Miniaturized Ultra-Wideband Bandpass Filter With Ultra-Wide Stopband Using π-Type Unit With Inductive Loading on Integrated Passive Device

In this brief, a new miniaturized ultra-wideband (UWB) bandpass filter (BPF) with ultra-wide stopband (UWS) usingπ-type unit with inductive loading on integrated passive device (IPD) is proposed. theπ-type with non-periodic response is equivalent to the coupled line with open-ends diagonally for the first time. The proposed compact lumped BPF based on threeπ-type units is not only easy to design UWB response without strong coupling, but also has the advantage of the UWS due to the non-periodic phase of the unit. Besides, the high frequency selectivity can be obtained for two transmission zeros near the passband. In final, a prototype with 3-dB fractional bandwidth of 111% is designed and fabricated at 4 GHz (f ₀). The upper-stopband attenuation higher than 24 dB is extended to more than 45 GHz (> 11.25f ₀). It occupies only 0.008λ ₀ × 0.032\,\,λ ₀, whereλ ₀is the free-space wavelength atf ₀.