Common mode choke

1. A common mode choke configured to receive a differential signal over a first signal channel and a second signal channel comprising:

a first planar coil forming the first signal channel for receiving a first signal component of the differential signal,

a second planar coil forming the second signal channel for receiving a second signal component of the differential signal, the first and second planar coils comprising substantially mirror images of one another and arranged side by side in a common plane,

the first planar coil and second planar coil being electromagnetically coupled by a closed coupling loop, wherein the closed coupling loop comprises a first coil portion arranged in a path complementary to at least a portion of the first planar coil, a second coil portion arranged in a path complementary to at least a portion of the second planar coil, and

a connecting portion arranged to connect the first and second coil portions to form a closed loop, wherein the connecting portion comprises:

a first track and a second track, the first track configured to connect a first end of the first coil portion to a corresponding first end of the second coil portion and the second track configured to connect a second end of the first coil portion to a corresponding second end of the second coil portion, the first and second tracks being configured to extend in the same plane.

2. The common mode choke of claim 1 , wherein the closed coupling loop is planar and configured to extend at least in part in a plane adjacent to but spaced apart from the common plane.

3. A common mode choke configured to receive a differential signal over a first signal channel and a second signal channel comprising:

a first planar coil forming the first signal channel for receiving a first signal component of the differential signal,

a second planar coil forming the second signal channel for receiving a second signal component of the differential signal, the first and second planar coils comprising substantially mirror images of one another and arranged side by side in a common plane,

the first planar coil and second planar coil being electromagnetically coupled by a closed coupling loop, wherein the closed coupling loop comprises a first coil portion arranged in a path complementary to at least a portion of the first planar coil, a second coil portion arranged in a path complementary to at least a portion of the second planar coil, and

a connecting portion arranged to connect the first and second coil portions to form a closed loop, wherein the connecting portion comprises:

a first track and a second track, the first track configured to connect a first end of the first coil portion to a complementary first end of the second coil portion and the second track configured to connect a second end of the first coil portion to a complementary second end of the second coil portion, the first and second tracks being configured to extend in different planes.

4. The common mode choke according to claim 1 , wherein the common mode choke is symmetrical about a plane extending between the first and second planar coils.

5. The common mode choke of claim 1 , further comprising: a plurality of closed coupling loops, wherein each of the plurality of closed coupling loops are configured to electromagnetically couple the first and second planar coils.

6. The common mode choke of 5 , wherein at least two of the plurality of closed coupling loops extend in the same plane.

7. The common mode choke of claim 5 , wherein one or more of the plurality of closed coupling loops extends in plane above the common plane and one or more of the plurality of closed coupling loops extends in plane below the common plane.

8. The common mode choke of claim 1 , wherein the first planar coil includes a straight section and a coiled section and the second planar coil includes a straight section and a coiled section, and wherein the straight sections of the first and second planar coils are arranged parallel to one another.

9. The common mode choke of claim 5 , wherein the number of closed coupling loops is equal to or one greater than the number of turns of the first or second planar coil.

10. The common mode choke of claim 1 , wherein one or both of the first planar coil and the second planar coil comprises spirals and have an outer spiral end and an inner spiral end arranged in the common plane, and wherein the inner spiral end connects to a bridge track that extends in a plane adjacent to but spaced apart from the common plane to provide a connection point that lies outside of the spiral.

11. The common mode choke of claim 1 , wherein the first planar coil and the second planar coil are each arranged over a plurality of parallel planes, with corresponding parts of the first planar coil and the second planar coil being arranged in common planes of the plurality of parallel planes.

12. An electronic device including the common mode choke of claim 1 .

13. The electronic device of claim 12 comprising a transmitter or a receiver configured to transmit or receive the differential signal arranged over the two signal channels wherein the first planar coil of the common mode choke is configured to connect to one of the first and second signal channels and the second planar coil of the common mode choke is configured to connect to the other of the first and second signal channels.

14. An electronic device including the common mode choke of claim 3 .

15. The electronic device of claim 14 , further comprising a transmitter or a receiver configured to transmit or receive the differential signal arranged over the two signal channels wherein the first planar coil of the common mode choke is configured to connect to one of the first and second signal channels and the second planar coil of the common mode choke is configured to connect to the other of the first and second signal channels.