Research On Direct Data Synthesis Method Of Audio Superimposed Signal

In order to understand the characteristics of the object to be measured,it is necessary to apply an excitation to the object to be measured,and then measure the output signal of the object to be measured.The applied excitation signal can be a simple function or a specific arbitrary waveform.Sometimes,a mixed signal formed by the superposition of multiple simple functions is also required.If a plurality of signal sources are used to simulate superposition to generate a mixed signal,the instrument system is bulky and inconvenient to use;if the mixed signal is quantized into an arbitrary wave signal,editing and transmitting the arbitrary wave signal is time consuming and laborious.Using the field programmable feature of the FPGA,the FPGA is configured as a mixed signal synthesized by direct data of several standard function signals without changing the overall function of the existing function/arbitrary wave generator,so that the function/arbitrary wave generator has one more Kind of work mode.Therefore,this design studies a direct data synthesis method for audio superimposed signals.The feasibility,technical key and circuit implementation of the method are studied.Digital logic-based modeling of basic waveform signals,such as sine waves,triangular waves,pulse waves,piecewise linear function waves,etc.According to the periodic signal,the function expression of the plurality of component superposition signals can be derived based on the theoretical basis of the Fourier series expansion.By comparing the advantages and disadvantages of several superimposed signal synthesis methods,a direct data synthesis scheme of superimposed signals is proposed,and the hardware circuit structure of the direct data synthesis generator of superimposed signals is given.According to the principle of direct data waveform generation,the influence of phase truncation error and amplitude quantization error on the output spectrum of DDS is quantitatively analyzed.The DDS spurious suppression method is proposed and applied in circuit design.In the process of theoretical analysis of the superposition signal synthesis method,if there are many components,the component parameter optimization and the component amplitude value weight optimization are performed,the data is optimized and the error analysis is performed,and the synthesis after the optimization process is performed.The relative error between the value and the original component composite value is less than 0.1%.Finally,according to the above theoretical analysis,the characteristics of digital circuits and the situation that each signal component occupies hardware resources,under the existing conditions of the laboratory,28 sine wave components,4 pulse wave components and 4 triangular wave components are realized inside the FPGA.The direct data synthesis circuit of the superimposed signal is compiled and passed.Comparing the optimized data with the data before optimization,the quantization error between the two is negligible.The research of this method does not increase the hardware cost,and the parameter setting is convenient.