Fully-tunable filtering power dividers exploiting dynamic transmission-zero allocation

Abstract

A new class of Wilkinson-type power dividers with reconfigurable quasi-elliptic-type filtering characteristics is reported. Their design exploits the connection of resonators to the branches of a Wilkinson-type power divider through impedance inverters that in turn produce power transmission zeros (TZs) at their natural frequencies. In this manner and by making frequency-controllable these resonators, the created TZs can be tuned to attain an adaptive bandpass-filtering/power-division double functionality in terms of centre frequency, passband-width, and stopband bandwidth/attenuation characteristics. Furthermore, bandstop-filtering actions can be generated through this technique in wide-band power divider realisations for the suppression of in-band interfering signals. Key advantages of the proposed filtering power divider include: unequal transmission-band spectral widths and out-of-band power-rejection profiles for the transfer functions of the two power-divider branches, as well as the intrinsic switching-off of one or both of them. The theoretical foundations of the engineered fully-tunable filtering power divider and its corresponding RF design guidelines are expounded in this work. In addition, a UHF-band microstrip prototype is manufactured and characterised for practical-demonstration purposes.