GB2257836A - Retractable antenna - Google Patents
Retractable antenna Download PDFInfo
- Publication number
- GB2257836A GB2257836A GB9115135A GB9115135A GB2257836A GB 2257836 A GB2257836 A GB 2257836A GB 9115135 A GB9115135 A GB 9115135A GB 9115135 A GB9115135 A GB 9115135A GB 2257836 A GB2257836 A GB 2257836A
- Authority
- GB
- United Kingdom
- Prior art keywords
- antenna element
- antenna
- elongate
- conductors
- concentric
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000004020 conductor Substances 0.000 claims abstract description 52
- 230000001413 cellular effect Effects 0.000 abstract description 6
- 238000000576 coating method Methods 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 230000000295 complement effect Effects 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 239000003989 dielectric material Substances 0.000 description 2
- 230000009977 dual effect Effects 0.000 description 2
- 238000005538 encapsulation Methods 0.000 description 2
- -1 polytetrafluoroethylene Polymers 0.000 description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 229910000906 Bronze Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- DMFGNRRURHSENX-UHFFFAOYSA-N beryllium copper Chemical compound [Be].[Cu] DMFGNRRURHSENX-UHFFFAOYSA-N 0.000 description 1
- 239000010974 bronze Substances 0.000 description 1
- KUNSUQLRTQLHQQ-UHFFFAOYSA-N copper tin Chemical compound [Cu].[Sn] KUNSUQLRTQLHQQ-UHFFFAOYSA-N 0.000 description 1
- 229920002457 flexible plastic Polymers 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000001465 metallisation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/08—Means for collapsing antennas or parts thereof
- H01Q1/10—Telescopic elements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/12—Supports; Mounting means
- H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
- H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
- H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
- H01Q1/242—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use
- H01Q1/243—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use with built-in antennas
- H01Q1/244—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use with built-in antennas extendable from a housing along a given path
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Support Of Aerials (AREA)
- Details Of Aerials (AREA)
Abstract
An antenna assembly comprises an elongate antenna element 11 mounted in a support 5 and movable between a retracted position (see Figure 2) and an extended position. A helical antenna element 12 is carried at one end of the elongate element. The support 5 comprises a pair of concentric conductors 9, 10 which provide a coaxial feed to the antenna elements 11, 12. Suitably the support 5 comprises a dielectric tube 6 having respective conductive portions 9, 10 provided on the inner and outer faces thereof. The elongate antenna element is slidably mounted within the central conductor 9. In the retracted position both ends of the elongate antenna element are electrically connected to the central conductor 9. The elongate antenna element is thus rendered inactive as a radiating element and essentially becomes part of the central coaxial feed coupled directly to the helical antenna element. The antenna arrangement is ideally suited for use in a portable cellular radio telephone. <IMAGE>
Description
RETRACTABLE ANTENNA
This invention relates to an antenna assembly comprising a retractable antenna which may be applied, for example, to a portable radio and, in particular a hand portable radio telephone.
A radio intended for two-way communication generally operates with either an external fixed rod or retractable antenna, or with an internal antenna. The fixed rod type of antenna has a predetermined length.
Whilst such antennas can be relatively short, they are not conducive to a compact design nor are they particularly suitable for a radio intended to be carried in a pocket or other receptacle offering restricted space. On the other hand, retractable antennas are convenient for this purpose because they can be folded away when the radio is not in use.
Retractable antennas are commonly of the telescopic tube type, although retractable fixed length antennas are also known.
Some known portable radios such as that disclosed in US
Patent No. 3,087,117 have two antennas, i.e. an internal element together with a retractable element, and are also equipped with means for automatically switching between the two elements according to the physical position of the retractable element. Hence the retractable antenna is operable in the extended position, while the internal antenna element becomes operable when the retractable element is in the retracted position.
An important consideration with a dual antenna system is that both antennas should provide efficient operation under different conditions as appropriate.
For example, while the external antenna element may provide better sensitivity and range performance during normal use, the less efficient internal antenna must provide satisfactory performance during stand-by operation.
