Communications: radio wave antennas – Antennas – With radio cabinet
Patent
1995-04-24
1997-08-26
Wimer, Michael C.
Communications: radio wave antennas
Antennas
With radio cabinet
343725, 343895, H01Q 124
Patent
active
056614950
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an antenna device for portable communication equipment, specifically for hand portable telephones, comprising circuits for transmitting and/or receiving radio signals as well as a chassis and a feeding point providing the electrical coupling of the antenna device to the communication equipment, the antenna device comprising a hollow helical antenna fixed externally on the chassis and an antenna rod slidable through the helical antenna, which antenna rod includes a substantially straight radiator.
Antennas for hand-portable telephones may be divided generally into two main groups, quarter-wave and half-wave radiators, although types somewhere between and outside these may occur.
Characteristics of a quarter-wave radiator are: (radiating portion length approximately 8 cm at 900 MHz), to the 50 Ohm impedance of the telephone, without impedance transformation, disturbing,
Characteristics of a half-wave length radiator are: (radiating portion length approximately 16 cm at 900 MHz), transformation to the 50 Ohm impedance of the telephone, 18-20 cm including a connector,
In the specification and claims below the terms half-wave radiator and quarter-wave radiator refer to antennas having substantially the above characteristics, respectively.
A straight radiator mounted on the outside of the chassis of a hand portable telephone occupies considerable space and is exposed to strain which, for example can result in breaking. Further, only lower antenna performance is required when no call is going on. For this reason, the straight radiator is often made retractable and is combined with a helical antenna having lower antenna performance, but being considerably less bulky.
U.S. Pat. No. 4,868,576 describes an antenna device of the aforementioned type, the device comprising a retractable capacitively coupled half-wave radiator in combination with a helical antenna of half-wave type. This known device solves the above problem for a telephone of large size, but is dependent on a half-wave radiator to provide satisfactory antenna performance. However, the physical dimensions of modern hand portable telephones are so small that a half-wave radiator would be very difficult to fit therein lengthwise, without providing with a complicated telescopically retracting feature. It is also lacks an aesthetically pleasing appearance since its length is out of proportion to the small size of modern telephones.
Further, the half-wave radiator requires an impedance transformer taking up room inside the telephone and causing higher costs due to additional components.
The European Patent Application 0 467822 A2 discloses another antenna system for a hand portable telephone comprising a retractable quarter-wave radiator provided in its upper end with a helical antenna of the quarter-wave type, which substantially has no coupling to the quarter-wave radiator. The quarterwave radiator is only connected in the fully extended position and the helical antenna only in the fully retracted position. This systems solves the above-mentioned problem for a small-size telephone, but has the drawback of the telephone completely lacking antenna function as soon as the retractable quarterwave radiator is not in one of its end positions. Besides, it is both an aesthetic and a strength drawback to provide the helical antenna in the upper end of the quarter-wave radiator.
SUMMARY OF THE INVENTION
An antenna device of the above mentioned type according to the invention meets the demands for small antenna size, antenna function during extension and retraction as well as simple and durable design. The invention is characterized in that the helical antenna is of quarter-wave type and is coupled constantly via the feeding point to the circuits, in that the straight radiator is a quarter-wave radiator and in that the substantially antenna device is provided with a switching device, which couples via the feeding point the quarter-wave radiator to the circuits in parallel with the helical antenna when th
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patent: 5262792 (1993-11-01), Egashira
patent: 5317325 (1994-05-01), Bottomley
patent: 5446469 (1995-08-01), Makino
patent: 5479178 (1995-12-01), Ha
Allgon AB
Wimer Michael C.
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