Design and implementation of dual-band and triple-band substrate integrated coaxial line filters

In this article, dual-band and triple-band filters are proposed based on the substrate integrated coaxial line (SICL) technique. The SICL resonator and the coupling between the bandpass-bandpass resonators and bandpass-bandstop resonators are investigated, then single-bandpass, dual-bandpass, and triple-bandpass filters are designed, fabricated, and measured. The dual-band or triple-band filters are equivalent to the combinations of one bandpass and one or two bandstop filters, and so can be easily synthesized from the generalized lowpass prototypes with Chebyshev responses. The measured results are in good agreement with the simulations. A size reduction of more than 45% has been achieved compared with the published substrate integrated waveguide filters.