Blackman window

Applying this expression with the four-term Blackman windowed Fourier transform approach led to sufficient accuracy based on a relatively short trajectory (10 ps), i.e., the authors fotmd excellent agreement between the experimentally obtained spectra for liquid water and ice. Using this approach and decomposing the total dipole moment... 

Windows are weighting functions applied to data to reduce the order of the discontinuity at the boundary of the periodic extension. Harris [71] has given a comprehensive review of the properties of over 30 windowing functions and we illustrate their properties with reference to a Blackman window, W. ... 

Application of the Blackman window removes the side lobes and gives a smooth spectrum with a peak at 10/2tt Hz, but a lower intensity than obtained from the truncated data. Berens and Wilson [72] use a four-term Blackman-Harris window in computing the rotational spectra of CO and Ar from m.d. They note that by... 

Figure 7. The spectrum obtained by Fourier transforming (37), -truncated data, -----Blackman window,. maximum entropy.

The choice of a particular apodization depends on what one is aiming at. If the optimum resolution of 0.605// is mandatory, the boxcar truncation (no apodization at all) should be chosen. If a loss of resolution of 50% compared to the boxcar can be tolerated, the Happ-Genzel, or even better, the Blackman-Harris three term apodization is recommended. Since the Blackman-Harris window shows the highest side lobe suppression and is furthermore nearly zero at the interval ends, it can be considered the top performer. 

FIGURE 20.19 Computer simulation of FFT with Blackman-Harris windowing. The application of windowing prior to the FFT drastically reduces the effects of leakage. Within 23.44 Hz on either side of the fundamental, leakage is more than 90 dB down. Source Tektronix, Beaverton, OR.)... 

---