1. Introduction

The estimation of frequency, amplitude and phase of single-frequency and multifrequency signals has applications in many fields of engineering. In general, estimation methods are based on Fourier analysis or parametric modeling. The advantage of Fourier-based methods is their computational efficiency, compared with the mathematical complexity of the parameters-based algorithms, which demand a high amount of computational resources. The standard method for Fourier analysis in digital signal processing is the discrete Fourier transform (DFT). For some real-time applications, the direct application of the conventional DFT may result in an excessive computational cost. However, certain applications require an online spectrum analysis only over a subset of M frequencies of an N-point DFT ðM < NÞ. For this scenario, the common practice is to utilize a single-bin sliding DFT (Sb-SDFT) technique. These recursive algorithms efficiently calculate a unique spectral component of an N-point DFT. Nevertheless, the direct application of DFT-based methods for spectral analysis may lead to inaccuracies due to the spectral leakage phenomenon. These unwanted effects are related to the frequency variation and improperly selected sampling time window. This problem can be

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© The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons

distribution, and eproduction in any medium, provided the original work is properly cited.

solved using an adaptive coherent sampling mechanism. One of these mechanisms is known as variable sampling period technique (VSPT) and is characterized for the dynamic adjustment of the sampling period to exactly N times the fundamental frequency, thereby avoiding the above-mentioned problems.

The chapter is organized as follows: Section 2 presents a brief review of Sb-SDFT. Section 3 evaluates and compares the four selected Sb-SDFT algorithms in diverse operational conditions, identifying the similarities between them. In order to mitigate the inaccuracies resulting from the spectral leakage effect, a scheme for coherent sampling based on VSPT is introduced in Section 4. Altogether a unified model is also presented to generalize this scheme to all Sb-SDFT along with simulation results. Finally, the conclusions of this chapter are drawn in Section 5.
