Wave transmission lines and networks – Long line elements and components – Waveguide elements and components
Reexamination Certificate
1998-04-03
2001-01-09
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Long line elements and components
Waveguide elements and components
C333S248000
Reexamination Certificate
active
06172583
ABSTRACT:
BACKGROUND AND FIELD OF THE INVENTION
The present invention relates to the art of waveguides and, more particularly, to improved means for interconnecting a plurality of waveguide sections. The waveguide system is suitable for use over a wide UHF frequency band with either analog, NTSC, television signals or digital, DTV, television signals.
DESCRIPTION OF THE PRIOR ART
Waveguide systems are known in the art for efficiently transmitting RF energy from a transmitter to a broadcasting antenna located on the top of a tower. Such a tower may have a height on the order of 1,000 feet, requiring a vertical waveguide of the same length. The antenna located on the top of the tower may have a length on the order of 50 feet. Such an arrangement is disclosed in the United States Patent to Niekamp, et al. 4,894,625. That patent discloses a waveguide system including a lower horizontally extending waveguide which extends from a coaxial cable connection at an RF transmitter to a vertical waveguide which extends vertically for a length corresponding to that of the height of a tower and, thence, to a horizontally extending waveguide at the top of the tower which, in turn, feeds RF energy to the vertically extending antenna. The horizontal and vertical waveguide portions of this waveguide antenna system, as described in the Niekamp patent, are of rectangular cross section. The vertical waveguide being of rectangular cross section and being of approximately 1,000 feet, represents a substantial wind load. This wind load may be reduced by a vertical waveguide which is circular in cross section.
One form of circular waveguide known in the art has been described as a lunar waveguide. Such a waveguide has advantages over a simple circular shaped waveguide because it may have a smaller diameter for the same frequency of operation and, hence, provides a reduction in wind load. Such a lunar waveguide is illustrated in prior art such as L. J. Chu U.S. Pat. No. 2,477,510 and to S. A. Schelkunoff U.S. Pat. No. 2,199,083 and in the Niekamp patent, supra.
In addition to low wind load, such a lunar waveguide may be employed in a single size to cover the entire UHF frequency band (from approximately 470 MHz to 806 MHz). Consequently, such a waveguide may be employed in transmitting multiple digital television signals (DTV) as well as multiple analog television signals (NTSC) or combinations of each.
As noted in the Niekamp patent, supra, such a lunar waveguide may be considered as an elongated circular wrapped rectangular waveguide having an elongated metallic annular wall having an upper end and a lower end. A partition member, known as a septum, extends radially inward from the annular wall. The inner edge of the septum may be rounded somewhat and is referred to as a ridge. This ridge may be located near the central or longitudinal axis of the annular wall and extends along the septum longitudinally for a length corresponding with that of the annular wall.
If such a lunar waveguide is employed as the vertical waveguide portion, it may extend upwardly within a tower for a distance on the order of 1,000 feet. The 1,000 foot vertical waveguide is broken into a plurality of waveguide sections each being of a length of approximately 10 to 30 feet for ease of installation. Each waveguide section has opposing ends. The facing ends of adjoining sections may be secured together by means of annular extending flanges and fastening means, such as nuts and bolts. More specifically, at the end of each waveguide section an annular flange extends radially outward from the outer surface of the waveguide. These annular flanges are provided with an array of holes for receiving bolts. When adjoining sections are aligned end to end, the facing flanges are positioned so that the mounting holes are in registry and then the bolts and nuts are secured in place.
If the waveguide is constructed following the teachings of the prior art, such as the lunar waveguide antenna illustrated in the Niekamp patent, certain problems will arise. As is known, most of the current flow in a cylindrical waveguide takes place at the interior surface of the waveguide. This current will be intense along the inner surface of the ridge with the maximum taking place at the inner most area of the ridge within the waveguide. This will cause the metal in this area of the ridge to heat up at a greater temperature than that at other areas spaced further away from the center of the waveguide. The bolts and nuts restrain the outer wall and this heating causes the metal of the lip to deform somewhat. Later, as the RF power is reduced or turned off, the ridge will cool causing a gap to take place at the inner most narrow contact surface area of the adjoining ridges. When RF power is returned or increased, there will be a tendency for arcing to take place at these gaps between adjoining ridges. This arcing will decrease the efficiency of the waveguide and cause eventual failure of the joint between the adjoining ridges.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a waveguide system which includes a plurality of waveguide sections, each taking the form of an elongated longitudinally extending tubular member having a substantially circular shaped wall, in cross section, that coaxially surrounds a longitudinal axis. This circular wall has a longitudinal trough portion which extends radially inward toward the longitudinal axis. The trough portion is defined by a pair of circumferentially spaced wall portions that extend inwardly and are joined together by a connecting wall portion. The wall portions together define a ridge having an inner surface on the interior side of the wall and an outer surface on the exterior side of the wall. Each waveguide section has opposing ends with each end having a longitudinally extending peripheral lip. At each end of a waveguide section an annular mounting flange extends essentially radially outward from the exterior side of the wall. A plurality of spaced apart fastening means interconnect the annular mounting flanges of adjoining waveguide sections in such a manner that at least one of the interconnecting means is located in the trough portion for securely fastening the sections together including the respective ridges defined by the trough portion.
REFERENCES:
patent: 2199083 (1940-04-01), Schelkunoff
patent: 2477510 (1949-07-01), Chu
patent: 2677111 (1954-04-01), Stahl et al.
patent: 3136965 (1964-06-01), Lunden
patent: 4144506 (1979-03-01), McCammon et al.
patent: 4894625 (1990-01-01), Niekamp et al.
patent: 76604 (1981-06-01), None
Riley et al, “Machined Two-Piece Microwave Waveguide”;U.S Statutory Invention Registration H 321; Aug. 4, 1987.*
Niekamp Rex Leonard
Smith Spencer J.
Lee Benny
Tarolli, Sundheim, Covell Tummino & Szabo L.L.P.
LandOfFree
Waveguide system having a trough and with inward extending... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Waveguide system having a trough and with inward extending..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Waveguide system having a trough and with inward extending... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2502325