Guido Dolmans

A 26

This paper presents an asynchronous SAR ADC for flexible, low energy radios. To achieve excellent power efficiency for a relatively moderate resolution, various techniques are introduced to reduce the power consumption: custom-designed 0.5 fF unit capacitors minimize the analog power consumption while asynchronous dynamic logic minimizes the digital power consumption. The variability of the custom-designed capacitors is estimated by a specialized CAD tool and verified by chip measurements. An implemented 8-bit prototype in a 90 nm CMOS technology occupies 228 μm × 240 μm including decoupling capacitors, and achieves an ENOB of 7.77 bit at a sampling frequency of 10.24 MS/s. The power consumption equals 26.3 μW from a 1 V supply, thus resulting in an energy efficiency of 12 fJ/conversion-step. Moreover, the fully dynamic design, which is optimized for low-leakage, leads to a standby power consumption of 6 nW. In that way, the energy efficiency of this converter can be maintained down to very low sampling rates.

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This paper presents a multistandard ultra-low-power (ULP) 2.36/2.4GHz transceiver for personal and body-area networks (PAN/BAN). The presented radio complies with 3 short-range standards: Bluetooth Low Energy (BT-LE), IEEE802.15.4 (ZigBee) and IEEE802.15.6 (Medical Body-Area Networks, MBAN). A proprietary 2Mb/s mode is also implemented to support data-streaming applications like hearing aids. Current short-range radios for Zigbee and BT-LE typically consume more than 20mW DC power, which is rather high for autonomous systems with limited battery energy. The dual-mode MBAN/BT-LE transceiver achieves a power consumption of 6.5mW for the RX and 5.9mW for the TX by employing a sliding-IF RX and a polar TX architecture. However, it suffers from limited RX image rejection and needs a PA operating at a higher supply voltage. In this paper, an energy-efficient radio architecture with a suitable LO frequency plan is selected, and several efficiency-enhancement techniques for the critical RF circuits (e.g., a push-pull mixer and a digitally-assisted PA) are utilized. As a result, the presented transceiver dissipates only 3.8mW (RX) and 4.6mW (TX) DC power from a 1.2V supply, while exceeding all of the PHY requirements of above 3 standards.

W 8 bit 10 MS/s Asynchronous SAR ADC for Low Energy Radios

In order to simultaneously optimize network lifetime and latency in wireless sensor networks (WSN), an always-on wake-up receiver (WuRx) can be used to monitor the radio link continuously. For truly autonomous sensor nodes employing energy scavenging, only 50µW power is available for the WuRx [1]. An envelope detector is a popular choice in WuRx because of its low power consumption. However, the detector is always the bottleneck of the receiver sensitivity since it attenuates low level input signal and adds excessive noise. One way of improving sensitivity is to amplify the signal before the detector, for example at RF [2, 3] or IF [4] stages, to enhance the SNR at the output.

A 1.9nJ/b 2.4GHz multistandard (Bluetooth Low Energy/Zigbee/IEEE802.15.6) transceiver for personal/body-area networks

This paper describes an ultra-low power (ULP) single chip transceiver for wireless body area network (WBAN) applications. It supports on-off keying (OOK) modulation, and it operates in the 2.36-2.4 GHz medical BAN and 2.4-2.485 GHz ISM bands. It is implemented in 90 nm CMOS technology. The direct modulated transmitter transmits OOK signal with 0 dBm peak power, and it consumes 2.59 mW with 50% OOK. The transmitter front-end supports up to 10 Mbps. The transmitter digital baseband enables digital pulse-shaping to improve spectrum efficiency. The super-regenerative receiver front-end supports up to 5 Mbps with -75 dBm sensitivity. Including the digital part, the receiver consumes 715 μW at 1 Mbps data rate, oversampled at 3 MHz. At the system level the transceiver achieves PER=10 -2 at 25 meters line of site with 62.5 kbps data rate and 288 bits packet size. The transceiver is integrated in an electrocardiogram (ECG) necklace to monitor the hearts electrical property.

A 2.4GHz/915MHz 51µW wake-up receiver with offset and noise suppression

Applications like wireless sensor nodes require ultra low-power receivers with power-efficient ADCs. Moreover, the power-efficiency should be maintained for a wide range of sampling rates to enable system-level flexibility. Previously, the use of SAR ADCs has been proposed for low-power applications [1], [2]. This work describes the implementation of an 8bit asynchronous SAR ADC that achieves a 30fJ/Conversion-step power-efficiency for sampling rates between 10kS/s and 10MS/s.

