[mathcad] Re: DSP method

Author: Chris Whitford Posted: Tue, 17 Jan 2006 10:09:30 +0000

The Nyquist frequency doesn't limit the accuracy of the phase measurement.
This is determined more by the total length of the data, and how sharp the
correlation is. You can interpolate to find the peak of the correlation,
but this is only one sample from a distribution. If the same experiment
were repeated multiple times, one would expect to find a scatter on this
position. Depending on the quality of the data this scatter could more or
less than the time step.

Chris

At 01:10 17/01/2006 -0500, you wrote:
>Since the data is sampled at discrete time-steps your time resolution is
>Nyquist limited. So for example, if the data is sampled at 2 kHz, you
>cannot resolve anything finer than 1 kHz - or 1 ms precision. So
>increasing the sample rate to 2x greater than the highest frequency you
>anticipate that you will need to resolve will work. Be careful to use the
>correct low-pass filters to prevent aliasing the data.

+ Chris Whitford
+ Research Fellow, University of Leicester, Space Research Centre,
+ Physics and Astronomy Department, University Road, LEICESTER LE1 7RH, UK
+ Tel: +44 (0)116 252 3496, Fax: +44 (0)116 252 2464
+ email: "chw" http://www.star.le.ac.uk/

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