Design And Research Of Notch Filter And Balance Filter Aimed At Radio Astronomy System

The core essence of radio astronomy observation technology is radio receiving technology.With the development of science and technology in recent years,the electromagnetic environment around us has become more and more complicated.Therefore,it is very important to design a receiver with high sensitivity and anti-electromagnetic interference for the radio observation system.In the low temperature environment,the high temperature superconducting thin film material has a very low surface resistance value,using high temperature superconducting material to designed filter with high Q value,low loss and so on.As an important device in the receiver front-end system,it is very meaningful to apply a filter designed with a superconducting material to a radio astronomical observation system.Based on the work done during the master's degree,this paper systematically studies the design of the notch filter,balanced filter and multi-passband filter.The main research contents are as follows:(1)A wideband bandpass filter with multi-mode resonator structure is proposed.The operating bandwidth of the filter is 1-2 GHz and the rectangular coefficient is 1.195.In order to suppress the GSM signal(center frequency at 1800 MHz)in the passband range,two spiral-type uniform impedance resonators are embedded in the band-pass filter to generate a stop-band characteristic to suppress unwanted signals.The notch filter design using a high-temperature superconducting material,thereby reducing the loss,the filter applied to the front of the radio observation system receiver can improve the system's sensitivity and anti-electromagnetic interference.(2)A balanced filter is designed using a new shunt-line step impedance resonator(SLSIR)structure.Firstly,the advantages and disadvantages between the three kinds of balanced coupling methods,such as electric,magnetic and mixed electromagnetic,which are designed by using SLSIR structure are compared.Then,a high-order single passband balanced filter is designed by using mixed electromagnetic coupling method.Finally,in order to further widen the range of the stopband in the case of differential mode,the A+B method is used to design the eighth-order balanced filter based on the mixed electromagnetic SLSIR structure,which has the characteristics of high selectivity and wide stopband.(3)A dual-band passband and tri-band bandpass filter using shunt-line SIR structure and ring SIR structure are proposed respectively.In the first part,the mode characteristics of the shunt-line SIR structure are analyzed,and a fourth-order dual-band bandpass filter is designed using a curved shunt-line SIR structure.This filter has a passband center frequency controllable and high selectivity and so on.In the second part,the proposed multi-mode ring SIR structure is compared with the traditional SIR structure resonator,and the mode characteristic of this resonator is analyzed by the odd-even mode analysis method.Finally,the resonator is used to design a tri-band bandpass filter in which the first passband and the second passband are generated by the ring SIR structure and the third passband is generated by the filter feed structure,the advantages of the filter is the bandwidth of each passband can be independently controlled.