Harmonic‐suppressing bandpass filter based on coupled triangular open‐loop stepped‐impedance resonators

Abstract

This work develops two harmonic‐suppressing bandpass filters. One has a direct‐coupled‐resonator structure and the other has a cross‐coupled‐resonator structure. The triangular open‐loop stepped‐impedance resonator is used to synthesize filters because it can create two tunable transmission zeros to suppress multi‐spurious responses in the upper stopband. The coupling coefficients of typical coupled pairs of resonators and the external quality factors of two basic feeding configurations are exploited in filter synthesis. A three‐pole Chebyshev filter and a four‐pole selective‐response filter are designed and fabricated herein. The first spurious peaks of these two experimental filters occur at five times and four times the operating frequency, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 187–191, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24866

LTCC Vertically-Stacked Cross-Coupled Bandpass Filter for LMDS Band Applications

“…When the cross coupling path is out of phase with the main path coupling, a pair of transmission zeros can be created at the skirt of the passband to improve frequency selectivity. Numerous studies have emphasized the improvement of cross-coupled filters [4][5][6][7][8][9][10][11][12][13][14][15]17] and direct-coupled filters [16,18]. In one investigation [4], the hightemperature superconductor films were used to design fourth-order open-loop filters with low insertion loss.…”

Analysis of Different Loop Resonators and Their Application in Band‐Stop Filter Design

“…The measured return loss is 1.3 dB and insertion loss is better than 12.5 dB in the whole stop‐band with a central frequency of 2.2 GHz and the spurious band is pushed after about 4.5 f 0 . At last in Table presents a brief comparison of some filters with wide spurious‐free band in recent years.…”

Application of the tapping positions to harmonic suppression bandpass filter design

“…So many methods were presented to suppress the harmonics of bandpass filters, for example, adding bandstop filter or lowpass filters to the origin filter, using resonators which could suppress harmonics to design bandpass filter [1][2][3][4][5][6][7][8][9][10][11][12][13].…”