Jia Mao

A Low-Power and Flexible Energy Detection IR-UWB Receiver for RFID and Wireless Sensor Networks

This paper presents an energy detection Impulse Radio Ultra-Wideband (IR-UWB) receiver for Radio Frequency Identification (RFID) and Wireless Sensor Networks (WSN) applications. An Application-Specific Integrated Circuit (ASIC) consisting of a 3-5 GHz analog front-end, a timing circuit and a high speed baseband controller is implemented in a 90 nm standard CMOS technology. A Field-Programmable Gate Array (FPGA) is employed as a reconfigurable back-end, enabling adaptive baseband algorithms and ranging estimations. The proposed architecture is featured by high flexibility that adopts a wide range of pulse rate (512 kHz-33 MHz), processing gain (0-18 dB), correlation schemes, synchronization algorithms, and modulation schemes (PPM/OOK). The receiver prototype was fabricated and measured. The power consumption of the ASIC is 16.3 mW at 1 V power supply, which promises a minimal energy consumption of 0.5 nJ/bit. The whole link is evaluated together with a UWB RFID tag. Bit error rate (BER) measurement displays a sensitivity of -79 dBm at 10 Mb/s with 10-3 BER achieved by the proposed receiver, corresponding to an operation distance over 10 meters under the FCC regulation.

A 2.4-GHz ISM RF and UWB hybrid RFID real-time locating system for industrial enterprise Internet of Things

ABSTRACT This paper presents a 2.4-GHz radio frequency (RF) and ultra-wide bandwidth (UWB) hybrid real-time locating system (RTLS) for industrial enterprise Internet of Things (IoT). It employs asymmetric wireless link, that is, UWB radio is utilised for accurate positioning up to 10 cm in critical sites, whereas 2.4-GHz RF is used for tag control and coarse positioning in non-critical sites. The specified communication protocol and the adaptive tag synchronisation rate ensure reliable and deterministic access with a scalable system capacity and avoid unpredictable latency and additional energy consumption of retransmissions due to collisions. The tag, consisting of a commercial 2.4-GHz transceiver and a customised application-specific integrated circuit (ASIC) UWB transmitter (Tx), is able to achieve up to 3 years’ battery life at 1600 tags per position update second with 1000 mAh battery in one cluster. The time difference of arrival (TDoA)–based positioning experiment at UWB radio is performed on the designed software-defined radio (SDR) platform.

A 90nm CMOS UHF/UWB asymmetric transceiver for RFID readers

This paper presents an integrated asymmetric transceiver in 90nm CMOS technology for RFID reader. The proposed reader uses UHF transmitter to power up and inventory the tags. In the reverse link, a non-coherent Ultra-wide Band (UWB) receiver is deployed for data reception with high throughput and ranging capability. The transmitter delivers 160 kb/s ASK modulated data by an integrated modulator and a Digital Controlled Oscillator (DCO) in UHF band with 11% tuning range. The DCO consume 6 mW with 0.12 mm2 area. On the other side, adopting two integration channels, the 3–5 GHz energy detection receiver supports maximum 33 Mb/s data rate both in OOK and PPM modulations. The receiver front-end provides 59 dB voltage gain and 8.5 dB noise figure (NF). Measurement results shows that the receiver achieves an input sensitivity of −79 dBm at 10 Mb/s, with power consumption of 15.5 mW.

A Hybrid Low Power Biopatch for Body Surface Potential Measurement

This paper presents a wearable biopatch prototype for body surface potential measurement. It combines three key technologies, including mixed-signal system on chip (SoC) technology, inkjet printing technology, and anisotropic conductive adhesive (ACA) bonding technology. An integral part of the biopatch is a low-power low-noise SoC. The SoC contains a tunable analog front end, a successive approximation register analog-to-digital converter, and a reconfigurable digital controller. The electrodes, interconnections, and interposer are implemented by inkjet-printing the silver ink precisely on a flexible substrate. The reliability of printed traces is evaluated by static bending tests. ACA is used to attach the SoC to the printed structures and form the flexible hybrid system. The biopatch prototype is light and thin with a physical size of 16 cm × 16 cm. Measurement results show that low-noise concurrent electrocardiogram signals from eight chest points have been successfully recorded using the implemented biopatch.

Design and demonstration of passive UWB RFIDs: Chipless versus chip solutions

This paper reviews recent research on Ultra-Wideband (UWB) techniques for the next generation Radio Frequency IDentification (RFID) towards the Internet-of-Things (IoT), conducted by Vinn iPack Center at KTH, Sweden. First, we introduce an inkjet printed chipless UWB RFID for ultra-low cost applications such as item-level tracking. The identification number is coded by variations of the impedance over the transmission line, resulting in the OOK modulated data by means of pulse reflections in time domain. Prototypes were fabricated and measured for 4-bit tag and 8-bit tag, respectively. Thanks to the employment of fully printing process and paper substrates, the tag is potentially ultra-low cost in volume production. Second, a wirelessly powered RFID tag with an active UWB transmitter is studied for advanced applications such as wireless positioning and sensing. The tag is powered by UHF continuous waves, whereas it uses an UWB pulse generator to transmit data to the reader. It ensures the improved coverage and accurate positioning over traditional backscattering UHF tags. UWB readers, positioning, and sensing are also discussed in a system perspective. The two solutions reveal that UWB is a viable alternative to existing passive RFIDs adapting both low-cost applications and high-performance sensing and positioning applications.

