A Real-Time Digital Approach to Time Delay Spectrometry
A method of extracting Time Delay Spectrometry (1)(2) measurements using 56000 Digital Signal Processing (DSP) Software. The chirp output signal, mixer quadrature chirps, and IF low pass filters can be done digitally at audio sample rate (48 kHz). Time delays are removed with chirp phasing. The process of data gathering for Energy Time Curves (ETC) is similar to that of Energy Frequency Curves (EFC). Fully processed EFC measurements are stored in local memory. ETC measurements are completed with windowing(6) and block floating point FFT /3/. The Hardware is placed in a box which can be connected to a serial port (RS-232) as well as an IEEE-488 port for GPIB interface. Two channel synchronously sampled input and one channel output make other measurements possible (4)(5).
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