Communications: radio wave antennas – Antennas – Slot type
Reexamination Certificate
1997-09-12
2001-10-16
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Slot type
Reexamination Certificate
active
06304227
ABSTRACT:
BACKGROUND
The invention relates to a slot antenna.
Wireless radio systems are used in remote metering (e.g., utility metering) applications in which electronic components must be placed in spaces not originally designed for such components. In water metering applications, for example, a transceiver and an antenna typically must fit within a small underground housing originally intended only for a mechanical water meter. In such an application, antenna performance is impeded because the antenna must transmit through the walls and lid of the underground housing and through the ground itself.
SUMMARY
In one aspect, the invention features an antenna having two annular conductive elements separated by a slot, and a third conductive element connecting the annular conductive elements together at at least one end of the slot. In some embodiments the conductive elements may be of similar diameters; they may be of different heights; they may consist of conductive tape or conductive wire; they may be less than two inches in diameter. The antenna also may include a dielectric insulator, and it may include a feed point to which a feed element may connect. The antenna also may be less than 0.5″ in total height.
In another aspect, the invention features an antenna having two generally parallel conductive elements of different heights separated by a slot, and a third conductive element connecting the conductive members together at at least one end of the slot. In some embodiments, the generally parallel conductive members may extend along a dielectric material; and the third conductive element may connect the generally parallel conductive elements together at two ends of the slot.
In other aspects, the invention features methods of making an antenna. One method includes providing a generally straight slot antenna, and securing two ends of the generally straight slot antenna to form an annular slot structure. Another method includes positioning two annular conductive elements to form a slot between them, and connecting a third conductive element to each of the annular conductive elements to form at least one end of the slot. Another method includes positioning two conductive elements of similar lengths and of different widths to form a slot between them, and connecting a third conductive element between the other two conductive elements to form at least one end of the slot. Still another method includes providing a stamp having two annular conductive elements in the same plane connected together by a third conductive element, and bending the stamp so that the two annular conductive elements are no longer in the same plane but are essentially parallel to each other.
In another aspect, the invention features a stamp for use in forming an antenna. The stamp includes two annular conductive elements connected by a third conductive element, all three of which lie in substantially the same plane.
Advantages of the invention may include one or more of the following. An antenna may be made small enough to fit entirely or partially within a pre-drilled hole formed in a standard underground housing lid. The antenna also may be housed within a protective structure that passes through such a pre-drilled hole and that positions the antenna above the ground.
Vertical polarization of an antenna may be achieved with a very small vertical dimension (e.g., 0.5″ or less). A simple slot structure may be used to create an antenna having an omnidirectional radiation pattern. The conductors used to form the slot structure may have different heights (an “offset slot” structure), which allows, e.g., more clearance between the radiating slot and an underground housing lid. Furthermore, the antenna may be fed at a position offset from the center of the slot, which provides a simple way to match the input impedance of the antenna with the characteristic impedance of the conductor feeding the antenna. The antenna may include a dielectric other than air to reduce the wavelength of a transmitted or received signal in the antenna, which in turn allows, e.g., reduction of the slot length and therefore the antenna's overall dimensions.
The antenna may be fabricated easily and inexpensively from, e.g., a conventional straight slot antenna, a die-cut stamp, or conductive wires or strips.
Other advantages of the invention will become apparent from the following description and from the claims.
REFERENCES:
patent: 2501430 (1950-03-01), Alford
patent: 2611865 (1952-09-01), Alford
patent: 5155493 (1992-10-01), Thursby et al.
patent: 5202697 (1993-04-01), Bonebright et al.
patent: 5621419 (1997-04-01), Meek et al.
patent: 5917454 (1999-06-01), Hill et al.
patent: 2 291 272 A (1996-01-01), None
Hill Robert J.
Thomas David L.
Fish & Richardson P.C.
Schlumberger Resource Management Services, Inc.
Wimer Michael C.
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