Research On Back-end Detection Circuit Of Magnetoelectric Surface Acoustic Wave Sensor

Magnetoelectric surface acoustic wave?MESAW?sensors have received more and more attention from people for their great practical value,and will play a more important role in the fields of scientific research,production,military and others.The magnetoelectric surface acoustic wave sensor changes the resonant frequency of the SAW through a magnetic sensitive film?or substrate?,also it has the advantages of high sensitivity,small volume,and easy mass production.This thesis mainly carries out the following three aspects of work:Firstly,a single-port resonance type magneto-acoustic surface acoustic wave sensor was designed and fabricated.The sensor is mainly composed of four parts,which called surface acoustic wave resonator,insulating layer,magnetic sensitive layer and protective layer,separately,and the magnetic sensitive layer take advantage of the giant Young's modulus effect of FeCoSiB.By optimizing the soft magnetic properties and thickness of the FeCoSiB/SiO₂ film,the sensitivity??f/H?of the magnetic sensor was improved by 2 orders of magnitude to 41900 Hz/Oe?419Hz/?T?,and,as the result,we obtained magnetoelectric SAW sensor.The sensor's resonant frequency is 289.37 MHz and the Q factor is 1205.71.Secondly,this thesis designs a signal detection system with high speed,high precision,low power consumption,and meeting the needs of array sensors to detect the resonant frequency of MESAW sensors.This system is mainly composed of five parts:the oscillation circuit,the filter,the frequency division part,the shaper and the data processing part.The system consists of two signal paths:the measurement path and the reference path.The rest of the two signal paths except the SAW sensor in the oscillation circuit are the same.Finally,the signal frequency difference between the two paths is obtained through the data processing part to detect the external magnetic field.In order to reduce the system power consumption and complexity,we use sleepable integrated chips as the frequency division part and the shaper.This thesis proposes a new method of frequency measurement:delta-time and synchronous measurement.The method combines frequency measurement with time measurement,and the speed is increased by at least 2 orders of magnitude compared with the equal-precision frequency measurement method,and the accuracy is improved by 3orders of magnitude(the order of?is 10^-11).Finally,by using the EDA software such as the ADS?Advanced Design System?this thesis designed the system hardware circuit and outputted the PCB successfully.After debugged the parameters of all the devices,all the design goals were achieved.At the same time,based on FPGA technology,the related code of the frequency measurement module and the connection of its internal sub-modules were successfully designed by Verilog HDL language and the Vivado^?,which will applied in the measurement of the frequency.