Radioengineering (Apr 2008)
Wavelet Based Hilbert Transform with Digital Design and Application to QCM-SS Watermarking
Abstract
In recent time, wavelet transforms are used extensively for efficient storage, transmission and representation of multimedia signals. Hilbert transform pairs of wavelets is the basic unit of many wavelet theories such as complex filter banks, complex wavelet and phaselet etc. Moreover, Hilbert transform finds various applications in communications and signal processing such as generation of single sideband (SSB) modulation, quadrature carrier multiplexing (QCM) and bandpass representation of a signal. Thus wavelet based discrete Hilbert transform design draws much attention of researchers for couple of years. This paper proposes an (i) algorithm for generation of low computation cost Hilbert transform pairs of symmetric filter coefficients using biorthogonal wavelets, (ii) approximation to its rational coefficients form for its efficient hardware realization and without much loss in signal representation, and finally (iii) development of QCM-SS (spread spectrum) image watermarking scheme for doubling the payload capacity. Simulation results show novelty of the proposed Hilbert transform design and its application to watermarking compared to existing algorithms.
