Compensated interdigitated coupler

1. A coupler comprising:

at least four ports;

a least first and second planar sets of conductive strips, each set of conductive strips including a plurality of interconnected conductive strips, and each conductive strip of the first set being electromagnetically coupled to at least one conductive strip of the second set, each set of conductive strips being connected between at least two ports, and at least a portion of each conductive strip extending in a common direction with an adjacent conductive strip of the same set;

a ground conductor spaced from the first and second sets of conductive strips; and

at least first and second planar conductive tabs capacitively coupled primarily to the ground conductor, the first conductive tab coplanar with and extending directly from the portion of a first conductive strip of the first set, the second conductive tab coplanar with and extending directly from the portion of a second conductive strip of the second set.

2. The coupler of claim 1 , of which the first conductive strip is adjacent to a conductive strip of the second set, and the first tab extends from a side of the first conductive strip in a direction opposite from the adjacent conductive strip.

3. The coupler of claim 1 , of which the first and second sets of conductive strips are coplanar, and the conductive strips of the first and second sets are interdigitated.

4. The coupler of claim 3 , further comprising an interconnection connecting an intermediate position on the portion of at least one conductive strip of the first set of conductive strips with another conductive strip of the first set of conductive strips, and in which the first tab extends from the first conductive strip at a position spaced from the interconnection.

5. The coupler of claim 4 , of which the first conductive strip is adjacent to a conductive strip of the second set, and the interconnection is near an end of the first conductive strip and at an intermediate position on the portion of the adjacent conductive strip of the second set, the second tab extending from the adjacent conductive strip at a position spaced from the interconnection.

6. The coupler of claim 5 , of which the second tab is spaced closer to the interconnection than the first tab.

7. The coupler of claim 5 , of which the first and second tabs extend in generally the same direction.

8. The coupler of claim 7 , of which the ground conductor is a ground plane spaced from the plane of the first and second sets of conductive strips by a distance less than between the distance between the first and second tabs.

9. The coupler of claim 5 , of which the second tab is spaced further from the interconnection than a spacing between the first and adjacent conductive strips.

10. The coupler of claim 3 , of which the first and second tabs extend in generally the same direction, and the ground conductor is a ground plane spaced from the plane of the first and second sets of conductive strips by a distance less than a distance between the first and second tabs.

11. A coupler comprising:

a substrate having first and second faces;

a ground plane on the first face of the substrate;

at least four ports on the second face of the substrate;

first and second coplanar sets of interdigitated conductive strips in alternating configuration on the second face of the substrate, each set of conductive strips including a plurality of conductive strips, each conductive strip of the first set being electromagnetically coupled to at least one conductive strip of the second set, and each set of conductive strips being connected between two ports, with first and second conductive strips being connected between two ports, with first and second conductive strips of the first set having respective ends adjacent to an intermediate portion of respective of respective adjacent third and fourth conductive strips of the second set, the first and second conductive strips and a portion of the third and fourth conductive strips having outer sides not adjacent to another conductive strip;

at least a first interconnection interconnecting the respective ends of the first and second conductive strips, the interconnection extending across the intermediate portions of the third and fourth conductive strips;

at least a second interconnection interconnecting conductive strips of the second set, the first and second interconnection being spaced apart;

a first conductive tab extending along the second face of the substrate capacitively coupled to the ground place, spaced from the first interconnection and integrally connected to and extending from the outer side of each of the first and second conductive strips; and

a second conductive tab extending along the second face of the substrate capacitively coupled to the ground plane, spaced from the first interconnection and integrally connected to an extending from the outer side of each of the third and fourth conductive strips.

12. The coupler of claim 11 , of which each second tab is spaced closer to the first interconnection than is each adjacent first tab.

13. The coupler of claim 11 , of which the ground plane is spaced from the plane of the first and second sets of conductive strips by a distance less than the distance between adjacent first and second tabs.

14. The coupler of claim 11 , of which the second tab is spaced further from the first interconnection than a spacing between adjacent conductive strips.

15. A coupler comprising:

at least four ports;

at least first and second sets of conductive strips, each set of conductive strips including a plurality of interconnected conductive strips, each conductive strip of the first set being electromagnetically coupled to at least one conductive strip of the second set, each set of conductive strips being connected between at least two ports, and at least a portion of each conductive strip extending in a common direction with an adjacent conductive strip of the same set;

a ground conductor spaced from the first and second sets of conductive strips; and

at least first and second conductive tabs capacitively coupled primarily to the ground conductor, the first conductive tab extending directly from the portion of a first conductive strip of the first set in a first direction, the second conductive tab extending directly from the portion of a second conductive strip of the second set in a second direction generally opposite the first direction.

16. The coupler of claim 15 , of which the first conductive strip is adjacent to a conductive strip of the second set, and the first tab extends from a side of the first conductive strip in a direction opposite from the adjacent conductive strip of the second set.

17. The coupler of claim 15 , of which the first and second sets of conductive strips are coplanar, and the conductive strips of the first and second sets are interdigitated.

18. The coupler of claim 15 , of which the first tab extends directly from an intermediate position on the portion of a conductive strip of the first set, and the second tab extends directly from an intermediate position on the portion of a conductive strip of the second set.

19. The coupler of claim 1 , of which the first tab extends directly from an intermediate position on the portion of a conductive strip of the first set, and the second tab extends directly from an intermediate position on the portion of a conductive strip of the second set.