The Development Of Ku-band Ultralow Phase Noise Oscillator

As a core component of radar and signal generators,oscillators are widely used in various electronic systems.The new high-sensitivity detection radar system is demanding on the phase noise of the oscillator,the guarantee of system performance need rely on the low phase noise of the oscillator.Therefore,relevant researchers all over the world have been working on the development of ultra-low phase noise oscillators.This paper will develop an oscillator system based on a sapphire dielectric resonator.Based on the classical oscillation condition and phase noise Leeson model,this paper analyzes the relevant parameters affecting the phase noise of the oscillator,and then analyzes the high Q Whispering gallery mode of the resonator.The naming of the Whispering gallery mode and the distribution of the field are introduced.The parameters and distribution trends affecting the whispering gallery mode are analyzed by simulation software.The core of this paper is to design a high-Q resonator of sapphire working in Ku-band.The sapphire medium working at whispering gallery mode has a very low loss.At room temperature,the unloaded Q value can be reached 2×10~5,Under the condition of77K,the unloaded Q value can be achieved5×10~7.The relationship between the field distribution of the resonator,the field distribution of the whispering gallery mode,the resonant frequency,the Q value and the phase noise is analyzed theoretically in detail.The HFSS software is used to simulate the resonator.During the design,the system size,loop gain,coupling modes,processing cost and other factors are fully considered.Finally,the development of the sapphire resonator with the resonant frequency of 12.62 GHz is completed.The Q value reaches 72520 at the resonant frequency.The phase noise of the system is simulated according to the high Q sapphire resonator.In addition,the rest of the oscillation loop is selected around the resonant frequency of the resonator,and the design and development of the low noise amplifier,cavity filter,phase shifter and coupler are completed.The low-noise amplifier adopts a miniaturized and superior performance amplifier MMIC chip under the condition that the loop gain satisfies the oscillating condition.On the basis of the resonant frequency,A loop filter with superior performance and good suppression ability and phase shifter are designed.Considering the loop gain,the design of the coupler takes into account the insertion loss of the through-branch,so an asymmetric multi-section coupler with a coupling of 30 dB is designed and fabricated.Finally,all components are cascaded to form a sapphire ultra-low phase noise oscillator system at room temperature.Adjusting the loop gain and loop phase noise to meet the Barkhausen start-up condition,the system is finally tested,The final Realized targets are:output frequency is 12.62 GHz,output power is-17.2 dBm,phase noise is-129 dBc/Hz@10kHz,-136dBc/Hz@100kHz,and-146dBc/Hz@1MHz.