Research On High-speed Frequency-hopping Source Technology

The frequency synthesizer is an indispensable part of the electronic system such as communication,radar and microwave measurement,which determines the performance of the whole system.Frequency synthesis technology for aerospace and defense military industry has a very significant significance,so by the attention of many countries.Although the domestic study of this late start,but in recent years,progress quickly.With the rapid development of 5G communication technology and electronic countermeasures system,the parameters of the frequency synthesizer especially the frequency hopping time put forward higher requirements.For designers of frequency synthesizers,how to achieve faster frequency switching without sacrificing phase noise and spurious,is always a daunting challenge.This paper first introduces the principle of direct analog frequency synthesis(DAFS),phase-locked frequency synthesis(PLLFS)and direct digital frequency synthesis(DDFS),and gives the mathematics definition and physical meaning of the frequency synthesizer evaluation index system.The advantages and disadvantages of several common mixing frequency synthesis methods are compared and analyzed.On the basis of this,a frequency synthesis architecture for high-speed frequency-hopping is proposed based on the combination of DDS and PLL.The scheme reduce the PLL lock time by increasing the number of PLLs and makes full use of the advantages of DDS including fast switching speed and fine frequency resolution.The feasibility of the scheme is evaluated by using the method of theoretical calculation and simulation,and the theoretical indexes of the scheme are given.At the same time,we compare the output of DDS with different reference clock and find that when the reference clock frequency is 1.2GHz,the spur is the best.In this paper,the hardware and software of the reference power module,the local oscillator module,the DDS module and the mixing module are completed,and the system is jointly tested.From the test results,output frequency range is 750~1000MHz,the phase noise is better than-115 d Bc/Hz@10kHz,the spurs is better than-60 dBc and the frequency hopping time(not including communication time)is less than 600 ns,meet the requirements of this subject and at the same time has a certain significance on the development of high-speed frequency-hopping source.Finally,this paper analyzes the deviation between the test results and the theoretical results,and puts forward the possible causes of the results,and gives the corresponding solutions.At the same time some shortcomings in this paper are pointed out,and some suggestions for improvement are put forward.