Synchronous Sampling and Applications to Analytic Signal Estimation

Analysis of signals in Hilbert space is used for narrowband communications signals in both linear and exponential modulation formats (i.e. QAM, QPSK, FSK etc). Less well known perhaps is the use of the analytic signal in broadband, non-linear modulation analysis. Inter-symbol interference (ISI), Deterministic Jitter, phase noise, and AM-PM conversion are examples of non-linear system impairments whose measurement and analysis are simplified using analytic signal techniques in Hilbert space. Synchronous sampling allows for direct demodulation and extraction of baseband In-phase and Quadrature channels. Its application to measurement of both random and deterministic jitter, phase noise, and AM-PM effects is discussed, as well as calibration methods and other accuracy enhancement techniques. Synchronous sampling is contrasted to conventional waveform recorder timebases: real-time sampling, random equivalent-time sampling, and triggered sweep. Synchronous Sampling uses a phase locked timebase with delay control and carrier extraction to provide a rotating reference frame in Hilbert space, from which the signals are analyzed in three dimensions: I and Q vs. Time or Modulation Frequency.