Open AccessDesign and characterisation of dual‐mode suspended‐substrate stripline filter
Author(s) -
Binti Mohd Najib Norazwana,
Somjit Nutapong,
Hunter Ian
Publication year - 2018
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/iet-map.2017.1136
Subject(s) - stripline , dual mode , substrate (aquarium) , materials science , dual (grammatical number) , electronic engineering , optoelectronics , engineering , biology , art , ecology , literature
A new design technique of a dual‐mode ring‐resonator suspended‐substrate stripline filter is reported here to achieve low passband insertion loss, high quality factor, and good spurious response. A fourth‐order bandpass filter was designed and fabricated at the operational frequency of 2.07 GHz with two ring resonators packaged in a metallic cavity where each ring resonator is one wavelength long. The transmission zeros of the dual‐mode filter are generated due to the phase cancellation between the two paths in a ring, thus a sharp‐skirt selectivity filter response was achieved. Perturbation notch structure was implemented on each ring resonator to provide the electromagnetic coupling of two degenerate modes, thus a dual‐mode response of the filter can be synthesised. Measurement results of the first dual‐mode filter prototype showed a return loss and an insertion loss of better than 16.42 and 0.926 dB, respectively, while an out‐of‐band rejection of up to 55 dB was achieved. The novel filter design technique proved that no cross‐coupling is required to obtain the transmission zeros of the filter, thus the sharp‐skirt response was achievable.