The Design And Analysis Of Reconfigurable Microwave Components With Filtering Character

Filters,impedance transformers and power dividers are common components of modern microwave communication and radar systems.Microwave components with filtering characters are monomer multifunctional microwave devices that integrate filtering functions into traditional microwave devices which don’t have filtering functions.Reconfigurable character of microwave components means that the function(centre frequency,bandwidth and etc)of different RF modules can be tuned by using different tuning elemtns.The biggest advantage of this character is the ability that a single device can be reconfigured to adjust different scenarios by switching different functional features.Thus,the study in this field caters the requirement of intrgration and multifunction of modern electronic systems,which is very necessary.Fully reconfigurable bandpass filters,fully reconfigurable bandpass to bandpass with embedded-stopband filters,reconfigurable filtering impedance transformers and reconfigurable filtering power dividers based on different microstrip or lumped resonators is proposed in this dissertation,and their core design parameters and working principles are also analyzed.The main work of this paper is as follows:(1)The resonant character of common tunable dual mode resonator and stepped impedance resonator are analyzed,a dual mode fully tunable bandpass filter is designed on this basis.In this filter,by controlling the loading position and the series/parallel mode of tuning elements,the number of varactor diodes used in this filter is reduced,and the resonant frequency of the two resonant modes can be independently controlled;the centre frequency tuning range is expanded by tuning stepped impedance ratio of the stepped impedance resonator.(2)A reconfigurable bandpass to bandpass with embedded-notch filter and a reconfigurable bandpass to bandpass with embedded-stopband filter,whose centre frequency,bandwidth and filtering state can be independently tuned,are designed.These two filters are consisted by a tunable multi-mode resonator,a tunable external quality factor tuning circuit and an additional transmission path.The resonant modes of the multi-mode resonator constitutes the passband,and the center frequency and passband bandwidth can be tuned independently.The use of a tunable external quality factor tuning circuit greatly expands the adjustment range of the passband bandwidth while ensuring the stability of the passband.An additional transmission path can generate and control the transmission zero without affecting the passband to realize the switching of the filter state of bandpass to bandpass with embedded-stopband or embedded-notch.(3)Through the series-parallel connection of LC resonators,two single-pole single-zero impedance transformation units and two double-pole single-zero impedance transformation units are designed,and the impedance transformation character and the relative position of transmission zeros and poles are analyzed.On this basis,by combining different impedance transformation units,two fully tunable impedance transformers with two transmission poles,two transmission zeros and narrow band character and a three-pole,two-zero,broadband,fully tunable impedance transformer are designed.On the one hand,parameter sweeping is adopted here to analyze the influence of component values on impedance transformation character.On the other hand,the theoretical calculation method of each component values is given through analytical formula.(4)A single-frequency filtering power divider with independently tunable center frequency and passband bandwidth is designed.the varactor-loaded tunable dual-mode resonator is used to replace the quarter wavelength impedance trandformer in the traditional Wilkinson power divider,which can generate tunable transmission poles and zeros.On this basis,a dual-frequency filter power divider is designed by parallelly feeding two resonators with different resonance frequencies synchronously.