Design And Implementation Of 2.5GHz Bandwidth Low Noise Analog Channel

There will be many small signal conversions and transmissions in modern electronic systems.High-precision measurement of weak high-frequency small signals requires high-bandwidth,high-resolution oscilloscopes.One of the key points of developing an oscilloscope with high bandwidth and high vertical resolution is to design a signal conditioning channel with high bandwidth and low noise.Through theoretical analysis,principle and layout simulation,this thesis designs and implements an analog channel of an oscilloscope with a bandwidth of 2.5GHz and a peak-to-peak noise floor of less than 1.5div(1mV / div).The paper mainly studies the following:1.Conducted noise analysis on the signal conditioning channel.The noise calculation methods commonly used in the noise analysis of the signal conditioning channel and the types of common noise in the signal conditioning channel are introduced.The noise analysis and theoretical noise calculation of the variable gain amplifier circuit that affects the output noise of the signal conditioning channel are large.And proposed methods and measures to reduce the output noise of the signal conditioning channel.2.According to the low noise requirements of the post-stage acquisition system,the circuit structure of the signal conditioning channel is designed.Through theoretical analysis,software simulation,and test comparison,the broadband impedance conversion circuit and variable gain amplifier circuit of the signal conditioning channel are synthesized with low noise Designed and implemented a low-noise analog channel with 2.5GHz bandwidth.3.Trigger channel design.The high-speed comparison circuit required for trigger output is mainly designed,and the principle of the high-speed comparison circuit is analyzed to realize the broadband edge trigger of the oscilloscope.4.Design and implementation of analog channel control circuit.The control circuit of the analog channel of the oscilloscope based on the STM32 MCU is designed,and the functions of gain adjustment,state switching,temperature measurement,overvoltage protection and voltage offset of the analog channel are realized.Finally,this paper tests and verifies the relevant indicators of the analog channel.The-3dB bandwidth of the analog channel reaches 2.5GHz.At 1mV per div,the fullbandwidth noise floor of the signal conditioning channel is only 1.37 mVpp.The isolation is greater than 300: 1,and other relevant indicators meet the design requirements.