Digital synthesis of analog signals for audiometric applications
Simona Brigati, Fabrizio Francesconi, P. Malcovati, M. Poletti, Franco Maloberti · 2002
This paper presents a novel signal generator, based on the direct digital synthesis (DDS) technique, which fulfills the requirements of advanced audiometric systems. The described solutions face two different problems, namely the generation of a finely tunable pure sinewave and the generation of noise signals with controlled spectrum. In order to achieve tuning capabilities down to 1Hz at 20 kHz or 15 /spl mu/Hz at 100 Hz, a fractional division of a 40 MHz master clock with noise shaping of the resulting error is performed. Moreover, for noise generation a novel circuit based on pseudo-random sequences combined with analog SC filters is used.