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

Abstract

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.The architecture for the IR-UWB radio is shown in Fig. 25.2.1. The transmitter (TX) and receiver (RX) operate at the battery voltage, through a current limiter (CL) to protect the micro-battery from over-current and under-voltage. An internal storage capacitor allows higher current draws from the TX and RX during duty-cycled operation. Digital baseband blocks operate from a 1.2V V DD to reduce power consumption. To survive on the limited resources of the microbattery, all blocks on the radio have a low-power sleep state. RF and other analog blocks are duty-cycled at the bit level by the baseband controller, while baseband blocks are duty-cycled at the packet level by a separate sleep controller. The sleep controller remains on continuously unless an under-voltage condition occurs. The sleep controller begins and ends the wake-up procedure for each packet via I2C communication with modified I/Os to eliminate pull-up resistors. The I2C controller provides bidirectional communication with other stacked die in a sensor node.The receiver uses the non-coherent, energy-detection architecture shown in Fig. 25.2.2. Four RF gain stages amplify the 9.8GHz UWB pulses before downconverting with a squaring mixer. The signal then passes through a baseband gain stage before the signal path is split. Along one path, the pulses are passed directly to a comparator. The other path lowpass filters (LPFs) the signal to provide an auto-zeroed, DC-compensated reference level for comparison. A reset signal enables fast settling of the LPF for fast RX turn-on. Finally, a continuous-...

A 2.3 pJ/bit frequency-stable impulse OOK transmitter powered directly by an RF energy harvesting circuit with &#x2212;19.5 dBm sensitivity

“…at 2.5 GHz impulse generation, which can be performed by utilizing relaxed requirement of spectrum mask and ACPR: the output signal is just required to meet the restriction of Japanese extremely low power radio station, and thus the TX can be simplified for reducing power. The duty cycling operation can save power consumption P [2], which can be expressed by…”

“…While previous works have realized complicating I-UWB transceivers [1], [2], one of the next significant challenges for the short-range tag technology is how to minimize the cost for expanding its application especially toward low-end and large-volume markets.…”

MBus

“…The research community has pushed the envelope further, exploring an array of “microscale”—ultra-low power and millimeter-sized—building blocks including processors [8, 37], radios [4, 7, 26], other long-range communication technologies [6], ADCs [28], regulators [33], timers [15, 16], and sensing frontends [9, 17]. However, few of these components have been integrated into complete systems.…”

An ultra-low-power RF transceiver with a 1.5-pJ/bit maximally-digital impulse-transmitter and an 89.5-&#x03BC;W super-regenerative RSSI

“…The impulse radio is the potential candidate to realize both ultra-low power communication and localization with modest accuracy. The previous works have achieved impulse radio circuit with power dissipation of tens of microwatts [1,2]. Localization technology based on an received signal strength indicator (RSSI) in ultra-wideband (UWB) networks has been studied [3], which can be lowpower localization solution because time synchronization and clock precision can be considerably relaxed as compared to time of arrival (TOA) or time difference of arrival (TDOA) technique.…”