Acquisition Channel Dynamic Range Extension Circuit Design And Digital Correction Method

The dynamic signal analyzer is an instrument used for on-site testing,which can independently complete the generation,collection,storage,and analysis of dynamic signals.It has good instrument linearity and high resolution,and can complete highprecision sampling of large dynamic range signals.The dynamic range of a dynamic signal analyzer is determined by the conditioning acquisition channel.The development of a conditioning channel with a large dynamic range plays a key role in dynamic signal testing in the fields of mechanical fault diagnosis,multi-modal analysis,electronic design,and acoustic testing.Aiming at the problem of large dynamic sampling where large amplitude and extremely small amplitude signals coexist in a single range of the input conditioning channel of the dynamic signal analyzer,this thesis adopts a strategy of dual ADC synchronous acquisition with fixed gain ratio input,corresponding to the acquisition of large and extremely small signals,To obtain a larger gain for the small signal,through iterative processing of the gain bias of the data collected by the dual ADCs,uniform quantization accuracy,and delay correction,the dual-channel data integration is finally completed,thereby obtaining the expansion of the dynamic range of the system.The conditioning channel described in this thesis has the parameter index requirements of an analyzable bandwidth of 102.4 k Hz and a dynamic range of more than 120 d B.The main research content of this thesis has the following two points:(1)Design and implementation of low-noise front-end signal conditioning acquisition module for dual ADC acquisition.Carry out noise analysis on the channel and rationally design the gain adjustment circuit,and accurately divide the amplification factor of the gain adjustment circuit so that the dynamic range of the low-noise amplification and conditioning circuits at all levels can be maximized.The high-gain channel conditioning circuit is designed to match the low-gain channel to reduce the phase difference between channels and facilitate delay correction.The out-of-band rejection characteristic of the anti-aliasing filter is used to reduce the loss of ADC dynamic range caused by aliasing.(2)Design and implementation of the integration of data collected by dual ADCs and the correction method.Complete the integration of dual ADC acquisition data according to the characteristics of the dual-channel data,analyze the accuracy of the gain ratio coefficient required for the uniform quantization accuracy of the small-gain channel,and use an iterative algorithm to complete the precise iteration of the gain ratio and offset,using the Farrow delay filter to complete The correction of the inconsistency of the dualchannel data delay,divides the dual-channel data integration threshold according to the different effective data bits of the dual-channel sampling data,and finally completes the logic design and implementation of the data integration scheme.Finally,the indicators and noise characteristics of the dual-channel conditioning circuit are tested on the whole machine of the dynamic signal analyzer.The test results show that the input noise,noise floor,and harmonic distortion of the channel are relatively low,and the dual-ADC dynamic range used in this thesis Compared with single-chip ADC acquisition,the expansion scheme can increase the dynamic range by about 12 d B at the9 dB Vrms gear.