Theoretical analysis and the engineering design have been completed for a totally new way to acquire EPR spectra, which we call Time Locked Sub Sampling (TLSS). An offset coherent microwave reference is synthesized resulting in data of interest appearing as envelope modulation of an IF carrier. Another synthesizer creates a frequency equal to (4/3) of the intermediate frequency, and this is used for the conversion frequency of an analog to digital (A/D) converter. In the frequency domain, the data are no longer centered at 0 frequency but at an offset frequency. The familiar Nyquist condition that determines the cutoff frequency of an optimum low pass filter for the A/D converter is no longer valid; the generalized Nyquist condition must be used establishing the characteristics for a bandpass filter. For periodic signals as in field modulation or multiquantum EPR, constraints are imposed on the modulation frequency and the record length. The first TLSS experiments were performed and results are being analyzed. This initial series of experiments are being conducted using 14.3 Khz field modulation. Each scan results in a 137 Mb data file which is then post processed on a PC. ?
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