Research And Design Of L Band Frequency Source Based On DDS

With the continuous improvement of national economic level and the rapid development of wireless communication technology.In recent years,the development of radar technology in China is very rapid.It has developed rapidly as a weather radar related to war and people's life.In order to improve the detection accuracy of meteorological radar system to meet the needs of high-altitude meteorological detection,the technical indicators of meteorological radar put forward higher and higher requirements.Frequency synthesizers as an important part of modern meteorological radar,is to determine the meteorological radar performance indicators of the key factors.The frequency synthesizers phase noise,output spurious and other technical indicators will directly affect the radar performance.This paper aims to study the design of the local oscillator source in L-band meteorological radar receiver based on direct digital frequency synthesis technology.This paper first describes the research status of frequency synthesis technology at home and abroad.Then the technical characteristics of several frequency synthesis techniques and their respective advantages and disadvantages are analyzed.The theoretical development of the scheme is put forward.Through the comparison and analysis of the traditional scheme and the AD9914-based scheme,the feasibility of the scheme is demonstrated by the requirement of the project specific index.Because this paper is designed on the basis of direct digital frequency synthesis technology,so the direct digital Frequency synthesis technology work principle,technical characteristics,the output spectrum of a detailed introduction and analysis.After the solution is established,this paper designs the detailed hardware circuit of the program,including the DDS reference clock circuit,the DDS hardware circuit,the power supply circuit and the FPGA circuit.And it completes the introduction of the related chip and the design of the schematic diagram.Then the Verilog program is written in this paper.And the logic control of the DDS circuit is realized by FPGA.In addition to the external control of the frequency synthesizers by using FPGA,the USB chip can be used to combine with software provided by ADI realize the programming and control of the frequency synthesizers in the host computer.Finally,the function and performance of the designed frequency source are tested,and the test results are given.The possible problems in the test are summarized and analyzed.Based on the test of the frequency source,the vibration source designed for meteorological radar receivers in this paper can meet the design requirements.And also simplifies the circuit design,reducing the complexity of the system.