Research On The Generation Of Multi-channel Sinusoidal Signals In Audio Band

In the test system of scientific research and engineering practice,often require multiple signals as the excitation source,such as mechanical system,underwater acoustic detection system.The traditional method to obtain multi-channel signal is to use multiple signal generator / arbitrary wave generator,used together with large numbers of identical analog circuits and digital circuits.This method of large volume hardware,high cost,high power consumption.On the other hand,because each source is independent of the clock,the clock even if the absolute error and the temperature drift coefficient is extremely small,due to the accumulation of time,the output of each channel excitation after long time working,the signal channel does not match the degree of increase.Therefore,two key technologies need to be solved in multi-channel excitation system.The one is small size and low power consumption,and the others is Synchronization between channel signals.Now the rapid development of digital technology,especially the wide use of large capacity,high speed CPLD/FPGA.This paper makes full use of the digital resources of CPLD/FPGA to study the method of generating sinusoidal signal in the audio channel,and the circuit design and simulation.Firstly,a multi-channel audio signal generation method based on FPGA is studied,FPGA embedded RAM resources,the sine wave form can be cured in FPGA,based on the principle of SPWM waveform transformation,the paper studies the relationship between the number of extended channels and FPGA resources,and designs the analog circuits.The 8 channel SPWM logic signal is designed and simulated,and the sinusoidal signal is realized in the range of audio by taking the three channels as an example.The simulation design of SPWM logic signal and the occurrence of sine signal show that the method can realize the multi-channel signal in the audio range,the frequency can reach 10 k Hz.The circuit is simple,only one signal input line can bemade,the full use of digital resources,FPGA internal RAM resources,and the number of channels depends on the RAM resources within the FPGA In addition,each channel between the signals can also achieve isolation.Secondly,the method of generating multi-channel audio segment sine signal without memory resource is studied,by using the principle of sine multiplication,based on the CPLD 8 channel and the FPGA based on the 56 channel control circuit simulation design.Then,taking the three channels as an example,in the range of the audio,the design of the switching multiplication sine transform circuit is designed.The method does not need to occupy RAM resources,which is easy to expand the number of channels,the number of lines is 2N+1,where N is the number of channels.