An ultra-low-power 9.8GHz crystal-less UWB transceiver with digital baseband integrated in 0.18μm BiCMOS

Future biomedical and internet-of-things applications are driving the volume of wireless sensors into the cubic-mm regime. At the mm-scale, complete integration is necessary, and operation within the limits of a micro-battery becomes a primary challenge [1]. With CMOS scaling and ultra-low-power circuits reducing battery volume, the antenna and crystal quickly become the largest components in a cubic-mm node. Higher-frequency operation and silicon-based timing circuits are critical to integrate these components. This paper presents a fully-integrated 9.8GHz impulse-radio ultra-wideband (IR-UWB) radio with an on-chip 2mm monopole and the option of wire-bonding to an off-chip antenna. The crystal is replaced with a novel temperature-compensated relaxation oscillator. Due to modern mm-scale battery limitations, the peak current draw must be <100μA [2], far below typical radio power consumption. Furthermore, external capacitors are too large for mm-scale nodes; thus, duty-cycling only at the packet level is not an option. This IR-UWB radio includes current-limiting at the battery supply, and the integrated modem duty-cycles the RF front-end at the bit-level in order to operate from integrated storage capacitance. Finally, many recent transceivers operate at <1V [3,4]; however the voltage of a micro-battery is 3.2∼4.1V [2] and integrated conversion efficiency is <80% [1,5]. Thus, this radio is designed to operate the RF blocks over the entire battery voltage range.