Line isolation and interference shielding for a shielded conductor system

• US 4,399,419 A
• Filed: 07/13/1981
• Issued: 08/16/1983
• Est. Priority Date: 03/20/1980
• Status: Expired due to Term

• Current Assignee: Zenith Radio Corporation (LG Corporation)
• Original Assignee: Zenith Radio Corporation (LG Corporation)
• Inventors: Dobrovolny, Pierre
• Primary Examiner(s): Nussbaum, Marvin L.
• Application Number:
  US06/282,824
• Time in Patent Office: 764 Days
• Field of Search: 333/12, 333/24 R, 333/24 C, 333/27, 333/167, 333/181, 333/182, 333/185, 333/202, 333/206, 333/245, 333/243, 333/248, 333/260, 339/143 R, 339/143 C, 339/147 R, 334/85, 455/50, 455/63, 455/128, 455/283, 455/286, 455/287, 455/296-298, 455/300-301
• US Class Current: 333/12
• CPC Class Codes: H01B 11/1895 Particular features or applications
• CPC Class Codes: H01P 1/202 Coaxial filters cascaded coaxial cavities H01P1/205
• CPC Class Codes: H01P 1/225 Coaxial attenuators H01P1/23 takes precedence

Abstract

A method and structure is disclosed for isolating the shield of a shielded conductor system from a low frequency power source to which the shield may be connected. In one embodiment, the isolation technique includes providing an interruption in the conductor'"'"'s shield and situating within the interruption dielectric and magnetically absorptive material so as to create at least a pair of capacitance across the interruption, and such that the capacitances are separated by magnetically absorptive material. In this manner, low frequency isolation is achieved and the field within the cable is shielded from ambient high frequency electromagnetic interference which could otherwise leak through the interruption into a desired high frequency signal path within the conductor. In other embodiments, at least some of the dielectric material forms part of a series resonator to improve attenuation of electromagnetic interference at low VHF frequencies.

Claims

1. A method of isolating the shield of a shielded conductor system from a low frequency power source to which the shield may be coupled, and for shielding the field within the conductor system from ambient high frequency electromagnetic interference, comprising:

providing an interruption in the shield; and

filling the interruption with dielectric and magnetically absorptive material selected and disposed to create a capacitive coupling across the interruption to isolate the shield and magnetic absorption within the interruption to absorb energy associated with the ambient electromagnetic interference.

2. A method as set forth in claim 1 including providing an inductance within the interruption for coacting with at least some of the dielectric material to form a resonator.

4. The method as set forth in claim 2 including situating within said interruption discrete elements of dielectric material and magnetically absorptive material in alternating sequence.

5. A method as set forth in claim 4 further including providing an inductance within the interruption for coacting with at least one element of dielectric material to provide a series resonant circuit at a selected television frequency.

6. A method as set forth in claim 5 wherein said one element of dielectric material has an outer conductive coating thereon, and wherein said inductance is formed by a conductive finger connected between the dielectric element'"'"'s conductive coating and the shield.

7. A method as set forth in claim 4 wherein the shield includes a relatively large diameter portion separated by the interruption from a relatively smaller diameter portion, such that the relatively large diameter portion overlaps the smaller diameter portion, and wherein the dielectric and magnetically absorptive elements are disposed between overlapping portions of the shield.

8. A method as set forth in claim 4 wherein said dielectric and magnetically absorptive elements are aligned coaxially within the shield'"'"'s interruption.

9. A method as set forth in claim 4 wherein the shield is interrupted with a pair of radial flanges, arranged vis-a-vis, and wherein said dielectric and magnetically absorptive elements are sandwiched between the flanges and concentrically arranged such that the alternating sequence is in a direction radial to the conductor system.

10. A method as set forth in claim 4 wherein the interruption is provided by separating the shield into two parts, turning the ends of the separated parts and interleaving the turned ends so as to provide a total of at least three spaces between the interleaved parts, and wherein magnetically absorptive material is disposed in one of said spaces, and dielectric material is disposed in two of said spaces on opposite sides of the magnetically absorptive material.

