Tunable LNA filter design using coupled-inductor Q-enhancement

A tunable LNA filter using Q-enhanced inductors is designed in 0.25 μm BiCMOS Qubic4x technology. The design employs the inductor degenerated LNA, acting as a transconductance which converts the input voltage to output current which drives the second-order Q-enhanced filter. The filter also uses a special technique based on coupled-inductor negative resistance generator to make the quality factor and the center frequency tunable. The overall gain of the LNA filter is about 19.5 dB and the minimum noise figure is 6.4 dB. The center frequency is 942.5 MHz with a 42 MHz (3 dB) bandwidth.