An Algorithm For Selecting Sampling Rate In Arbitrary Waveform Generator

The direct digital waveform synthesis system(DDWS)contains a variable clock,which can output waveforms with different sampling rates.DDWS satisfies the situation where the waveform sampling rate changes,and is a key technology in the arbitrary waveform generator.For the AWG under DDWS technology,the selection of the sampling rate will affect the number of points of the output waveform and the complexity of the waveform generation process.When the waveform is transmitted with the maximum sampling rate,the number of points of the output waveform is uncertain,when the number of points is greater than the AWG's memory upper bound,the integral waveform cannot be output.Therefore,this paper mainly studies the sampling rate selection of AWG under DDWS technology.The main research contents of this thesis are as follows:1.Explain the principle of waveform generation by DDWS,and analyze the modulation process and principle under Amplitude Shift Keying(ASK),Frequency Shift Keying(FSK),Phase Shift Keying(PSK)and Quadrature Amplitude Modulation(QAM).Finally,take QAM as an example to analysis the process which from the baseband data generation to the final generation of the modulated signal in different modulation modes,and summarize waveform transmission process under different modulation methods.2.Analyze the anti-aliasing of the periodic waveform,and obtain the range of sampling rate under the anti-aliasing.Then according to the relationship between the sampling rate range and the waveform frequency,the specific selection method of the sampling rate is obtained by using the integer existence theorem between two points.Finally,the required memory depth at different sampling rates is quantitatively calculated and compared.3.Analyze the anti-aliasing of the modulated wave,and obtain a quantitative expression of the sampling rate range under the anti-aliasing.And obtains the general relationship between the sampling rate and the symbol rate in the modulation.Then,according to the different modulation methods,the conditions of sampling rate under different modulations are analyzed.Finally,the final expression of the sampling rate under different conditions is given.4.Prove the applicability and superiority of the proposed sampling rate selection method.Set different parameters to generate different waveforms,and calculate the required sampling rate according to the proposed method.Then,the waveform is outputted simultaneously with the maximum sampling rate at the calculated sampling rate,and the computational complexity,required memory depth,spectral characteristics,and power spectral density in the waveform output process are compared.The simulation results show that when the sampling rate is used to output the periodic waveform,the software computational complexity and the required memory depth in the waveform output process are greatly reduced.When the modulation wave is output,the sampling rate in this paper is used.The harmonic amplitude components in the spectrum of the output waveforms under binary ASK,PSK,QAM,and FSK lower,which improves the quality of the output waveform.