Development and evaluation of a long‐range 300‐m leaky coaxial cable in the 2.4‐GHz band for IEEE 802.11 b/g wireless network access

In installing wireless access systems for indoor use using IEEE 802.11b/g‐complied 2.4‐GHz band wireless local area network (LAN) units, problems that arise include blind zones and interferences caused by radio waves transmitted by neighboring access point units. To solve these problems, the use of leaky coaxial cables (LCXs) is a promising method. However, commercially available flexible LCXs with small diameters for 2.4‐GHz wireless LAN were not long enough for use in tunnels, underground facilities, and so on, and the communication characteristics of LCXs long enough for these places using wireless LAN units have not been reported. We have developed a flexible 300‐m long LCX for the 2.4‐GHz band and IEEE 802.11b/g‐complied wireless LAN units with high sensitivity. We evaluated its performance with four cable configurations and confirmed that this LCX provides wireless connections over 300 m along the cable and over 20 m lateral to the cable in an open‐air environment. We also found the coverage could be extended by a method of cable‐to‐cable links. IEEJ Trans 2010 DOI: 10.1002/tee.20604     

Examination of the dual‐band microwave wireless access system using radio on fiber technique

The Radio on Fiber (ROF) technique has great potential in wireless communication systems. In this paper, we report on a fundamental examination of microwave wireless access systems based on Radio on Fiber. First, we designed and constructed examination systems by applying dual band (2.4 and 5 GHz) multiservice transmission systems and confirmed that there was sufficient performance through a transmission experiment. Then, application of FP‐LD (Fabry Perot Laser Diode) was considered in order to reduce the system cost, and for the most part degradation of the transmission characteristics was not observed when FP‐LD was used. Finally, a BIDI (bidirectional) module which integrated LD and PD within one package was made to further reduce costs. By measuring the transmission performance, applying the BIDI module to ROF systems was shown to be effective. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(4): 32–40, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20471     

Observation space for lowest PDOP in absolute‐range‐based 2‐D wireless location systems

A closed‐form expression for the position dilution of precision (PDOP) in absolute‐range‐based two‐dimensional (2‐D) wireless location systems is derived. Then, using the closed‐form expression, the observation space (OS) required for achieving the lowest PDOP of $2/\sqrt{N}$ is studied, where N is the number of measuring points. The OS is measured by central angle of a sector which covers all measuring points. The target is located at the vertex of the sector. It is shown that, for achieving the lowest PDOP of $2/\sqrt{N}$, the OS is required to be larger than or equal to π/2 while N is even. When N = 3, the OS is instead required to be larger than or equal to 2π/3. It is also shown that the OS of 2π/3 is sufficient to achieve the lowest PDOP of $2/\sqrt{N}$ while N is odd. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Transmission characteristics of WDM signals amplified by semiconductor optical amplifiers in the 1.3‐µm wavelength band

Applications of semiconductor optical amplifiers to wavelength division multiplexing systems in a 1.3‐µm wavelength band are studied. The measured characteristics of gain and noise figure of the SOA, with small dependency on polarization states, confirm that it is applicable to repeater amplifiers and preamplifiers. When it is used as the preamplifier of a nonrepeated two‐channel 10 Gb/s system, an allowable line loss of 32 dB is attained with the aid of another SOA used for the postamplifier. The measured bit‐error rate of a system with one repeater amplifier is well simulated from the individual characteristics of the SOA and the optical receiver. Using a similar technique, it is predicted that more than 10 amplifiers can be applied in a system with cascaded repeater amplifiers, on the assumption that the polarization dependency of the gain is ignored. © 1998 Scripta Technica, Electr Eng Jpn, 126(1): 23–33, 1999     

Circuit and system design for an 860–960 MHz RFID reader front‐ends with Tx leakage suppression in 0.18 − µm CMOS technology

