This paper presents the design consideration of a polarization-transformation transmission filter, which is composed of a multilayered chiral slab. The optimal material parameters and thickness of each layer of the slab can be determined by using a genetic algorithm (GA). Substituting the constitutive relations for a chiral medium into Maxwell's equations, the electromagnetic field in the medium is obtained. A chain-matrix formulation is used to derive the relationship between the components of the incident, the reflected, and the transmitted electric fields. The cross- and co-polarized powers carried by the transmitted and reflected waves are represented in terms of their electric field components. The procedure proposed for the design of a polarization-transformation filter is divided into two stages. An ordinary filter without polarization-transformation and a polarization-transformation filter for the transmitted wave are designed with a multilayered non-chiral slab and a multilayered chiral slab at the first and the second stages, respectively. According to the specifications of the filters, two functionals are defined with the transmitted and reflected powers. Thus the optimal design of a polarization-transformation filter with the multilayered chiral slab is reduced to an optimization problem where the material parameters and thickness of each chiral layer are found by maximizing the functionals. Applying the GA to the maximization of the functionals, one can obtain the optimal material parameters and thicknesses of the multilayered chiral slab. Numerical results are presented to confirm the effectiveness of the two-stage design procedure. For three types of multilayered chiral slabs, optimal values of refractive indices, thicknesses, and chiral admittances are obtained. It is seen from the numerical results that the proposed procedure is very effective in the optimal design of polarization-transformation filters for the transmitted wave.

A constant voltage/constant current (CV/CC) parallel operation heterojunction bipolar transistor (HBT) power amplifier (PA) configuration is presented, and its design method is described. A resistor base feed (CC mode) HBT is connected to an inductor base feed (CV mode) HBT in parallel, and compensates the gain expansion of the CV mode HBT due to near class-B operation. By adding CC mode HBT, the total quiescent current can be decreased from 32 mA to 23 mA with adjacent channel leakage power ratio (ACPR) < -40.0 dBc. At the maximum output power region, the fabricated PA achieves output power (Pout) of 26.8 dBm and power added efficiency (PAE) of 42.0% with ACPR of -40.0 dBc, and shows the comparable performances with a conventional PA using CV mode HBT.

A pilot needs operational information about wind over sea as well as wave height to provide safety of hydroplane landing on water. Near-surface wind speed and direction can be obtained with an airborne microwave scatterometer, a radar designed for measuring the scatter characteristics of a surface. Mostly narrow-beam antennas are applied for such wind measurement. Unfortunately, a microwave narrow-beam antenna has considerable size that hampers its placement on flying apparatus. In this connection, a possibility to apply a conventional airborne radar altimeter as a scatterometer with a nadir-looking wide-beam antenna in conjunction with simultaneous range Doppler discrimination techniques for recovering the wind vector over sea at low speed of flight is discussed, and measuring algorithms of sea surface wind speed and direction are proposed. The principle considered and algorithms proposed in the paper can be used for creation an airborne radar system for operational measurement of the sea roughness characteristics and for safe landing of a hydroplane on water.

The tectonic activities that precede significant earthquakes release electromagnetic (EM) waves that can be used as earthquake precursors. We have been observing EM radiation in the ELF (extremely low frequency) band at about 40 observation stations in Japan for predicting significant earthquakes. The recorded signals contain, however, several noise components generated from the ionosphere, human activity, and so on. Most background noise in observed signal is attributed to lightning in the tropics. This paper proposes method based on PCA (principal component analysis) to extract signals from large data sets. The good performance of the proposed method is confirmed.

In this letter, the effect of an imperfect channel estimation and carrier frequency offset on the performance of transmit diversity OFDM systems is investigated. For the performance evaluation, the average bit error rate (BER) expression is derived in the presence of the imperfect channel information including both the inherent estimation error and the imperfect windowing error derived in a mismatched channel separation.

This paper describes a new training method of average voice model for speech synthesis in which arbitrary speaker's voice is generated based on speaker adaptation. When the amount of training data is limited, the distributions of average voice model often have bias depending on speaker and/or gender and this will degrade the quality of synthetic speech. In the proposed method, to reduce the influence of speaker dependence, we incorporate a context clustering technique called shared decision tree context clustering and speaker adaptive training into the training procedure of average voice model. From the results of subjective tests, we show that the average voice model trained using the proposed method generates more natural sounding speech than the conventional average voice model. Moreover, it is shown that voice characteristics and prosodic features of synthetic speech generated from the adapted model using the proposed method are closer to the target speaker than the conventional method.

