Probing apparatus with guarded signal traces

1. A probing apparatus comprising:

a first substrate comprising a first surface and a second surface opposite the first surface;

a plurality of electrically conductive first signal traces disposed on the first surface of the first substrate;

a plurality of probes, ones of the probes attached directly to ones of the first signal traces;

a plurality of first electromagnetic shielding structures disposed about the first signal traces, wherein each first electromagnetic shielding structure comprises a first guard trace disposed on the first surface of the first substrate and at least partially enclosing one of the first signal traces;

a wiring substrate;

an electrical interface to a source of test signals, the electrical interface disposed on the wiring substrate; and

a plurality of electrical connections electrically connecting the electrical interface to the signal traces and the guard traces.

2. The probing apparatus of claim 1 further comprising:

a plurality of signal terminals disposed on the second surface of the first substrate; and

a plurality of signal electrical connections through the first substrate electrically connecting ones of the signal terminals and ones of the first signal traces.

3. The probing apparatus of claim 2 , wherein the guard trace fully encloses the one of the first signal traces.

4. The probing apparatus of claim 3 , wherein each first electromagnetic shielding structure further comprises an electrically conductive plane embedded within the first substrate and adjacent the one of the first signal traces, and the plane is electrically connected through the first substrate to the first guard trace.

5. The probing apparatus of claim 3 further comprising:

a plurality of guard terminals disposed on the second surface of the first substrate; and

a plurality of guard electrical connections through the first substrate electrically connecting ones of the guard terminals and ones of the first guard traces.

6. The probing apparatus of claim 2 , wherein the first guard trace is disposed on the first surface of the first substrate partially around the one of the first signal traces without fully enclosing the one of the first signal traces.

7. The probing apparatus of claim 1 , wherein

the probing apparatus further comprising a plurality of pairs of terminals disposed on the second surface of the first substrate, each pair of terminals comprising a guard terminal electrically connected through the first substrate to one of the first guard traces and a signal terminal electrically connected through the first substrate to one of the first signal traces.

8. The probing apparatus of claim 7 , wherein each of ones of the first guard traces comprises a closed loop shape and a corresponding one of the first signal traces is disposed within the closed loop shape.

9. The probing apparatus of claim 7 , wherein the

electrical connections electrically connecting the electrical interface to the signal terminals and the guard terminals comprise flexible connections.

10. The probing apparatus of claim 9 , wherein:

the electrical interface comprises a plurality of channel connections disposed on a first surface of the wiring substrate,

the wiring substrate comprises a plurality of electrical connections from the channel connections through the wiring substrate to wiring substrate terminals disposed on a second opposite surface of the wiring substrate, and

the flexible connections are disposed between the second surface of the wiring substrate and the second surface of the first substrate and electrically connect ones of the wiring substrate terminals with ones of the signal terminals and ones of the guard terminals.

11. The probing apparatus of claim 7 , wherein each of the first electromagnetic shielding structures further comprises an electrically conductive plane disposed in the first substrate adjacent the first signal trace of the first electromagnetic shielding structure and electrically connected to the first guard trace of the first electromagnetic shielding structure.

12. The probing apparatus of claim 1 further comprising:

a plurality of electrically conductive second signal traces disposed on the wiring substrate and electrically connected to the interface;

a plurality of second electromagnetic shielding structures disposed about the second signal traces, wherein each second electromagnetic shield structure comprises a second guard trace at least partially enclosing one of the second signal traces.

13. The probing apparatus of claim 12 , wherein:

each of the electrical connections comprises one of the second signal traces or one of the second guard traces disposed on a first surface of the second substrate.

14. The probing apparatus of claim 13 , wherein each second electromagnetic shielding structure further comprises an electrically conductive plane embedded within the second substrate and adjacent the one of the second signal traces, and the plane is electrically connected through the second substrate to the second guard trace.

15. The probing apparatus of claim 13 , wherein a first plurality of the electrical connections further comprise signal electrical connections each electrically connecting one of the second signal traces with one of the first signal traces.

16. The probing apparatus of claim 15 , wherein a second plurality of the electrical connections further comprise guard electrical connections each electrically connecting one of the second guard traces with one of the first guard traces.

17. The probing apparatus of claim 16 , wherein each of the guard electrical connections is disposed to shield electrically a corresponding one of the signal electrical connections from electromagnetic interference.

18. The probing apparatus of claim 16 , wherein each of the guard electrical connections is disposed to surround a corresponding one of the signal electrical connections along a substantial length of the signal electrical connection.

19. The probing apparatus of claim 16 , wherein ones of the electrical connections comprise a coaxial cable electrically connected to a shielded pin electrical connector.

20. The probing apparatus of claim 15 , wherein the first substrate is disposed in a holder that is removably attached to the wiring substrate.

21. The probing apparatus of claim 20 further comprising bolts configured to attach removably the holder to the wiring substrate.

22. The probing apparatus of claim 1 , wherein the probes are electromagnetically unshielded.

23. The probing apparatus of claim 12 , wherein:

the interface, the second signal trace, and the second guard trace are disposed on a first surface of the wiring substrate, and

a second surface of the wiring substrate opposite the first surface of the wiring substrate faces the second surface of the first substrate.