Design And Research Of Nondestructive Testing System For RC Based On FMCM Radar

With the development of society,the structure of reinforced concrete(RC)has become an indispensable building structure.As an important part of the building,the quantity,spacing and cover thickness of reinforcement in the concrete will have an impact on the strength and stability of the building.However,the pulse radar used in the field of nondestructive testing is generally large in volume,short in life and high in cost.Based on that,the existing technology of nondestructive testing at home and abroad is analyzed,and the use of frequency-modulated continuous wave(FMCW)radar for nondestructive testing technology is focused on in the thesis.Then,a small size,long life and low cost of RC nondestructive testing system is designed in the thesis,in order to achieve that the thickness of reinforcement cover can be correctly detected by it.The specific work in the thesis is as follows:(1)By analyzing the principle of frequency-modulated continuous wave,the basic structure of the transmission-receiving system of the nondestructive testing has been established,and the core mathematical model of FMCW is deduced by using the principle of Dechrip modeling.At the same time,based on the influence of Dechrip processing,the scheme of frequency synthesizer with the structure of PLL has been designed as the system’s launch system,and the scheme of zero-if structure has been designed as the system’s receiving system in the thesis.Finally,the RF signal is designed as large time wide sawtooth wave to optimize the receiving data.(2)According to the principle of PLL and zero-if,a PLL frequency synthesizer with ADF4159 and zero-if receiving system with HMC685 is designed.The 6-order Butterworth Low-pass filter,and CMOS Power Amplifiers are also designed in the thesis.In terms of PCB layout,the CPWG is designed and impedance of CPWG is matched.The capacitance for power allocation is also designed to reduce signal attenuation and harmonic generation in the thesis.Finally,the scheme is simulated theoretically by using professional RF software to verify its feasibility.(3)STM32F103ZET6 is designed as the MCU of RC nondestructive testing system.The control program of the system is written in this thesis.The main function of program is controlling the PLL to generate the target frequency and collectting the receiving signal for calculation,so that the TFTLCD shows the depth of landfill of the reinforcement in the concrete.(4)Assembled and tested the system.After experimental test,the maximum operating frequency of the system is 2.155322 GHz,the period is 191μs,the flatness in the band is 0.531 dB,and the radar sensitivity is-70 dbm,which satisfies the design requirements.The RC nondestructive testing system adopts solid state transmitter,the volume is 31x10x0.33 cm.Compared with the traditional nondestructive testing pulse radar,the system can greatly reduce the cost and volume of radar,increase the life,and it can promot the popularization and development of nondestructive testing technology.