Ka-Band On-Chip Broad Stopband Bandpass Filters Based on GaN-on-Silicon

We propose a broad stopband on-chip bandpass filter (BPF) based on GaN-on-Silicon. The filter extends the ground plane between the resonators, and a U-shaped feed to form a band stop, which forms a transmission zero at the upper frequency for faster attenuation. The measurements show that the filter has a broad stopband with S<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> less than −15 dB from 30.4 to 110 GHz. The 3 dB bandwidth is 12.1%, and the S21 bandwidth greater than −15 dB is 23.7%. The quality factor is33.7 which is higher than the existing literature. This proposed filter has a good stopband attenuation rate with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.087\times 0.103~\lambda _{{g}2}$</tex-math> </inline-formula> (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.662\times 0.814$</tex-math> </inline-formula> mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) chip area.