Novel Single-Ended-to-Balanced Filter With Reconfigurable Working Modes, Frequency, Bandwidth, and Single/Dual-Band Operations

A novel single-ended-to-balanced (SETB) filtering circuit is proposed in this paper. The proposed circuit not only integrate controllable working modes between SETB filtering and SETB filtering power dividing (FPD) into one unit, but also has multi-level reconfigurable capabilities including tunable center frequencies, bandwidths, and switchable single/dual-band operations. It is constructed by a 5-port symmetrical microstrip network. By properly engineering the transmission response of the even and odd mode of the proposed circuit, the multiple reconfigurable functions can be realized in just one circuit in a mathematically sound way. The working modes between SETB filtering and SETB FPD are switched by leaving the corresponding ports open, while the control of center frequency, bandwidth, and single/dual-band operation is realized by tuning the capacitance value of loaded varactors. Detailed theoretical and experiment results have been given with good agreement.