Semi-rigid cable designed for the transmission of microwaves

• US 5,068,632 A
• Filed: 12/15/1989
• Issued: 11/26/1991
• Est. Priority Date: 12/20/1988
• Status: Expired due to Fees

• Current Assignee: Thomson-CSF
• Original Assignee: Thomson-CSF
• Inventors: Champeau, Andre
• Primary Examiner(s): Gensler, Paul
• Assistant Examiner(s): Lee, Benny T.
• Application Number:
  US07/451,821
• Time in Patent Office: 711 Days
• Field of Search: 333/238, 333/243, 333/246, 174/32, 174/117 FF, 174/36
• US Class Current: 333/238
• CPC Class Codes: H01P 3/085 Triplate lines

Abstract

A semi-rigid cable for the transmission of microwaves, such as those used for radar or for digital television. This cable has a symmetrical strip line with a dielectric having an almost rectangular section, with a width close to the thickness of the dielectric and external conductive strips with a width that is substantially greater than that of the central conductor. This symmetrical strip line is advantageously surrounded by an absorbent sheath. The entire unit is protected by an ordinary metallic shielding and by a standard external mechanical protective sheath.

Claims

1. A semi-rigid cable for transmission of microwave signals up to a pre-determined frequency comprising:

(a) a semi-rigid flat stripline having length, width, and thickness, and having

a central conductor (1)

two parallel metal strips (5,

     6),

a dielectric (4) disposed between said conductor (1) and strips (5,

     6),

said strips having a width (L₁), where

L₁ is approximately equal to one of either value NA and N, whichever value is greater, where

L₁₌ width of said strips,

A=width of said central conductor,

e=distance between said two parallel metal strip,

N≃

; and

(b) a conductive shielding sheath (7) completely surrounding and enclosing said stripline.

2. A semi-rigid cable designed for the transmission of microwaves, said cable comprising at least:

one solid linear central conductor with a given width;

a dielectric surrounding said central conductor and having a cross section which is almost rectangular, with two short sides, said dielectric having two parallel, large, plane, external faces with a given width, said faces being parallel with said central conductor and located symmetrically with regard to said central conductor so as to form a dielectric part of a line of a symmetrical strip line type;

two external conductive parallel layers having a given distance between them, formed of continuous metal strips with large faces with a given width, respectively coating major part of each of the two large plane external faces of said dielectric so as to form a symmetrical strip line with said central conductor and said dielectric;

at least one shielding metal sheath completely surrounding and enclosing said symmetrical strip line; and

the width of the faces of said external conductive layers being greater than the greatest value among said distance between said two conductive layers and said width of said central conductor.

6. A semi-rigid cable according to anyone of claims 2 to 5 designed for a given mode, further comprising, between said symmetrical strip line and said shielding sheath, a sheath made of a material that is absorbent for microwaves in a spectrum of frequencies where a higher mode than said mode may be propagated.

7. A semi-rigid cable according to claim 6, wherein said absorbent sheath has a cross-section with the shape of an ellipse with a large and a short axis, said large axis being substantially included in a median and parallel plane between said two external conductive layers.

3. A semi-rigid cable designed for the transmission of microwaves, said cable comprising at least:

one solid linear central conductor with a given width;

a dielectric surrounding said central conductor and having a cross section which is almost rectangular, with two short sides, said dielectric having two parallel, large, plane, external faces with a given width, said faces being parallel with said central conductor and located symmetrically with regard to said central conductor so as to form a dielectric part of a line of a symmetrical strip line type;

two external conductive parallel layers having a given distance between them, formed of continuous metal strips with large faces with a given width, respectively coating major part of each of the two large plane external faces of said dielectric so as to form a symmetrical strip line with said central conductor and said dielectric;

at least one shielding metal sheath completely surrounding and enclosing said symmetrical strip line; and

said dielectric has a thickness between the said two external conductor layers substantially of the same size as the width of said central conductor.

4. A semi-rigid cable designed for the transmission of microwaves, said cable comprising at least:

one solid linear central conductor with a given width;

a dielectric surrounding said central conductor and having a cross section which is almost rectangular, with two short sides, said dielectric having two parallel, large, plane, external faces with a given width, said faces being parallel with said central conductor and located symmetrically with regard to said central conductor so as to form a dielectric part of a line of a symmetrical strip line type;

two external conductive parallel layers having a given distance between them, formed of continuous metal strips with large faces with a given width, respectively coating major part of each of the two large plane external faces of said dielectric so as to form a symmetrical strip line with said central conductor and said dielectric;

at least one shielding metal sheath completely surrounding and enclosing said symmetrical strip line; and

said external conductive layers of the symmetrical strip line each having a width about three times greater than the greatest value among the distance between these two plane conductive layers and the width of said central conductor.

5. A semi-rigid cable designed for the transmission of microwaves, said cable comprising at least:

one solid linear central conductor with a given width;

a dielectric surrounding said central conductor and having a cross section which is almost rectangular, with two short sides, said dielectric having two parallel, large, plane, external faces with a given width, said faces being parallel with said central conductor and located symmetrically with regard to said central conductor so as to form a dielectric part of a line of a symmetrical strip line type;

two external conductive parallel layers having a given distance between them, formed of continuous metal strips with large faces with a given width, respectively coating major part of each of the two large plane external faces of said dielectric so as to form a symmetrical strip line with said central conductor and said dielectric;

at least one shielding metal sheath completely surrounding and enclosing said symmetrical strip line; and

said faces of said dielectric having a width that is greater than the width of said faces of said two external conductive layer of said symmetrical strip line, and wherein said short sides of the rectangular cross section of the dielectric are convex so as to give a rounded shape to the shielding sheath covering said symmetrical strip line.