A 12-mW 264-MHz high linearity sharp roll-off CMOS opamp-RC low-pass filter for MB-OFDM UWB systems

Abstract

This paper presents a high linearity wideband sharp roll-off Opamp-RC low-pass filter (LPF) for Ultra wideband (UWB) applications. The proposed LPF is composed of three biquads' transfer functions with different Q-factors in series. Sharp roll-off is attributed to the steep slope of the peaking of a biquad transfer function with a high Q-factor. The superposition of these biquads also helps extend the bandwidth of the overall LPF transfer function without the cost of extra power dissipation. The effects of biquad arrangements on noise and linearity performances are investigated. A simple operational amplifier (op-amp) is adopted to ensure high frequency characteristics and high linearity performance for the designed filter. The LPF is implemented in 0.13-mu m IBM CMOS process from 1.5 V supply. The measured cutoff frequency is 264 MHz with the pass-band ripple of less than 1 dB. Digital frequency tuning is implemented with 40% of tuning range around the cutoff frequency. The amount of out-of-band rejection at 290 MHz and at twice cutoff frequency is 12 dB and about 50 dB, respectively. Good linearity with IIP3 of 23 dBm is obtained. The 6th-order LPF dissipates only 12 mW with the active chip size of 400 x 640 mu m(2).