Takanori Yamazoe

Wireless operations for 13.56-MHz band RFID tag using amorphous oxide TFTs

This paper presents an RFID chip for 13.56-MHz band communication fabricated on a glass substrate by using amorphous In-Ga-Zn-O thin-film transistors. Low driving-voltage logic circuits were achieved with a small Vth, a high field effect mobility of 15cm2/Vs and “active load” inverters that had small consumption currents. The RFID tag was successively driven by 13.56-MHz wireless input.

A charge pump that generates positive and negative high voltages with low power-supply voltage and low power consumption for non-volatile memories

A charge pump that generates positive and negative high voltages with low power-supply voltage and low power consumption was developed. By controlling the body and gate voltage of each transfer HVNMOS, high output voltage can be obtained from a low power-supply voltage. For low power consumption, the clock frequency of the charge pump is varied according to its output voltage. Output voltages of a seven-stage negative charge pump and a five-stage positive charge pump, fabricated with a 0.15- µ m CMOS process, were measured. These measurements show that the developed charge pump achieves the target regulation positive high voltage (+ 6.5 V) and negative high voltage (− 6 V) at low power-supply voltage Vdd of 1.5 V while also achieving low power consumption.

Oxide TFT Rectifier Achieving 13.56-MHz Wireless Operation

We have fabricated a full-wave rectifier using fully depleted amorphous In-Ga-Zn-O thin-film transistors (TFTs). The rectifier is composed of four TFTs, and it rectified 13.56-MHz wireless input from a 200-mW commercial RFID reader/writer. We also have analyzed an output voltage and an operation frequency of the fabricated rectifier.

UHF RFID mobile reader for passive- and active-tag communication

A prototype UHF RFID reader chip for mobile-phone applications was developed. The reader architecture is designed for passive tags in compliance with the ISO/IEC 18000-6 Type C and the EPCglobal Class-1 Generation-2 protocols for UHF RFID air interface. The reader also supports communication with active tags. Experimentally measured performance shows the reader chip achieves very high sensitivities (namely, −86 dBm and −92 dBm) for passive and active RFID systems, respectively. The reader chip, with 1.8-V power supply, was fabricated in a 0.18-µm CMOS process.

A null-zone control method for RFID systems

A null-zone control method—which converts a null zone into a readable zone using only the standard antennas of a radio-frequency identification (RFID) reader—was developed. Outdoor evaluation of the method implemented in a RFID tag-reader system demonstrates the validity of the method; namely, it converts the null zone into a readable zone and attains high RFID-tag readability in the near field of the reader antenna.

The Achievement of Hibiki Project--For the Spread Use of RFID--

Hitachi, Ltd. completed Hibiki project, which had been conducted by the Ministry of Economy, Trade and Industry of Japan (METI) for 2 years from August 2004, to realize 5-yen RFID inlay. This paper describes the achievement of Hibiki project; the descriptions of Hibiki RFID specifications, the evaluation results of reading and writing distance and multiple tags reading results

Applying amorphous InGaZnO-TFT to RFID tag

Trial production of a thin-film radio frequency identification (RFID) tag with a built-in antenna was carried out using an amorphous InGaZnO (a-InGaZnO) thin-film transistor (TFT). A rectifier circuit, RF communication circuit, and logic circuit were formed using an a-InGaZnO TFT. Even after adding an antenna, which is the thickest part, the RFID itself had a thickness of about 1 μm. The RFID operated with a 13.56-MHz-band reader for IC cards and near field communication (NFC) devices. These results indicate the feasibility of an RFID tag that can be adhered to objects with a variety of shapes.

Low power and high receiving sensitivity wireless wake-up receiver with 2-stage power-supply control scheme for lithium-ion battery systems

A wireless wake-up receiver for lithium-ion battery systems was developed and evaluated. A 2-stage power-supply control scheme is added to the wake-up receiver for supporting low power, high receiving sensitivity, and short wake-up time simultaneously. When the battery system is in power-down mode, only a voltage detector in the wake-up receiver consumes a current while waiting for a wireless wake-up signal with low current and high receiving sensitivity. When the voltage detector detects the wake-up signal, all circuits in the wake-up receiver operate for detecting the wake-up signal with a short wake-up time. The wake-up receiver consumes only 0.3 μA of the power-down current for -32 dBm of the receiving sensitivity with 11 ms of the wake-up time.

Technology for adaptive error recovery in wireless communication environments

Environmentally adaptive error recovery (EAER) technology for wireless communication was developed to reduce the number of communication errors and the time needed for recovery in industrial wireless networks. EAER adapts the communication frequency to the radio environment by changing the radio frequency to a better one when communication errors occur by pre-measuring the radio environment at each slave. The pre-measurement is done by having slaves measure the radio environment using test signals sent by the master. EAER was able to continue the communication within three super frames when a noise signal was applied to a communication channel.

Oxide TFT rectifier achieving 13.56-MHz wireless operation with DC output up to 12 V

We have fabricated a rectifier using fully depleted amorphous In-Ga-Zn-O (a-IGZO) TFTs. The rectifier is composed of four TFTs and exhibited the rectification of 13.56-MHz wireless input from a commercial RFID reader/writer for the first time in oxide TFT devices. This result opens the possibility for wireless application of oxide TFTs.