Transmission line filter
First Claim
1. A coaxial filter having two ends for insertion between transmission lines comprising an inner conductor, at least one conductive outer sheath, first insulation means separating said inner conductor from said outer conductive sheath, a section of conductive line extending longitudinally within said first insulation means laterally spaced apart from said inner conductor and electrically coupled thereto, second insulating means covering said outer sheath and coaxial terminal connectors at the opposite ends of said coaxial filter to permit said coaxial filter to be interconnected between the transmission lines, one of said terminal connectors serving as the filter output and wherein the length of the section of conductive line is approximately λ
- /4, wherein λ
is the wavelength of the signal to be filtered by the coaxial filter.
1 Assignment
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Accused Products
Abstract
A transmission line filter having two conductors with insulation therebetween. A third conductor of a length related to the wavelength of the signal being filtered is spaced from one of the conductors but electrically coupled thereto. Terminal connectors are located at each end of the filter to interconnect the filter into the regular transmission line of the system in which the filter is being used. The filter can be formed of coaxial cable and can be a single frequency filter a multiple frequency filter of a bandpass filter arrangement. In a filter trap arrangement, one end of the third conductor is conductively connected to the other of the main conductors. A method for making a coaxial embodiment of the filter is achieved by initially placing the main line inner conductor together with the third conductor within the dielectric and subsequently chopping out sections of the third conductor line to adjust its length to the wavelength of the signal being filtered and to provide electrical connection to the outer shield which is subsequently placed over the dielectric. The filter provides unique application in controlling programs sent to subscribers in cable TV systems.
87 Citations
25 Claims
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1. A coaxial filter having two ends for insertion between transmission lines comprising an inner conductor, at least one conductive outer sheath, first insulation means separating said inner conductor from said outer conductive sheath, a section of conductive line extending longitudinally within said first insulation means laterally spaced apart from said inner conductor and electrically coupled thereto, second insulating means covering said outer sheath and coaxial terminal connectors at the opposite ends of said coaxial filter to permit said coaxial filter to be interconnected between the transmission lines, one of said terminal connectors serving as the filter output and wherein the length of the section of conductive line is approximately λ
- /4, wherein λ
is the wavelength of the signal to be filtered by the coaxial filter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
- /4, wherein λ
- 13. A multiaxial filter comprising an inner conductor, at least two outer conductive sheaths, first insulation means separating said inner conductor from said first outer conductive sheath, second insulation means separating said first outer conductive sheath from said second outer conductive sheath, both said outer sheaths having a colinear circumferential groove therein, said second sheath having a second circumferential groove therein spaced axially from said first groove, first interconnection means electrically connecting said first and second conductive sheaths within said first groove, and second interconnecting means electrically connecting said first and second outer conductive sheaths in said second groove, thereby effectively forming a folded over short circuit transmission line section onto said first conductive sheath.
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17. In a cable TV system, including a main cable line, a directional tap coupled to said main cable line and plurality of subscriber lines respectively coupled to said directional tap comprising:
a switchable trap serially connected in at least one of said subscriber lines, said switchable trap comprising a coaxial filter including an inner conductor, at least one outer conductive sheath, first insulation means separating said inner conductor from said outer conductive sheath, a section of conductive line extending longitudinally within said first insulation means laterally spaced apart from said inner conductor and electrically coupled thereto, second insulating means covering said outer conductive sheath means for conductively interconnecting one end of said section of conductive line to said outer sheath, and a controllable switch electrically connected within said switchable trap to selectively apply and remove the filtering on said subscriber line to thereby open and close said subscriber line. - View Dependent Claims (18, 19, 20)
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21. A method of making a coaxial filter comprising the steps of:
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a. extruding a dielectric over two accurately spaced apart longitudinal conductive lines; b. chopping out small sections of the dielectric at spaced intervals; c. cutting one conductive line at each chopped out section; d. upwardly bending a portion of said one conductive line at each chopped out section to protrude above the dielectric e. covering the dielectric with a conductive shield permitting said portions to protrude through said conductive shield; f. folding the protruding portions of the conductive line onto the conductive shield; g. electrically connecting the folded over portion onto the conductive shield; and h. placing an insulating covering over the conductive shield. - View Dependent Claims (22, 23, 24, 25)
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Specification