Modulation and codification of ultrasonic signals with EMFI transducers

The electromechanical film (EMFi) is a thin polypropylene film with electret properties, high flexibility and large bandwidth. Ultrasonic transducers built with EMFi film can overcome the limited bandwidth of currently available transducers for air applications, and permit the use of spread spectrum CDMA (Code Division Multiple Access) signal processing techniques, with potential benefits in many ultrasonic applications. In this communication we report the use of CDMA techniques with custom built EMFi transducers, applying signal modulation and codification and processing gain for enhanced signal detection and ranging.