US Patent No. 4,868,576 discloses an antenna for a portable cellular telephone comprising a helical coil at the base of a retractable elongate radiating element. The retractable element, which extends through the helical coil, has non-conductive portions at its two ends whereby in the extended position the elongate element is capacitively coupled to the helical coil, and in the retracted position the elongate element is substantially decoupled therefrom. The helical coil is fixedly mounted on the housing of the radio transceiver.
According to the present invention there is provided an antenna assembly comprising a first elongate antenna element movable between a retracted position and an extended position, a second antenna element, and a pair of substantially concentric conductors providing coaxial feed means to said first and second antenna elements, wherein in the retracted position the first antenna element constitutes at least part of the coaxial feed means to the second antenna element.
An antenna assembly in accordance with the present invention provides a compact and convenient dual antenna arrangement which is ideally suited for portable radio applications and which can be manufactured and assembled in a relatively straightforward manner and therefore at low cost. Both the antenna elements may be external to the radio housing for optimum radiation performance. In the - extended position the elongate antenna element is active, either alone or in combination with the second antenna element. In the retracted position the elongate antenna element essentially becomes part of the central coaxial feed to the second antenna element and is thereby rendered inactive as a radiating element without the need for elaborate switching means so that the second antenna element alone performs the sole antenna function.
It is noted that the term "elongate antenna element" as used herein encompasses for example a rod type antenna or a coil type antenna having a generally elongate configuration.
In a preferred embodiment the first antenna element is slidably mounted in a support, the concentric conductors being provided on said support. The support may comprise a dielectric tube (which need not be cylindrical), the coaxial conductors being provided respectively on the internal and external faces of said dielectric tube. Alternatively, the concentric conductors may be formed as a pair of self-supporting concentric cylinders spaced apart, e.g. by an air gap.
In either case the elongate antenna element may be slidably mounted within the inner conductor such that an electrically conductive part, preferably at the inner end thereof, physically contacts, and so is electrically coupled to, the inner conductor of the coaxial pair.
In the preferred embodiment means are also disposed at the other end of the elongate antenna element which electrically connect said other end of the elongate element to the central conductor of the coaxial pair when the elongate antenna element is in the retracted position. Hence both ends of the elongate antenna element are coupled to the inner conductor when the elongate antenna element is retracted. Thus in the retracted position substantially the whole length of the elongate antenna element is rendered inactive and becomes a functional part of the inner conductor.
Contact means may be provided which electrically connect the second antenna element directly to the central conductor of the coaxial pair of conductors when the first antenna element is in the retracted position. The same contact means may also serve to connect the elongate antenna element to the central conductor of the concentric pair when the elongate antenna element is in the retracted position. The elongate antenna element, when retracted, thus becomes a functional part of the coaxial feed to the second antenna element.
An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which:
Figure 1 is a schematic cross-section of a portable cellular radio telephone incorporating an antenna assembly in accordance with the present invention, showing the antenna in the extended position,
Figure 2 is a schematic cross-section of the portable cellular radio telephone in Figure 1 showing the antenna in the retracted position, and
Figure 3 is an enlarged cross-section showing a portion of the antenna and support in more detail.
The portable cellular radio telephone shown in the
Figures comprises a housing 1 enclosing a conventional transmitter 2 and receiver 3 coupled respectively via a duplexer 4 to the inner conductor 9 of the coaxial feed to the antenna assembly. The coaxial feed is discussed in more detail below.
The housing 1 also encloses all the other features conventionally found in a portable cellular telephone.
Since these aspects are not directly relevant to the instant invention no further details will be given here.
The antenna assembly, provided adjacent the top face of the radio housing 1, comprises a support 5 in the form of a dielectric tube 6. The dielectric material of the tube 6 may, for example, be polytetrafluoroethylene (PTFE) or polyethylene.
The bore of the dielectric tube 6 is provided with a conductive coating 9, for example of nickel plated copper. A conductive coating 10, for example of copper is also provided on the outer face of the tube 6. The inner and outer conductive coatings 9 and 10 are electrically isolated from each other. The inner and outer conductors may alternatively be formed by metal cylinders spaced apart by the dielectric tube 6. The outer conductor is electrically connected to ground potential, the ground metallization suitably being provided on the internal faces of the housing 1.
