Open-Loop Short-Circuit Branch Line Dual-Mode Bandpass Filter for Low-Bands 5G Applications

Abstract

This paper introduces a new design of microwave bandpass filter based on microstrip open-loop short-circuit dual-mode resonator. The principle of the short circuit branch line of the filter is to split the mode of the fundamental wave or harmonic wave of the quarter wavelength. Two transmission zeros (TZs) poles are formed near the center frequency, which improves the out of band rejection of microstrip filter. The actual test results show that when the frequency range of the filter is 694MHz–806MHz, and the relative bandwidth is 29.4%. This class of proposed filter exhibits the compact size and the good quality factor.