Design of a Compact Dual-Mode Dual-Band Bandpass Filter Using Stacked-Loop Resonators Structure

Design, fabrication and measurement of a high-selectivity dual-mode dual-band bandpass filter are presented in this paper. The resonance frequencies of the filter are 1.8 GHz and 2.4 GHz which are generated by a meander-loop resonator and a square-loop resonator. The two dual-mode single-band-loop resonators are stacked on each other and create a dual-band bandpass filter. Some advantages of our design are compact size, high selectivity, low loss and also no dependence of two bands, resonance frequencies on each other. The measurement results exhibit that the minimum insertion losses are 0.19 dB for 1.8 GHz and 0.32 dB for 2.4 GHz. Moreover return losses are better than 43.2 dB and 40.6 dB for 1.8 GHz and 2.4 GHz, respectively. The proposed filter has a size of 18 x 18 mm(2). This microstrip filter is fabricated on RT/Duroid6010 substrate with dielectric constant 10.8 and thickness 1.27 mm and its equivalent circuit is also offered. The measured results exhibit good agreement with the simulated ones.