Design of a K-band chip filter with three tunable transmission zeros using a standard 0.13-μm CMOS technology

A novel bandpass filter (BPF), which is fabricated with a commercial CMOS process, demonstrating a low insertion loss in the passband and multiple transmission zeros in stopbands, is presented for 24-GHz automotive ultrawideband (UWB) radar systems. The filter combines a second-order asymmetrically compact resonator filter with a sourceload coupling mechanism to realize three transmission zeros; two zeros are arranged in the lower stopband, and one zero is located in the upper stopband. To achieve a compact layout size and a low insertion loss, a semilumped approach, which is accomplished with mixed utilization of high-impedance coplanar waveguide lines and lumped capacitors, is used to construct the chip filter. A K-band experimental prototype that has a very compact size of 0.35 \times 0.8\ mm² was realized. The average insertion loss in the filter's passband is about 2.7 dB, the return loss is greater than 15 dB within the frequencies of 2427.5 GHz, and the attenuation levels at the three transmission zeros all greater than 35dB.