Input-reflectionless low-pass filter on multilayered diplexer-based topology

A class of two-layered input-reflectionless diplexer-based LPF is reported in this letter. By using a resistively-terminated wideband microstrip vertical transition by the first time for this application, an input-reflectionless response for the conceived LPF device is realized. The RF operational foundations and theoretical examples of this input-reflectionless LPF design approach have been shown and experimentally verified with the development and characterization of a two-LPF-unit microstrip prototype with extended reflectionless stopband.Ministerio de Economía, Industria y CompetitividadEuropean Commissio

High-Order Dual-Port Quasi-Absorptive Microstrip Coupled-Line Bandpass Filters

In this article, we present the first demonstration of distributed and symmetrical all-band quasi-absorptive filters that can be designed to arbitrarily high orders. The proposed quasi-absorptive filter consists of a bandpass section (reflective-type coupled-line filter) and absorptive sections (a matched resistor in series with a shorted quarter-wavelength transmission line). Through a detailed analysis, we show that the absorptive sections not only eliminate out-of-band reflections but also determine the passband bandwidth (BW). As such, the bandpass section mainly determines the out-of-band roll-off and the order of the filter can be arbitrarily increased without affecting the filter BW by cascading more bandpass sections. A set of 2.45-GHz one-, two-, and three-pole quasi-absorptive microstrip bandpass filters are designed and measured. The filters show simultaneous input and output absorption across both the passband and the stopband. Measurement results agree very well with the simulation and validate the proposed design concept