Inverted Style Balun with DC Isolated Differential Ports

Abstract

The present invention is directed to a balun that includes a first coupler structure having a first port of a balanced port pair and an unbalanced port. A second coupler structure includes a second port of the balanced port pair. The second coupler port structure being connected to the first coupler structure such that the second port of the balanced port pair is DC isolated from the first port of the balanced port pair without decoupling components.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a vertical interdigital coupler in accordance with one embodiment of the present invention;

FIG. 2 is a plan view of a transmission line layer of a vertical interdigital coupler in accordance with the present invention;

FIG. 3A-3B are diagrammatic depictions of the even mode and odd mode coupling field lines for the coupler depicted in FIG. 2;

FIG. 4 is a diagram illustrating the coupler cross-sectional area in accordance with the present invention;

FIGS. 5A-5C are schematic diagrams illustrating vertical interdigital coupler design considerations;

FIG. 6 is a balun in accordance with one embodiment of the present invention;

FIG. 7 is a chart illustrating the performance of the balun depicted in FIG. 6;

FIG. 8 is a chart illustrating the insertion loss of the balun depicted in FIG. 6 as a function of frequency and even-mode impedance;

FIG. 9 is a chart illustrating the insertion loss of the balun depicted in FIG. 6 as a function of frequency and odd-mode impedance;

FIG. 10 is a balun in accordance with another embodiment of the present invention;

FIG. 11 is a chart illustrating the insertion loss of the balun depicted in FIG. 10 as a function of frequency and even-mode impedance;

FIG. 12 is a chart illustrating the insertion loss of the balun depicted in FIG. 10 as a function of frequency and odd-mode impedance;

FIG. 13 is a balun in accordance with yet another embodiment of the present invention;

FIG. 14 is a chart illustrating the performance of the balun depicted in FIG. 13;

FIG. 15 is a chart illustrating the insertion loss of the balun depicted in FIG. 13 as a function of frequency and even-mode impedance;

FIG. 16 is a chart illustrating the insertion loss of the balun depicted in FIG. 13 as a function of frequency and odd-mode impedance;

FIGS. 17A-17E are charts illustrating the design tradeoffs of the present invention relative to a Merrill balun;

FIG. 18 is a power divider in accordance with another embodiment of the present invention;

FIG. 19 is a combiner in accordance with yet another embodiment of the present invention;

FIG. 20 is a perspective view of the device depicted in either FIG. 6, 10, 13, 18 or 19 in accordance with the present invention; and

FIG. 21 is an exploded view of the device depicted in either FIG. 6, 10, 13, 18 or 19 in accordance with the present invention.

Claims

1. A balun comprising: a first coupler structure including a first port of a balanced port pair and an unbalanced port;a second coupler structure including a second port of the balanced port pair, the second coupler structure being connected to the first coupler structure such that the second port of the balanced port pair is DC isolated from the first port of the balanced port pair without decoupling components.

2. The balun of claim 1, wherein the first coupler structure includes a first transmission line layer coupled to a second transmission line layer, and a third transmission line layer coupled to the second transmission layer, the second transmission line layer being sandwiched between the first transmission line layer and the third transmission line layer, and wherein the second coupler structure including a fourth transmission line layer coupled to a fifth transmission line layer, and a sixth transmission line layer coupled to the fifth transmission layer, the fifth transmission line layer being sandwiched between the fourth transmission line layer and the sixth transmission line layer, and wherein the first transmission line layer is connected to the sixth transmission line layer and wherein the third transmission line layer is connected to the fourth transmission line layer.

3. The balun of claim 2, wherein the first port of a balanced port pair is connected to the first transmission line layer and the second port of the balanced port pair is connected to the fourth transmission line layer.

4. The balun of claim 2, wherein the second transmission line layer has a first end connected to ground potential and a second end connected to the unbalanced port.

5. The balun of claim 2, wherein the fifth transmission line is grounded at both ends.

6. The balun of claim 2, wherein each transmission line layer includes a conductive transmission line conforming to a predetermined geometric configuration, the conductive transmission line being disposed on a dielectric material.

7. The balun of claim 6, wherein the predetermined geometric configuration includes a planar pattern (X-Y plane) selected from a group of planar patterns that includes linear planar patterns, non-linear planar patterns, spiral patterns, substantially rectangular patterns.

8. The balun of claim 2, further comprising a resistive element connected between the first transmission line layer and the fourth transmission line layer to form a power combiner/divider structure.

