Design Of Ultra-wideband Radar Frequency Synthesis System

With the rapid development of China's economy and technology,the application of radar in the military field has become more and more extensive,which has also brought about a huge impact and change on people's lives.As one of the key systems of radar,the frequency synthesis system can not only provide local oscillator signals for radar receivers,but also provide excitation signals for radar transmitters.Frequency synthesis systems are called the "heart" of electronic systems,and are often used in modern advanced electronic systems,such as detection / telemetry,radar,and microwave communications.Their performance indicators determine the key indicators of electronic systems.In modern radar,in order to improve the sensitivity and anti-jamming capability of the radar,frequency synthesis systems with low phase noise,low spurs,ultra-wideband and frequency agility have become an important research direction of radar systems.This subject is to design a high-performance small-volume frequency synthesis system for a certain type of radar.The frequency synthesis system designed by this subject has a frequency range of 1GHz ~ 8GHz,phase noise is better than-90 dBc / Hz @ 1kHz,frequency interval is 10 MHZ,spurious is better than-50 dBc,frequency hopping time is less than 50 us and volume is not more than 150(mm)* 100(mm)* 30 mm.The system breaks through the traditional theory and integrates functions such as phase lock,frequency division and switching filtering in a system.This advanced broadband microwave frequency rapid synthesis system can not only generate microwave signals,but also greatly reduce the volume and weight of the sub-system,which can greatly simplify the structure of the electronic machine.It is a new generation of aviation radar,meteorological radar,satellite detection,The core component of the development of electronic equipment such as microwave communication.The main work of this subject is as follows:1.Research on the theory of frequency synthesis technology.The research status of frequency synthesis system is explained from home and abroad.The advantages and disadvantages of the main frequency synthesis techniques are analyzed.The working principle of the phase-locked loop is elaborated,several frequency synthesis schemes are proposed,and the scheme for the C-band reference source to expand to the low end through frequency division and switch filtering is determined.2.FPGA control unit.Introduced the selection of FPGA chip and circuit schematic design,and programmed the control program on Quartus II,then introduced the program into modules.Finally,the simulation verification of the program is carried out on Modelsims.3.Design of C-band baseband source module.According to the performance requirements of the radar system,the specific indicators and design schemes of the C-band baseband source were clarified.The baseband source signal is synthesized using the phase-locked loop(PLL)principle,and the key technical indicators are theoretically calculated and simulated.The selection of the device is introduced in detail,the PCB drawing and the physical drawing are given,and finally the hardware test of the C-band baseband source module is performed.4.Design of low-frequency module and system joint tuning.The design innovation of this article is on the premise of ensuring that the main performance indicators of the C-band baseband source meet the requirements of the overall system,adding a crossover part to make the signal frequency bandwidth wider and the main performance indicators of the entire system can still meet the requirements.The design scheme and chip selection are introduced first,and then the PCB diagram and physical diagram are given.Finally,the system is jointly tuned with the C-band baseband source.The results show that the design index of the frequency synthesis system meets the subject index requirements,and the design goals of this paper are achieved.