Electromagnetically shielded slot transmission line

• US 20050156690A1
• Filed: 12/23/2004
• Published: 07/21/2005
• Est. Priority Date: 12/24/2003
• Status: Active Grant

• Current Assignee: Molex Incorporated
• Original Assignee: Molex Incorporated
• Inventors: Brunker, David L., Zaderej, Victor
• Granted Patent: US 7,151,420 B2
• Time in Patent Office: Days
• US Class Current: 333/238
• CPC Class Codes: H01P 3/023 Fin lines; Slot lines
• CPC Class Codes: H05K 1/0221 Coaxially shielded signal lines comprising a continuous shielding layer partially or wholly surrounding the signal lines
• CPC Class Codes: H05K 1/024 Dielectric details, e.g. changing the dielectric material around a transmission line
• CPC Class Codes: H05K 2201/0715 provided by an outer layer of PCB
• CPC Class Codes: H05K 2201/09036 Recesses or grooves in insulating substrate recess in metallic substrate H05K2201/09745
• CPC Class Codes: H05K 2201/09236 Parallel layout layout of balanced signal pairs H05K1/0245; superposed layout H05K2201/09672
• CPC Class Codes: H05K 2201/09618 Via fence, i.e. one-dimensional array of vias
• CPC Class Codes: H05K 2201/09981 Metallised walls
• CPC Class Codes: H05K 3/107 by filling grooves in the support with conductive material H05K3/045, H05K3/101, H05K3/1258 and H05K3/465 take precedence
• CPC Class Codes: H05K 9/0018 with provisions to reduce aperture leakages in walls, e.g. terminals, connectors, cables

Abstract

An electro-magnetically shielded slot-transmission line is formed by metallizing the opposing sides of a slot cut through a dielectric substrate. A ground plane is deposited on the bottom of the substrate. Conductive vias through the substrate and that contact the ground plane are located on both sides of the metallized slot surfaces. Conductive pads on the upper surface and which contact the vias provide additional shielding.

Claims

1. A transmission line comprising:

a substantially planar dielectric substrate having upper and lower opposing surfaces;

a first slot formed through the upper surface of said dielectric substrate, said slot having first and second opposing faces spaced apart from each other by an intervening space, both opposing slot faces each have a conductive surface that is capable of carrying differential signals thereon;

a planar ground conductor coupled to, and substantially covering the lower surface of the dielectric substrate, said ground conductor being at a reference potential for signals carried on the conductive surfaces on the opposing slot faces; and

,

a first conductive via, extending through the substantially planar dielectric substrate from the lower surface to the upper surface, said first conductive via being located adjacent to the conductive surface on said first opposing face and electrically contacting the planar ground conductor.

2. The transmission line of claim 1, a first substantially planar conductive pad on the upper surface of said substantially planar dielectric substrate, said conductive pad extending away from the first conductive via on the upper surface and toward the conductive surface on said first opposing face, said conductive pad being electrically coupled to said conductive via.

3. The transmission line of claim 2, further including a second conductive via, extending through the substantially planar dielectric substrate from the lower surface to the upper surface, said second conductive via being located adjacent to the conductive surface on said second opposing face and electrically contacting the planar ground conductor.

4. The transmission line of claim 3, further including a second substantially planar conductive pad on the upper surface of said substantially planar dielectric substrate, said conductive pad extending away from the second conductive via on the upper surface and toward the conductive surface on said second opposing face, said conductive pad being electrically coupled to said conductive via.

5. The transmission line of claim 4, further comprised of a planar ground conductor electrically coupled to said first and second substantially planar conductive pads on the upper surface and extending over the upper surface of the dielectric substrate.

6. The transmission line of claim 1, further including a non-air dielectric material at least partially filling said intervening space.

7. The transmission line of claim 1, further including a second planar ground conductor coupled to, and substantially covering the area above the upper surface of the dielectric substrate, said second planar ground conductor being at a reference potential for signals carried on the conductive surfaces on the opposing slot faces.

9. The transmission line of claim 7, further including a substantially planar conductive pad on the upper surface of said planar dielectric substrate, said substantially planar conductive pad being electrically coupled to a corresponding conductive via, each conductive pad extending away from its corresponding via toward the first conductive surface on the first opposing face of said first slot transmission line and toward the second conductive surface on the second opposing face of said second slot transmission line so as to provide a reference potential between the first and second slot transmission lines.

10. The transmission line of claim 7, wherein said conductive vias are substantially equidistant from the second opposing face of said first slot transmission line and the first opposing face of the a second slot transmission line.

11. The transmission line of claim 7, further including:

a second planar ground conductor substantially covering the area above the first slot transmission line and the second slot transmission line, said second planar ground conductor being electrically coupled to the plurality of conductive vias between the first and second slot transmission lines.

8. A circuit board comprising:

a substantially planar dielectric substrate having upper and lower opposing surfaces;

a first slot transmission line formed in the upper surface of said dielectric substrate, said first slot transmission line having first and second opposing faces spaced apart from each other by an intervening space, both opposing slot faces each have a conductive surface that is capable of carrying a first differential signal thereon;

a second slot transmission line formed in the upper surface of said dielectric substrate, said second slot transmission line also having first and second opposing faces spaced apart from each other by an intervening space, both opposing slot faces of said second slot transmission line each have a conductive surface that is capable of carrying a second differential signal thereon, at least part of said second slot transmission line being parallel to and laterally displaced from said first slot transmission line in the dielectric substrate;

a planar ground conductor coupled to, and substantially covering the lower surface of the dielectric substrate, said ground conductor being at a reference potential for signals carried on the conductive surfaces on the opposing slot faces of said first and second slot transmission lines; and

,

a plurality of conductive vias extending through the substantially planar dielectric substrate, said conductive vias being electrically connected to, and extending from the planar ground conductor, through the upper surface of the dielectric substrate, said conductive vias being located between the first and second slot transmission lines.