Majid Baghaei Nejad

System-on-flexible-substrates: electronics for future smart-intelligent world

In this paper, we present architecture, circuit implementation and integration issues of embedded smart systems on flexible substrates for future ubiquitous intelligent world. The work is exampled by several concepts of innovative, self-powered, long-range interconnected radio-frequency identification and sensor networks in warehouse and intelligent goods distribution systems. Two types of RFID concepts are designed for this network. The first one is a self-powered, ultra-low power UWB RFID. A power scavenging system is designed which can draw energy from the 802.11 access point and its surrounding electromagnetic waves. In the second demonstration, we developed a chipless passive RFID based on time-domain reflection principle. As this RFID is chipless and needs only interconnections and antenna, it is potentially fully printable on flexible substrate such as a paper board. Finally, some implementation and experimental results are presented

Design of a Digital Baseband Processor for UWB Transceiver on RFID Tag

In this paper we present a novel digital baseband processor designed for UWB transceiver on RFID tag. It is a low power and low voltage (1.8 V) full digital ASIC which is implemented in 0.18 mum CMOS technology. The processor receives serial signals (consist of data and commands) from the RF receiver, and based on received command carries out various functions such as receive data and write to the memory, compare data, send data, set/reset tag, kill tag and etc. The processor mainly consists of eight sub modules: Receive buffer, transmit buffer, random number generator (RNG), slot counter, memory controller, reset counter, comparator, controller.

Chip-Package and Antenna Co-Design of a Tunable UWB Transmitter in System-on-Package with On-Chip versus Off-Chip Passives

In this paper we present a self-powered CMOS ultra wideband radio transmitter integrated in a liquid-crystal polymer (LCP) based system on package (SoP) module with an embedded small antenna. Chip-package-antenna co-design is performed for this module in the presence of unwanted packaging parasitic effects and optimizes the transmission efficiency. Our contribution includes new modeling of the RF-package and antenna and co-optimizing the chip and package design with on-chip versus off-chip passives trade-offs. The SoP module consists of an innovative tunable low power CMOS transmitter for IR-UWB communication, a double-slotted small-size embedded UWB antenna, and a power converter. The output amplitude and duration of the transmitter can be tuned to transmit a signal meeting the FCC mask in different pulse repetition rate for long and short range applications. This ability can also be used to compensate the process and temperature variations as well as the parasitic effects of packaging and antenna. The antenna has a return loss of better than -10dB. The power converter consists of a chain of surface mounted Schottky diodes and capacitors, which converts incident electromagnetic waves to DC supply and thus power up the transmitter. The final module is implemented in LCP substrate with integrated passive components and embedded antenna. The chip part is implemented in 0.18mum CMOS process

An Innovative Semi-UWB Passive Transponder for Wireless Sensor and RFID Applications

In this paper, we present a self-powered CMOS impulse-based ultra wideband radio system for RFIDs and wireless sensor networks (WSN) applications. It is integrated in a liquid-crystal polymer (LCP) based system on package (SoP) module with an embedded small antenna. Our contribution includes using two different standards in up and downstream link. In downstream link, due to demand of low complex, low cost and low power circuit, a very simple and extremely low power pulse width demodulator is used to extract the data from received RF signal. An IR-UWB transmitter is used to transmit the data in upstream link. Power supply is taken from the received RF electromagnetic wave with help of a Schottky diode voltage multiplier. Unlike traditional wireless systems, due to great advantages of UWB communication this transponder does not suffer from multi-path fading, collision problem and multi-user interference. The front-end circuit consists of the power converter; PWM receiver, IR-UWB transmitter, and embedded UWB antenna are designed for integration on liquid-crystal polymer (LCP) substrate

Low power tunable CMOS I-UWB transmitter design

In this paper an on-chip tunable Impulse-Ultra Wide Band Transmitter is presented. It is capable of modifying the power emission to comply with the FCC regulations at different pulse rates up to 300 MHz using two external controls. The maximum power consumption is 1.2 mW and 142 muW at 300 MHz and 10 MHz PRF respectively with a leakage current of 100 nA. The prototype has been designed in 0.18 UMC technology and placed in a QFN lead-less package.

