Analog Front-end Design Of 1.5GHz Sampling Oscilloscope Module

Oscilloscope is one of the indispensable instruments for electronic engineers and technicians.It is widely used in electronic industry,aerospace,communication engineering and other fields.With powerful functions,it can assist electronic engineers and technicians to complete all kinds of test and measurement tasks.With the continuous progress of electronic information technology,analog signals are gradually developing towards high frequency,complex and variable trend.For the capture and analysis of these high frequency electrical signals,as well as the attention to the details of the signal,high bandwidth,high resolution digital oscilloscope emerged at the historic moment.However,the design of such a high index oscilloscope is inseparable from the signal conditioning channel with low noise and high bandwidth.Therefore,this paper takes the design of low noise signal conditioning channel as the task objective and studies the following contents:1)Overall design of hardware circuit and noise analysis.In this thesis,the overall structure of the hardware circuit is designed reasonably according to the requirements of the subject index,flicker noise and white noise that involved in the operational amplifier and thermal noise related to its peripheral circuit is introduced,This thesis focuses on the main noise of the operational amplifier and its periphery,simplifies and builds the operational amplifier equivalent noise analysis model,and carries on the quantitative calculation by using general circuit analysis method.2)Design of signal conditioning channel.The passive attenuation network is designed according to the input dynamic range index requirements of the project,and the impedance transformation network is designed based on the separation of high and low frequency paths.The calculation method of the gain of high and low frequency paths is introduced,and the necessity of adjusting them to be consistent is analyzed.The amplifying circuit is designed reasonably according to the gain multiples of each vertical sensitivity gear.Meanwhile,the equivalent output noise of the cascade operational amplifier is calculated according to the theoretical results of noise analysis,and compared with the noise index of the subject.3)Design of trigger conditioning circuit and power supply system.The external trigger conditioning circuit and the channel trigger conditioning circuit are designed around the requirements of analog bandwidth,trigger sensitivity,dynamic range and other indicators.In particular,the channel trigger conditioning circuit adopts an innovative scheme based on D-trigger,which provides a new idea for realizing the channel trigger of high frequency signals.The overall power demand of the whole analog front end is analyzed and calculated,and the power supply chip is selected according to the power demand of each supply voltage,and the factors such as carrying capacity and ripple noise,and finally the power supply system with low ripple noise is designed.According to the requirements of the index,the topic finally built a low-noise signal conditioning channel with a bandwidth of 1.5GHz with discrete devices,and tested the channel bandwidth,rise time,gain accuracy and root mean square noise,and the test results met the requirements.