Abstract
This paper proposes a compact ultra-wideband filter, which skillfully utilizes the magnetic and capacitive coupling to obtain sharp rejection. And, the filter contains a small number of lossy elements, thus the low insertion loss and compact size will not be compromised. The measured results show that the filter prototype has a measured 3dB fractional bandwidth of 128% from 2.8GHz to 11.4GHz, a minimum insertion loss of 0.3dB within the passband, a superior 20dB stopband rejection from 12.4GHz to 24GHz, and a very compact circuit size of 0.23λ×0.31λ, where λ is the guided wavelength of the microstrip structure at the center frequency f0 = 7.1GHz.
