The Research On Key Technologies Of Time-Domain Radar Receivers

Time-domain radar is a kind of ultra-wideband(UWB)radar transmits and receives a series of impulse signals,possessing many desired characteristics comparing with frequency-domain radar using continuous sinusoidal waves as carrier waves.Timedomain radars have advantages of high distance resolution,long detection range and higher penetrability so they are suitable for localization,target detection,medical monitoring,nondestructive testing,through-wall imaging and ground penetrating applications.The function of time-domain radars receivers is converting the input analog signals to digital signals for post processing.The receiver's performance determines the detection performance of the whole radar system,so the design of excellent receivers is a matter of primary importance in time-domain radar design.The study of sampling methods and practical circuits suitable for time-domain radar receivers contributes to the development and popularization of time-domain radars.This dissertation starts with a theoretical problem of the time-domain signals' analysis as Gaussian pulse signals,in time domain and frequency domain respectively,because the property of time-domain signals is the basic factor in the design of timedomain radars.Then the equivalent sampling method which is especially suitable for high speed sampling is deduced and discussed,and it is the reason why time-domain receivers could work.The following content compares the system organization of the sequential equivalent sampling method and the random equivalent sampling method,and propose a novel equivalent sampling method that combinates advantages of both the two traditional equivalent sampling methods.After the theoretical part,this dissertation introduces the design process of timedomain radar receivers in detail.The receiver is consisting of four parts: high-speed sample and hold circuit,time-delay generating circuit,time-interval measurement circuit and digital control circuit.The high-speed sample and hold circuit consist of fourSchottky-diode balance bridge,symmetric spike pulse generating circuit and voltage hold and clear circuit.The test result indicates that the designed high-speed sample and hold circuit have the time resolution ratio of 100 ps and could work at the repetition frequency of 20 KHz.The time-delay generating circuit consists of two ramp generating circuits with far different slopes and the test result indicates that the circuit could generate a series of time delays form 500 ns to 2000 ns.The time-interval measurement circuit utilizes the methods of time-interval to voltage,and could pump charge into the hold capacitance.Test results indicate that the time-interval measurement circuit could measure time intervals between 100 ns to 2000 ns with excellent linearity.Finally,the embedded system based on MCU of STM32H743 is used to offering system clock,controlling the timing sequence and transmitting data to computers.Test results indicate that the time-domain receiver designed in this dissertation could acquire the amplitude and time information of input pulse signals and finally reconstruct the signal satisfactorily.