Design Of Intermediate Frequence Data Acquisition Module In CTS System

The development of society and the country ' s economic construction have increasingly high requirements for atmospheric exploration,especially weather forecasting.Obtaining accurate weather forecast information will bring great advantages to all aspects of aviation,navigation,agriculture,water conservancy and other countries.Atmospheric temperature and humidity profiles are the focus of atmospheric detection.Accurate large temperature and humidity profiles will improve the accuracy of weather forecasting.As a passive microwave remote sensing device,microwave radiometer has a wide range of applications in the field of atmospheric detection.The core of the microwave radiometer is a CTS(Chirp transform spectrometer)system,which is a frequency measurement system based on the principle of linear pulse compression frequency modulation physical transformation.It uses the characteristics of the linear frequency modulation signal after being compressed into the time domain pulse signal through the acoustic surface device.Calculate the spectrum information of the signal to be measured.The CTS system is mainly divided into RF processing part and IF data processing part.The IF signal output from the RF end needs to be converted into digital signal input data processing part.The data conversion part is the IF data acquisition module designed in this paper.In this paper,through consulting a large number of related literatures of CTS systems and data acquisition systems in microwave radiometers at home and abroad,according to the requirements of CTS system,a high-speed IF data acquisition module is designed to achieve up to 2.5GSPS,12-bit IF signal sampling,using high speed The serial data transmission interface is input to the IF data processing section.By briefly analyzing the principle and performance of the CTS system,the overall performance indicators and overall framework of the IF data acquisition module are first determined,and the AD9625,a core chip analog-to-digital converter of the data acquisition module,is selected to determine the actual working requirements of the A/D converter.The AD9625 is a core peripheral circuit component and its performance specifications,including the power supply,clock,analog front-end processing,and interface sections.For the power supply part,a switching power supply is combined with a linear regulated power supply for step-down,achieving a highly efficient,stable,and low-ripple voltage output.The clock part uses a complete phase-locked loop to regulate the output frequency and obtain the clock signal required by the module.The analog front-end circuit mainly includes a single-ended to differential circuit,an ADC driving circuit,and a bandwidth limiting circuit,so as to match the input signal voltage range and bandwidth with the ADC input requirements.The interface part mainly includes the selection of the connector and the voltage conversion circuit.The use of modular ideas for the hardware circuit design and simulation verification of each part of the external circuit,and finally use the PCB software and characteristic impedance calculation software to complete the overall layout and wiring of the IF data acquisition module,output the corresponding Gerber file,complete the IF data Acquisition module design.