Super High-Selectivity Fifth-Order Bandpass Filter with Twelve Transmission Zeros

Abstract

A fifth-order bandpass filter (BPF) with super high selectivity using three pairs of coupled lines and two open stubs is proposed. Twelve transmission zeros (TZs) from 0 to 2f 0 (f 0 denotes center frequency of the passband) and five transmission poles (TPs) in the passband can be obtained to realize good out-of-band suppression and sharp roll-off skirts. For demonstration, a simple BPF prototype centered at 2.04 GHz is designed, fabricated with measured 3-dB fractional bandwidth of 18% and very high transition band roll-off rates of over 567 dB/GHz. Good agreement between the simulations and measurements validates the design method.

Design and fabrication of a novel multilayer bandpass filter with high‐order harmonics suppression using parallel coupled microstrip filter

“…Transmission zeros (TZs) and transmission poles (TPs) can be used to achieve the desired filter performance in the passband and stopband [14–17]. In [14], a BPF with super high selectivity is designed using three pairs of coupled lines and two open stubs [14]. In [15], a combination of TZs and TPs is used to achieve sharp roll‐off skirts in wideband BPFs based on coupled lines.…”

“…Transmission zeros (TZs) and transmission poles (TPs) can be used to achieve the desired filter performance in the passband and stopband [14][15][16][17]. In [14], a BPF with super high selectivity is designed using three pairs of coupled lines and two open stubs [14]. In [15], a combination of TZs and TPs is used to achieve sharp rolloff skirts in wideband BPFs based on coupled lines.…”

High‐selectivity bandpass filter using six pairs of quarter‐wavelength coupled lines

“…Note that the design of the filters using parallel-coupled lines requires complicated parameter tuning for achieving high selectivity and wide stopband. In order to simplify the filter structure, the BPFs using seriescascaded parallel-coupled lines have been presented in our previous works [9,10].…”