Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
2001-04-11
2002-09-10
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S829000, C343S846000
Reexamination Certificate
active
06448933
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains generally to the field of antennas and antenna systems for wireless communication devices (WCD). In particular, the present invention relates to a PIFA-edge antenna and an omnidirectional diversity antenna system which exhibit improved wireless data transmission and reception for portable wireless communications devices, such as “laptop” computers, coupled to a computer network such as a wireless local area network (LAN).
BACKGROUND OF THE INVENTION
Prior art wireless communication devices have constantly strived toward improved performance while following the continuing trend toward lower cost, and ever more compact antenna designs. In wireless LAN data transfer operations, loss of signal strength, interruptions in a data transfer, and the well known deleterious effects of signal interference, including phase cancellation and polarization rotation due to multiple surfaces reflecting RF signals, all present potential sources of error during data transfer which must be reduced if not eliminated altogether so that the wireless LAN exhibits a level of stability and error-free operation approaching that of known hard-wired LAN computing and communication environments.
One related approach to the significant problem of multiple surfaces reflecting RF signals in an office environment (known as multipath propagation interference) is disclosed in U.S. Pat. No. 5,677,698 entitled, “Slot Antenna Arrangement for Portable Personal Computers,” which issued on Oct. 14, 1997 to Snowdon. This related approach discloses two orthogonal slot antennas on the rear surface of a laptop computer that provides a modicum of polarization diversity for vertical and horizontal polarized RF signals only when the cover, or lid, of a laptop computer is oriented in the raised position. Thus, any advantages provided by this related antenna system only apply during the brief amount of time over the operating life of laptop computers outfitted with the antenna system disclosed that the cover is open. Thus, there exists in the related art a known obstacle to reliable operation of a wireless LAN system; namely, multipath interference propagation effects.
Local area networks (LAN) are used in the wireless transmission and reception of digitally-formatted data between sites within a building, between buildings, or between outdoor sites, using transceivers operating at frequencies in the range 2.4-2.5 GHz., 5.2-5.8 GHz., and others. Antennas operating over these frequency bands are required for the transceivers in LAN devices. A LAN structure permits many computerized devices to communicate with each other and/or with other computerized devices associated with the LAN. These other computerized devices may comprise such things as computer servers linked by optical or traditional electrically conducting conduit(s) to remote locations via a global computer system (e.g., the so-called internet or world wide web) as well as portable computers and personal digital assistants locally coupled to the LAN. In addition, peripheral computer equipment are often electronically coupled to the LAN either directly with conduit or using wireless network technology (e.g., RF transceivers). These peripheral devices typically include printing equipment, scanning equipment, photocopy equipment, facsimile transmission equipment, and the like. Individual stations, or nodes, of a LAN may be randomly positioned relative the other stations in the LAN without regard to sources of multipath propagation interference. Thus, as exhibited in the prior art, a need exists to provide continuous, reliable access to all the devices coupled to a wireless LAN including the need for simple, low cost, and effective antenna systems to combat the ever present effects of multipath propagation interference. Accordingly, continuous improvement in the operation and packaging of omnidirectional antenna assemblies enhance operational performance of a wireless LAN and are desirable for transceiver units disposed in computerized devices coupled to a wireless LAN. Unfortunately, a significant drawback of omnidirectional antenna designs is the susceptibility to multipath propagation interference which reduces RF signal strength by phase cancellation, often resulting in unacceptable errors during data transfer operation when digital information is being transferred over a wireless LAN.
In many wireless systems it is desirable to employ some form of antenna diversity to combat multipath effects in the communication system. The antenna diversity can be accomplished via several approaches, as known and used in the prior art; namely, frequency diversity, time diversity, spatial diversity, and polarization diversity.
Frequency diversity refers to a technique whereby an antenna system rapidly alternates among several different frequencies within a desired operating band of frequencies to reduce multipath propagation interference by simply spreading data being transferred in a wireless LAN over discrete portions of a usable frequency bandwidth which naturally avoids interference between diverse frequencies.
Time diversity refers to a technique whereby radio-frequency (RF) data transmission and receipt are timed to occur when only a single signal is being transmitted or/or received at a time over a wireless LAN, thereby simply avoiding the potential for plural RF data signals from interfering with each other by carefully controlling each transmission and reception operation.
Spatial diversity refers to a technique whereby two or more antennas are strategically placed at physically different locations to reduce multipath propagation interference during data transfer transmission and receipt.
Polarization diversity refers to a technique whereby data transmission and data receipt are provided at a common frequency but having distinct signal polarization such as vertical polarization, horizontal polarization, or polarization upon a pre-selected azimuth (expressed with values having a magnitude between 0 degrees and +/−90 degrees).
Many prior art systems use a pair of patch antennas to form a spatially diverse antenna configuration. Such an antenna may be formed on a resin-based, ceramic, or other suitable dielectric substrate. A typical patch antenna includes the substrate, an electrically conducting patch member formed on one surface of the substrate, and a ground plane disposed on the opposing surface of the substrate. A via aperture, or other electrically conducting feed pathway, electrically couples the electrically conducting patch to an RF receiver/transmitter (i.e., transceiver). The use of high dielectric constant materials for the substrate results in an antenna which is physically small, especially when a ceramic substrate is utilized although such ceramic-based substrate patch antennas tend to be relatively expensive. Furthermore, connecting the antenna to a low cost circuit board often requires special connectors and cabling, which add cost to the system.
SUMMARY OF THE INVENTION
The present invention teaches, discloses and enables those of skill in the art of wireless communication device (WCD) design and implementation to practice a PIFA-edge antenna and a novel diversity antenna system operable over a wide range of conditions and exhibiting superior performance as part of a wireless LAN environment. The antenna system of the present invention provides reliable and consistent omnidirectional performance while reducing the deleterious effects of multipath propagation interference which is often present in office environments having a variety of surfaces that passively reflect a broad range of frequencies useful within the broad spectrum the electromagnetic radiation (e.g., radio frequency or “RF”) for transmitting analog or digital voice, data, images, and the like (herein “data”) typically transmitted across the typical LAN.
In particular, the present invention teaches a polarization and spatial diversity antenna system suitable for use with a laptop computer, hand-held device such as a so-called persona
Hill Robert
Trumbull Thomas
Fulbright & Jaworski L.L.P.
Nguyen Hoang
Tyco Electronics Logisitics AG
Wong Don
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