A Tunable Bandpass Filter Using Q-enhanced and Semi-passive Inductors at S-band in 0.18- Μm Cmos

A fully-integrated bandpass filter using Q-enhanced and semi-passive inductors is design, implemented and verified experimentally in a standard 0.18-μm CMOS process. The inductors achieve high-Q factors by using a tapped-inductor feedback technique to produce negative resistances. Compared with conventional transformer feedback, the proposed technique not only compensates resistive losses with low-power consumption but also provides a highinductance inductor which is suitable for low-frequency applications. The 2-pole Chebyshev series-C coupled bandpass filter provides a frequency tuning range of 300MHz around 2.65GHz. Measurements shown that it consumes 2.4 mW to achieve 1.0-dB insertion loss, 12dB return loss, 6.3-dB noise figure, and −2.5-dBm input P1dB with a 950-MHz bandwidth at 2.8GHz. And it consumes 5.6 mW to achieve 1.5-dB insertion loss, 10-dB return loss, 7.9-dB noise figure, and −4dBm input P1dB with a 700-MHz bandwidth at 2.5 GHz. The overall chip size of the filter is 0.7mm× 0.9mm including all testing pads.