Dual-band step-impedance bandpass filter for multimode wireless LANs

Abstract

A step-impedance bandpass filter is presented for multimode wireless LANs. The filter has a new dual-band feature of two tunable passbands at desired frequencies and high out-of-band suppression, generated by incorporating step-impedance resonators in a comb-filter topology. It saves more than half the circuit size compared with the switch-type dual-band topology. The simulation and measurement results show the dual-band feature of two passbands at 2.45 and 5.75 GHz with 85 dB suppression at 3.5 GHz.

A Compact Multiband BPF Using Step-impedance Resonators with Interdigital Capacitors

“…Most of wireless systems can be operated in two or more frequency bands. More advanced techniques were applied to design band-pass filters such as step-impedance resonators (SIR) used to control harmonic frequencies as desired in dual band BPFs with hairpin structure [1], comb structure [2], and parallelcouple structure [3]. The triple-band BPFs were developed using tri-section step-impedance resonator (TSSIR) with inter-coupled hairpin structure to reduce size and obtain high out of band suppression [4], open stub-embedded TSSIRs arranged in anti-parallel coupled structure to generate an extra zero between harmonics [5], folded hairpin structure and new coupling scheme to improve performance and reduce size [6], [7], cross-coupled arrangement for sharpen passband skirts [8], and pseudo interdigital coupling structure to reduce size and improve stopband rejection [9].…”

Compact dual-band bandpass filter using open loop resonator loaded by in-line beeline for wideband applications

“…The problem of this filter is it's large implementation area. In [6] and [7] the stepped-impedance resonator are used to achieve dual-band bandpass filters that have high insertion loss. The proposed filter in [8] has good skirt attenuation rate on the edge of the first and the second pass bands and its stopband is relatively wide, but the complex filter structure is needed to achieve good selectivity and wide stopband, at the same time.…”

8 pole high temperature superconductor microstrip dual band bandpass filter design

“…Although theoretically there is no reason why a cross-coupled dual-band filter cannot be achieved in category II, in practice the coupling strength requirements are normally too strong to be realized. Category II dual-band bandpass filters are normally achieved by employing the harmonic of the fundamental resonator mode [2], using quarter-wavelength admittance inverters between resonators [3] instead of electromagnetic coupling or even using cross-coupled asynchronously tuned resonators [4].…”