Research On Pattern Reconfigurable Antenna Based On Metasurface

Through-wall detection is an important means to positioning and tracking.In the military,disaster relief,anti-terrorism,alert and other fields,through-wall detecting radar occupies a very important position.At present,most of through-wall detecting radars are using the Ultra-wideband system.The radars which used Ultra-wideband system have a series of advantages,such as strong anti-multipath effect,high resolution,fast transmission rate and strong penetration.Shortcomings are concentrated in the electromagnetic compatibility and matching issues.In this paper,author designs through-wall detecting radar based on the ultra-wideband shock pulse system.The attenuation of the wall model was simulated in the design process,the indexes of each module are calculated.And author designed the hardware part of transmitter,receiver and control system according to the indicators.This paper mainly studies the following aspects:1.Studied the characteristics of the ultra-wideband pulse.Author carried on the modeling and simulated the penetrating characteristics of electromagnetic waves at different frequencies.The resonance and attenuation characteristics of the electromagnetic wave are analyzed.And the attenuation of electromagnetic waves in different thickness walls is studied.And then,the through-wall detection radar frequency band is selected in 1.5 GHz ~ 4.5 GHz according to penetration,resolution,system indicators and some other needs.2.Given the overall design of the through-wall detecting radar.The through-wall radar is divided into several systems: transmitter,receiver,control module and antenna.And the time domain and frequency domain waveform of the impulse signals at different pulse width are studied.Then,author gave the calculation formula of radial resolution and azimuth resolution.3.Author designed the transmitter system of through-wall detecting radar.The launch pulse power was determined according to the radar equation and wall attenuation.The signals of three ports of mixer are simulated,and the hardware circuit of the transmitter is designed according to the working frequency band and the transmitted pulse power.In the design process of the transmitter,the circuit design of impulse pulse source is studied and analyzed in detail.Finally,the transmitter and the physical map are given.4.Designed a receiver system of through-wall detecting radar.Author calculated noise and sensitivity of the receiver,and Designed hardware circuit of the receiver according to the power of target echo signal and ADC.Then,made a key note of I / Q demodulation and Quick switch section.In the final,the layout and physical map of the receiver are given.5.The control system of radar is studied.Author analyzed the performance indicators of ADC and influence.Then the equivalent sampling circuit and the hardware part of the control system is given.Finally,the Balun,FPGA and USB were simulated and analyzed.