Communications: radio wave antennas – Antennas – Spiral or helical type
Reexamination Certificate
1999-11-03
2001-06-19
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Spiral or helical type
C343S702000, C343S876000, C343S906000
Reexamination Certificate
active
06249262
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to antennas for radio communication devices. in particular, this invention relates to, but is not necessarily limited to, a switchable antenna for a radio communication device.
BACKGROUND OF THE INVENTION
Antennas for radio communication devices, such as two-way radios, are known in the art to transceive electromagnetic waves that propagate through space. The type of electromagnetic waves transceived by these two-way radios is radiofrequency (RF) waves that serve as carriers of information. When encoded with information, such carriers are commonly referred to as RF signals.
Conventionally, circuitry of a two-way radio is designed to process RF signals transceived on one or more frequencies within a band of the RF spectrum. For example, the very high frequency (VHF) band for radio communications ranges from 30 MHz to 300 MHz. Accordingly, two-way radios in a VHF radio communication system transceive RF signals using the one or more frequencies within the VHF band.
As is known in the art, the circuitry described in the above needs to couple to an antenna to transceive RF signals. The length of such an antenna depends on wavelength of the RF signals and this wavelength is related to the frequency of the RF signals. Generally, a lower frequency RF signal requires an antenna that is longer than an antenna for a higher frequency RF signal. Hence, there is a problem when a two-way radio has to transceive RF signals varying within a bandwidth that is too wide for an antenna with a fixed length. U.S. Pat. No. 4,772,895 describes an antenna having two helical elements operably coupled to increase the antenna's bandwidth and thereby alleviate this problem. However, such an antenna also has a fixed length that cannot be easily modified to transceive RF signals not within its bandwidth. Therefore, there is a need for an antenna that can transceive RF signals varying within a bandwidth and also be easily modified for RF signals not within this bandwidth.
SUMMARY OF THE INVENTION
According to one aspect of the invention, there is provided a switchable antenna for a radio communication device comprising:
a base antenna assembly comprising a housing with a base antenna;
a secondary antenna assembly comprising a housing with a secondary antenna, said secondary antenna assembly being mounted to said base antenna assembly; and
a switch for selectively electrically coupling adjacent ends of said base antenna and said secondary antenna.
REFERENCES:
patent: 4772895 (1988-09-01), Garay et al.
patent: 6005523 (1999-12-01), Rudisill
patent: 6069592 (2000-05-01), Wass
Khoo Peng How
Lee Chye Lin
Lim Giap Hong
Seow Boon Eu
Dorinski Dale W.
Motorola Inc.
Nguyen Hoang
Wong Don
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