Ultra-wide stopband low-pass filter using symmetrical cascaded modified hairpin resonators

Abstract

An elliptical function low-pass filter (LPF) with ultra wide stopband and sharp cutoff frequency is proposed. This filter is composed of symmetrical cascaded modified hairpin resonators and U-shaped resonators. The transition band is from 1 to 1.21 GHz with 23 and 220 dB, respectively. For this filter, the return loss is better than 17 dB in 80% of passband width, where the insertion loss is less than 0.3 dB. The band-stop rejection is greater than 20 dB from 1.21 to 26.35 GHz and 40 dB from 1.35 to 12.5 GHz. To validate the design and analysis, the proposed LPF has been designed and fabricated on a 20 mil thick RO4003 substrate with a relative dielectric constant 3.38 and loss tangent of 0.0021. The filter is evaluated by experiment and simulation with a good agreement. V C 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:314-321, 2014.

Compact D-CRLH resonator for low-pass filter with wide rejection band, high roll-off, and transmission zeros

“…Important parameters of LPF are roll-off rate or selectivity, relative stopband bandwidth (RSB), normalized structure size (NSS), and FOM, which are defined as in [11, 23]where, α max and α min are the 20 and 3 dB attenuation point, f s is the 20 dB stopband frequency, f c is the 3 dB cut-off frequency, and λ g is the guided wavelength at 3 dB cut-off frequency. The measured stopband bandwidth is taken for the attenuation level of −11.5 dB (from 3.2 to 6.9 GHz).…”

Planar elliptic function lowpass filter with sharp roll-off and wide stopband

“…As shown in Table , the proposed filter exhibits sharp roll‐off and wide stopband among the quoted filters with high thickness substrate. Wide stopband offered by the reported filters is due to the material property of the fabricated substrates, such as low thickness and very low loss tangent.…”

“…The slope of transition can be improved by introducing more number of reactive elements, which increases insertion loss in passband and layout area of the filter. Many different methods and topologies have been proposed recently to develop lowpass filter with excellent electrical characteristics utilizing (i) compact microstrip resonant cells with uniquely shaped defected ground structures , (ii) double equilateral U‐shaped defected ground structure , (iii) hexangular‐shaped resonator , (iv) symmetrical cascaded‐modified hairpin resonators , (v) stepped‐impedance hairpin units , (vi) stub‐loaded coupled‐line hairpin unit , (vii) open complimentary split ring resonator , (viii) symmetrically loaded multiple patch resonators on high impedance transmission line . Although these reported filters are good choice in modern communication systems, they suffer (i) additional radiation due to partially opened ground plane , (ii) poor roll‐off , and (iii) low stopband suppression level .…”

Design and fabrication of microstrip lowpass filter using asymmetric hairpin resonator

“…In References , the transfer function and LC equivalent circuit is used to obtain TZs and analyze the design theory. In Reference , a LPF is proposed, that is, consist of symmetrical cascaded modified hairpin resonators and U‐shaped resonators. The proposed LPF has characteristics such as high return loss in the passband and ultrawide stopband.…”