Chaotic radio for audio communications

Chaotic wireless communication system suitable for audio transmission has been designed and implemented. The chaotic module was based on Chua´s circuit and it has been realized from inductor, capacitor, resistor, and non-linear negative resistor. The negative non-linear resistor was constructed from resistors and operational amplifier. Chaotic masking technique has been selected as a mean of chaotic data modulation whereas synchronization relies on Pecora-Carroll technique. The chaotically-modulated signal has been further frequency modulated to frequency centered at 9 MHz making the system immune to non-linearity of the communication channel. Such frequency modulation process was achieved by voltage-controlled oscillator inside 74HC4046 IC. On the receiving end, the FM demodulation was performed by employing phase-locked loop technique. Measured results of the presented radio system are also given.