A K-Band Quartz Glass Absorptive Bandpass Filter With On-Chip Power-Divider-Like Architecture

In this letter, a novel integrated absorptive bandpass filter based on two-paths architecture with on chip power-divider-like three-port networks and filtering cores is presented. An imaginary impedance element is added in the middle of the absorptive resistor network for mitigating the common mode reflected waves in the stopband, and wideband reflection loss in the stopband is achieved. A quartz glass bandpass absorptive filter is designed and fabricated, with a die size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6.65 \times 4.89$</tex-math> </inline-formula>mm. Measurement shows the filter is centered at 21.5 GHz with a 3-dB bandwidth (BW) of 3.3 GHz, an insertion loss (IL) of 1.8dB, and a wideband absorptive response from dc to 40 GHz.