Research On Ultra Wideband Data Acquisition Systems Based On Bandwidth Interleaved Technology

Ultra-wideband data acquisition(DAQ)system is the basis for cutting-edge appli-cations such as ultra-wideband radars,5G/6G communication technologies,and high-end electronic test instruments.With the continuous increment of the signals'bandwidth and rate in electronic systems,their transient and complexity characteristics also rise accord-ingly,which puts forward higher requirements on the sampling rate and bandwidth of elec-tronic systems.Due to the limitations of the existing Analog to Digital Converter(ADC)integrated circuit technology,single-channel ADCs have failed to meet high bandwidth and high sampling rate requirements of DAQ systems.The parallel architecture-based DAQ systems have become an effective solution to overcome the limitation of the single-channel ADC's performance.Based on the status quo of DAQ systems' high-speed and high-bandwidth require-ments,this dissertation studies the parallel DAQ system based on Bandwidth Interleaved(BI).A series of studies have been carried out on the goal of perfect reconstruction(PR)of the input signal in BI-DAQ systems.Problems in BI-DAQ systems,such as the de-composition of the analog input signal,phase synchronization between analog and digital local oscillators,phase compensation of overlapping band between subbands,amplitude and phase response compensation of passband,have been studied and solved in this dis-sertation.The specific research content is as follows:(1)After analyzing and discussing the characteristics of various parallel DAQ sys-tems,this dissertation studies the BI-based parallel DAQ system to realize the high-bandwidth and high-speed DAQ system.A complete mathematical model for the PR of the input sig-nal in the BI-DAQ system is established,which provides reliable theoretical support for subsequent research works.Based on the existing low-speed and low bandwidth ADC chip,the dissertation explores a DAQ architecture that can increase the bandwidth and sampling rate of the acquisition system in multiples.(2)This dissertation focuses on the spurious distortion of subbands' digital back-end recovery and phase synchronization of analog and digital local oscillators in BI-DAQ systems.In the process of subbands recovery,the spurious distortion introduced by up-sampling and up-conversion is analyzed,and finite impulse response(FIR)filters with linear phase response are used to eliminate the spurious to avoid introducing additional errors.Meanwhile,the probability distribution and statistical characteristics of random phase error between analog and digital local oscillators are analyzed and discussed via two-dimensional Lissajous-Bowditch figures.According to the synchronization relation-ship between the analog local oscillator and the sampling clock,a synchronization phase error compensation mechanism based on synchronization timestamp is proposed.The mechanism can realize phase synchronization between analog and digital local oscillators in a Field Programmable Gate Array(FPGA)without any additional circuits.The exper-imental results show that FIR filters with linear phase response can refrain all kinds of spurious introduced during the subband recovery in digital back-end,and the proposed synchronization mechanism for local oscillators can eliminate the random phase between analog and digital oscillators in BI-DAQ systems,which provides a prerequisite for the PR of BI-DAQ systems.(3)The effect of phase error of overlapping band between adjacent subbands of BI-DAQ system is studied with deducing the fringe condition.A "linear+nonlinear" phase compensation structure based on digital all-pass filter(APF)is proposed for compensating the phase difference between subbands in the overlapping band.The design problem of fil-ter coefficients and parameters in the structure is transformed into a nonlinear optimization problem.On this basis,a hybrid particle swarm optimization Levenverg-Marquardt(HP-SOLM)nonlinear optimization algorithm is proposed.The Levenverg-Marquardt(LM)algorithm accelerates the iteration speed of the PSO algorithm and reduces the random-ness of PSO's iteration results.At the same time,the PSO algorithm solves the problem of selecting the initial value of the LM algorithm.By mapping the iterative variables of the LM algorithm,this algorithm overcomes the problem that the unconstrained optimization algorithm(LM)may lead to the instability of APF in the proposed compensation struc-ture.The experimental results show that the phase response compensation structure of overlapping band designed by HPSOLM can reduce the influence of overlapping band on the amplitude-frequency response to 0.33 dB,which eliminates the influence of the phase difference between subbands in overlapping band,and avoids the additional amplitude response error in the process of BI-DAQ systems'reconstruction.(4)Aiming at the PR problem of BI-DAQ systems,a divide-and-conquer-based PR strategy is proposed which divides the PR problem into amplitude and phase response PR,respectively.The error estimation methods of amplitude and phase response distortion are proposed based on sinusoidal sweep signal and broad-spectrum signal.According to the estimated distortion errors,an FIR filter with linear phase and an APF are designed to compensate the amplitude and phase response distortion of the system,respectively.The matrix description of amplitude response compensation is derived,and the problem of amplitude compensation filter design is transformed into a problem of linear system solution,which is solved by the Krylov subspace iteration method based on Gauss-Seidel preconditioning,which realizes the amplitude PR of the BI-DAQ system.After that,an APF is used to compensate the phase distortion of BI-DAQ systems.For wider pass-band in BI-DAQs,volatile phase response distortion may lead to the compensation APF with problem of a high order.This dissertation proposes an APF design method based on the improved graphic method.The proposed algorithm can deal with the the precision problem of the APF filter design with high order,and guarantee the stability of APF.The experimental results show that the amplitude response compensation filter designed by the Krylov subspace itseration method based on the BiCGStab algorithm has higher compen-sation accuracy than the filter designed by the traditional frequency sampling method with same filter order.Meanwhile,the improved graphic method proposed in this paper is used to design an all-pass filter,and the compensated group delay fluctuation of the BI-DAQ system is ±0.4 Ts,which realizes the PR of the BI-DAQ system.Based on the research of BI-DAQ systems,a high-speed broadband DAQ system with a sampling rate of 40 GSa/s and bandwidth of 10 GHz is implemented in a digital storage oscilloscope prototype,which provides an experimental platform for the verification of key technologies in BI-DAQ systems.In addition,the synchronization problem of multi-ADC and multi-FPGA in parallel DAQ systems is studied and the corresponding solution is proposed.The test results show that the BI-based parallel DAQ architecture can improve the sampling rate and bandwidth in multiple based on the single-chip ADC performance.The amplitude-frequency response of BI-DAQ system fluctuates less than ±0.5 dB and the rise time is 37.17 ps,which is in the leading position among all kinds of literatures and products in domestic.