A 2.4 GHz ULP OOK Single-Chip Transceiver for Healthcare Applications

Wireless body-area networks (WBAN) are used for communication among sensor nodes operating on, in or around the human body, e.g. for healthcare purposes. In view of energy autonomy, the total energy consumption of the sensor nodes should be minimized. Because of their low complexity, a combination of the super-regenerative (SR) principle [1–3] and OOK modulation enables ultra-low power (ULP) consumption. This work presents a 2.4GHz ULP OOK singlechip transceiver for WBAN applications. A block diagram of the implemented transceiver is shown in Fig. 26.3.1. Next to the direct modulation TX [4] and SR RF [5] front-ends, this work integrates analog and digital baseband, PLL functionality and additional programmability for flexible data rates, and achieves ultra-low power consumption for the overall system.

A 30fJ/conversion-step 8b 0-to-10MS/s asynchronous SAR ADC in 90nm CMOS

In the newly emerging body area networks (BANs), substantial demands come from both medical applications and consumer electronics (CE) applications. Due to the heterogeneous service requirements, MAC protocol design becomes a new challenge for BANs. To address this problem, a priority-guaranteed MAC protocol is proposed in this paper. In this protocol, data and control channels are split to support collision-free high data rate communication. Application-specific control channels are adopted to provide priority guarantee to the life-critical medical applications. Furthermore, traffic-specific data channels are deployed to improve resource efficiency and latency performance. Monte Carlo simulations are carried out for performance evaluation. Simulation results demonstrate that significant improvements on throughput and energy efficiency are achieved with the priority-guaranteed MAC protocol.

A 2.4GHz ULP OOK single-chip transceiver for healthcare applications

Applications like wireless sensor nodes require ultra-low-power ADCs. However, each application has different requirements for accuracy and bandwidth. Recent power-efficient ADCs for sensor applications are mostly designed for a fixed accuracy and a limited range of sample rates. An efficiently scalable sample rate (10kS/s to 10MS/s) has been demonstrated before, but without scalability of resolution. In, an ADC with both flexible resolution and sample rate is reported; however, its power efficiency is not as good as the point-solutions in. This paper describes a SAR ADC that achieves both good power efficiency (6.5-to-16fJ/conversion-step) and a wide range of flexibility (7-to-10b resolution, sample rates up to 4MS/s) to cover a large variety of applications, thereby reducing cost, design-time and overall complexity. To optimize the power efficiency for each resolution, both the DAC and comparator are reconfigurable. A 2-step conversion scheme is proposed for 9 and 10b settings to further reduce the power consumption. Finally, the use of an asynchronous architecture and dynamic circuitry ensures that the power consumption scales inherently proportional to the sample rate.

A New Priority-Guaranteed MAC Protocol for Emerging Body Area Networks

In order for wireless body area networks to meet widespread adoption, a number of security implications must be explored to promote and maintain fundamental medical ethical principles and social expectations. As a result, integration of security functionality to sensor nodes is required. Integrating security functionality to a wireless sensor node increases the size of the stored software program in program memory, the required time that the sensor’s microprocessor needs to process the data and the wireless network traffic which is exchanged among sensors. This security overhead has dominant impact on the energy dissipation which is strongly related to the lifetime of the sensor, a critical aspect in wireless sensor network (WSN) technology. Strict definition of the security functionality, complete hardware model (microprocessor and radio), WBAN topology and the structure of the medium access control (MAC) frame are required for an accurate estimation of the energy that security introduces into the WBAN. In this work, we define a lightweight security scheme for WBAN, we estimate the additional energy consumption that the security scheme introduces to WBAN based on commercial available off-the-shelf hardware components (microprocessor and radio), the network topology and the MAC frame. Furthermore, we propose a new microcontroller design in order to reduce the energy consumption of the system. Experimental results and comparisons with other works are given.

A 7-to-10b 0-to-4MS/s flexible SAR ADC with 6.5-to-16fJ/conversion-step

This paper presents an ultra-low-power (ULP) 2.3/2.4GHz multi-standard transmitter (TX) for wireless sensor networks and wireless body area networks. Several 2.3/2.4GHz wireless standards have been proposed for such applications, including IEEE802.15.6 (BAN) for body area networks, IEEE802.15.4 (Zigbee) and Bluetooth Low Energy (BLE) for sensor networks and IEEE802.15.4g (SUN) for smart buildings. Recent standard compliant short-range TXs [1-6] typically consume DC power in the range of 20 to 50mW. This is rather high for autonomous systems with limited battery energy. Implemented in a 90nm CMOS technology, the presented TX saves at least 75% of power consumption by replacing several power-hungry analog blocks with the digitally-assisted circuits. This TX is compliant with all 4 of these standards, while dissipating only 4.5mA from a 1.2V supply.