Compact Microstrip Lowpass Filter With Sharp Roll-Off and Wide Stopband Using Semicircle Ended Stub Resonator

Abstract

Abstract-In this paper, a semicircle ended stub resonator, cascaded to a modified radial patch to design a compact lowpass filter with sharp roll-off and wide stopband is proposed. This filter has 3 dB cutoff frequency at 1.54 GHz. The transition band is only 0.26 GHz from 1.54 GHz to 1.8 GHz with corresponding attenuation levels of −3 dB and −20 dB respectively. Maximum insertion loss is 0.1 dB in the passband, and the stopband bandwidth with the attenuation level better than −20 dB is extended from 1.8 GHz up to 13.93 GHz. So, a wide stopband is achieved. The proposed filter is designed, fabricated and measured, where there is a good agreement between the simulation and measurement results. The results show that a roll-off rate of 65.4 dB/GHz together with a relative stopband bandwidth of 154% with the suppression level of −20 dB is obtained while achieving a high figure of merit (FOM) of 23509.

Wide stopband harmonic suppressed low-pass filter with novel DGS

“…The state‐of‐the‐art comparison of the proposed LPF with respect to the recently published works is show in Table where different terms meaning are as given in Ref. [ ]. In this table, RL, IL, ᶓ, RSB, SF, NSC, AF, and FOM are return loss, IL, roll‐off rate, relative stopband, suppression factor, normalized circuit size, architecture factor, and figure of merit, respectively.…”

“…To meet the stringent bandwidth policies, there is also the demand of a wide stopband harmonic suppressed planar low‐pass filter (LPF) in various applications like microwave amplifier's impedance matching networks. In addition, the LPF also needs to possess the characteristics like the compactness, low pass‐band insertion loss (IL), and the sharp selectivity …”

“…In addition, the LPF also needs to possess the characteristics like the compactness, low pass-band insertion loss (IL), and the sharp selectivity. [1][2][3][4][5] Due to the current controlling behavior of the defected ground structures (DGSs) on the ground plane, they find appropriate applications in the harmonic suppression. [6][7][8][9][10][11] The harmonic attenuation and the stopband frequency range are proportional to the filter size and, therefore, to achieve harmonic suppression over the wide bandwidth and the compactness simultaneously, a number of LPFs are reported in Refs.…”

Unsymmetrical Finger-Shape DGSS for Developing a Compact, High-Order, Harmonic-Suppressed Bandpass Filter

“…Comparisons with some published harmonic-suppressed BPFs. : order of filter FBW: fractional bandwidth IL: insertion loss RL: return loss FOM: figure of merit[22] …”