Integrated C-band (4–8 GHz) frequency-tunable & bandwidth-tunable active band-stop filter in 0.13-µm SiGe BiCMOS

An active notch filter for interference rejection at C band is presented. In the design, a sharp notch, typically -50 dB for the entire C-band, is synthesized by subtracting BPF output from all-pass output. Unlike prior works, notch attenuation does not depend on the Q of the BPF LC tank. The proposed filter has been fabricated in a 0.13 μm SiGe BiCMOS process. Measurement results show 0~1 dB gain, 8~10.8 dB NF, and -6~-9 dBm IP_-1dB in the pass band at 4-8 GHz. The filter draws 20-27.6 mA from a 3.3 V supply and the die area is 0.63×0.63 mm².