Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
1999-09-22
2001-09-11
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S895000
Reexamination Certificate
active
06288681
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an antenna for transmitting and receiving radio frequency signals; and, more particularly, to a dual-band antenna for mobile telecommunication units, capable of operating in two frequency bands.
DESCRIPTION OF THE PRIOR ART
Nowadays, a variety of mobile telecommunication services are being or in the process of being commercially offered in all over the world. While some of these mobile telecommunication services utilize the same frequency band by employing a separate modulating system, majority of these mobile telecommunication services in general utilize different frequency bands from each other as exemplified by the cellular system and the personal communication system(PCS), the cellular system and the PCS system utilizing a frequency band of 824 to 894 MHz and 1.75 to 1.87 GHz, respectively.
A retractable antenna, in which a monopole antenna and a helical antenna are joined to each other and which is contractibly mounted on an upper portion of a mobile phone unit, is most widely used.
When the retractable antenna is extended out from the mobile unit, the monopole antenna operates independently or together with the helical antenna to transmit and receive a signal of a desired frequency band. When it is contracted in the mobile unit, only the helical antenna operates.
This retractable antenna, while suitable for operating only in one frequency band, is unsuitable for use in two or more different mobile telecommunication services, each telecommunication service operating in a different frequency band, while maintaining a desired radiation pattern. The reasons are as follows: Firstly, in order to make it possible for the antenna to operate at the frequency bands of both of the cellular system and the PCS, a complex matching circuit must be realized, matching a part or all of the bands, since a bandwidth between the cellular system and the PCS is in the neighborhood of 1 GHz; secondly, it is difficult to use one antenna for two different frequency bands since the central frequency of one mobile telecommunication frequency band is not a multiple of the harmonic component of that of the other mobile telecommunication frequency band; and thirdly, even if the antenna has been matched for use in two or more frequency bands, it is often difficult to realize a desired radiation pattern with the antenna at each of the frequency bands. In other words, in order to be serviced by a mobile telecommunication service, it is desirable for the customer to have a mobile phone unit designed for that particular frequency band thereof.
Therefore, in order to alleviate such a problem, a mobile phone unit, and hence, the parts therefor, capable of being used in mobile telecommunication services operating at different frequency bands, is desired.
There is shown in
FIG. 1
a conventional dual-band helical antenna which operates in two frequency bands. As shown, the dual-band helical antenna includes a support
120
made of insulating materials and coils
130
and
140
wound on an upper port
100
and a lower part
110
of the support
120
, respectively, thereby forming two helical antennas. The helical antennas are designed to have different resonance frequencies, respectively. Further, an inner portion of the support
120
is provided with a coaxial line. At this time, a winding number and a length of each of the coils wound on two helical antenna and a distance between the coils thereon, etc, are different for one another in such a way that each of the helical antennas is provided with a different resonance frequency.
Therefore, when a voltage is applied through a coaxial line in the support
120
, two helical antennas resonate at two different frequency bands, respectively.
However, the above described antenna has a shortcoming in that since the helical antenna is divided into the upper part and the lower part of the support, it is rather bulky and hence occupies a large space in the mobile phone unit, thereby posing an obstacle to current trend in mobile phone design of downsizing, i.e., to make the phone as light and as small as possible.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of the invention to provide a dual-band antenna for mobile telecommunication units capable of operating in two frequency bands.
Another object of the present invention is to provide a dual-band antenna for mobile communication units which is small in size.
In accordance with one aspect of the present invention, there is provided a dual-band antenna for mobile communication units comprising a support made of insulating materials; a first helical conductor wound on the support and having a first resonance frequency; a second helical conductor wound on the support and having a second resonance frequency, the second helical conductor being separated from the first helical conductor; and a coaxial feeder connected to an end of each of the helical conductors and for applying a voltage thereto.
REFERENCES:
patent: 4442438 (1984-04-01), Siwiak et al.
patent: 5708448 (1998-01-01), Wallace
patent: 5861859 (1999-01-01), Kanayama
patent: 5990848 (1999-11-01), Annamaa et al.
patent: 6018321 (2000-01-01), Simmons et al.
patent: 6023251 (2000-02-01), Koo et al.
patent: 6031493 (2000-02-01), Tsuda et al.
patent: 6054966 (2000-04-01), Haapala
patent: 6075488 (2000-06-01), Hope
Kim Jong Kyu
Park In Shig
Seo Ho Seok
Korean Electronics Technology Institute
Rosenman & Colin LLP
Vo Tuyet T.
Wong Don
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