Design And Implementation Of X-band Voltage Controlled Oscillator Based On Filter Fusion

With the rapid development of wireless communication,higher design requirements have been put forward for the RF transceiver front-end.The oscillator is the core part of the RF transceiver front-end,and its performance directly determines the performance of the RF transceiver front-end.Therefore,the design of the oscillator has always been the focus of the system circuit design.Based on the current high requirements for RF frontend integration in wireless communications,this paper studies the fusion design of RF front-end components,puts forward a design method for the fusion of oscillators and filters,and gives the simulation and physical test results.The main contents are as follows:Firstly,this paper introduces the basic idea of filter fusion and the development of X-band voltage-controlled oscillators at home and abroad.At the same time,the advantages of voltage-controlled oscillators designed with fusion technology are analyzed.By comparing with the traditional cascading method of the RF front-end,it can be seen that the fusion design can not only effectively reduce the physical size of the circuit design,but also improve the system circuit performance and reduce the design cost,thus explaining the significance of this paper.Secondly,this paper introduces the basic theory,working principle and main index parameters of the oscillator and voltage-controlled oscillator;the matching method selected by the oscillator circuit during the design of the oscillator is analyzed;according to the above design requirements,design an X-band Voltage controlled oscillator(Voltage Controlled Oscillator,VCO),and completed the physical test.The test result were as follows: the resonance frequency of the VCO was 11.030240 GHz,the phase noise value was-92.45dBc/Hz@100kHz,-107.09dBc/Hz@1MHz.Compared with an oscillator that does not use an eighth-wavelength open-path matching structure,the oscillator has obvious second-harmonic suppression,which lays the foundation for a new fusion design method.Thirdly,based on the theory of microwave filter and Substrate Integrated Waveguide(SIW),this paper designed a SIW filter based on Defected Ground Structure(DGS).Loading the Defected Ground Structure on the SIW resonator can effectively reduce the circuit design size and improve the out-of-band rejection of the overall filter.The test results were as follows: the resonance frequency of the filter was 11.10 GHz,the passband range of the filter was 10.74-11.31 GHz,the insertion loss of the resonance was 2.2dB,and the return loss was lower than-23.7dB.Finally,this paper designs an X-band voltage-controlled oscillator based on filter fusion.By using the filter as a part of the output circuit of the voltage-controlled oscillator circuit,that is,the input impedance of the filter is directly set as the conjugate of the output circuit impedance of the oscillation circuit,thereby implementing a filter fusion design.The actual test results of the filter fusion VCO were as follows: the resonance frequency of the VCO was 10.92358 GHz,the phase noise value was-106.52dBc/Hz@100kHz,-114.71dBc/Hz@1MHz.The second harmonic suppression was 59.814 dBc.Compared with the oscillator designed by the traditional cascade design method and the oscillator designed by fusion with the SIW structure filter,the overall size of the oscillator is greatly reduced,and the gain is also improved.It can be seen that this fusion design can effectively achieve multiple functions such as miniaturization,high performance,and low cost of the RF front-end circuit components.