A Research Of Oscillator Based On SIW Cavity Coupling Structure

With the rapid development of the communication system,the electronic technology is changing with each passing day.With the change of the market,the demand for the source is also getting more and more.Phase noise is an important indicator of oscillator,decides the quality of the information trasmission between communication systems.Therefore,the research of low phase noise oscillator still has important practical significance.This paper designs three kinds of microwave oscillator: multi cavity coupled SIW oscillator,SIW-CSRR oscillator and microstrip dual mode oscillator.Then compared the characteristics of the three kinds of oscillator.First,a multi cavities coupled SIW oscillator is designed.The conjecture that the area of the SIW resonator is inverse to the frequency and the shape of the cavity effect the resonant frequency is presented.The conjecture is verified by a large number of simulations and analysis.Based on this,the circular cavity is selected as the source and load of the resonator.In order to reduce the area of the resonator,two parallel paths between the source and the load are designed by using the HMSIW structure.This structure makes three transmission paths between the source and the load,and improves the Q value of the resonator.The X band oscillator is designed by the parallel feedback structure,and the stable output is realized.The oscillation frequency is 10.75 GHz,the output power is-0.54 dBm,the phase noise is-105.88 dBc/Hz@100kHz.It has a stable output power but the area is too large.In order to compare with the smaller structure,a SIW-CSRR parallel feedback oscillator is designed based on the cut-off waveguide theory and the CSRR theory,the area of this structure is very small.SIW is equivalent to the cut-off waveguide,and the CSRR pair on the upper surface is equivalent to the capacitive structure,so the resonance is excited at the frequency below the cut-off frequency,and the coupling strength is controlled by controlling the CSRR coupling pair.But the CSRR structure is very sensitive to the size,which leads to a high requirement for machining precision.The oscillation frequency is 8.08 GHz,the output power is-2.14 dBm,and the phase noise is-101.17 dBc/Hz@100kHz.In order to compare with microstrip oscillator,based on the microstrip open-loop resonator theory,then adding crosstalk stubs todesign a microstrip open loop dual-mode filter by.Do simulation and analysis at 2GHz and 8GHz respectively,it is found that the microstrip structure is better than the SIW structure in UHF,but the SIW structure is better than the microstrip structure in VHF.The oscillation frequency of the oscillator based on the filter is 2.015 GHz,the output power is-5.52 dBm,and the phase noise is-117.02 dBc/Hz@100kHz.