9. The balun of claim 8, wherein the first port of the balanced port pair is connected to the first transmission line layer and the second port of the balanced port pair is connected to the fourth transmission line layer and a first port of a second balanced port pair is connected to the third transmission line and a second port of the second balanced port pair is connected to the sixth transmission line.

10. The balun of claim 1, wherein the first coupler structure and the second coupler structure are each characterized by a physical coupler form factor based on a cross-sectional area, a predetermined geometrical configuration, and a selected coupling constant.

11. The balun of claim 10, wherein the cross-sectional area is proportional to: AN=(s+w)[2h+(N−1)d+Ntm]; andwherein s is a horizontal spacing between adjacent transmission line conductors, w is a horizontal width of each transmission line conductor, h is a vertical distance from an outermost transmission line conductor to a ground plane, N is a total number of transmission line layers in each of the first coupler structure and the second coupler structure, d is a vertical distance between sandwiched transmission line conductors, t is a vertical thickness of each transmission line conductor, and m is a ratio in a horizontal direction of conducting material to dielectric material.

12. The balun of claim 11, wherein the first coupler structure and the second coupler structure are characterized by a finite even-mode impedance (Ze) and a finite odd-mode impedance (Zo), the ratio (R=Ze/Zo) being greater than or equal to one (1).

13. The balun of claim 12, wherein Zo is a function of d, w s, and t.

14. The balun of claim 12, wherein Ze is a function of at least h.

15. The balun of claim 11, wherein N is equal to three (3).

16. The balun of claim 10, wherein the predetermined geometric configuration is substantially linear.

17. The balun of claim 10, wherein the predetermined geometric configuration includes at least one substantially rectangular geometric pattern.

18. The balun of claim 10, wherein the predetermined geometric configuration is a non-linear geometric configuration.

19. The balun of claim 10, wherein the predetermined geometric configuration includes at least one meandered line segment.

20. The balun of claim 10, wherein the predetermined geometric configuration includes a spiral configuration.

21. The balun of claim 1, wherein the first coupler structure and the second coupler structure are characterized by a finite even-mode impedance (Ze) and a finite odd-mode impedance (Zo), the ratio (R=Ze/Zo) being greater than or equal to one (1).

22. The balun of claim 1, wherein the first coupler structure is a vertical interdigital coupler structure and the second coupler structure is a vertical interdigital coupler structure.

23. The balun of claim 22, wherein the vertical interdigital coupler structures comprise broadside couplers.

24. The balun of claim 1, wherein the first coupler structure is a vertical interdigital coupler structure and the second coupler structure comprise edge-coupled structures.

25. A balun comprising: a first coupler structure including a first port of a balanced port pair and an unbalanced port; anda second coupler structure including a second port of the balanced port pair, the second coupler structure being connected to the first coupler structure such that the first port of the balanced port pair and the second port of the balanced port pair are isolated from ground potential without decoupling components.

26. The balun of claim 25, wherein the first coupler structure includes a first transmission line layer coupled to a second transmission line layer, and a third transmission line layer coupled to the second transmission layer, the second transmission line layer being sandwiched between the first transmission line layer and the third transmission line layer, and wherein the second coupler structure including a fourth transmission line layer coupled to a fifth transmission line layer, and a sixth transmission line layer coupled to the fifth transmission layer, the fifth transmission line layer being sandwiched between the fourth transmission line layer and the sixth transmission line layer, and wherein the first transmission line layer is connected to the third transmission line layer and the fourth transmission line layer and wherein the fourth transmission line layer is also connected to the sixth transmission line layer.

27. The balun of claim 26, wherein the first port of a balanced port pair is connected to the first transmission line layer and the second port of the balanced port pair is connected to the fourth transmission line layer.

28. The balun of claim 26, wherein the second transmission line layer has a first end connected to ground potential and a second end connected to the unbalanced port.

29. The balun of claim 26, wherein the fifth transmission line is grounded at both ends.

30. The balun of claim 25, wherein the first coupler structure includes a first transmission line layer coupled to a second transmission line layer, and a third transmission line layer coupled to the second transmission layer, the second transmission line layer being disposed between the first transmission line layer and the third transmission line layer, and wherein the second coupler structure including a fourth transmission line layer coupled to a fifth transmission line layer, and a sixth transmission line layer coupled to the fifth transmission layer, the fifth transmission line layer being disposed between the fourth transmission line layer and the sixth transmission line layer, and wherein the first transmission line layer is connected to the third transmission line layer and wherein the fourth transmission line layer is also connected to the sixth transmission line layer.

