A quintuple mode resonator based bandpass filter for ultra-wideband applications

This paper presents a new configuration of quintuple mode resonator for designing a bandpass filter for ultra-wideband applications. The multiple-mode resonator is constituted by two capacitive ended rectangular stubs and connected with a high impedance microstrip line. Inter-digital coupled feed lines are designed to excite the resonator. Standard analytical approach based on odd-/even-mode analysis is applied to examine the resonant characteristics of the multi-mode resonator. The proposed filter has the characteristics of low insertion loss, wide stopband along with compact size. The bandwidth (|S-11| <= - 10 dB) of the proposed filter has been observed to vary from 3.11 to 10.63 GHz with low insertion loss value uniform around - 0.8 dB. A wide stopband with attenuation of more than 15 dB (11.27-20 GHz) is observed for the proposed design. The filter occupies a compact area equal to 23.4 mm x 10 mm (about 0.43 lambda(g) x 0.09 lambda(g), where lambda(g) is the guided wavelength at 6.85 GHz). The simulated results agree well with the measured results validating the effectiveness of the work.