This paper presents an integrated prototype of a mixed-signal sinewave analyzer. It extracts, in the digital domain, the DC level and the amplitude of the harmonics of a distorted analog sinewave signal. It is based on a double modulation, squarewave and sigma-delta, together with a simple digital processing algorithm. The presented prototype has been integrated in a 0.35 mum technology. It is intended for the characterization of sinewave signals in the range of audio. Experimental measurements in the lab verify the feasibility of the approach and the functionality of the prototype