A 15 mW 69 dB 2 Gsamples/s CMOS analog front-end for low-band UWB applications

The paper presents a CMOS analog front-end (AFE) for a short range impulse radio system in low-band ultrawideband (UWB) based on 2 ns width PAM. The wideband amplifier provides 69 dB gain from 30 MHz to 1.2 GHz, realized by a limiting amplifier with an active-inductor load and a cross-coupled g_m gain-boosting cell in each gain stage. The received signal is digitized at 2 GHz sampling rate by 8 parallel 1-bit ADCs, each of which is composed of transmission-gate type sample-and-hold circuits and a dynamic differential comparator. A timing generator based on a 4-stage ring oscillator in a PLL is employed to provide 8-phase 250 MHz clocks. Realized in 0.18 μm CMOS technology, the AFE occupies a 1.0×1.2 mm² active area with the 3^rd order loop filter integrated in the same die. This chip also includes an integrated pulse generator for loop-back self-testing purposes. The receiver AFE achieves 200 μV sensitivity and consumes 15 mW from a 1.8 V supply.