Transferring data using ultrasound

Question

Yamaha InfoSound and ShopKick application use technologies that allow to transfer data using ultrasound. That is playing an inaudible signal (>18kHz) that can b

Answer 1

Can't say for Yamaha InfoSound and ShopKick, but what we used in our project was a variation of frequency modulation: the frequency of the carrier is modulated by a digital binary signal, where 0 and 1 correspond to 17 kHz and 18 kHz respectively. As for demodulator, we tried heterodyne. More details you could find here: http://rnd.azoft.com/mobile-app-transering-data-using-ultrasound/