| With the development of electronic information technology,higher performance requirements are put forward for oscilloscopes.As an important part of oscilloscopes,wideband signal conditioning channels,whose bandwidth,gain,and anti-interference characteristics determine the indicators and performance of oscilloscopes.The use of subband sampling technology to improve the input bandwidth and sampling rate of the oscilloscope is the development trend of domestic oscilloscope development.Based on the sub-band decomposition technology,this thesis designs and implements the analog signal conditioning front-end of a high-speed broadband oscilloscope,which mainly includes the following three aspects:（1）The study of broadband signal conditioning link.This thesis studies the sub-band decomposition technology and designs an analog front-end scheme that decomposes 10 GHz ultra-broadband into two sub-bands by combining the specific requirements of the oscilloscope;studies the relevant characteristics of microstrip lines and GCPW,and designs high-frequency signal lines through theoretical calculations and simulations to meet the requirements of high-frequency signal transmission.（2）Gain adjustment circuit and ADC drive design.A circuit scheme suitable for gain adjustment of two sub-bands and ADC driving is studied.Combined with the relevant noise theory,through appropriate device selection and simulation verification,the circuit design is completed,and basic functions such as gain adjustment,bias adjustment,and bandwidth limitation are realized.Aiming at the control requirements in the link,a control program based on STM32 is designed to realize the control of the analog front-end.（3）Research on the frequency conversion scheme of the second sub-band.The frequency conversion of the second sub-band is studied.By using the high-frequency local oscillator mixing method,a circuit scheme that converts the input frequency from 5GHz to 10 GHz to the output frequency range of 500 MHz to 5.5 GHz is designed and implemented.The link is susceptible to external electromagnetic interference.The theory of cavity shielding and cavity resonance is studied.Through CST three-dimensional electromagnetic simulation,the shielding cavity structure of the frequency conversion circuit is continuously optimized and designed,which effectively suppresses the external frequency interference problem.Finally,through the PCB test of each module,the performance indicators of each module of the modular design are verified,among which: the bandwidth of the preattenuation module reaches 13 GHz,the bandwidth of the post-amplifier module reaches6 GHz;the first sub-band of the gain adjustment range can reach-42 d B to 20 d B;the second sub-band can reach-62 d B to 28 d B.The overall system input bandwidth is up to10 GHz with bias adjustment and bandwidth limiting.The overall performance indicators meet the design requirements,ensuring the subsequent ADC acquisition and digital signal reconstruction requirements. |
