Research And Design Of Guided Wave Radar Level Meter Based On Similar Equivalent Sampling

The Guided Wave Radar Level Meter is a kind of level sensor based on the Time Domain Reflectometry.Because of its accurate measurement and stable performance,it has been widely used in chemical production and other fields.However,due to the relatively backward domestic technology,most of the Guided Wave Radar Level Meters on the market rely on imports and are very expensive.Therefore,it is of practical significance to research and design high-performance and low-cost Guided Wave Radar Level Meters.Due to the requirements of measurement blind zone and accuracy,the transmitted signal of the Guided Wave Radar Level Meter is a kind of high-frequency signal with extremely narrow pulse width.It is very difficult to transmit and sample and receive high-frequency signals.Therefore,the research focus of this paper is the research and design of the signal transmitting circuit module and signal sampling circuit module of the Level Meter.Firstly,this paper introduces the transmission line theory and the Time Domain Reflectometry involved in the measurement process of the Guided Wave Radar Level Meter in detail,and then formulates the design requirements and technical indicators of the Guided Wave Radar Level Meter,and completes the system scheme design of the Guided Wave Radar Level Meter.In the research and design of the high-frequency signal transmission module,according to the technical indicators,the high-frequency signal of the Level Meter is selected as the Ultra Wide Band signal with the pulse width of about 2ns,and the Ultra Wide Band signal transmission circuit with the radio frequency triode as the core is designed.The relevant design parameters are determined after the simulation analysis of the signal transmission circuit in the software of Advanced Design System.Secondly,in the design of high-frequency signal sampling module,after comparing several signal sampling methods,the method of similar equivalent sampling is selected to complete the sampling processing of high-frequency signal of the Level Meter,and the bridge sampling circuit,sampling pulse circuit and signal holding circuit are designed to realize similar equivalent sampling,and the relevant design parameters are determined after simulation analysis in the software of Advanced Design System,which greatly reduces the design cost while meeting the design requirements.Finally,after researching and analyzing the Signal Integrity problems that affect the quality of high-frequency signals,the design of the Printed Circuit Board is completed,and the Level Meter circuit prototype is made for experimental testing.Relevant simulation results and experimental test data show that the Guided Wave Radar level Meter designed by the paper can successfully transmit Ultra Wide Band signals with a pulse width of about 2ns,and can complete the similar equivalent sampling processing of high-frequency transmission signals and echo signals,and stretch it into low-frequency signal which is easy to be collected and processed by single-chip processor,Finally,realizing the basic level measurement function.