11. A method as set forth in claim 10 wherein said dielectric and magnetically absorptive elements are aligned coaxially in said interruption.

12. A method as set forth in claim 10 wherein said dielectric and magnetically absorptive elements are aligned radially with respect to the conductor system.

3. A method of isolating the shield of a shielded conductor system from a low frequency power source to which the shield may be coupled, and for shielding the field within the conductor system from ambient high frequency electromagnetic interference, comprising:

providing an interruption in the shield; and

situating within the interruption a series of dielectric elements separated by abutting magnetically absorptive material to create a capacitive coupling across the interruption to isolate the shield and magnetic absorption within the interruption to absorb energy associated with the ambient electromagnetic interference.

13. A method of providing A.C. line isolation between a shielded conductor system and a television tuner input adapted to receive television signals from the conductor system, and for shielding the desired high frequency field within the conductor system from ambient electromagnetic interference, comprising:

providing an interruption between an outer shield associated with the conductor system, and an outer conductor associated with the tuner input; and

disposing within the interruption a series of dielectric elements separated by abutting magnetically absorptive material to create a capacitive coupling across the interruption to isolate the shield and magnetic absorption within the interruption to absorb energy associated with the ambient electromagnetic interference.

14. A method as set forth in claim 13 wherein the interruption is established by providing an area of axial overlap between the outer conductor of the tuner input and the shield, and wherein the dielectric elements and magnetically absorptive material are disposed in said area of axial overlap.

15. A method as set forth in claim 14 wherein the outer conductor of the tuner input has a relatively large diameter and the shield associated with the conductor system has a relatively small diameter, and wherein the dielectric elements and magnetically absorptive material are disposed in an area of axial overlap between the relatively large diameter outer conductor and the relatively smaller diameter shield.

16. A method as set forth in claim 14, wherein said dielectric elements and magnetically absorptive material comprises at least two discrete elements of dielectric material separated by a discrete element of magnetically absorptive material.

17. A method of providing A.C. line isolation in a path coupling the shield of a shielded conductor to a conductor associated with the input of a television tuner, and for shielding the desired field within the shielded conductor from ambient electromagnetic interference, comprising:

providing an interruption in the path of coupling between the conductor associated with the tuner input and the shield; and

filling the interruption with dielectric and magnetically absorptive material so as to create a first capacitance which decouples the path at A.C. line frequencies and shunts a substantial portion of electromagnetic interference induced in the outer skin of the shield, a region of magnetic absorption for absorbing residual electromagnetic interference not shunted by said first capacitance, and a second capacitance to provide additional A.C. decoupling of said path and to couple the signal within the shielded conductor to the tuner input and away from the region of magnetic absorption.

18. In a system employing a shielded conductor which carries a desired high frequency signal, and whose shield is adpated to be coupled to a low frequency power source, an isolator for isolating the conductor'"'"'s shield from the low frequency power source and for shielding the desired field within the conductor from ambient high frequency electromagnetic interference, comprising:

means defining an interruption in the shield; and

magnetically absorptive material and dielectric material situated within the interruption such that said materials are closely adjacent each other, said materials being selected and disposed to create a capacitive coupling across the interruption to isolate the shield and magnetic absorption within the interruption to absorb energy associated with the ambient electromagnetic interference.

19. An isolator as set forth in claim 18 including an inductance within the interruption for coacting with at least some of the dielectric material to form a resonator.

20. In a system employing a shielded conductor which carries a desired high frequency signal, and whose shield is adapted to be coupled to a low frequency power source, an isolator for isolating the conductor'"'"'s shield from the low frequency power source and for shielding the desired field within the conductor from ambient high frequency electromagnetic interference, comprising:

means defining an interruption in the shield; and

a series of dielectric elements separated by magnetically absorptive material filling said interruption to create a capacitive coupling across the interruption to isolate the shield and magnetic absorption within the interruption to absorb energy associated with the ambient electromagnetic interference.

21. An isolator as set forth in claim 20 wherein discrete elements of dielectric material are disposed in said interruption in alternating sequence with one or more discrete elements of magnetically absorptive material.

