Cui Zhou

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 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.

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

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

Any around-the-body wireless system faces challenging requirements. This is especially true in the case of audio streaming around the head e.g. for wireless audio headsets or hearing-aid devices. The behind-the-ear device typically serves multiple radio links e.g. ear-to-ear, ear-to-pocket (a phone or MP3 player) or even a link between the ear and a remote base station such as a TV. Good audio quality is a prerequisite and mW-range power consumption is compulsory in view of battery size. However, the GHz communication channel typically shows a significant attenuation; for an ear-to-ear link, the attenuation due to the narrowband fade dominates and is in the order of 55 to 65dB [1]. The typically small antennas, close to the human body, add another 10 to 15dB of losses. For the ear-to-pocket and the ear-to-remote link, the losses due to body proximity and antenna size reduce, however the distance increases resulting in a similar link budget requirement of 80dB.

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

A 90nm, IR UWB, duty-cycled transceiver chipset, for operation from 7 to 9.8GHz and compliant to the IEEE802.15.4a and the upcoming IEEE802.15.6 standard, is presented. The complete, duty-cycled transmitter provides +1dBm peak output power, consuming 4.4mW. The receiver front-end shows −88dBm sensitivity at 0.85Mbps and a digital synchronization algorithm enables real-time duty cycling, resulting in a mean power consumption of 3mW.

A meter-range UWB transceiver chipset for around-the-head audio streaming

This paper presents an 8-bit asynchronous SAR ADC for flexible, low energy radios. The prototype in a 90nm CMOS technology achieves an ENOB of 7.7bit at a sampling frequency of 10.24MS/s while consuming 26.3µW from a 1V supply. Excellent power efficiency is achieved by using asynchronous dynamic logic, custom 0.5fF unit capacitors, a low-complexity design and an optimized layout. The measured prototype achieves a FoM of 12fJ/conversion-step, which is a 2.5x improvement over previous state-of-the-art 8-bit converters. Moreover, the fully dynamic design, which is optimized for low-leakage, leads to a standby power consumption of 6nW.

A high-band IR-UWB chipset for real-time duty-cycled communication and localization systems

The introduction of the IEEE802.15.6 standard (15.6) for wireless-body-area networks signals the advent of new medical applications, where various wireless nodes in, on or around a human body monitor vital signs. Radio communication often dominates the power consumption in the nodes, thus low-power transceivers are desired. Most state-of-the-art low-power transceivers support only proprietary modes with OOK or FSK modulations, and have poor sensitivity or low data rate [1,2]. In this work, a 15.6-compliant transceiver with enhanced performance is proposed. First, the data-rate is extended to 4.5Mb/s to cover multi-channel EEG applications. Second, while a best-in-class energy efficiency of 0.33nJ/b is achieved in the high-speed mode, a dedicated low-power mode reduces the RX power further in low-data-rate operation. Third, a sensitivity 5 to 10dB better than the 15.6 specification is targeted to accommodate extra path loss due to shadowing effects from human bodies.

A 12fJ/conversion-step 8bit 10MS/s asynchronous SAR ADC for low energy radios

Slope and digital-ramp converters are normally limited to very low sampling rates, since they require a digital counter at a highly oversampled clock rate. In this work, an asynchronous digital slope architecture is introduced that only requires a nonoversampled clock, thus enabling a much higher speed of operation. At the same time, the low complexity and the inherent accuracy of the slope-architecture enable very good power-efficiency without using complex calibration techniques. A two-channel time-interleaved 5-bit asynchronous digital slope ADC was implemented in a 90-nm CMOS technology and occupies 160 μm × 200 μm. The measured prototype achieves an ENOB of 4.6 bit, while operating at 250 MS/s and consuming 0.8 mW from a 1-V supply.

9.7 A 0.33nJ/b IEEE802.15.6/proprietary-MICS/ISM-band transceiver with scalable data-rate from 11kb/s to 4.5Mb/s for medical applications

The main bottleneck to achieve energy autonomy in body area networks (BAN) is the design of an ultra low power yet reliable wireless system. In this paper, we first demonstrate the feasibility of an ultra low power receiver by presenting our implemented receiver chip that could operate on a total power of 479.5 uW, which is more than one order of magnitude lower than commercially available low power transceivers working at 2.4 GHz. We then show the reliability of this chip, which can achieve a receiver sensitivity of −72 dBm for a data rate of 1 Mbps. We further demonstrate that this receiver sensitivity is sufficient to guarantee reliability by evaluating this chip in different to-body communication in BAN environments. By using typical BAN channels, simulation results show that our system can provide a reliable link in both the standing and walking situations. With the measured data, we show that a transmit power of −15 dBm is sufficient for our receiver to achieve reliable communication link in different BAN environments. This transmit power requirement is 15 dB lower than the widely known low power Zigbee system. It could thus significantly facilitate the ultra low power transmitter design, and minimize the human exposure to radio frequency electromagnetic fields. The design and evaluation of our receiver presented in this paper therefore provides a way to move towards the energy autonomy of BAN, and opens access to many new applications in BAN.