Galvanic isolation mechanism for a planar circuit

• US 20070069833A1
• Filed: 09/28/2006
• Published: 03/29/2007
• Est. Priority Date: 09/28/2005
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens Milltronics Process Instruments, Inc. (Siemens AG)
• Inventors: Serban, Gabriel
• Granted Patent: US 7,545,243 B2
• Time in Patent Office: Days
• US Class Current: 333/34
• CPC Class Codes: H01P 1/2007 Filtering devices for biasing networks or DC returns
• CPC Class Codes: H01P 1/203 Strip line filters
• CPC Class Codes: H01P 5/08 for linking dissimilar lines or devices H01P1/16, H01P5/04 take precedence; linking lines of the same kind but with different dimensions H01P5/02

Abstract

A mechanism for coupling a coaxial cable (108) to a planar circuit to provide galvanic isolation between the coaxial cable and the planar circuit while providing low transmission loss and reflections between the coaxial cable (108) and the circuit. The mechanism comprises a co-planar waveguide (211) coupled to the coaxial cable (108), a microstrip line (240) connected to the circuit, a galvanic isolation component (234) and a ground plane (222). The co-planar waveguide (211), the microstrip line (240) and the galvanic isolation component (234) are formed on one side (203) of a two-sided substrate (202). The ground plane (222) is formed on the other side (205) of the substrate (202) and underlies at least a portion of the co-planar waveguide (211) to form a grounded co-planar waveguide (221). The ground plane (222) includes a notch (224) underlying a portion of the co-planar waveguide (211) to provide a transition region (225) from the co-planar waveguide (211) to the grounded co-planar waveguide (221).

Claims

1. A galvanic isolation mechanism for a planar circuit, said planar circuit formed on a two sided substrate, said galvanic isolation mechanism comprising:

a process line, said process line formed on one side of the substrate (202);

a circuit line, said circuit line formed on the same side of the substrate (202) as said process line;

a DC isolation component, said DC isolation component formed on the same side of the substrate as said process line, said DC isolation component coupled to one end of said process line and to one end of said circuit line, said DC isolation component providing a block for DC signals between said process line and said circuit line;

a ground plane, said ground plane formed on the other side of the substrate, said ground plane underlying at least a portion of said process line and said circuit line.

2. The galvanic isolation mechanism as claimed in claim 1, wherein said ground plane includes a notch, said notch underlying a section of said process line.

3. The galvanic isolation mechanism as claimed in claim 1, wherein said process line comprises a coplanar waveguide and said circuit line comprises a microstrip line, said coplanar waveguide including a center conductor and at least one side ground plane.

4. The galvanic isolation mechanism as claimed in claim 3, wherein said coplanar waveguide includes a transition section, said transition section coupling said coplanar waveguide to said DC isolation component, and said at least one side ground plane including a shaped end section adjacent said transition section.

5. The galvanic isolation mechanism as claimed in claim 1, further including a second ground plane, said second ground plane being formed on the other side of the substrate, said second ground plane being separated from said ground plane by a gap.

6. The galvanic isolation mechanism as claimed in claim 5, wherein said second ground plane ) includes a tip, said tip having a configuration substantially matching the configuration of said notch.

7. The galvanic isolation mechanism as claimed in claim 1, further including a backing layer, said backing layer covering a portion of the substrate and being formed on the bottom surface of the substrate and underlying said ground plane.

8. The galvanic isolation mechanism as claimed in claim 1, wherein said DC isolation component comprises a microwave DC block formed as a microstrip structure on the surface of said substrate.

9. The galvanic isolation mechanism as claimed in claim 1, further including a coaxial cable connector, said coaxial cable connector having a terminal connected to said side ground plane, and another terminal connected to said process line.

10. A galvanic isolation mechanism for a planar circuit, comprising:

a substrate having a first side and an opposing second side;

a process line formed on a first side of the substrate;

a circuit line formed on the first same side of the substrate;

a DC isolation component formed on the first side of the substrate and coupled to an end of the process line and coupled to an end of the circuit line, the DC isolation component effective to block DC signals between the process line and the circuit line; and

a ground plane formed on the second side of the substrate and underlying at least a portion of the process line and underlying at least a portion of the circuit line.

11. The galvanic isolation mechanism as claimed in claim 10, wherein said ground plane has a notch underlying a portion of said process line.

12. The galvanic isolation mechanism as claimed in claim 11, wherein the process line comprises a coplanar waveguide and the circuit line comprises a microstrip line, the coplanar waveguide having a center conductor and at least one side ground plane.

13. The galvanic isolation mechanism as claimed in claim 12, wherein the coplanar waveguide includes a transition section that couples the coplanar waveguide to the DC isolation component, and the at least one side ground plane has a shaped end section adjacent the transition section.

14. The galvanic isolation mechanism as claimed in claim 13, further including a second ground plane formed on the first side of the substrate and separated from the ground plane by a gap.

15. The galvanic isolation mechanism as claimed in claim 14, wherein the second ground plane includes a tip having a configuration substantially matching the configuration of the notch.

16. The galvanic isolation mechanism as claimed in claim 15, further comprising a backing layer covering a portion of the substrate and formed on the bottom surface of the substrate and underlying the ground plane.

17. The galvanic isolation mechanism as claimed in claim 16, wherein the DC isolation component comprises a microwave DC block formed as a microstrip structure on a surface of the substrate.

18. The galvanic isolation mechanism as claimed in claim 17, further comprising a coaxial cable connector having a terminal connected to the side ground plane, and second terminal connected to the process line.