Multi‐spurious harmonics suppression in folded hairpin line bandpass filter by meander spur‐line

Abstract

The present article exhibits the improvement in wide stopband harmonic suppression techniques of fourth‐order compact hairpin‐line Chebyshev type narrowband (4%) bandpass filter centered at 2.5 GHz by meander spur‐line. Initially, the compactness of 42% over the conventional hairpin‐line cell has been achieved by folding the open‐end arms of the hairpin line to folded hairpin‐line cell. Accordingly, the improvement of the skirt characteristics and the shifting of the harmonics to higher frequencies have been observed with the cost of harmonics attenuation levels' degradation. Subsequently, an improvement in the stopband rejection level of 40 dB up to 4f0 has been achieved by incorporating meander spur‐line to all the coupled edges of the adjacent folded cells of the compact filters along with compactness of 38%.

Compact High-Selectivity Wide Stopband Microstrip Cross-Coupled Bandpass Filter With Spurline

“…In general, spurline is a microstrip defect created by etching one defected slot of L shaped in the microstrip line [16][17]. As shown in Fig.…”

“…However, there is a compromise between stopband rejection bandwidth and rejection level in [13][14][15]. Very recently, double-fold uniform impedance hairpin resonators have been placed in cross-coupled configuration to design a compact filter (size of 0.22λ g ×0.25λ g ) [16]. Subsequently, conventional spurlines with optimum dimensions have been incorporated to achieve the stopband bandwidth up to 3.16f 0 and a rejection level of 35 dB.…”

“…In the present article, conventional spurlines of [16] have been modified by meander spurline to provide higher degree of slow-wave effect for the signal and to achieve more phase velocity compensation for the same filter structure with the same specifications. The effectiveness of the meander spurline over the conventional spurline has been justified by the equivalent lumped elements analysis and two prototype filters with two different spurlines have been fabricated on FR4 substrate material having dielectric constant ε r = 4.4, thickness h = 1.6 mm, and loss tangent tanδ = 0.02.…”