Active probe powered through driven coax cable

1. A coupling system comprising:

a head-end circuit comprising:

a first terminal configured to couple to an active probe via a cable;

a second terminal configured to couple to an electronic instrument; and

active circuitry coupled between the first terminal and the second terminal and configured to:

apply direct-current (DC) power to the cable; and

remove a DC voltage offset resulting from the applied DC power before a signal from the active probe reaches the electronic instrument.

2. The coupling system of claim 1 , wherein the head-end circuit comprises:

a common node coupled to the first terminal;

a current source coupling the common node to a supply voltage; and

a voltage source coupling the common node to the second terminal.

3. The coupling system of claim 1 , wherein the head-end circuit presents a wideband impedance to the cable, wherein the wideband impedance matches a characteristic impedance of the cable to prevent signal reflections and standing waves.

4. The coupling system of claim 1 , further comprising the active probe, wherein an output impedance of the active probe matches a characteristic impedance of the cable when the coupling system is configured to operate in a high bandwidth system.

5. The coupling system of claim 1 , further comprising the active probe, wherein an output impedance of the active probe presented to the cable is a high impedance characteristic of a current source when the coupling system is configured to operate in a low bandwidth system.

6. The coupling system of claim 1 , wherein the head-end circuit is configured to operate at one or more of:

a same standardized voltage offset at which the active probe operates; or

a same standardized DC current at which the probe operates.

7. The coupling system of claim 1 , wherein the head-end circuit is comprised in one of:

an adapter serving the active probe;

a relay multiplexer capable of coupling the head-end circuit to the active probe; or

a front-end of a channel of the electronic instrument.

8. An active probe system comprising:

an active probe configured to receive a signal;

a cable having one end coupled to the active probe; and

a head-end circuit coupling another end of the cable to an electronic instrument, and configured to:

apply direct-current (DC) power to the cable; and

remove a DC voltage offset resulting from the applied DC power before the signal from the active probe reaches the electronic instrument.

9. The coupling system of claim 8 , wherein the active probe is configured to only receive its power from the cable.

10. The coupling system of claim 8 , wherein the head-end circuit comprises:

a common node coupled to the other end of the cable;

a current source coupling the common node to a supply voltage; and

a voltage source coupling the common node to the electronic instrument.

11. The coupling system of claim 8 , wherein the head-end circuit presents a wideband impedance to the cable, wherein the wideband impedance matches a characteristic impedance of the cable to prevent signal reflections and standing waves.

12. The coupling system of claim 8 , wherein an output impedance of the active probe matches a characteristic impedance of the cable when the coupling system is configured to operate in a high bandwidth system.

13. The coupling system of claim 8 , wherein an output impedance of the active probe presented to the cable is a high impedance characteristic of a current source when the coupling system is configured to operate in a low bandwidth system.

14. The coupling system of claim 8 , wherein the head-end circuit and the active probe are configured to operate at one or more of:

a same standardized voltage offset; or

a same standardized DC powering current.

15. A measurement system comprising:

a measurement instrument; and

a head-end circuit comprising:

a first terminal configured to couple to an active probe via a cable;

a second terminal configured to couple to the measurement instrument; and

active circuitry coupled between the first terminal and the second terminal and configured to:

apply power to the cable; and

remove a voltage offset resulting from the applied power before a signal from the active probe reaches the measurement instrument.

16. The measurement system of claim 15 , wherein the head-end circuit comprises:

a common node coupled to the first terminal;

a current source coupling the common node to a supply voltage; and

a voltage source coupling the common node to the second terminal.

17. The measurement system of claim 15 , wherein the head-end circuit presents a wideband impedance to the cable, wherein the wideband impedance matches a characteristic impedance of the cable to prevent signal reflections and standing waves.

18. The measurement system of claim 15 , further comprising the active probe, wherein an output impedance of the active probe matches a characteristic impedance of the cable when the coupling system is configured to operate in a high bandwidth system.

19. The measurement system of claim 15 , further comprising the active probe, wherein an output impedance of the active probe presented to the cable is a high impedance characteristic of a current source when the coupling system is configured to operate in a low bandwidth system.

20. The measurement system of claim 15 , wherein the head-end circuit is comprised in one of:

an adapter serving the active probe;

a relay multiplexer comprising an additional plurality of head-end circuits, wherein the multiplexer is capable of coupling any one of the head-end circuit and the additional plurality of head-end circuits to the active probe; or

a front-end of a channel of the measurement instrument.