An innovative receiver architecture for autonomous detection of ultra-wideband signals

Ultra wideband radio is an emerging wireless standard that uses sub-nanosecond pulses to transmit data, resulting in several GHz bandwidths. The problem of generating a synchronized template respect to the received signal grows in complexity as the signal bandwidth increases. In this paper, innovative, low cost, non-coherent receiver architecture is proposed for autonomous detection of ultra wideband signals. The receiver self-generates a synchronous template and hence, no transmitter-reference synchronizer is required. We validate its performance via simulations compared with coherent receivers and conventional non-coherent receivers, the new architecture is found much more robust to timing noise and hence greatly facilitates the synchronise problem in UWB receiver

Design and implementation of a high efficient power converter for self-powered UHF RFID applications

This paper is an investigation of off-chip solution of power converters for passive UHF RFID transponders. The power converter, consisting of a chain of Schottky diodes and capacitors, is designed and then implemented on Rogers4350 PCB substrate. The ISM unlicensed frequency bands 915 MHz is used for RF signal. The de-embedded measurement results show that with minimum input power of -4.7dBm, the power converter achieves 1.8V/5muA output driving capability, which is sufficient for the transponder operation. It corresponds to a 3.6m operating distance when 4-W EIRP radiation is allowed

A wirelessly-powered UWB sensor tag with time-domain sensor interface

This paper presents a wirelessly-powered sensor tag with a time-domain sensor interface for wireless sensing applications. The tag is remotely powered by RF wave. Instead of traditional approaches employing conventional ADCs for quantization and transmitter for data communication, in this work, a Pulse Position Modulator incorporating simple impulse radio UWB (IR-UWB) transmitter is proposed to convert and transmit the analog sensing information in time domain. The analog signal is compared with an adjustable triangular wave for analog to time conversion in signal-varying environments. Then a UWB transmitter converts the PPM signal to very short pulses and sends it back to the reader. The time interval of UWB pulses represents the original input signal in time domain which can be measured on the reader side by a time-to-digital conversion. This approach not only simplifies the ADC design but also relaxes the number of bits transmitted on the tag side. The sensor tag is designed in 180nm CMOS process. Simulation results demonstrate that the proposed approach reduce transmission power consumption by nearly 3 orders of magnitude over traditional approaches, while consuming only 85 μW for 1.5 MS/s sampling rate.

An 8-bit 166nw 11.25 kS/s 0.18um two-Step-SAR ADC for RFID applications using novel DAC architecture

SAR ADCs have been mostly used for moderate-speed, moderate-resolution applications that power consumption is one of the major concerns (e. g. RFID). Furthermore two-step ADCs are classified as high-speed, low to moderate-accuracy ADC. In this paper an ultra low power two-step-SAR ADC for RFID application is presented. Several techniques are used to further reduce the power consumption and relatively elevate the speed of the ADC. These techniques include a low power comparator with no static current and a dual-stage (Resistor-string / capacitive dividing) architecture as digital-to-analog converter (DAC). In this DAC architecture fine search will be performed by only two C and 15C capacitors which reduced the silicon area significantly. The circuit designed in 0.18um CMOS technology and simulations show that the 8-bit ADC, consumes almost 166nW at 11.25kS/s. The results show that the proposed ADC has higher speed with almost the same power consumption in comparison with its charge redistribution counterpart.

Remotely UHF-Powered Ultra Wideband RFID for Ubiquitous Wireless Identification and Sensing

A new term of ubiquitous computing and communication is booming up which will transform our future corporate, community and personal life [1]. Early form of ubiquitous information and communication was happened in the use of mobile phones and nowadays it has become a vital part of everyday life for many million of people even more than internet. Recently, many research and developments are ongoing to bring this phenomenon more into everyday life by embedding smart systems into more objects which can interact to each other and people through a wireless link. It will provide connectivity for anything from anywhere, anyplace and for anyone. These connections create a network between items which lead to Internet of Things (IoT). Several kinds of information can be exchanged through the network such as environment status, and location which make a huge field of novel applications and market. To realize the IoT several technical innovation in different number of fields are essential. In order to have an embedded module in almost everything, first a simple and low cost system is vital. Second, embedding sensor technology into the items allows the system to detect changes in the physical status of things, which allows the system to changes or modifies some parameters of the system. And finally, system miniaturization allows smaller things have the ability of connection. A combination of all of these developments will create the IoT which connect the world’s objects intelligently. Different challenges need to be addressed. Energy issues such as low-power chipset design, energy harvesting, efficient and compact energy storage are some of the key issues. Many research need to be done in this area. Embedding sensor for data collection is another enabler for development of IoT. Low-power processing power and memory are important to process and store the sensor data. Different integration such antenna and passive integration need to be studied. Efficient communication protocol, modulation scheme and transmission speed is required to be studied. New methods for power management at different levels of the network are needed. Itegration of a smart device into the package or into the product is demanded. Different solutions such as system-on-chip and system-on-package should be investigated. Manufacturing challenges must be solved and the implementation cost must be lowered. Radio frequency Identification (RFID) technology is a promising solution for IoT realization. It has been used mostly in supply chain management and logistic for several years [2].