The Design Of The Intelligent Phase-locked Amplifier

Lock-in amplifier, especially digital orthogonal vector lock-in amplifier, is themain instrument in the field of weak signal detection, which has high accuracy, goodstability, high SNR prominent advantages, and has been widely used in physics,chemistry, biology, medicine, and a variety of engineering field. In order to meet thehigh real-time, a fast calculation speed and high precision requirements, this paperselects the ARM and FPGA embedded platform to design intelligent lock-in amplifiersystem.This paper focuses on the design of digital orthogonal vector phase-lockedamplifier design. First of all, this paper introduces its principle and basic structure, andanalyzes the main parameters such as sample frequency, cut-off frequency and order ofthe low pass filter, and so on, impacting its performance, and put forward based onARM and FPGA embedded platform of intelligent lock-in amplifier solutions. Second,according to the structure of digital orthogonal vector phase-locked amplifier, design thesystem hardware, mainly including choosing AD8331as the preamplifier and variablegain amplifier in asignal channel, which can provide the bandwidth of the20M,74.5dB gain; choosing the AD9430as ADC, which can provide120M sampling rate,375μV resolution; choosing the AD9518-1as adc sampling clock, which can set thesampling clock in12.5M to120M adjustable; using FPGA (EP3C10) design thefrequency resolution for the0.028Hz, the highest frequency of20MHz reference signalgenerator, phase sensitive detectors, IIR low-pass filter, phase and amplitude operationmodule, etc. Again, according to control functions of the intelligence of phase-lockedamplifier, design the system software including new add hardware, FPGA and clockgenerator drivers design on the ARM platform, and QT application design based on theLinux operating system etc. Finally, combined with the previous design, gives indexesanalysis according the results of the simulations and experiments.