Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-06-01
2001-05-01
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S702000, C343S725000
Reexamination Certificate
active
06225951
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to antennas, and more particularly to antennas used with wireless communications devices.
BACKGROUND OF THE INVENTION
Radiotelephones generally refer to communications terminals which provide a wireless communications link to one or more other communications terminals. Radiotelephones may be used in a variety of different applications, including cellular telephone, land-mobile (e.g., police and fire departments), and satellite communications systems. Radiotelephones typically include an antenna for transmitting and/or receiving wireless communications signals.
Radiotelephones and other wireless communications devices are undergoing miniaturization. Indeed, many contemporary radiotelephones are less than 11 centimeters in length. As a result, there is increasing interest in small antennas that can be utilized as internally-mounted antennas for radiotelephones. Inverted-F antennas may be well suited for use within the confines of radiotelephones, particularly radiotelephones undergoing miniaturization. As is well known to those having skill in the art, conventional inverted-F antennas include a conductive element that is maintained in spaced apart relationship with a ground plane. Examples of conventional inverted-F antennas are described in U.S. Pat. Nos. 5,684,492 and 5,434,579 which are incorporated herein by reference in their entirety.
In addition, it may be desirable for radiotelephones to operate within multiple frequency bands in order to utilize more than one communications system. For example, GSM (Global System for Mobile communication) is a digital mobile telephone system that typically operates at a low frequency band, such as between 880 MHz and 960 MHz. DCS (Digital Communications System) is a digital mobile telephone system that typically operates at high frequency bands, such as between 1710 MHz and 1880 MHz. The frequency bands allocated in North America are 824-894 MHz for Advanced Mobile Phone Service (AMPS) and 1850-1990 MHz for Personal Communication Services (PCS). Accordingly, internal antennas, such as inverted-F antennas are being developed for operation within multiple frequency bands.
There is also interest in utilizing retractable antennas that can be extended from communications devices, such as radiotelephones. Retractable antennas may enhance signal transmission and reception, particularly in communications devices utilizing code-division multiple access (CDMA) wireless telephone transmission technologies. Unfortunately, communications devices that utilize both internal antennas and retractable antennas may require complex switching schemes which, in turn, may increase manufacturing costs and may present reliability concerns.
SUMMARY OF THE INVENTION
In view of the above discussion, antenna systems for use within wireless communication devices such as radiotelephones are provided. An antenna system according to an embodiment of the present invention includes a multi-frequency band antenna disposed within a housing of a communications device, such as a radiotelephone. The multi-frequency band antenna is electrically connected with a transceiver within the housing (or with a receiver and/or a transmitter within the housing). An elongated antenna member is movably mounted within the housing and is extendible from the housing so as to have an extended position and a retracted position.
The elongated antenna member includes an elongated conductive element that is capacitively coupled with the multi-frequency band antenna when the elongated antenna member is in the extended position. The multi-frequency band antenna is electrically isolated from the elongated conductive element when the elongated antenna member is in the retracted position.
The multi-frequency band antenna is configured to resonate within a first (i.e., low) frequency band having a first central frequency and within a second (i.e., high) frequency band having a second central frequency, wherein the second central frequency is greater than the first central frequency. When the elongated antenna member is in an extended position, the elongated conductive element is configured to resonate as a half-wave monopole antenna when the multi-frequency band antenna resonates within the first frequency band. Also, when the elongated antenna member is in an extended position, the elongated conductive element is configured to resonate as a full-wave monopole antenna when the multi-frequency band antenna resonates within the second frequency band.
Antenna systems according to the present invention may be particularly well suited for use within a variety of communications systems utilizing different frequency bands. Furthermore, the combination of an internal multi-frequency band antenna and a retractable antenna member according to the present invention may not require complex switching mechanisms. In addition, antenna systems according to the present invention may not require additional impedance matching networks, which may save internal radiotelephone space and which may lead to manufacturing cost savings.
REFERENCES:
patent: 5434579 (1995-07-01), Kagoshima et al.
patent: 5684492 (1997-11-01), Kagoshima et al.
patent: 5777586 (1998-07-01), Luxon et al.
patent: 5812097 (1998-09-01), Maldonado
patent: 5952975 (1999-09-01), Pedersen et al.
patent: 6075489 (2000-06-01), Sullivan
patent: 6097339 (2000-08-01), Filipovic et al.
patent: 6137998 (2000-10-01), Holshouser et al.
Holshouser Howard E.
Sanford Gary G.
Myers Bigel & Sibley & Sajovec
Phan Tho
Telefonaktiebolaget L.M. Ericsson
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