A passive UHF-RFID tag with inkjet-printed electrochromic paper display

In this paper, an inkjet-printed electrochromic (EC) paper display integrated with passive UHF-RFID tag is introduced as a solution for passive electronic shelf labels (ESL). To address the system challenges of the limited power budget of passive UHF-RFID tags and the material aging of EC display, a feedback comparator integrated digital display driver is proposed based on the study of electrochromic, bi-stable and aging features of the EC display. Modularized baseband with different enable conditions and clock domains is implemented in the system design level. Moreover, to maintain the system functions when the input power is lower than the display refresh power, a duty-cycled power management unit (PMU) is activated to reduce the load current during energy scavenging and drive the display in short intervals, enabling the fast charging of the voltage rectifier and the correct output of the regulated supply for the core circuit. The design is fabricated in a 0.18-um CMOS process with an area of 2.25 mm2. Fed with EPC C1G2 protocol write command, experiments demonstrate correct refresh of EC display with 4 cm2 effective area. System sensitivity at the antenna reference point is basically immune to the display load. Further improvements can be achieved after careful chip-to-antenna impedance matching and PMU efficiency optimization.

A Subgigahertz UWB Transmitter With Wireless Clock Harvesting for RF-Powered Applications

A subgigahertz ultrawideband (UWB) transmitter (TX) with wireless clock harvesting is presented for RF-powered applications such as RF identifications and implantable devices in the 180-nm CMOS process. The proposed low-power TX consists of a harmonic injection-locked ring oscillator (ILRO), a synchronized pulse generator, and a driver stage. Through wireless injection locking, a 450-MHz carrier is extracted using the subharmonic of an ultrahigh frequency signal radiated by a reader. Following the ILRO, the carrier is gated and amplified to generate the UWB pulses. This approach avoids power-hungry frequency synthesis circuitry and bulky crystal reference, and it relaxes the timing synchronization between the reader and the tag. Due to aggressive duty cycling and the fast setup time (<; 50 ns at an input power of -15 dBm), the proposed TX is power scalable with an energy consumption of 35 pJ/pulse. To comply with the Federal Communications Commission regulations, the maximum pulse rate is up to 5 MHz with a peak-to-peak pulse amplitude of 0.75 V and a corresponding power consumption of 175 μW, which is favorable to RF-powered applications.

Design of a self-organized Intelligent Electrode for synchronous measurement of multiple bio-signals in a wearable healthcare monitoring system

This paper presents an Intelligent Electrodes and Active Cable based wearable medical system. Within each Intelligent Electrode, an Application Specific Integrated Circuit (ASIC) is integrated which includes a gain-bandwidth selectable analog front-end circuit, an 8-bit SAR ADC and a digital controller. The key of the ASIC is the analog front-end circuit with tunable gain and bandwidth which can be configured for Electrocardiogram (ECG), Electroencephalogram (EEG) or Electromyogram (EMG) measurement. Common mode interference is effectively rejected due to the circuits high Common Mode Rejection Ratio (CMRR), which is higher than 135 dB up to 100 Hz and better than 110dB up to 1 kHz. Since a dedicated data transmission protocol is implemented on chip, the Intelligent Electrodes can establish a self-organized network and perform synchronous measurements for multiple bio-signals.

A UWB-Based Sensor-to-Time Transmitter for RF-Powered Sensing Applications

An ultrawideband (UWB)-based sensor-to-time transmitter consisting of a remote control (RC) time-constant interface and an ultralow-power pulse generator is presented. The sensing information is directly extracted and transmitted in the time domain, exploiting UWB pulses with a high timedomain resolution. This approach eliminates the need for an analog-to-digital converter and baseband blocks of sensor tags; meanwhile, it reduces the number of bits to be transmitted for energy saving. The sensor interface measures the discharging time of the RC time constant proportional to the sensor variation. The UWB pulses are triggered with intervals of the RC discharging time, without any digitizing or modulations. The circuit prototype is implemented in the standard 0.18-μm CMOS process. Resistance measurement results show that the proposed system exhibits an effective number of resolution bits (ENOB) of 7.7 bits with an average relative error of 0.42% in the range of 200-1500 Ω. The overall energy consumption of conversion and transmission per sample is measured to be 0.58 nJ with a 1.27-Vp-p pulse amplitude, which is favorable to radio-frequency-powered wireless sensing applications.

A 35 pJ/pulse injection-locking based UWB transmitter for wirelessly-powered RFID tags

This paper presents an energy-efficient injection-locking based UWB transmitter for RFID tags in a 0.18 μm CMOS technology. The transmitter is powered by 900 MHz UHF signals radiated by a reader wirelessly, and responds UWB pulses by locking-gating-amplifying the sub-harmonic of the UHF signal. A simple harmonic injection-locking ring oscillator (ILRO) is utilized to generate a 450 MHz carrier for sub-GHz UWB, eliminating power-hungry and complex timing components such as PLL and crystal on tags. The measurement results show that the sensitivity of the ILRO is -15 dBm under 21% locking range without any extra amplifier. Thanks to fast setup time of the ILRO, the proposed transmitter is power-scalable with 35 pJ/pulse energy consumption by duty-cycling. The amplitude of the transmitted UWB pulse is 0.75 Vpp, allowing a pulse rate up to 5 MHz under the FCC regulations. The entire power consumption of the transmitter is 175 μW, which is favorable to wirelessly-powered RFID applications.