Design Of Audiobeam Loudspeaker Based On TMS320VC5509A

Audiobeam loudspeaker, which can emit sound waves to a specific listening area without mutual interference, is a novel loudspeaker. Because of its characteristics of sound focusing, high directivity and long propagation distance, it can be widely used in those occasions where the listening area need to be restricted or secrets should be kept, such as car, airplane, exhibition hall, market, ATM, etc. It has become a research focus recently.The conventional audiobeam loudspeaker is implemented with analog circuit, which has the disadvantages of low accuracy, bad stability and long development cycle. To solve these problems, an advanced audiobeam loudspeaker experiment system based on the 16-bit fixed-point digital signal processor (DSP) is developed in this thesis. The main contents of this thesis are as follows:A complete signal processing algorithm based on the signal processing theories of audiobeam loudspeaker and characteristics of fixed-point digital signal processor is designed. The signal processing algorithm consists of amplitude modulation algorithm, signal preprocessing algorithm and carrier signal generation algorithm.A hardware system design scheme of audiobeam loudspeaker based on 16-bit DSP chip TMS320VC5509A (VC5509A for short) produced by TI company is described in this thesis. It is composed of VC5509A basic system, ADC module (analog to digital converter), DAC module (digital to analog converter), ultrasonic power amplifier and ultrasonic transducer array, etc.The software design of audiobeam loudspeaker system is introduced. The key modules are as follows:the main program, timer interrupt initialization subroutine, AD initialization subroutine, DMA interrupt subroutine and signal preprocessing subroutine. Double sampling and ping-pang cache structure are applied in the software design. The usage of double sampling can reduce the computation greatly and improve the system's real-time while meets the signal processing requirement. Ping-pang cache structure can provide more time for signal processing and realize complex signal processing algorithms because the structure can process the signal while acquisition data from analog to digital converter. The audiobeam loudspeaker system designed in this thesis can realize complex signal processing algorithms flexibly, generate carrier signal accurately and has advantages of well stability, high reliability and high precision.