RF Reflectionless Filtering Power Dividers

Abstract

A new class of Wilkinson-type power dividers with co-integrated bandpass-filter (BPF) functionality and input-reflectionless behavior is presented. They make use of a resistively terminated bandstop-filter (BSF) branch that is connected at their input terminal and exhibits a quasi-complementary transfer function with regard to the ones of the BPF-type power-divider arms. Thus, the RF-input-signal energy that is not transmitted by this triple-function reflectionless filtering power divider (FPD) to its output ports is dissipated by the loading resistor of its input BSF-type branch. Design formulas and theoretical synthesis examples for first-to-fourth-order FPD schemes and arbitrary power-division ratios are given. Furthermore, the extension of this concept to FPD realizations with multi-passband response and reflectionless capabilities at both the input and output accesses is shown. Theoretical design guidelines and limitations of center-frequency-tunable reflectionless FPD implementations are also provided. For experimental-demonstration purposes, a frequency-tunable 3-dB microstrip prototype with second-order transfer function is also manufactured and tested.