Ryosuke Fujiwara

A UWB-IR Transmitter With Digitally Controlled Pulse Generator

A novel transmitter for ultra-wideband (UWB) impulse radio has been developed. The proposed architecture enables low-power operation, simple design, and accurate pulse-shape generation. The phase and amplitude of the pulse are controlled separately and digitally to generate a desired pulse shape. This digital control method also contributes to the low-power transmission and eliminates the need for a filter. The transmitter is fabricated using a 0.18-mum CMOS process. The core chip size is only 0.40 mm2. From experimental measurements, it was found that the generated signal satisfied the FCC spectrum mask, and the average power dissipation was only 29.7 mW at A 2.2-V supply voltage. Therefore, the developed UWB transmitter generates accurate pulses with low power consumption and simple design architecture

A novel UWB impulse-radio transmitter with all-digitally-controlled pulse generator

A novel transmitter for ultra-wideband (UWB) impulse radio was developed. The proposed architecture realizes low power, low complexity, and generation of a highly accurate pulse. The phase and amplitude of a pulse are controlled separately and digitally to generate a highly accurate pulse. This control method also contributes to the transmitters low power and eliminates the need for a filter. The transmitter was fabricated by a 0.18-/spl mu/m bulk CMOS process. The core chip size is only 0.40 mm/sup 2/. Measurement of this transmitter found that the FCC spectrum mask is satisfied and average power dissipation is 29.7 mW under a supply voltage of 2.2 V. These results show that the developed UWB transmitter can generate an accurate pulse with low power and low complexity.

TOA/TDOA hybrid relative positioning system using UWB-IR

We developed a TOA/TDOA hybrid relative positioning system with UWB-IR technology. The proposed system reduces both the number of base stations and the wireless communication times in a positioning sequence. We evaluated the system performance over various distances between base stations by using computer simulations and experiments, assuming that the target nodes were outside the area surrounded by the base stations. For the experiments, we implemented the system with UWB transceivers that we developed. From the experimental results, we confirmed that the proposed system could detect the relative positions of the target nodes using two base stations 4 m apart and with a measured angle accuracy of 8.6 degrees.

1-cc Computer: Cross-Layer Integration With UWB-IR Communication and Locationing

The first one-cc or one-cubic-centimeter computer (OCCC) that integrates a sensor, ultra-wideband impulse radio (UWB-IR) transmitter, computing engine, and battery is demonstrated. Cross-layer integration includes SPIKE control, which achieves a record low power communication of 3.4-nW/bps with reduced operating time. Miniaturization techniques, such as wafer-level chip-size packaging and flip-chip packaging, were used to shrink the module to a volume of 1 cc. The fabricated OCCC is shown to operate as designed, communicating at distances of 10 and 30 m and at transmission rates of 10.7 Mbps and 258 kbps, respectively. The life of a 150-mAh battery in an OCCC that operates once every five minutes is estimated to be longer than 10 years. The communication-location integration (CLI) technique, which achieves 22-cm location accuracy with only a 1.3% chip area overhead, is also proposed.

A CMOS UWB-IR Receiver Analog Front End with Intermittent Operation

A low power receiver analog front end (AFE) for ultra-wideband impulse radio (UWB-IR) was developed in 0.18 mum CMOS. All circuits of the receiver AFE operate intermittently with a sampling clock of an analog-digital converter (ADC). The sampling rate of the ADC is equal to pulse repetition frequency of the received signals. Power consumption of the receiver AFE is decreased 60% by intermittent operation without degrading of receiver sensitivity. As a result, the power consumption of the receiver AFE is 38 mW at 258 kbps data rate.

Rapid signal acquisition for low-rate carrier-based ultra-wideband impulse radio

In this paper, a rapid signal-acquisition method is proposed for carrier-based ultra-wideband impulse-radio systems in low-data-rate applications such as sensor networks. For low-data-rate ultra-wideband impulse radio systems, highly precise synchronization must be established over relatively long periods. In the proposed method, signal-acquisition times are reduced by assigning different blocks responsibility for synchronization with the pulse and with the spreading code. Furthermore, dividing up the symbols to produce a smaller unit for integration enables signal acquisition even when there is a realistic difference between the transmitter and receiver-local frequencies. Results of simulation indicate that, for a given Eb/N0, the proposed method reduces acquisition times from those required by the conventional method.

Intermittent Operation Control Scheme for Reducing Power Consumption of UWB-IR Receiver

A low power ultra-wideband impulse radio (UWB-IR) receiver was developed in 0.18-mum CMOS. All circuits of the receiver AFE operate intermittently with a sampling clock of an analog-digital converter (ADC). The sampling rate of the ADC is equal to the pulse repetition frequency of the received signals. Power consumption of the receiver AFE is reduced by 60% using a developed intermittent operation scheme without degrading of receiver sensitivity. As a result, the power consumption of the receiver AFE is 38 mW. The receiver has a data rate of 258 kb/s over a distance of 52 m and of 10.7 Mb/s over a distance of 14 m.

0.7-GHz-Bandwidth DS-UWB-IR System for Low-Power Wireless Communications

A direct-sequence ultra-wideband impulse radio (DSUWB-IR) system is developed for low-power wireless applications such as wireless sensor networks. This system adopts impulse radio characterized by a low duty cycle, and a direct-sequence 0.7-GHz bandwidth, which enables low-power operation and extremely precise positioning. Simulation results reveal that the system achieves a 250-kbps data rate for 30-mdistance wireless communications using realistic specifications. We also conduct an experiment that confirms the feasibility of our system.

1-cc Computer: Cross-Layer Integration with 3.4-nW/bps Link and 22-cm Locationing

The first 1-cc computer (OCCC) which integrates a sensor, a wireless transceiver, a computing engine and a battery is demonstrated. Cross-layer innovation includes SPIKE control, which achieves record-low 3.4-nW/bps power with 3-ms UWB current control (one order lower than those of reported). Another proposal is communication-location integration (CLI), which achieves 22-cm location accuracy with 1.3% area overhead. Fabricated OCCC is verified to operate as designed.

Adaptive channel diversity method based on ISA100.11a standard for wireless industrial monitoring

An adaptive channel diversity (ACD) ISA100.11-based method in wireless systems for industrial monitoring has been developed. The reliability performance (packet error rate vs. throughput) is calculated using measured data. It improves communication reliability by dynamically selecting higher quality frequency channels. Static analysis evaluation using a 30-device system with a star topology showed that using this method can reduce system latency by about 65% under wireless LAN conditions and that the effect is evident when the radio link quality is measured during periods of interference noise. The ACD method can thus be used to measure communication link quality in wireless radio environments and thus help reduce interference from other wireless systems.