Multi-carriage impedance tuner with single lead screw

1. An impedance tuner having an RF transmission line, the impedance tuner comprising:

a single lead screw;

a plurality of movable carriages connected to said single lead screw, wherein each of the plurality of carriages connected to the single lead screw is configured for independent movement relative to other carriages to move the carriages along an axis parallel to the RF transmission line;

a motorized drive system for independently moving the plurality of carriages along the single lead screw.

2. The impedance tuner of claim 1 , wherein the plurality of carriages connected to the single lead screw is two carriages.

3. The impedance tuner of claim 1 , wherein the plurality of carriages connected to the single lead screw is more than two carriages.

4. The impedance tuner of claim 1 , further comprising:

a controller coupled to the motorized drive system and configured to provide drive commands to control operation of the motorized drive system.

5. The impedance tuner of claim 1 , further comprising at least one probe carried by each of the plurality of carriages and configured for motion transverse to the RF transmission line.

6. The impedance tuner of claim 1 , wherein the RF transmission line is a slabline, comprising a center conductor disposed between opposed ground plane structures.

7. The impedance tuner of claim 1 , wherein the lead screw does not rotate, and the motorized drive system comprises, for each of the multiple carriages, a motor on the carriage turning a nut on the lead screw.

8. The impedance tuner of claim 7 , wherein the lead screw nut on the lead screw in at least one of the carriages is internal to the carriage motor.

9. The impedance tuner of claim 7 , wherein the lead screw nut on the lead screw coupled to at least one of the carriages is external to the carriage motor.

10. An impedance tuner for presenting variable impedances to a device under test, comprising:

an RF transmission line;

a plurality of movable carriages mounted for movement along an axis parallel to the RF transmission line;

a motorized carriage drive system configured to move each of the plurality of carriages along said axis independently, said drive system comprising:

a single lead screw;

each of the plurality of movable carriages including a carriage motor coupled to said single lead screw by a corresponding lead screw nut and configured to apply rotary force to the leadscrew nut to turn the nut on the leadscrew and translate the rotary force into linear movement of the nut and carriage along the single lead screw.

11. The impedance tuner of claim 10 , where the lead screw nut on the single lead screw in at least one of the carriages is internal to the carriage motor.

12. The impedance tuner of claim 10 , where the lead screw nut on the lead screw coupled to least one of the carriage motors is external to the carriage motor.

13. The impedance tuner of claim 10 , wherein the plurality of carriages connected to the single lead screw is two carriages.

14. The impedance tuner of claim 10 , where the plurality of carriages connected to the single lead screw is more than two carriages.

15. The impedance tuner of claim 10 , further comprising:

a controller coupled to the motorized drive system and configured to provide drive commands to control operation of the motorized drive system.

16. The impedance tuner of claim 10 , further comprising at least one probe carried by each of the plurality of carriages and configured for motion transverse to the RF transmission line.

17. The impedance tuner of claim 10 , wherein the RF transmission line is a slabline, comprising a center conductor disposed between opposed ground plane structures.

18. The impedance tuner of claim 10 , where the lead screw does not rotate.