Research And Design Of LTCC Filter Based On Reconfigurable Coupling Matrix

In recent years,the mobile communication industry has developed rapidly.The filters,as an important frequency selection device,have put forward higher requirements for their property.With the proposal of software-defined radio,the research on reconfigurable filters and their miniaturization has attracted widespread attention from scholars.This paper studies the design method of reconfigurable filter based on low temperature co-fired ceramic(LTCC)technology.And based on this method,a 4th-order reconfigurable LTCC filter is devised.The tunable components are distributed on the upper and lower surfaces of the substrate,which enables the filter to obtain a smaller size.The tuning range of center frequency(CF)is 2.86-3.2GHz,and that of the 3d B bandwidth(BW)is 170-320 MHz.By studying the traditional design theories and methods of reconfigurable filters,this paper proposes a filter design method based on reconfigurable coupling matrix.The proposed reconfigurable coupling matrix contains three tunable variables,which can independently tune the CF,BW and transmission zeros(TZs)of the filter.In addition,the method also includes the establishment of the mapping relationship between the physical components and the tunable variables.Based on the above design method,a 2nd-order reconfigurable LTCC filter is devised in this essay.The filter is composed of stepped impedance resonator(SIR)and can tune the CF with constant absolute BW.After measurement,the CF of the filter can be tuned between2.83-3.21 GHz,and the 3d B BW is 223±5MHz.In order to verify the generality of the above design method,a 4th-order reconfigurable microstrip line filter is designed in this paper.By introducing cross-coupling between the first and fourth resonators of the filter,the stop-band performance is improved.The BW and TZs of the filter can be tuned independently and continuously,and part of the bias-voltages can be calculated according to the tunable variables in the coupling matrix.After measurement,the tuning range of 3d B BW is 69-123 MHz,and that of the normalized TZs is 1.55-2.The essay discusses the theory and method of devising reconfigurable filter and the technology of devising reconfigurable LTCC filter,and manufactures three reconfigurable RF filters,all of which get excellent results.The research in this essay has grand value to the design theory and design method of reconfigurable filters.