Miniaturized Microstrip Bandpass Filters with Resonators

A novel microstrip bandpass filter design with two spiral resonators is presented in this paper. The proposed filter has good frequency selectivity and its dimensions are smaller in comparison with conventional ones. A numerical simulation of the filter with the central frequency of 2000 MHz was made to receive the S-parameters. A prototype with dimensions of 18.9 x 5 = 94.5 mm(2) was implemented on a substrate with a dielectric constant epsilon = 4.4, dielectric loss tangent tg delta = 0.02 and thickness h = 1.5 mm. The measured characteristics are in good agreement with the results of the electromagnetic simulation.