Design Of Analog Channel For Broadband Large Dynamic Acquisition System

In order to meet the increasing complexity and instantaneity of modern electromagnetic interference testing requirements,time-domain measurement structure is widely used in modern electromagnetic interference measurement receivers,which puts forward higher requirements for the bandwidth and dynamic range of broadband acquisition system as the digital acquisition part of the receiver.Due to the production process and cost constraints of analog-to-digital converter,it is difficult for digital acquisition system to ensure large dynamic range at the same time of high-speed sampling,so it is necessary to combine large dynamic range signal conditioning circuit to improve the dynamic range of acquisition system.In this paper,the research and design of the analog channel of the broadband large dynamic acquisition system as intermediate frequency acquisition module in a time domain electromagnetic interference measurement receiver system are described,and the key technologies in the analog channel are discussed in detail.Guided by theories of analog electronics,radio frequency circuit design theory and operational amplifier application technology,this design realizes the analog channel of broadband large dynamic acquisition system based on PXIe card by using commercial consumable analog devices and optimizing circuit structure,which provides circuit platform for subsequent analog conversion and digital signal processing.This topic includes the following research contents:Firstly,a method for improving the dynamic range of a broadband acquisition system using a multi-channel synchronous acquisition structure is briefly introduced.According to the design requirements of the analog channel,a scheme of vertical conditioning channel for analog channel with fully differential signal amplifier circuit as the main structure is proposed.Secondly,the main modules of vertical conditioning channel of analog channel are discussed in detail.The resistor power dividing network is designed and tested to meet the demand of DC signal power dividing.A single-ended to differential amplifier circuit is designed for high signal to noise ratio requirements.A gain adjustment module is designed for large dynamic range input signals.Then the noise figure and signal-to-noise ratio of the signal conditioning channel are calculated theoretically.At the same time,the driving circuit of analog-to-digital converter is designed by multi-stage lifting of common-mode voltage,which completes the connection between signal conditioning circuit and analog-to-digital converter.Thirdly,the design of trigger channel is described in detail.The amplitude of external trigger signal is adjusted by an optional attenuation circuit and the selection of multiple trigger sources is realized by using a multiplexer.According to the characteristics of the input port of the comparator,a voltage lifting circuit is designed,and the analog signal is converted into a high-speed digital signal recognized by a digital processor by using a high-speed comparator.Finally,the analog channel is debugged and its important indicators are tested.The experimental results show that the analog channel finally achieves the technical requirements of 300 MHz bandwidth and 90 dB input dynamic range.