Research On Novel Broadband Balanced Devices With Wideband Harmonic Suppression

With the rapid development of modern communication technology,limited spectrum resources have gradually become a major problem for restricting the development of communications.As a frequency selection circuit,the filter can make effective use of specific spectrum resources.Compared with the traditional single-ended filter,the balanced filter not only can realize the filtering function but also can suppress the common noise of the system,which can greatly improve the overall performance of the system.In addition,for some systems that require balanced input/output,balanced multi-function circuits can be used to instead of traditional single-ended circuits to achieve miniaturization of the circuit system.Therefore,a balanced circuit with common mode noise suppression plays an important role in communication systems.In recent years,some balanced circuits such as balanced filters,balanced couplers,and balanced power divider have been extensively studied.Based on the structure of microstrip line and double-sided parallel strip line(DSPSL),this paper takes the miniaturization of the balanced structures,high common mode rejection,and high selectivity as the research goals and several novel balanced circuits are designed.The main contents are:1.Balanced bandpass filter based on signal interference technology.By introducing two different transmission paths between the input and output ports,the signal is superposition and cancelled,and transmission zeros are generated on each side of the passband,which improves the selectivity of the passband.And due to the coupling between the source and the load,additional transmission zeros are generated at the low frequency side of the common mode signal,which achieves broadband common mode suppression.Related papers have been published in IEEE Transactions on Plasma Science.2.High-performance balanced bandpass filter based on the double-sided parallel strip line(DSPSL).The proposed structure mainly uses the principle of inversion signal cancellation to achieve high common mode suppression.This paper uses phase swap structure which is based on double-sided parallel strip line(DSPSL)to replace the traditional halfwavelength transmission line structure,and the miniaturization of the balanced filter circuit is achieved to a large extent under the condition that the performance is basically unchanged.In addition,the band-pass effect is achieved by using the coupled line with loaded stub structure to instead of the dual-mode ring structure,which verifies the simplicity of the design based on the DSPSL phase swap structure.Related papers have been published in IEEE Transactions on Circuits and Systems II: Express Briefs and International Journal of RF and Microwave Computer-Aided Engineering.3.Six-port quadrature couplers based on double-sided parallel strip line(DSPSL).By replacing the half-wavelength transmission line with the DSPSL phase swap structure,the phase imbalance and amplitude imbalance of the quadrature coupler are greatly improved,and common mode suppression is achieved in the wideband range.Compared with the traditional circuit,the designed quadrature coupler circuit is more compact.Related paper is ready for submission to IEEE Transactions on Microwave Theory and Techniques.