This paper presents an RF Front‐END for an 860–960thinspaceMHz passive RFID Reader. The direct conversion receiver architecture with the feedback structure in the RF front‐end circuit is used to give good immunity against the large transmitter leakage and to suppress leakage. The system design considerations for receiver on NF and IIP3 have been discussed in detail. The RF Front‐END contains a power amplifier (PA) in transmit chain and receive front‐end with low‐noise amplifier, up/down mixer, LP filter and variable‐gain amplifier. In the transmitter, a differential PA with a new power combiner is designed and fabricated in a 0.18‐µm technology. The chip area is 2.65 mm × 1.35 mm including the bonding pads. The PA delivers an output power of 29 dBm and a power‐added efficiency of 24% with a power gain of 20 dB, including the losses of the bond‐wires. Copyright © 2011 John Wiley & Sons, Ltd.     

Experimental studies of optical Raman amplifiers for 1.3‐µm wavelength band and its application to 20 Gbit/s × 2 WDM transmission

Configurations of a Raman amplifier suitable for a 1.3‐µm wavelength band are discussed and their properties are experimentally investigated. Pump light with a wavelength of 1.23 µm that is necessary for the Raman amplification in the 1.3‐µm wavelength band is obtained using a 1.06‐µm fiber laser and Raman laser technique. Concerning the Raman laser, wavelength conversion from 1.06 µm to 1.23 µm is effectively achieved using a cavity configuration including fiber Bragg gratings and a dispersion‐shifted fiber. On the other hand, a conventional dispersion compensation fiber which has an essential property of high nonlinearity is applied in order to obtain large gain at 1.3 µm. Net gain of 35 dB and output power of 15 dBm are achieved. To confirm the applicability of the Raman amplifiers to high‐speed optical transmissions, experiments of 20 Gbit/s × 2 WDM repeaterless transmission through a 80‐km conventional single‐mode fiber are carried out. The 1.3‐µm signal should be degraded due to the dispersion caused by the dispersion compensation fiber in the Raman amplifier; However, bit error rate of less than 10 to 12 is obtained at both wavelengths, which is sufficient performance for practical uses. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(1): 58–65, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10137     

A bidirectional isolated DC/DC converter as a core circuit for 3.3‐kV/6.6‐kV power conversion systems in the next generation

This paper describes a bidirectional isolated DC/DC converter considered as a core circuit for next‐generation 3.3‐kV/6.6‐kV high‐power‐density power conversion systems. The DC/DC converter is intended to use power switching devices based on SiC and/or GaN, which will be available on the market in the near future. A 350‐V, 10‐kW, and 20‐kHz DC/DC converter is designed, constructed, and tested in this paper. It consists of two single‐phase full‐bridge converters with the latest trench‐gate Si‐IGBTs and a 20‐kHz transformer with a nano‐crystalline soft‐magnetic material core and litz wires. The transformer plays an essential role in achieving galvanic isolation between the two full‐bridge converters. The overall efficiency from the DC‐input to DC‐output terminals is accurately measured to be as high as 97%, excluding gate drive circuit and control circuit losses from the whole loss. Moreover, loss analysis is carried out to estimate effectiveness in using SiC‐based power switching devices. The loss analysis clarifies that the use of SiC‐based power devices may bring a significant reduction in conducting and switching losses to the DC/DC converter. As a result, the overall efficiency may reach 99% or higher. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(2): 75–83, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20505     

Control schemes and transient characteristics of a high‐speed phase shifter for power flow control in power transmission systems

In recent years, attention has been paid to the concept of FACTS (Flexible AC Transmission Systems), along with significant progress in power electronic technology. A high‐speed phase shifter, which is one of the most promising devices in the FACTS concept, has the potential of power flow control and/or voltage stability in power transmission systems. In this paper, theory and experiment reveal that conventional high‐speed phase shifters may cause power swings in a transient state as a result of coupling between instantaneous active and reactive power control loops. Thus, two new control schemes for a high‐speed phase shifter are proposed to achieve both power flow control and power swing damping. The second proposed control scheme is based on the control scheme of an already proposed series active filter. Simulated and experimental results agree well with analytical results, not only in steady states but also in transient states. © 1999 Scripta Technica, Electr Eng Jpn, 128(2): 74–82, 1999