Study On Metal Detector Based On Doppler Effect

Metal detector is more and more widely used in manufacture and daily life, the range of application as large as from food and medicine security to clothes product, from ore purity to security check. It works well in these fields and it is acquiring continuous improvement.This thesis discusses the research on metal detector based on Doppler effect. First, the thesis discusses how to use Doppler effect to detect metal, and to analyses and verify the principle. Then the thesis gives the details for the overall project of electric circuit design by dividing the electric circuit into two parts: high frequency part and low frequency part.The thesis also discusses how to choose work frequency, how to design RF oscillator and RF amplifier based on wide-band MMIC amplifier, and how to design RF mixer in high frequency part and emphases on how to choose oscillator and mixer's parameters and the possible troubles they may cause.The thesis discusses how to design low pass filter, low frequency amplifier, and voltage converter and emphases on how to choose low frequency amplifier's operating point and voltage converter's reference voltage.The designed circuit is simple and working stably, and its cost is low.