Miniaturized lowpass filter with ultra-wide stopband using dual-plane defected structures

Abstract

A miniaturized lowpss filter (LPF) with ultra-wide stopband is proposed by using the complementary rectangle split ring defected microstrip structure (CRSR-DMS) and the quad U-shaped defected ground structure (QU-DGS). The presented CRSR-DMS can provide a sharp rejection rate and two obvious attenuation poles while the QU-DGS can produce four independently controlled transmission zeros. Based on the characteristics of the defected structures, the proposed LPF is constructed by using four cascaded CRSR-DMS units and four cascaded QU-DGS units. The measurement result of the designed filter with 3 dB cut-off frequency at 2.0 GHz shows that the obtained 20 dB rejection band ranges from 2.12 GHz to more than 20 GHz within a small circuit area of 0.73λg + 0.13λg, λg being the guided wavelength at 2.12 GHz.

Compact microstrip lowpass filter with ultrasharp response using a square-loaded modified T-shaped resonator

“…The group delay of presented LPF is very flat because the maximum mutability in the proposed LPF at 55% passband is only 0.04 ns. Comparisons between the designed LPF performance and similar reported structures [14][15][16][17][18][19][20][21][22][23][24][25][26][27] are shown in the Table . In this table, the sharpness of transition band is calculated as follows [13]:…”

Design of an ultra-compact lowpass filter with ultra-sharp roll-off for UHF application

“…The effect of inductors and capacitors can be implemented by open stubs, short stubs, coupled lines, and the layout patterns of the PCB. This method would not easy to achieve compact size [16,17,18,19,20], and it may not meet the requirement of this UWB lowpass filter.…”