Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
2000-02-24
2001-04-17
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S825000, C343S848000
Reexamination Certificate
active
06218992
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. Historically, monopole and dipole antennas have been employed in various radiotelephone applications, due to their simplicity, wideband response, broad radiation pattern, and low cost.
However, 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.
In addition, it is becoming desirable for radiotelephones to be able to operate within multiple frequency bands in order to utilize more than one communications system. For example, GSM (Global System for Mobile) is a digital mobile telephone system that operates from 880 MHz to 960 MHz. DCS (Digital Communications System) is a digital mobile telephone system that operates from 1710 MHz to 1880 MHz. The frequency bands allocated for cellular AMPS (Advanced Mobile Phone Service) and D-AMPS (Digital Advanced Mobile Phone Service) in North America are 824-894 MHz and 1850-1990 MHz, respectively. Since there are two different frequency bands for these systems, radiotelephone service subscribers who travel over service areas employing different frequency bands may need two separate antennas unless a dual-frequency antenna is used.
Inverted-F antennas are designed to fit within the confines of radiotelephones, particularly radiotelephones undergoing miniaturization. As is well known to those having skill in the art, inverted-F antennas typically include a linear (i.e., straight) conductive element that is maintained in spaced apart relationship with a ground plane. Examples of 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.
Conventional inverted-F antennas, by design, resonate within a narrow frequency band, as compared with other types of antennas, such as helices, monopoles and dipoles. In addition, conventional inverted-F antennas are typically large. Lumped elements can be used to match a smaller non-resonant antenna to an RF circuit. Unfortunately, such an antenna would be narrow band and the lumped elements would introduce additional losses in the overall transmitted/received signal, would take up circuit board space, and add to manufacturing costs.
High dielectric substrates are commonly used to decrease the physical size of an antenna. Unfortunately, the incorporation of higher dielectrics can reduce antenna bandwidth and may introduce additional signal losses. As such, a need exists for small, internal radiotelephone antennas that can operate within multiple frequency bands, including low frequency bands.
SUMMARY OF THE INVENTION
In view of the above discussion, the present invention can provide various configurations of compact, broadband inverted-F antennas for use within communications devices, such as radiotelephones. According to one embodiment, an inverted-F antenna has an elongated, meandering conductive element maintained in adjacent, spaced-apart relationship with a first ground plane, such as a printed circuit board. An elongated, meandering conductive element according to this embodiment, includes a set of spaced-apart, U-shaped undulations that extend towards the first ground plane. The U-shaped undulations capacitively couple to the first ground plane and allow the antenna to resonate at lower frequencies than a conventional inverted-F antenna.
According to another embodiment of the present invention, a second ground plane may be oriented in a direction transverse to the first ground plane so as to be positioned in adjacent, spaced-apart relationship with one or more of the U-shaped undulations. The one or more U-shaped undulations are capacitively coupled to the second ground plane, as well as to the first ground plane.
According to another embodiment of the present invention, one or more raised portions extend outwardly from a ground plane and capacitively couple to portions of an elongated conductive antenna element.
According to another embodiment of the present invention, one or more inductive elements may be electrically connected to an elongated conductive element. An inductive element may comprise helical turns formed in an elongated conductive element or one or more electronic components that serve an inductive function.
Antennas according to the present invention may be particularly well suited for use within a variety of communications systems utilizing different frequency bands. Furthermore, because of their small size, antennas according to the present invention may be easily incorporated within small communications devices. In addition, antenna structures 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: 5007105 (1991-04-01), Kudoh et al.
patent: 5420599 (1995-05-01), Erkocevic
patent: 5668560 (1997-09-01), Evans et al.
patent: 5926139 (1999-07-01), Korisch
patent: 5966097 (1999-10-01), Fukasawa et al.
patent: 6005524 (1999-12-01), Hayes et al.
patent: 6130650 (2000-10-01), Curtis et al.
Ali Mohammod
Hayes Gerard James
Sadler Robert A.
Ericsson Inc.
Le Hoang-anh
Myers Bigel & Sibley & Sajovec
Nguyen Hoang
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