31. The balun of claim 30, wherein the first port of a balanced port pair is connected to the second transmission line layer and the second port of the balanced port pair is connected to the fifth transmission line layer, and wherein the second transmission line layer is connected to the fifth transmission line layer.

32. The balun of claim 30, wherein the first transmission line layer and the third transmission line layer have a first end connected to ground potential and a second end connected to the unbalanced port.

33. The balun of claim 30, wherein the fourth transmission line layer and the sixth transmission lines layer are grounded at both ends.

34. A device configured to operate within a predetermined band of frequencies, the device comprising: a first coupler structure including a first portion of a first balanced port, a first port of a second balanced port and an unbalanced port;a resistive element connected to the first coupler structure; anda second coupler structure including a second portion of the first balanced port and a second portion of the second balanced port, the second coupler structure being connected to the first coupler structure by way of the resistive element such that the first and second portions of the first balanced port pair and the first and second portions of the second balanced port pair are isolated from each other substantially within the predetermined band without decoupling components.

35. The device of claim 34, wherein the first coupler structure includes a first transmission line layer coupled to a second transmission line layer and a third transmission line layer coupled to the second transmission layer, the second transmission line layer being disposed between the first transmission line layer and the third transmission line layer, the second coupler structure including a fourth transmission line layer coupled to a fifth transmission line layer and a sixth transmission line layer coupled to the fifth transmission layer, the fifth transmission line layer being disposed between the fourth transmission line layer and the sixth transmission line layer, the first transmission line layer being connected to the sixth transmission line layer and the third transmission line layer being connected to the fourth transmission line layer.

36. The device of claim 35, wherein the first portion of the first balanced port pair is connected to the first transmission line layer and the second portion of the first balanced port pair is connected to the fourth transmission line layer.

37. The device of claim 35, wherein the first portion of the second balanced port pair is connected to the third transmission line layer and the second portion of the second balanced port pair is connected to the sixth transmission line layer.

38. The device of claim 35, wherein the resistive element is disposed between the first transmission line layer and the fourth transmission line layer.

39. The device of claim 35, wherein the second transmission line layer has a first end connected to ground potential and a second end connected to the unbalanced port.

40. The device of claim 35, wherein the fifth transmission line is grounded at both ends.

41. The device of claim 34, wherein the sum of the signal power of the first balanced port and the signal power of the second balanced port is substantially equal to the signal power of the unbalanced port.

42. The device of claim 34, wherein the unbalanced port is configured as an input port and the first balanced port and the second balanced port are configured as output ports.

43. The device of claim 34, wherein the unbalanced port is configured as an output port and the first balanced port and the second balanced port are configured as input ports.

44. A balun comprising: a first coupler structure including a first port of a balanced port pair and an unbalanced port, the first coupler structure includes a first transmission line layer coupled to a second transmission line layer and a third transmission line layer coupled to the second transmission layer, the second transmission line layer being disposed between the first transmission line layer and the third transmission line layer;a second coupler structure including a second port of the balanced port pair, the second coupler structure also including a fourth transmission line layer coupled to a fifth transmission line layer and a sixth transmission line layer coupled to the fifth transmission layer, the fifth transmission line layer being disposed between the fourth transmission line layer and the sixth transmission line layer, the first transmission line layer being connected to the sixth transmission line layer and the third transmission line layer being connected to the fourth transmission line layer such that the first port of the balanced port pair is DC isolated from the second port of the balanced port pair.

45. The balun of claim 44, wherein the first port of a balanced port pair is connected to the first transmission line layer and the second port of the balanced port pair is connected to the fourth transmission line layer.

46. The balun of claim 44, wherein the second transmission line layer has a first end connected to ground potential and a second end connected to the unbalanced port.

47. The balun of claim 44, wherein the fifth transmission line is grounded at both ends.

48. The balun of claim 44, wherein the first port of the balanced port pair is DC isolated from the second port of the balanced port pair without decoupling components.

49. The balun of claim 44, wherein each transmission line layer includes a conductive transmission line disposed on a dielectric material.

50. The balun of claim 44, wherein the first coupler structure and the second coupler structure are arranged as vertically interdigital coupler structures.