Analysis and design of a 250-MHz Gm-C filter with discrete tuning scheme in 0.18-μm CMOS for UWB receiver

A low noise, 250-MHz fifth order 0.1 dB ripple chebyshev G_m-C filter, with a discrete tuning scheme in 0.18-μm CMOS is presented. The tuning circuit employs an amplitude locked loop (ALL) to find the correct tuning word to maintain f_c within 250MHz ±5% for VDD variation of 1.8±0.1V, temperature variation of -40°C to 125°C and across process corners. Compared to conventional tuning schemes, proposed discrete scheme demonstrates lower input referred noise of 11.3 nV/√Hz with tighter bandwidth accuracy and consistent performance across PVT. Analysis of G_m cell non-idealities such as r_o and C_dg on filter response to ensure optimum design is another contribution of this paper.