I. Introduction
Many applications require processing of the spectral content of the input mechanical signal. Conventional techniques for condition monitoring of mechanical machines based on vibration monitoring for early failure detection generally use algorithms operating in the frequency domain, rather than in the time domain [1]. The complexity and inaccessibility of the systems being monitored ask for permanently mounted vibration analysis systems. Low cost and small size monitoring systems would ensure a rapid penetration in a range of applications [2], [3].