Research On Key Technologies Of Reconfigurable Filter Circuits In The RF Integrated System

With the increasing digitization of modern warfare,radio frequency(RF)wireless systems with multi-function and different purposes are widely used in a common military electronic information platform.And the problems of system complication,poor stealth and electromagnetic interference need to be solved.Therefore,the RF integrated system came into being and became the effective way to solve those problems.The communication,radar,electronic warfare and other functions could be integrated in the RF integrated system,where the hardware and information resources are highly shared.For the multifunctional RF integrated system that needs to implement the combat mission and covers multiple operating bands,the reconfigurable technology could achieve high integration and dynamic configuration of multiple functions on the same RF hardware platform.With reconfigurable technologies,the volume of system and production cost could be greatly reduced.In this dissertation,under the research background of modern RF integrated system,the theoretical analysis,design method and the experimental verification of the key technologies of reconfigurable filter circuits and high-performance RF reconfigurable passive circuits are discussed.The main research work of this dissertation is summarized as the following aspects.1.Two reconfigurable filters with constant absolute bandwidth(ABW)are proposed.Firstly,based on the cross coupling topology and two kinds tunable resonators,a fourth-order generalized Chebyshev reconfigurable bandpass filter with a pair of transmission zeros is presented.To achieve the constant ABW within the frequency tuning range,the variation of the coupling coefficient and external quality factor with the varied frequency are analyzed by using the synthesis methodology of the lowpass prototype filter network and the general coupling matrix.Secondly,a balanced reconfigurable bandpass filter with high common mode suppression and constant ABW is proposed.By adjusting the loading position of the varactors in the resonators and tuning varactors loaded onto the end of feeding lines,the constant ABW is achieved.2.Three kinds of high-performance reconfigurable filters based on quasi-lumped elements are proposed.By using the quasi-lumped elements realized by the microstrip line and based on the lowpass prototype filter synthesis methodology,three reconfigurable filters with different filtering responses are presented.Firstly,a reconfigurable lowpass filter is realized by directly cascading the reconfigurable bandstop filtering section and the fixed-frequency lowpass filtering section.The tunable frequency and high roll-off rate are obtained by adjusting the lower edge of the reconfigurable bandstop filtering section,and the stopband bandwidth is extended by the fixed-frequency lowpass filtering section.Secondly,a reconfigurable bandpass filter by cascading the high-pass and low-pass filtering sections is proposed.Both the operating frequency and bandwidth of the bandpass filter can be reconfigured independently by controlling cut-off frequency of the the high-and low-pass filter sections.Finally,a bandpass-to-bandstop reconfigurable filter with wide frequency tuning range is proposed.The bandpass-bandstop filtering response transformation is realized by the PIN diode,which is utilized to change the circuit topology.3.With the design theory of the constant ABW reconfigurable filter,several reflectionless reconfigurable filtering circuits are proposed based on the balanced-circuit and complimentary-duplexer architecture.Firstly,two technologies of the reflectionless reconfigurable filter based on the balanced-circuit and complimentary duplexer architecture are studied,which could be applied to the design of filter circuit with different frequency response.To validate the methodology,a single-band two-port-reflectionless reconfigurable bandpass filter,a single-band input-reflectionless reconfigurable bandpass filter,a dual-band two-port-reflectionless fixed-frequency bandpass filter and a dual-band two-port-reflectionless reconfigurable bandpass filter with passband switch function are proposed.And all the four reflectionless filters are with the constant ABW performance.Moreover,the filtering response transformation among single-/dual-passband and all-band-off state can be realized by the dual-band reflectionless reconfigurable filter.Then,with the same reflectionless filter technologies,an all-port-reflectionless diplexer with constant ABW and an input-reflectionless reconfigurable filtering power divider are presented.The feasibility of the proposed technology of the reconfigurable reflectionless filtering circuits is verified by the experimental results,and the methodology can be used to design the fixed/reconfigurable circuits with different filtering response.