22. An isolator as set forth in claim 21 wherein the dielectric and magnetically absorptive elements are disposed in an abutting relationship with each other.

23. An isolator as set forth in claim 21 further including an inductance within the interruption for coacting with at least one element of dielectric material to provide a series resonant circuit at a selected television frequency.

24. An isolator as set forth in claim 23 wherein said one element of dielectric material has an outer conductive coating thereon, and wherein said inductance includes a conductive finger connected between the dielectric element'"'"'s conductive coating and the shield.

25. An isolator as set forth in claim 21 wherein the shield includes a relatively large diameter portion separated by the interruption from a relatively smaller diameter portion, such that the relatively large diameter portion overlaps the smaller diameter portion, and wherein the dielectric and magnetically absorptive elements are disposed between overlapping portions of the shield.

26. An isolator as set forth in claim 21 wherein said dielectric and magnetically absorptive elements are aligned coaxially within the shield'"'"'s interruption.

27. An isolator as set forth in claim 21 wherein the shield is interrupted with a pair of radial flanges arranged vis-av-s, and wherein said dielectric and magnetically absorptive elements are sandwiched between the flanges and concentrically arranged such that the alternating sequence is in a direction radial to the cable.

28. An isolator as set forth in claim 21 wherein the interruption is provided by separating the shield into two parts, turning the ends and interleaving the turned ends of the separated parts so as to provide a total of at least three spaces between the interleaved parts, and wherein magnetically absorptive material is disposed in one of said spaces and dielectric material is disposed in two of said spaces on opposite sides of the magnetically absorptive material.

29. An isolator as set forth in claim 28 wherein said dielectric and magnetically absorptive elements are aligned coaxially within the interruption.

30. An isolator as set forth in claim 28 wherein said dielectric and magnetically absorptive elements are aligned radially with respect to the conductor.

31. In a television receiver having a tuner connected via a coupling path to at least the shield of a shielded conductor for receipt of a television signal carried by the conductor, an isolator for isolating the shield from A.C. line voltages which may be coupled to the tuner and for shielding the field within the conductor from ambient high frequency electromagnetic interference, comprising:

means defining an interruption in the coupling path; and

a series of dielectric elements separated by abutting magnetically absorptive material disposed in the interruption so as to create a capacitive coupling across the interruption to isolate the shield and magnetic absorption within the interruption to absorb energy associated with the ambient electromagnetic interference.

32. An isolator as set forth in claim 31, wherein discrete elements of dielectric material are disposed in said interruption in alternating sequence with one or more discrete elements of magnetically absorptive material.

33. An isolator as set forth in claim 32, wherein the tuner has a coaxial connection for coupling to the conductor, wherein said connection has an outer diameter greater than the outer diameter of the conductor for partly overlapping the conductor, and wherein the interruption is provided between the conductor'"'"'s shield and the overlapping portion of the tuner connection.

34. An isolator as set forth in claim 33, wherein the dielectric and magnetically absorptive elements are aligned coaxially within the interruption.

35. An isolator as set forth in claim 34 including an inductance within the interruption for coacting with at least one element of dielectric material to form a resonator at a selected television frequency.

36. In a television receiver having a tuner receiving an RF signal carried by a shielded conductor, an isolator for isolating the conductor'"'"'s shielded from A.C. line voltages which may be coupled to the tuner and for shielding the field within the shielded conductor from ambient high frequency electromagnetic interference, comprising:

shield means connected to the tuner and having a diameter which is larger than the diameter of the conductor'"'"'s shield, said shield means being disposed to coaxially overlap the shielded conductor; and

a pair of dielectric elements and a ferrite element disposed within said axial overlap, all said elements being disposed in abutting relationship with each other and aligned coaxially within the overlap.

37. In a system employing a shielded conductor which carries a desired high frequency signal and whose shield may be coupled to a low frequency power source, an isolator for isolating the conductor'"'"'s shield from the low frequency power source and for shielding the desired field within the conductor from ambient high frequency electromagnetic interference, comprising:

means defining an interruption in the shield; and

magnetically absorptive material and at least one resonator situated within the interruption.

