Research Of Microwave Low Phase Noise Oscillator

With the fast development of the radar and communication system,low phase noise,low power consumption,low cost,miniaturized and integratable sources must have the better quality.Phase noise largely decides the quality of information transmission between systems.So the research of low phase noise oscillator is very meaningful.Based on the substrate integrated waveguide(SIW),this thesis introduces three kinds of oscillator: series feedback oscillator,parallel feedback oscillator and based the active resonator oscillator.(1)In order to study the performance of series feedback oscillator,Ku-band low phase noise oscillator which based on SIW cavity resonator is proposed.The experiment proposed that the high order mode of the SIW cavity resonator is used as the free oscillation frequency.Due to the high order mode possesses the higher unloaded quality factor.But the higher modes would cause the bigger volume than using its own as fundamental mode.Making a compromise,the diagonal TE102 of the cavity is the working mode.To further improve selectivity of the resonator,the defected L-slot is placed at the edge of the electric field of the TE102.The Ku-band series feedback oscillator can realize the stable oscillation,using the negative resistance circuit structure compensating the loss of resonator.The measured results show that the free oscillation frequency is 15.55 GHz,the output power is-0.23 dBm and the phase noise is-100.76 dBc/Hz @100 kHz,-130.43dBc/Hz@1MHz.(2)To analyze the performance of parallel feedback oscillator,the C-band QMSIW quasi-elliptic filter oscillator and the X-band hybrid SIW(HSIW)cavity oscillator are implemented,respectively.In X-band HSIW resonator,the input and output coupling strength is determined by the rectangular SIW.And the optimal value of the insertion loss and loaded Q-factor can be achieved.If the transition structure of SIW to microstrip is coplanar waveguide(CPW),the proper coupling strength needs very high machining accuracy of the slot.It is hard to apply in reality,but hybrid cavity solves the problem.The measured results of this oscillator show that oscillating frequency is 9.5 GHz,output power is 1.67 dBm,and the phase noise is-112.84 dBc/Hz@100kHz.Using the QMSIW technology in C-band quasi-elliptic filter,its size would reduce 80%.The T-slot is utilized to control the mixed coupling strength between the QMSIW cavities.The source-load coupling and mixed coupling between the QMSIW cavities realize two transmission zeroes by two transmission paths.Loaded quality factor of the filter is greatly increased.The measured results of this oscillator show a phase noise of-112.69 dBc/Hz at 100 kHz offset frequency from 6.96 GHz carrier with 4.96 dBm output power.(3)To study the performance of oscillator based on the active resonator,the one port negative resistance circuit is designed as the active compensated element.The active resonator based on circuit structure of the QMSIW quasi-elliptic is implemented.This technology solves that the insertion loss and the loaded Q-factor can't be improved at the same time.In compensated circuit,coupling location and strength must be strictly controlled.The coupling location can't influence the characteristic of the original filter.And the coupling strength must be weak coupling,to avoid self-oscillation of the compensated structure.The measured results of the oscillator show phase noise of-133.06 dBc/Hz at 1MHz offset frequency from 7 GHz carrier with 4.3 dBm output power.