor capable of providing a galvanic contact to the exposed portions comprises a longitudinal metal conductor having spaced apart protruding sections such that the conductive rings are capable of being in electrical registration with the protruding sections operative to short circuit a major portion of the antenna thereby de-tuning the antenna.

12. Apparatus according to any one of claims 5 to 11 and wherein the antenna having the exposed protruding portions comprises a helix antenna and said electrically conductive exposed portions are constituted by spaced apart exposed turns of said helix antenna, and wherein said conductor capable of providing a galvanic contact to said exposed portions comprises a longitudinal metal conductor, operative to short circuit a major portion of the antenna thereby rendering the antenna detuned.

13. Apparatus according to Claim 12, wherein said exposed turns have larger diameter 25 than the diameter of the remaining turns of said helix antenna.

14. Apparatus according to Claim 12 or 13 wherein the longitudinal metal conductor has spac ed apart protruding sections for electrically engaging turns of the helix antenna.

15. Apparatus according to any one of claims 10 to 14, wherein the longitudinal extent of said longitudinal conductor. is smaller than about J4, wherein; is the wavelength that corresponds to the operational &equency of said telephone radio device.

16. Apparatus according to any one of claims 10 to 15, wherein said longitudinal conductor is associated with a shield member.

1

17. Apparatus according to any one of claims 10 to 16 insofar as dependent on claim 8 or claim 9 and wherein the longitudinal conductor is mounted to the vehicle adapter.

18. A radio device for use in the method claimed in any one of claims 1 to 4 or in the apparatus claimed in any one of claims 5 to 17, the radio device including means for generating electrical energy to be emitted as electromagnetic radiation, a radio antenna and a section which in use is a hot section and which is coupled to the means for generating electrical energy and to the radio antenna for conveying to the antenna the electrical energy to be emitted as electromagnetic radiation by the antenna; the antenna having electrically conducting exposed protruding portions which are adapted to make contact, io when required, with a conductor connected to an external device, the exposed protruding portions when connected to the conductor being capable of providing a galvanic contact to the conductor thereby to short circuit at least part of the antenna and de-tune the antenna, the exposed protruding portions and the conductor thereby providing a galvanic connection for electrical energy to be emitted as electromagnetic radiation from the said section to the external device.

19. A method according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

20. Apparatus according to any one of claims 5 to 16 and substantially as hereinbefore described with reference to the accompanying drawings.