Hence, the support 5 constitutes a coaxial feed to the antenna elements which will now be described.
The antenna assembly comprises two distinct antenna elements, namely an elongate antenna element 11 and a helical element 12. The elongate element comprises a central conductor 7 which may be a solid rod antenna or, alternatively, may be in the form of a close-wound coil which not only enhances flexibility of the elongate element and so reduces the risk of breakage, but also reduces the physical length of the antenna.
The coil may be made of silver plated beryllium-copper wire. The elongate antenna element 11 may be chosen to have an equivalent electrical length, for example, of a quarter-wavelength or three-eights wavelength. The conducting portion 7 of the elongate element 11 is enclosed within an insulating sleeve 8 made for example of a flexible plastics material. At the base of the elongate antenna element there is provided an impedance matching inductor 13 having one end connected to the conductor 7 of the elongate antenna element 11 and the other end connected to an electrically conductive end portion 17 which is in electrical contact with the inner conductor 9 of the dielectric tube 6 (see Figure 3). The inductor 13 is present within the insulating sleeve 8.The end portion 17 of the elongate antenna element 11 has a circumferential recess 20 which accommodates a radially biassed phosphor bronze spring 21. The conductive spring 21 bears against the inner conductor 9 of the support 5 for optimal electrical contact therewith.
The elongate antenna element 11 is slidably mounted in the bore of the dielectric tube 6 and the conductive spring 21 remains in electrical contact with the inner conductor 9 at all times.
The end of the elongate antenna element 11 remote from the support 5 carries a helical antenna element 12.
The helical coil 12 is very compact and has a short physical length but is wider in diameter than the elongate antenna element 11. The effective electrical length of the helical antenna element 12 is, for example, a quarter-wavelength. The helical coil 12 is embedded in a dome-shaped dielectric encapsulation 14.
In the present embodiment the helical antenna element 12 is permanently electrically connected to the elongate antenna element 11. The lower end of the helical coil 12 is also electrically connected to a contact member in the form of a collett 15 which protrudes through the underside of the encapsulation 14. A complementary contact in the form of an electrically conductive collett 16 is provided within the upper end of the support 5. The collett 16 is provided in the bore of the tube 6 and is electrically connected to the inner conductor 9.
When the antenna is in the extended position as shown in Figure 1, the electrically conductive end portion 17, which is coupled to the lower end of the impedance matching inductor 13, makes electrical contact via the conductive spring 21 with the inner conductor 9 on the support 5. The support 5 thus acts as a coaxial feed to the elongate antenna element. As mentioned previously, the inner conductor 9 on the dielectric tube is coupled to the radio transmitter 2 and receiver 3 via a duplexer 4. Since the helical antenna element 12 is connected to the elongate antenna element 11 both elements are functionally active as a combined antenna in the extended position.
As can be seen most clearly in Figure 3, the end portion 17 has a narrower portion 22 adjacent the inductor 3 defining a shoulder 23 which abuts the underside of the collett 16 when the antenna is fully extended and so acts as a stop to prevent further withdrawal of the antenna.
In the retracted position shown in Figure 2, the elongate antenna element is substantially entirely enclosed within the coaxial support 5. The conductive end portion 17 nevertheless remains in electrical contact with the inner conductor 9 via the conductive spring 21. Also, the conductive collett 15 depending from the helical antenna element 12 now engages, and hence makes electrical contact with, the complementary conductive collett 16 at the top end of the coaxial support 5. The elongate antenna element is thus rendered inactive as a radiating element in that it essentially becomes part of the central coaxial feed coupled directly to the helical antenna element 12.
The helical antenna element is thus electrically coupled directly to the central conductor of the coaxial feed. The collett pair 15 and 16 constitutes both a low inductance, low resistance antenna switch and also a detent feature by which the user is able to feel when the antenna is fully retracted. When the antenna is extended the contact between colletts 15 and 16 is broken. The outer end of the elongate antenna element is therefore no longer connected to the inner conductor 9 of the coaxial support and the extended portion of the elongate element resumes its function as a radiating antenna element.
