Harmonic

Version 0.1.0, January 2011

Harmonic provides a program for analysis of data in the harmonic domain. Data is analysed for visibility of fringes, domain shifts and chirp.

Motivation; Technology; License

Harmonic is based on code I originally wrote and developed in Labview over 6 years to aid in my research. Due to a lack of reverse compatability with Labview and many unwanted saves in new versions I decided to rewrite the program using only free software to ensure its portability (and that of myself and my research). Harmonic uses the PlotLinear widget to visualise data. Transformation of the data is carried out using the fftw3 library developed by Matteo Frigo and Steven G. Johnson [1]. The code compiles & works (more or less) under gtk+2. Harmonic is released under the GNU GPL version 2 or (at your option) any later versions. See the accompanying license file for details.

Usage

Data is loaded (A variety of devices are supported -- see Data Format in the Properties menu -- if none work please send a sample to the email in AUTHORS to update the list) and transformed to the inverse domain using a Fourier transform that takes data windowed according to the spectrum start and stop values. Multiple windows can be selected using the j index. As the Fourier transform is most efficient when a power of 2, the zero pad vaue adds clips or extends the window with zeros to meet this. Make sure to set the offset to a good baseline to avoid ripples in the inverse domain due to Gibbs phenomenon. Similar analysis is applied in the inverse domain. The domain shift does a triangular weighted mean over the harmonic peak (set the centre and full width of the triangle to get best results). The visibility also requires the full width of the peak at zero frequency to normalise itself. Multiple peaks can also be analysed using the k index. See the documentation obtained through the help menu for more detailed instructions.

References

1. M. Frigo and S.G. Johnson, “The design and implementation of FFTW3,” in Proc. IEEE, Vol. 93, Iss. 2, pp. 216–231 (2005).

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