A novel compact microstrip dual-mode wideband bandpass filter design using tuning stubs

Abstract

In this article, a novel dual-mode wideband bandpass filter having tuning stubs is proposed. Proposed filter has two stopbands in the lower and higher sides of the passband as the filter is configured as a bandstop filter by using direct-connected feedlines. Hence, a passband can be created inside a wide stopband by means of the open-circuited stubs, which are called as tuning stubs, located into the opposite corners of the input and output (I/O) ports, which are arranged so as to form a quarter wavelength resonator. Tuning stubs are placed inside a meander loop resonator to keep the compact configuration. On the other hand, center frequency of the passband can be controlled by changing the lengths of the tuning stubs. Additionally, by means of a perturbation patch placed at the orthogonal corner of the loop resonator, selectivity of the passband can also be controlled by exciting the degenerate modes of the side stopbands. Designed filter has been fabricated, simulated and measured in a good agreement. © 2014 Wiley Periodicals, Inc.