Compact Photoconductive-Based Sampling System with Electronic Sampling

Critical issues associated with the design of a rugged, compact "real time" sampling system using photoconductive switches as the signal generator and sample will be investigated. The design concept is based upon an optoelectronic equivalent time sampling principle developed by the Principal Investigator. It involves first the phase locking of the temporal waveform to be measured to the optical pulses and subsequent sampling of the locked waveform. The photoconductive switches are used both as optical-microwave mixer and sampler. The optical-microwave intermixing process generates a low frequency replica of the high frequency waveform to be sampled. The frequency ratio of these waves is the time expansion factor. Since there is no electro-mechanical moving part involved, the sampling is done at a fast rate. The record acquisition time of 10 s per sweep can be achieved. Other issues concerning electronic sampling delay, epoch time, number of sampling points per epoch, resolution time, photoconductor carrier lifetime, sensitivity, signal-to-noise ratio, dynamic range, etc., will also be investigated. A preliminary experiment demonstrating the operation principle of the equivalent time sampling will be carried out. A complete Phase II system design of a pulse parameter testing instrument which will meet most requirements as specified in Subtopic 8.7.3T will be presented at the end of Phase 1.