38. An isolator as set forth in claim 37 wherein said resonator includes a dielecric element and distributed inductance associated therewith for establishing a condition of series resonance at selected television frequencies.

39. An isolator as set forth in claim 37 wherein the resonator includes dielectric material and an inductance coupled to the dielectric material.

40. An isolator as set forth in claim 39 wherein said dielectric material has an outer conductive coating, and wherein the inductance is coupled between the conductive coating and the shield.

41. An isolator as set forth in claim 40 wherein the inductance comprises a part of the shield which projects into the interruption.

42. An isolator as set forth in claim 41 wherein the dielectric material'"'"'s conductive coating is held from electrical contact with the shield except via the inductance.

43. An isolator as set forth in claim 42 wherein said dielectric and magnetically absorptive materials are discrete elements disposed around the conductor, and further including in the interruption at least one additional discrete dielectric element which does not function as a resonator.

44. An isolator as set forth in claim 43 wherein the magnetically absorptive and additional dielectric element are annular in shape and have substantially the same outer diameter, and wherein the dielectric element forming part of the resonator has a relatively smaller outer diameter to inhibit its conductive coating from contacting the shield.

45. An isolator as set forth in claim 43 wherein the magnetically absorptive element and all the dielectric elements are annular in shape and have substantially the same outer diameter, and wherein the shield is formed to avoid contact between itself and the dielectric element which forms part of the resonator.

46. In a television system having a tuner for receiving an RF signal from a shielded conductor, an isolator for isolating the conductor'"'"'s shield from low frequency power which may be coupled to the tuner and for shielding the RF field within the conductor from ambient high frequency electromagnetic interference, comprising:

conductive means coupled to the tuner and mated with the conductor'"'"'s shield so that an area of axial overlap occurs between the conductor'"'"'s shield and the conductive means;

at least first and second dielectric elements disposed in said area of axial overlap;

a magnetically absorptive element disposed between the first and second dielectric elements; and

an inductance associated with the first dielectric element to resonate with the first dielectric element at at least one selected television frequency.

47. An isolator as set forth in claim 46 wherein the dielectric elements abut the magnetically absorptive element.

48. An isolator as set forth in claim 46 wherein the first dielectric element has a conductive coating thereon, and wherein said inductance includes a conductive finger connected between the conductive coating and the conductive means.

49. An isolator as set forth in claim 48 wherein the conductive finger comprises a part of the conductive means, the dimensions of the finger and the properties of the first dielectric element being selected to establish series resonance at a frequency in the lower VHF television band.

50. An isolator as set forth in claim 48 wherein the conductive means and the first dielectric element are shaped to avoid electrical contact between the conductive means and the conductive coating except by means of the conductive finger.

51. An isolator as set forth in claim 46 wherein said first dielectric element has a conductive coating thereon with a gap in the coating to create a distributed form of said inductance, and including a relatively short electrical connection between said conductive means and the conductive coating.

52. An isolator as set forth in claim 51 wherein the first dielctric element is annular in shape with said conductive coating on the outer periphery thereof and another conductive coating on an inner periphery thereof, and wherein the mean circumference of the first dielectric element and its dielectric constant are selected to establish a condition of series resonance.

53. An isolator as set forth in claim 52 wherein series resonance is selected to occur at a frequency in the low VHF television band.

54. An isolator as set forth in claim 52 wherein the first dielecric element and its conductive coatings are selected to establish a condition of series resonance at multiple selected frequencies.

55. An isolator as set forth in claim 46 including an additional dielectric element and an inductance associated therewith for establishing another condition of series resonance.

56. For a television receiver having a tuner connected via a coupling path to at least the shield of a shielded conductor for receipt of a television signal carried by the conductor, the improvement comprising:

means defining an interruption in the coupling path; and

a series of dielectric elements separated by abutting magnetically absorptive material disposed in the interruption so as to create a capacitive coupling across the interruption and magnetic absorption within the interruption.