2 n -Way Wideband Filtering Power Dividers With Good Isolation Enhanced by a Modified Isolation Network

Abstract

In this article, a class of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2^{n}$ </tex-math></inline-formula> -way wideband filtering power dividers (FPDs) is presented and designed with a wide isolation band. It consists of ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2^{n}-1$ </tex-math></inline-formula> ) two-way power-dividing units and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> three-line coupled lines. The basic two-way power divider is achieved by replacing a simple isolation resistor of the conventional Wilkinson power divider with a modified isolation network, so as to improve the bandwidth of better-than-20-dB isolation band from 40% to 120%. The modified isolation network is composed of one quarter-wavelength coupled line, two quarter-wavelength transmission lines, and one resistor. The three-line coupled line is introduced at each output of the proposed FPD to improve its frequency selectivity and passband bandwidth. Furthermore, after placing one additional isolation resistor on each three-line coupled line, the number of output ports in the proposed power divider could be doubled without introducing more two-way power-dividing units. Finally, a prototype two-way and two prototype four-way wideband FPDs with different occupied sizes are designed and fabricated. The feasibility of the proposed design method is verified by the good agreement between the simulated and measured results.