LTCC MLC Band-pass Filter using Quarter-Wavelength Hairpin Resonators for WLAN

摘要

In this paper, a quarter-wavelength hairpin resonator is proposed to reduce the size of planar resonators for a LTCC MLC band-pass filter. The quarter-wavelength hairpin resonator operates as stepped impedance resonator (SIR) without changing the width of the planar resonator. It is composed of two sections those are parallel coupled line and transmission line. The characteristic impedance of two sections is different each other. By using the p equivalent circuit for parallel-coupled lines, the equivalent circuit of the band-pass filter with quarter-wavelength hairpin resonators can be expressed. And the electromagnetic coupling of the parallel coupled lines and the other coupling element at the arbitrary position of resonators can be transformed to a inverter between two resonators. The design formulas of the band-pass filter using the coupling element at the arbitrary position are derived from even and odd-mode analysis. The formulas can take account of the arbitrary coupling of lumped and/or distributed resonators. The advantage of this filter is its abilities to change freely the coupling structure between two resonators. Experimental filters for wireless LAN are implemented and their performances are shown.