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摘要
In this paper, a microstrip reconfigurable wideband filtering power divider (FPD) with tunable center frequency (CF), bandwidth (BW), and power division is presented. The proposed structure consists of two trimode stub-loaded resonators, a three-line coupled structure loaded two varactor diodes, and two output parallel-coupled lines loaded a lumped capacitor. The CF and BW of wideband filtering response can be tuned by controlling the varactor diodes loaded onto the open end of trimode resonators. Meanwhile, the power division ratio (PDR) is controlled by tuning the coupling strength between the center line and sidelines of three-line coupled structure. Compared with the conventional wideband FPDs, the capacitor loaded onto the parallel-coupled line of two output ports is to enlarge the coupling, which can increase the return loss (RL), and thus relieve the limitation of the line space between two coupled lines. A complete design procedure with analytical design equations for driving parameters of the structure is described. The measured results show that the CF can be tuned from 0.86 to 1.32 GHz with RL better than 16 dB, while the 1-dB BW can be tuned from 180 to 710 MHz. The measured isolation is better than 21 dB from dc to 2.5 GHz. Then, the achieved PDR can be tuned from 1:1 to 3:1. The proposed circuit can be also utilized as a switchless bandstop filter, where the isolation is better than 20 dB from dc to 19 GHz. The proposed tunable wideband FPD exhibits good RL, wide range of frequency and BW control, wide harmonic suppression, high isolation, and multifunctional application.
