Compact UWB bandpass filter using ring open stub loaded multiple-mode resonator
A novel ultra-wideband (UWB) bandpass filter with a compact size, improved upper-stopband performance and reduced radiation loss has been studied and designed using a multiple-mode resonator (MMR). The MMR is formed by attaching three pairs of ring open stubs in shunt to a high impedance microstrip line. By simply adjusting the radius of the circles of the ring stubs, the resonant modes of the MMR can be roughly allocated within the 3.1–10.6 GHz UWB band while suppressing the spurious harmonics in the upper-stopband. Meanwhile, the insertion loss is higher than 20.0 dB in the upper-stopband from 11.7 to 33.5 GHz in simulation. Finally, the filter is fabricated and measured. The EM-simulated and measured results are presented and excellent agreement between them is obtained.
