.2.4 The G Wireless Digital Audio Transmission Module Design And Realization

With the rapid development of LSI (Large Scale Integration) and computer science, the digital technology has been widely used. The development of digitization has become the necessary trend in modern wireless video and audio transmission system. The mission of this project is to design a low-cost wireless digital audio transceiver modules based on the old analog wireless video and audio transceiver modules.According to the requirement of the subject, the construction of the system is planed and designed based on the current theory. For digital audio encoding and decoding modules, delta-sigma modulation is introduced and audio data, preambles with accessorial data are multiplexed according to the digital audio interface standard; For carrier wave, PLL frequency synthesizer is used; For frequency modulation, voltage control oscillator is taken; For demodulation, PLL frequency discrimination is adopted.On the basis of analyzing the old system and theory, the element circuits of wireless digital audio transceiver modules are designed in detail including the digital audio encoding and decoding circuits with the surrounding circuits, the FSK circuit based on PLL frequency synthesizer, the power amplifier circuit, the frequency discrimination and AGC circuit. The surrounding circuits design mainly includes the clock circuit, mute circuit and antenna switching circuit. The precise clock source is crystal oscillator made of 74HC04; The mute circuit can conceal the error and solve the problem of noise; The antenna switching circuit in the receiver is to select one antenna from two which receives signal better. It can improve the quality of the receiving audio signal, restrain the noise effectively and promote the system performance. The key of the FSK design is the calculation,simulation and optimization of the charge pump PLL chip, VCO and loop filter. The automatic gain control achieves higher dynamic range.The circuits are adjusted and actually tested. The result of the test indicates the accomplishment of target and verifies the rationality of circuit.