| CPC G01R 31/2887 (2013.01) [G01R 31/308 (2013.01); G01R 35/005 (2013.01)] | 10 Claims |

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1. A test system for testing a device, the test system comprising:
a source of pulsed radiation configured to provide a generating radiation beam and a receiving radiation beam, wherein the generating and receiving radiation beams are pulsed radiation beams;
a first signal conversion device arranged to receive a pulse of the generating radiation beam and configured to output a signal pulse in response to receiving a pulse of the generating radiation beam;
a second signal conversion device arranged to receive a pulse of the receiving radiation beam and configured to sample a signal pulse in response to receiving a pulse of the receiving radiation beam;
a transmission line arrangement configured to direct a signal pulse from the first signal conversion device to a device under test and to direct a signal pulse reflected from the device under test or transmitted through a device under test to the second signal conversion device; and
a direct-drive delay line positioned in the optical path of the generating radiation beam and/or the receiving radiation beam, the direct-drive delay line being configured to introduce an optical delay between the generating and receiving radiation beams such that a pulse of the generating radiation beam is incident on the first signal conversion device at a different time to a corresponding pulse of the receiving radiation beam being incident on the second signal conversion device;
wherein the direct-drive delay line comprises:
at least one reflector positioned in the optical path of the generating and/or receiving radiation beams; and
a synchronous linear motor configured to move the reflector so as to vary the optical path length of the generating and/or receiving radiation beams so as to vary the optical delay between the generating and receiving radiation beams.
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