It is noted here that the characteristic impedance ZO of the respective transmission lines which feed the elongate antenna element 11 and the helical antenna element 12 when the elongate antenna element is respectively extended and retracted is substantially the same despite the different nature of the central conductor in the two cases. This is because, in the case of a coaxial transmission line with a circular cross-section, Z0 is determined by the equation
where tr is the relative permittivity of the dielectric material of tube 6, do is the diameter of the outer conductor of the coaxial feed, and di is the diameter of the inner conductor of the coaxial pair.
Clearly tI t and do do not change between the extended and retracted positions. More significantly, however, it will be seen that with the present arrangement di does not change since the overall diameter of the central conductor 9 is fixed and is not altered by the action of the elongate antenna element 11 sliding internally within the inner conductor 9.
In an alternative embodiment the helical antenna element 12 may be electrically isolated from the elongate antenna element 11. In this case contact means such as a conductive member extending through the insulating sleeve 8 may be provided for electrically connecting the outer end of the elongate element to the inner conductor 9 of the coaxial support when the antenna is in the fully retracted position. In the retracted position the collett switch 15, 16 would still be effective to couple the helical antenna element 12 to the central conductor of the coaxial feed. The collett pair 15 and 16 thus constitute a low inductance, low resistance antenna switch for the helical antenna element 12. When the antenna is extended the contact between colletts 15 and 16 is broken thus decoupling the helical antenna element.
Also electrical contact is broken between the contact means at the outer end of the elongate antenna element 11 and the inner conductor 9 of the coaxial support whereby the elongate element, which remains electrically coupled at the lower end portion 17 to the inner conductor 9, resumes its function as a radiating antenna.
In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the present invention. For example, instead of being formed of a solid dielectric tube the antenna support may comprise a pair of concentric metal cylinders held in spaced relationship by insulating spacers. In this case the dielectric may be the air in the gap between the concentric cylinders. Furthermore, it is noted here that neither the dielectric tube and the bore thereof, nor the concentric metal cylinders need be circular in cross-section, but may instead be square, rectangular, oval or indeed any other suitable shape.
Claims (11)
1. An antenna assembly comprising a first elongate antenna element movable between a retracted position and an extended position, a second antenna element, and a pair of substantially concentric conductors providing coaxial feed means to said first and second antenna elements, wherein in the retracted position the first antenna element constitutes at least part of the coaxial feed means to the second antenna element.
2. An antenna assembly as claimed in claim 1, wherein the first antenna element is slidably mounted within the inner conductor of the concentric pair of conductors.
3. An antenna assembly as claimed in claim 1 or claim 2, wherein the first antenna element is slidably mounted in a support, the concentric conductors being provided on said support.
4. An antenna assembly as claimed in claim 3, wherein the support comprises a dielectric tube and the concentric conductors are provided respectively on the internal and external faces of said tube.
5. An antenna assembly as claimed in any of the preceding claims, wherein the concentric conductors comprise a pair of self-supporting conductive cylinders in spaced relationship.
6. An antenna assembly as claimed in any of the preceding claims, wherein means are provided at one end of the first antenna element which electrically couple said one end of the first antenna element to the inner conductor of the concentric pair of conductors.
7. An antenna assembly as claimed in claim 6, wherein means are provided at the other end of said first antenna element which electrically connect said other end of the first antenna element to the inner conductor of the concentric pair of conductors when the first antenna element is in the retracted position.
8. An antenna assembly as claimed in any of the preceding claims, including contact means which electrically connect the second antenna element to the central conductor of the concentric pair of conductors when the first antenna element is in the retracted position.
9. An antenna assembly as claimed in claim 8, wherein the contact means also connects the first antenna element to the central conductor of the concentric pair of conductors when the first antenna element is in the retracted position.
