C-band complementary metal-oxide-semiconductor bandpass filter using active capacitance circuit

In this study, a second-order Chebyshev active bandpass filter with three finite transmission zeros at C-Band is presented. This filter utilises an active capacitance technique to compensate resistive losses of resonators, and a shunt-feedback inductor between input and output to achieve the transmission zeros in the bandpass filter. Moreover, one transmission zero is in the lower stopband, and two transmission zeros are in the upper stopband, thus improving the selectivity of the filter significantly. The filter is designed and fabricated in a standard 0.18 μm CMOS technology with a chip area of 0.92 mm × 0.76 mm including all testing pads. The filter achieves 0.77 dB insertion loss, 18 dB return loss, and 32% 3 dB bandwidth at 5.3 GHz with 2.2 mW power consumption. The measured NF and input P1 dB is 4.3 dB and 2.5 dBm, respectively. Finally, the rejection levels at these transmission zeros are greater than 14.4 dB.