Open AccessEquiripple design of low‐pass filter using stub‐loaded Z‐shaped coupled‐line section
Author(s) -
Huang Xiaodong,
Zhou Yuting,
Jin Xiuhua,
Yang Liu,
Cheng Chonghu
Publication year - 2021
Publication title -
iet microwaves, antennas and propagation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.555
H-Index - 69
eISSN - 1751-8733
pISSN - 1751-8725
DOI - 10.1049/mia2.12204
Subject(s) - stub (electronics) , ripple , transmission line , m derived filter , low pass filter , filter (signal processing) , stopband , prototype filter , electrical impedance , electronic engineering , acoustics , band pass filter , constant k filter , frequency response , physics , engineering , electrical engineering , voltage
Design procedure of a novel transmission line low‐pass filter is presented. The filter has a flexible rejection response for a prescribed cut‐off frequency and an in‐band ripple factor. It is compact by using a Z‐shaped coupled‐line section, which is loaded with open‐circuited stubs. All of the transmission line elements are identical in electrical length, and the impedances can be calculated by solving certain specific equations according to prescribed in‐band specifications. The simulated results show that the circuit can generate low‐pass responses with third‐, fifth‐, and seventh‐order filtering functions. The filter order depends on the number and position of the loading stubs. For verification, two sample filters with cut‐off frequency of 0.5/0.3 GHz are fabricated using a three‐/five‐layer PCB process, which generate seventh‐order low‐pass filtering responses with good selectivity. The experimental results agree well with the predictions.