Communications: radio wave antennas – Antennas – Spiral or helical type
Reexamination Certificate
1999-06-10
2001-05-29
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Spiral or helical type
C343S702000, C343S901000
Reexamination Certificate
active
06239768
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dual band antenna system, more particularly to such an antenna system for use in a portable handheld communication device and which is operable both in an extended and retracted state.
2. Prior Art of the Invention
Portable handheld communication devices, such as a cordless phone, a cellular phone and a PCS (Personal Communications Service) phone, have become increasingly popular. The portable handheld communication devices should be compact and lightweight. It is known to design such a device with a whip antenna that is selectively retracted and extended. The user wishes to keep the device turned on so that a call can be received and the user be notified of such receipt, but at the same time retract the antenna into the case of the device so that the device can be placed in a pocket or purse. Therefore, there is a need for an antenna system operable in dual bands.
A retractable antenna system in accordance with known prior art comprises a ¼ wavelength whip and a helical antenna placed on top of the whip. The conventional antenna is illustrated in
FIGS. 1A and 1B
.
Referring to
FIG. 1A and 1B
, a sleeve
14
is mounted to the upper surface of an case
13
. There is a distance between a ¼ wavelength whip
11
and a ¼ wavelength helical
12
, thereby not affecting each other. This antenna system operates only as a ¼ wavelength helical antenna when the whip antenna is retracted into the case of the device, and operate only as a ¼ wavelength whip antenna when the whip antenna is extended out of the case.
When the antenna system is retracted into the case as illustrated in
FIG. 1A
, only helical section
12
operates. When the antenna system is extended out of the case as illustrated in
FIG. 1B
, a stopper
15
connected to one end of a whip section
11
is caught in the sleeve
14
and only the whip section
11
operates. The helical antenna
12
is electrically separated from the sleeve
14
. This antenna system has problems in that the bandwidth of the helical antenna is narrow and radiation efficiency of the antenna is low. The connection point between the whip
11
and the helical
12
is weak, thereby easily breaking. Also, the antenna uses only single band.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide an antenna system in which the bandwidth of the helical antenna is wide and the radiation efficiency thereof is improved.
Another object of the present invention is to provide an antenna system operating in the frequency band of 800 MHz and 1.8 GHz.
In accordance with an aspect of the invention, there is provided a dual band retractable antenna system, comprising a helical antenna for operating at stand-by mode, the helical having ¼ wavelength; a whip antenna, which penetrates the helical, for operating at busy mode, the whip having ¼ wavelength; a stopper for catching the whip when the antenna is extended out; a sleeve mounted to one end of the helical, for operating as a feed point when the whip is extended out; a capacitive coupling means placed between the helical and the sleeve, for capacitively coupling the helical to the sleeve; and a matching circuit coupled between the sleeve and the antenna system, so that the antenna system operates for both frequency bands.
REFERENCES:
patent: 5661496 (1997-08-01), Baek et al.
patent: 5754141 (1998-05-01), Thompson et al.
patent: 5969684 (1999-10-01), Oh et al.
patent: 6054958 (2000-04-01), Holshouser et al.
Cho Choong Ki
Lee Kyung Min
Oh Jeong Kun
Park Duk Jae
Park Jung Mi
Ace Technology
Le Hoang-anh
Lowe Hauptman & Gilman & Berner LLP
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