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Highly‐tunable and wide stopband microstrip bandpass filters
Author(s) -
Iqbal Amjad,
Smida Amor,
Waly Mohamed I,
Mallat Nazih Khaddaj
Publication year - 2021
Publication title -
international journal of rf and microwave computer‐aided engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.335
H-Index - 39
eISSN - 1099-047X
pISSN - 1096-4290
DOI - 10.1002/mmce.22610
Subject(s) - stopband , varicap , materials science , band pass filter , resonator , transition band , capacitance , biasing , electronic engineering , optoelectronics , microstrip , prototype filter , chebyshev filter , insertion loss , filter (signal processing) , topology (electrical circuits) , low pass filter , electrical engineering , physics , voltage , engineering , electrode , quantum mechanics
This paper presents the design of a highly‐tunable single‐ended and balanced filter with improved upper stopband performance. The proposed filters are designed using a spurline and a U‐shaped stepped impedance resonator (SIR) with a varactor diode connected to the open‐circuited end. A spurline is introduced in both designs to achieve wide stopband performance by suppressing the higher‐order modes. The proposed filters have high tunable ranges (single‐ended: 2.35‐3.99 GHz; balanced: 2.39‐4 GHz), low insertion losses (IL) (single‐ended: 0.07‐0.2 dB; balanced: 0.21 to 1.1 dB) and wide upper stopband performance (single‐ended: 3.79 f 1 with a rejection level higher than 20 dB; balanced: 3.79 f 1 with a rejection level higher than 20 dB). Performance of both filters are experimentally validated by comparing the experimental results with the simulated ones. Both filters can cover most of the fifth‐generation (5G) wireless communication bands with different biasing voltages (capacitance). When both filters are compared with state‐of‐the‐art filters, the proposed filters are found to achieve high tunable ranges with low IL and wide upper stopband performance.