End-coupled microstrip slow-wave resonator filter

A novel microwave narrow-band bandpass filter using end-coupled microstrip slow-wave resonators is proposed. The new filter is not only compact in size due to the slow-wave effect, but it also exhibits a wide upper stopband resulting from the dispersion property. A three-pole microstrip filter of this type has, for the first time, been designed and fabricated. The longitudinal dimension of the filter is smaller than the half-wavelength of a 50 Ω line at a midband frequency of 1.53 GHz. No spurious response occurs for the frequency up to 5.5 GHz.