Steganography is a technique that conceals the very existence of communication by means of hiding secret messages in innocuous cover objects. We previously developed a steganographic method that uses standard MIDI files (SMFs) as cover objects. Our method could conceal the secret messages in SMFs without changing their sound. We also investigated the effectiveness of our method against steganalysis. This steganalytic research revealed that files embedded using our method are vulnerable to detection, because stego SMFs lose the imprints borne by sequencers. In this study, we describe two improved methods of steganography that enable even stego SMFs to keep the sequencer's imprint. As a result, we improved the resistance of SMFs against steganalysis but there was a slight reduction in the embedding rate.

The applications of biometrics in the real world include various types of large-scale "one-to-many" identification, which require high performance classification technology. This paper presents a system with a classification algorithm that integrates multiple features observed in a set of fingerprints and uses them, to pre-select candidates, for more efficient personal identification from a very large fingerprint enrollment database. The algorithm determines a fingerprint's pattern type by using both ridge structure analysis and direction-based neural networks. It measures such additional feature characteristics as core-delta distance and ridge counts in parallel, along with confidence indexes associated with each feature. The pre-selector then integrates the set of obtained features from multiple fingers, after weighting them according to each feature's inherent ability to contribute to the selection process and the expected errors in observations of that feature. The system calculates the similarity between pairs of sets on the basis of feature differences, statistically evaluates the conditional probability of each pair being a correct match, and selects most similar collection of candidates for detailed matching. Experimental results confirm that it achieves an effective pre-selecting capability of 0.2% average selection (false acceptance or penetration) rate with 2% selection error (false rejection) rate.

This paper studies the local Poisson property of aggregated IP traffic. First, it describes the scenario where IP traffic presents a Poisson-like characteristic within some limited range of time scales when packets from independent traffic streams are aggregated. Each of the independent traffic streams corresponds to a series of correlated IP packets such as those of a transport connection. Since the Poisson-like characteristic is observed only within some limited range of time scales, we call this characteristic the local Poisson property. The limited range of time scales of the local Poisson property can be estimated from a network configuration and characteristics of transport connections. Second, based on these observations, we seek the possibility to apply an ordinary Poisson process to evaluation of the packet loss probability in IP networks. The analytical investigation, where IP traffic is modeled by a superposition of independent branching Poisson processes that presents the local Poisson property, suggests that the packet loss probability can be estimated by a finite-buffer queue with a Poisson process when the buffer size is within a certain range. The investigation is verified by simulations. These findings expand the applicability of conventional Poisson-based approaches to IP network design issues.

Future electric lights will be comprised of white LEDs (Light Emitting Diodes). White LEDs with a high power output are expected to serve in the next generation of lamps. In this paper, an indoor visible data transmission system utilizing white LED lights is proposed. In the proposed system, these devices are used not only for illuminating rooms but also for an optical wireless communication system. This system is suitable for private networks such as consumer communication networks. However, it remains necessary to investigate the properties of white LEDs when they are used as optical transmitters. Based on numerical analyses and computer simulations, it was confirmed that the proposed system could be used for indoor optical transmission.

Implementation issues on generalized multi-protocol label switching (GMPLS) -based photonic switching networks are experimentally analyzed. A resilient control plane architecture using in-fiber and out-of-fiber control channels is proposed to resolve issues of establishing the control plane in out-of-band networks. The resilient control plane is demonstrated in a photonic cross-connect (PXC) -based GMPLS network involving a 1,000 km transmission line. Fast signaling for provisioning and restoration operation is accomplished by implementing in-fiber control channels as primary, and the out-of-fiber control channels effectively operate as secondary and restore messaging of the control information between neighbors. The control channel protection is initiated by the link management protocol (LMP). Using the test bed, optical layer routing operation is investigated to assess the effects on the signal quality of wavelength paths, and transparent routing of the wavelength paths over one-hop and two-hops route is demonstrated within 1 dB difference regarding the Q factor. Stable operation of loss of light (LOL) -triggered restoration is demonstrated by setting the optical level threshold 5 dB higher than the amplified spontaneous emission (ASE) noise level.

