Abstract:Taking FPGA as the control core,a dual signal single channel transmission device was designed.The pulse frequency modulation(PFM) and pulse width modulation(PWM) are used to modulate the signal,and simultaneous transmission is achieved by infrared light.The audio signal is sampled by high-speed AD of FPGA at transmitting end,and then the audio signal modulation is achieved through the PFM and PWM;the optical pulse is demodulated and output by FPGA at the receiving end.The transmission circuit and the receiving circuit adopts complete discrete components,and it has the advantages of low cost,low power consumption and high transmission efficiency.The design results show that 1 ~10 kHz audio signal and digital signal can be in a channel for real-time transmission without distortion within 12 meters.Transmission signal can transmit to the different directions after crossing the relay station,and the relay station power consumption is only 0.08W,which meet the energy requirements.