A monolithically integrated photoreceiver compatible withInP/InGaAs HBT fabrication process

We demonstrate, for the first time, the characteristics of an InP/InGaAs HBT-compatible pin-PD and a monolithically integrated pin/HBT photoreceiver. The pin-PD can produce a short pulse with an FWHM of 80.8 ps followed by an elongated tail, when illuminated by optical pulses with an FWHM of 40 ps and a wavelength of 1.3 μm. The fall time of the output is determined by the transit time of holes generated in the n ⁺-InGaAs layer. The monolithically integrated photoreceiver, consisting of the pin-PD and a transimpedance preamplifier, can operate at 2.5 Gb/s with a sensitivity of -9.8 dBm. This performance was mainly limited by the characteristics of the pin-PD     

Anodic oxidation of potassium cyanide on the graphite electrode

The mechanism of anodic oxidation of cyanide on the graphite electrode was investigated by voltammetry, controlled potential coulometry, constant potential electrolysis and colorimetry. Cyanide was oxidized at the first order with respect to cyanide ion and at the zero order with respect to hydroxyl ion on the rate determining step. On the other hand, the result of controlled potential coulometry indicated that n_app was 2 at high OH? concentration, but approached unity at low OH? concentration. When constant potential electrolyses were carried out using electrolytes containing concentrated OH? and diluted OH?, the presence of cyanate was confirmed in both products. In addition to this, since oxalate anion was detected in the product at low OH? concentration, cyanogen, (CN)₂ was considerable to form an intermediate. Based on these results, two probable mechanisms were proposed. The discharge of cyanide ion is considerable to determine the overall rate in both mechanisms. Furthermore, it is informed that the side reaction forming oxalate anion proceeds at low OH? concentration.     

Plastic deformation of Al13Fe4 particles in Al–Al13Fe4 by high-speed compression

Spray-formed Al–Fe alloys having undergone high-speed deformation were examined under a high-voltage electron microscope. Two types of specimens were examined; one containing fine Al₁₃Fe₄ particles, and the other containing large particles. In the former specimen, deformation is found to proceed in three patterns, depending on specimen thickness and strain rate: (1) without deformation of the Al₁₃Fe₄; (2) breaking of the Al₁₃Fe₄; or (3) melting of the Al₁₃Fe₄. Local melting is found to alter some of the Al₁₃Fe₄ particles, to impart five-fold symmetry in diffraction or an amorphous structure. In the latter specimen, introduction of glide dislocations enabled us to determine a shear system in the mc102 monoclinic c2/m crystal of Al₁₃Fe₄. On the bases of these observations, the mechanism of high-speed deformation is discussed while taking into account the highly stressed and/or heated states of Al₁₃Fe₄ embedded in Al matrix.     

Control Method for Harmonic Voltage Injection to Achieve Noise Reduction in Position‐Sensorless Control of Permanent‐Magnet Synchronous Motors at Low Speeds

In this study, we examine the relationship between harmonic voltage injection, acoustic noise, and position estimation performance in a PMSM when a position‐sensorless control method involving harmonic voltage injection is used at low speeds. Further, we propose a novel control method for voltage injection; this method can be used to reduce acoustic noise in the motor. The proposed control method is verified by performing numerical simulations and carrying out experiments using a four‐pole, 2‐kW, 2100‐rpm IPMSM (interior permanent‐magnet synchronous motor). © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(3): 49–56, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21246     

Starting Procedure of Rotational Sensorless PMSM in the Rotating Condition

This paper investigates a starting procedure of rotational sensorless permanent magnet synchronous motor (PMSM) in the rotating condition, which is suitable for some applications with higher maximum rotor frequency and longer current sampling time. Instantaneous estimation of initial rotor position and frequency, right after gates start, is essential for restarting the operation of inverters. Existing estimation methods are not available for the aforementioned applications because of their higher maximum rotor frequency and longer current sampling time. To cope with this problem, we propose a novel initial rotor frequency estimation method. The proposed estimation method is verified by experiments using a 2-kW interior PMSM and a numerical simulation.     

Electrical Properties of Halogen-Doped CdTe Layers on Si Substrates Grown by Metalorganic Vapor-Phase Epitaxy

Electrical properties of halogen-doped CdTe layers grown on Si substrates using iodine and chlorine dopants are presented. No change in electrical properties of the layers was observed with chlorine as a dopant. However, doping with iodine resulted in highly conductive n-type layers or highly resistive p-type layers depending upon the growth conditions, even though a similar amount of dopant was introduced into the growth chamber. Layers grown at 560°C, with a vapor-phase Te/Cd precursor ratio of 3.0, were p-type. The resistivity of the layers remained unchanged for low dopant supply rates, but increased abruptly when the dopant supply rate was increased beyond a certain value. On the other hand, layers grown at 325°C with Te/Cd ratios from 0.1 to 0.25 were n-type. A maximum free electron concentration of 1.3 × 10¹⁷ cm⁻³ was obtained at room temperature. The types and conductivities of the grown layers were strongly dependent on the growth conditions.     

Differential precoder IC modules for 20-and 40-Gbit/s opticalduobinary transmission systems

This paper reports on 20- and 40-Gbit/s differential precoder modules for optical duobinary transmission systems. These precoder modules overcome the speed limit of a conventional precoder by parallel processing. The proposed precoders handle two or four parallel signals before multiplexing with data rates of one-half or one-quarter the transmission bit rate, and the final preceded signal is obtained by multiplexing the precoder output bit by bit, production-level 0.2-μm gate-length GaAs MESFET's were used to fabricate the precoders. The precoders are mounted in an RF package. They successfully performed 20- and 40-Gbit/s precoding for the first time, and the 20-Gbit/s precoder achieved a maximum precoding rate of 22 Gbit/s, which is 76% faster than that of the conventional circuit using the same MESFETs. The 40-Gbit/s precoder performs 40-Gbit/s precoding when combined with a 40-Gbit/s multiplexer unit. Twenty-Gbit/s optical duobinary transmitter and receiver circuits using the 20-Gbit/s precoder module successfully generate fully encoded optical duobinary signal at this rate for the first time. These circuits show a receiver sensitivity of -28.6 dBm for a bit error rate of 1×10^-9     

A 60-GHz optical frequency shifter using coupled inverted slotlines

A millimeter-wave optical frequency shifter (OFS) using coupled inverted slot lines (ISL's) is integrated on an X-cut LiNbO₃ substrate, Theoretical analysis shows that the use of the coupled ISL's makes it possible to decrease the distance between the arms of a Mach-Zehnder interferometer for optical frequency shifting. The ISL coupling characteristics measured at 60 GHz coincide well with the calculated ones. A 60-GHz frequency shifting of a 1.3-μm optical carrier is experimentally demonstrated using two- and four-branch OFS's. The theoretical analysis and experimental results of the two-branch OFS show that the ratio of the frequency-shifted signal intensity to the optical image intensity is in proportion to the difference between the applied dc-bias voltage and the half-wave voltage. The four-branch OFS consists of two two-branch OFS's excited 180° out of phase, and can suppress the optical image and original carrier simultaneously. The measurements of the four-branch OFS reveal the optical image suppression of over 12 dB and the original carrier suppression of 5 dB below the desired 60-GHz frequency-shifted signal