RETRACTED: Novel method for skirt response improvement of open‐stub low‐pass filter

Abstract

A direct circuit replacement method using interdigital low‐pass structure directly replaced all open stubs of odd‐order open‐stub low‐pass filter to achieve sharp skirt response. The characteristics of the interdigital structure are analyzed by lumped element equivalent circuits and investigated by full‐wave electromagnetic simulator, IE3D. These simulated results were then applied as a guideline for the replacement. Two open‐stub low‐pass filters were designed by this method to enhance the skirt response near 3‐dB cutoff frequency. The measured results show very good improvement on skirt response and the rejection level in stop band. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2434–2438, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22764

Advances in Planar Filters

“…Several solutions have been proposed recently with the aim to reduce size (10)(11)(12) or improve cutoff rate (13) or out-of-band performance (14) of planar low-pass filters. Although all reported solutions are based on conventional filter topologies such as stepped-impedance, open-stub, or coupled-lines, the final designs are often quite complex.…”

Planar low‐pass filters based on hilbert fractal

“…Full numerical details of the comparison are given in Table 1, where available data for recently published low‐pass filters [6–9] is also presented. The proposed DHL‐based filters compare very favorably to recently published filters: they are of approximately same overall size as [6, 8], but exhibit better return loss and rejection, respectively. Filter [7] is very compact but exhibits large insertion loss and poor pass‐band return loss.…”

“…The proposed DHL‐based filters exhibit better pass‐band return loss, better rejection in the stop‐band and smaller insertion loss, while in the same time they achieve more than two times smaller size then their conventional counterparts. Full numerical details of the comparison are given in Table 1, where available data for recently published low‐pass filters [6–9] is also presented. The proposed DHL‐based filters compare very favorably to recently published filters: they are of approximately same overall size as [6, 8], but exhibit better return loss and rejection, respectively.…”

“…From the fabrication point of view, it is often required that these filters involve only etching on one side of the substrate, without any modifications to the ground plane or use of vias. Setting aside configurations that rely on defect ground structures [1–5], a number of planar low‐pass filters have been proposed recently with the aim to reduce size [6, 7], improve cutoff rate [8] or out‐of‐band performance [9] of planar low‐pass filters. Although all reported solutions are based on conventional filter topologies such as stepped‐impedance, open‐stub, or coupled‐lines, final designs are often quite complex.…”

“…From the fabrication point of view, it is often required that these filters involve only etching on one side of the substrate, without any modifications to the ground plane or use of vias. Setting aside configurations that rely on defect ground structures [1][2][3][4][5], a number of planar low-pass filters have been proposed recently with the aim to reduce size [6,7], improve cutoff rate [8] or out-of-band On the other hand, fractal curves have already demonstrated their potential to allow straightforward design of miniature band-pass filters while preserving their performances [10][11][12]. However, fractal curves have been rarely used in the design of low-pass filter, and then only as patterns for a defected ground structure [13].…”