Design of a novel four-band microstrip bandpass filter using double-layered substrate

Abstract

A novel four-band microstrip bandpass filter using double-layered structure is proposed. The basic components used to build the proposed filter are four pairs of stepped impedance resonators on the top metal layer and middle metal layer. The four pairs of resonators have different fundamental frequencies. The first and second fundamental frequencies are designed to operate at 3 and 5 GHz on the middle layer; the third and fourth fundamental frequencies are designed to operate at 7 and 9 GHz on the top layer. Due to cross-coupling effect, attenuation poles at both sides of the passbands can be created to improve the filter selectivity. The full-wave simulator IE3D is used to design the four-band bandpass filter and to calculate the coupling coefficients of the resonators.

Compact wide-stopband quad-band bandpass filter with tunable transmission zeros

“…Recently, many studies for multi-band BPFs have been published in the literatures [1]- [5]. In [1], double substrates were used to stack four pairs of resonators.…”

“…In [1], double substrates were used to stack four pairs of resonators. However, the high mode frequency response was not further designed.…”

“…By adjusting the coupled capacitance C between the feeding lines, four pairs of transmission zeros can be controlled to approach or leave the passbands. Due to the use of the double-layered structure, the filter has compact size compared with previous works [1][2][3][4][5]. The proposed BPF occupies an area of only 22.4 mm × 12.7 mm, approximately 0.14 λ g × 0.08 λ g , where λ g is the guided wavelength at 1.5 GHz.…”

Design and Fabrication of a Quad-Band Bandpass Filter Using Multi-Layered Sir Structure

“…Methods to design the dualband BPF are well developed and reported [5][6][7][8]15]. However, only a few methods for quad-band bandpass filters have been reported till now [9][10][11][12].…”

“…The challenges for circuit designers to design a quad-band BPF are to achieve compact size and good passband selectivity simultaneously. As known, conventional stepped impedance resonators (SIRs) can shift the higher order resonant mode to the desired frequency, thus the SIRs are suitable for a wide stopband, an ultra-wide band (UWB) or a multi-band use [12].…”