10. An antenna assembly substantially as herein described with reference to Figures 1 to 3 of the accompanying drawings.
11. A portable radio transceiver comprising a housing enclosing transmitting and receiver circuitry, and an antenna assembly as claimed in any of the preceding claims, said antenna assembly being coupled to said transmitting and receiving circuitry.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9115135A GB2257836B (en) | 1991-07-13 | 1991-07-13 | Retractable antenna |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9115135A GB2257836B (en) | 1991-07-13 | 1991-07-13 | Retractable antenna |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9115135D0 GB9115135D0 (en) | 1991-08-28 |
| GB2257836A true GB2257836A (en) | 1993-01-20 |
| GB2257836B GB2257836B (en) | 1995-09-27 |
Family
ID=10698301
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9115135A Expired - Fee Related GB2257836B (en) | 1991-07-13 | 1991-07-13 | Retractable antenna |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2257836B (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2275369A (en) * | 1993-02-19 | 1994-08-24 | Matsushita Electric Industrial Co Ltd | Retractable antenna device |
| GB2282705A (en) * | 1993-09-09 | 1995-04-12 | Mitsubishi Electric Corp | Antenna system having plural antenna portions |
| EP0650215A3 (en) * | 1993-09-29 | 1995-09-06 | Nippon Telegraph & Telephone | Antenna device. |
| GB2266019B (en) * | 1992-04-08 | 1995-12-13 | Nokia Mobile Phones Ltd | Radio with retractable antenna |
| US6198448B1 (en) | 1997-07-29 | 2001-03-06 | Tokin Corporation | Lightweight antenna assembly comprising a whip antenna and a helical antenna mounted on a top end of the whip antenna |
| US10826179B2 (en) | 2018-03-19 | 2020-11-03 | Laurice J. West | Short dual-driven groundless antennas |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2219911A (en) * | 1988-06-17 | 1989-12-20 | Mitsubishi Electric Corp | Rf transceiver with movable antenna |
-
1991
- 1991-07-13 GB GB9115135A patent/GB2257836B/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2219911A (en) * | 1988-06-17 | 1989-12-20 | Mitsubishi Electric Corp | Rf transceiver with movable antenna |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2266019B (en) * | 1992-04-08 | 1995-12-13 | Nokia Mobile Phones Ltd | Radio with retractable antenna |
| US5534878A (en) * | 1992-04-08 | 1996-07-09 | Nokia Mobile Phones Limited | Radio with retractable antenna |
| GB2275369A (en) * | 1993-02-19 | 1994-08-24 | Matsushita Electric Industrial Co Ltd | Retractable antenna device |
| US5426440A (en) * | 1993-02-19 | 1995-06-20 | Matsushita Electric Industrial Co., Ltd. | Retractable antenna device having a rodlike antenna and a helix antenna which is electrically isolated from the rodlike antenna in the retracted condition of the antenna device |
| GB2275369B (en) * | 1993-02-19 | 1996-05-29 | Matsushita Electric Industrial Co Ltd | Antenna device |
| GB2282705A (en) * | 1993-09-09 | 1995-04-12 | Mitsubishi Electric Corp | Antenna system having plural antenna portions |
| GB2282705B (en) * | 1993-09-09 | 1997-10-15 | Mitsubishi Electric Corp | Antenna system having plural antenna portions |
| EP0650215A3 (en) * | 1993-09-29 | 1995-09-06 | Nippon Telegraph & Telephone | Antenna device. |
| US5617105A (en) * | 1993-09-29 | 1997-04-01 | Ntt Mobile Communications Network, Inc. | Antenna equipment |
| US6198448B1 (en) | 1997-07-29 | 2001-03-06 | Tokin Corporation | Lightweight antenna assembly comprising a whip antenna and a helical antenna mounted on a top end of the whip antenna |
| US10826179B2 (en) | 2018-03-19 | 2020-11-03 | Laurice J. West | Short dual-driven groundless antennas |
| US11605890B2 (en) | 2018-03-19 | 2023-03-14 | Laurice J. West | Short dual-driven groundless antennas |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2257836B (en) | 1995-09-27 |
| GB9115135D0 (en) | 1991-08-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20100713 |