Abstract
The Interpolated DFT is a non time-consuming supplement to the DFT algorithm. It allows to achieve a much greater frequency measurement accuracy than the DFT and is easily applicable to multitone spectrums. A very simple variant of the Interpolated DFT, proposed and analyzed in previous papers, was implemented in the frequency meter. The introduced device allows to check the correctness of the theoretical limitation and simulation results obtained earlier. The instrument is based on a microcontroller with a DSP unit and a 14-bit fast AD converter. The actual properties of the meter were introduced in the paper. The accuracy of the frequency measurement, the influence of the number of samples in a series and the influence of measured signal amplitude variation during acquiring a series of samples on the accuracy are consistent with the theoretical limits and simulation results with one exception. A boundary of the accuracy of frequency measurement related to used single-precision floating point format occurred. The limiting parameters of the introduced meter are: rate of measurements up to 410 per second and standard deviation about 7.6·10-8.DOI: http://dx.doi.org/10.5755/j01.eie.23.3.18331
Highlights
Modern frequency spectrum analysis often involves the Discrete Fourier Transform calculation
The goal of this paper is to compare the practical properties of the Interpolated DFT with that of the theoretical limits
Frequency measurement is based on frequency estimation by the Interpolated DFT method
Summary
Modern frequency spectrum analysis often involves the Discrete Fourier Transform calculation. In the following years other versions of Interpolated DFT method were introduced [2]–[6] and applied in various areas [7], [8]. The goal of this paper is to compare the practical properties of the Interpolated DFT with that of the theoretical limits. For this purpose, a frequency meter that implements one of the Interpolated DFT method was built. By calculating the FFT the digital spectrum is obtained. Frequency measurement is based on frequency estimation by the Interpolated DFT method. Only one coefficient has to be calculated to use the proposed Interpolated DFT method with a new window. For other mentioned popular windows systematic error is about a thousandth of the value of the frequency bin
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