TIME-FREQUENCY REPRESENTATION ENHANCEMENT: APPROACH BASED ON IMAGE FILTERING METHODS

Abstract

The task of filtering of the time-frequency representations, obtained by the S-method, using advanced digital image processing filters, both local and nonlocal is considered. Such enhancement is important for design of the time-varying filters for processing of nonstationary frequency modulated signals. The class of local filters is represented by spatial domain filtering using median and related filters. Orthogonal transform based denoising is represented by DCT domain filtering. The block matching 3-D filter is considered as a representative of nonlocal filter class. It is demonstrated that the noise in the time-frequency representations based on Smethod has rather complicated nature: non-Gaussian pdf, spatially correlated properties with varying parameters. It is shown that direct application of the considered filters to such a challenging noisy environment is not possible. Then, several filter modifications are proposed and analyzed with respect to integral and local parameters – MSE and MAE. The block matching 3-D filter is shown to provide the best results but at the expense of quality loss in representation of weak components.

Keywords

• частотно-часовий розподіл
• s-метод
• цифрова обробка зо