Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
1999-10-15
2001-09-18
Phan, T. (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S7000MS, C343S828000, C343S873000
Reexamination Certificate
active
06292144
ABSTRACT:
FIELD OF THE INVENTION
The invention generally concerns portable communication antennas. The invention particularly concerns antennas for portable communication devices.
BACKGROUND OF THE INVENTION
One trend is toward the expansion of capabilities of portable communication devices. This includes the merger of formerly separate devices, such as cell phones and organizers, and the expansion of the capabilities of individual devices, such as the use of a single cell phone for more than one band of operation, e.g., AMPS and PCS bands, or the addition of voice communications, paging or other functions to phones, data terminals and other portable communication devices. As the delivery of services to communication devices and the capability of communication devices increases, the need for bandwidth of operation similarly increases. Voice communications may occur on one or more operational bands, E-mail communications on another, news information on yet another and so on.
A conflicting trend is the reduction in size of portable communication devices. A major impediment to the reduction in size is the need to include an antenna, typically in the form of a whip, helix or a combination of both, that has a length corresponding to a half or quarter of the wavelength of the operational frequency. Dual band operations typically require a switching between multiple radiators in such a whip/helix antenna structure. Expansion beyond two bands, if it can be accomplished at all, adds even more complexity. In addition, the general nature of an extendable whip with or without a helix requires the communication device to have a length which is equal or close to the length of the whip to permit its retraction and extension. The whip style antennas also suffer from reliability problems. They break, bend, and can wear from cycling, to the point where electrical contact to communication device circuits as intended becomes unreliable.
One solution to this problem has been the use of conformal patch antennas. These antennas obviate the need for an extendable whip, and in some forms can provide dual band operation. The general structure of the antenna is a patch area separated from a ground plane, generally referred to as a planar inverted F (PIFA) structure in the art. The difficulty with the patch style antenna is its size and shape. Patches in portable communication devices require a ground plane which extends slightly beyond the perimeter defined by the patch. This makes placement of the antenna, typically within the communication device, difficult to accommodate. The area of the patch is also likely to be blocked, at least partially, by a user's hand during operation.
Thus, there is a need for an improved conformal antenna for portable communication devices which meets the need for adequate radiation performance, is reliable, and does not add significantly to the dimensions of the portable device. Due to the increasing services offered by portable communication devices, such an improved antenna should be expandable to multiple bands, and should be capable of broad band operation. These and other needs are met or exceeded by the multiband antenna of the present invention.
SUMMARY OF THE INVENTION
The antenna of the present invention is a conformal antenna having an elongate radiator element grounded to a ground plane generally opposite the elongate radiator element, and driven by a feed connected to the elongate radiator element at a point between its connection to the ground plane and its open end. The elongate radiator element and ground plane are conformed with dielectric which, due to its wavelength shortening effect, reduces the required length of the elongate radiator element to less than a quarter wavelength. Conformed with dielectric, as used herein, means on or within the surface of the dielectric. The dielectric material with which the antenna is conformed and any additional dielectric material between the elongate radiator element and the ground plane is preferably low loss tangent material.
The elongate radiator element of the present antenna can be formed as a strip or wire. Its elongate nature and the overall design of the present invention permit simple expansion beyond a single band and simple broad banding operation through use of additional generally parallel elongate radiator elements. The additional elongate radiator elements may be commonly connected to a feed element, such as a microstrip disposed generally perpendicular to the elongate radiator elements, or separate feed elements to each elongate radiator are possible. The elongate radiator elements have different lengths for different bands. Any particular one of the elongate radiator elements is shorter than the quarter wavelength for the center frequency of its corresponding band of operation. Broad banding is obtained by multiple length elements stagger tuned, by their length, to closely staggered or slightly overlapping bands of operation.
The antenna is a suitable replacement for external whip antennas commonly used in portable communication devices such as cell phones and personal communication systems. It is preferably conformed with dielectric which conforms to a portion of an outer surface of the communication device, in a location which should be away from portions that are typically grasped in a user's hand. Such a location is feasible, in part, due to the small footprint of the antenna of the invention. In a multiband embodiment, despite close proximity of the multiple elongate radiator elements, only the elongate radiator element tuned by its length to the instantaneous operating frequency band will be active due to the substantial impedance mismatches of the remaining elements to the transmitter/receiver of the communication device.
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Taflove Allen
Vasilyeva Lena
Greer Burns & Crain Ltd.
Northwestern University
Phan T.
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