Research And Implementation Of Synchronous Control Method For Waveform Synthesis Module Based On MUX DAC

The requirements of modern test system for the type,bandwidth and number of excitation signals are increasing.Direct Digital Synthesis(DDS)is one of the mainstream excitation signal generation methods.Since its essence is digital sampling technology,the sampling rate index of DAC is the main factor limiting the bandwidth of output signal.MUX DAC(Multiplexer DAC)is widely used in the field of broadband signal synthesis because it has multiple parallel data input channels and can achieve ultrahigh sampling rate index through the parallel-series conversion of internal data flow.When waveform synthesis module based on DDS technology generates multichannel excitation signal,the condition of synchronization between channels is data source synchronization and DAC synchronization.However,the working clock of the internal data processing module of MUX DAC is the clock after N frequency division,and the clock phase after N frequency division is random.This leads to multi-chip MUX DAC internal data flow synchronization difficulties,thus affecting the synchronization of multiple excitation signals.This thesis focuses on the research and implementation of the multi-channel synchronization control method of waveform synthesis module using MUX DAC,which mainly includes:1.Research on synchronization control method of multi-channel waveform synthesis module.Through the modeling of waveform synthesis module based on DDS technology,the synchronization conditions of multi-channel waveform synthesis module are obtained : data source synchronization,trigger signal synchronization and DAC synchronization.The difficulty lies in the difficulty of data flow synchronization in multichip MUX DAC caused by frequency division clock.A variety of synchronization control methods are studied for this difficulty,and they are compared and analyzed from the perspectives of synchronization speed,synchronization accuracy and the number of synchronization channels.Then combined with the above synchronization control method,the waveform synthesis module output signal delay adjustment method is further studied.2.Design and implementation of dual-channel waveform synthesis module.In order to verify the feasibility of the phase-locked loop synchronization control method and delay adjustment method in the above synchronization control method,this thesis plans to design a 2.5 GSPS dual-channel waveform synthesis module,and realize the synchronization accuracy of 50 ps between channels,the delay adjustment range of 0 ?2ns and the delay adjustment resolution of 10 ps.The waveform synthesis module adopts the architecture of ' address generator + waveform lookup table + DAC ',and adopts multi-memory parallel data generation structure according to the sampling rate index.The clock circuit uses the phase-locked loop output to directly provide the sampling clock for the DAC.At the same time,in order to introduce the MUX DAC into the phase-locked loop feedback loop,it is decided to use the discrete phase detector and the voltage controlled oscillator chip.A third-order active loop filter with a bandwidth of 122 k Hz is designed from the perspective of voltage demand,loop stability and phase noise.In addition,this thesis plans to realize the delay adjustment range and delay adjustment resolution index through the ' coarse adjustment + fine adjustment ' scheme,that is,to realize the 0 ? 2 ns delay adjustment range by adjusting the waveform sample points,and to realize the 10 ps delay adjustment resolution by adjusting the sampling clock by reference clock.Finally complete the waveform synthesis module corresponding logic design.In this thesis,several synchronization control methods and delay adjustment methods of waveform synthesis module are studied and verified.A waveform synthesis module with 50 ps synchronization accuracy between two channels is realized by phase locked loop,and 37.612 us fast synchronization,0 ? 2ns delay adjustment range and 10 ps delay adjustment resolution can be realized.This will promote the research of synchronization control method and delay adjustment method of multi-channel waveform synthesis module based on MUX DAC in China.