A new approach to correcting the array amplitude failure by a combination of B-spline techniques and genetic algorithms is proposed. Some array elements indicate the control knots for a B-spline curve by their nominal positions and amplitudes; others distribute the excitation amplitudes according to the sampling points on the curve. The inherent smoothness of the B-spline curves reduce the effect of excessive coupling between adjacent elements. Genetic algorithms are used to search for a quasi-optimized B-spline curve to produce the ultimate amplitude distribution for correcting the array failure. To demonstrate the method's effectiveness, simulation results for correcting failures with three- and four-element failures are presented.

Adaptive arrays with signal blocking have the advantages of fast convergence and robustness to pointing errors as well as of rejecting a coherent interference in addition to incoherent ones. In this paper, we propose a novel method for performance improvement in such arrays with no increase in complexity. The proposed method utilizes all of the array elements to obtain the adaptive output so that its performance is superior to that of the conventional method which does not utilize one of the elements. Their performances are compared analytically and by computer simulation.

This paper investigates based on laboratory experiments the multiuser interference suppression effect of the coherent adaptive antenna array diversity (CAAAD) receiver employing an optical fiber feeder in the intermediate frequency (IF) stage, aiming at the practical use of adaptive antenna array beam forming techniques based on the W-CDMA air interface. We employed a configuration in which the optical fiber conversion, i.e., electrical-to-optical (E/O) conversion (vice versa (O/E)), is performed on a received signal amplified by an automatic gain control (AGC) amplifier in the IF stage, to abate the impact of the noise component generated by the E/O (O/E) converters. We first show by computer simulation the superiority of the optical fiber conversion in the IF stage to that in the radio frequency (RF) stage based on the achievable bit error rate (BER) performance. Furthermore, experimental results elucidate that the loss in the required transmit signal energy per bit-to-background noise power spectrum density ratio (Eb/N0) of the implemented CAAAD receiver at the average BER of 10-3 employing the optical fiber feeders in the IF stage compared to that with coaxial cables is within a mere 0.2 dB (six antennas, three users, two-path Rayleigh fading channel model, and the ratio of the target signal energy per bit-to-interference power spectrum density ratio (Eb/I0) of the desired user to that of the interfering users for fast transmission power control (TPC) is ΔEb/I0=-15 dB).

Immune system protects living body from an extraordinarily large variety of bacteria, viruses, and other pathogenic organisms. Based on immunological principles, new computational techniques are being developed, aiming not only at a better understanding of the system, but also at solving engineering problems. Our overall goal for this paper is twofold: to understand the real immune system from the information processing perspective, and to use idea generated from the immune system to construct new engineering application. As one example of the latter, we propose an artificial immune system architecture inspired by the human immune system and apply it to pattern recognition. We test the proposed architecture by the simulations on arbitrary sequences of analog input pattern classification and binary input pattern recognition. The simulation results illustrate that the proposed architecture is effective at clustering arbitrary sequences of analog input patterns into stable categories and it can produce stronger noise immunity than the binary network .

In order to increase the capacity of a DS-CDMA system, several kinds of interference suppression techniques have been studied, such as multiple access interference (MAI) cancellers and adaptive array antennas. However, their performance tends to degrade in high traffic-load situations. To compensate for the degradation, a receiver cascading an adaptive array antenna and a multistage parallel interference canceller (PIC) is studied in this paper. This receiver first uses an adaptive array antenna to suppress interference signals spatially, and uses a multistage PIC to suppress in-beam interference effectively. The performance of the cascaded receiver is evaluated with two schemes for antenna weight generation by computer simulations assuming a Rayleigh-distributed L-path channel. When antenna weights are generated for each user by an LMS algorithm, the cascaded receiver has shown better performance at the cost of a large number of pilot symbols and symbol by symbol weight update. Its performance degradation is 2.8 dB at the BER of 10-4 even when the number of users increases from one to 24. On the other hand, when antenna weights are generated for each path by a DMI algorithm, its performance is degraded due to the inaccurate weight generation which occurs when the SINR of the desired signal is small. This degradation can be mitigated by using all signals of the desired user received by all antenna patterns of desired user for RAKE combining when the difference among arrival angles of the paths of the desired user is small.

Recently, we have discovered wave propagation phenomena which are continuously existing waves of changing phase states between two adjacent oscillators from in-phase to anti-phase or from anti-phase to in-phase in van der Pol oscillators coupled by inductors as a ladder. We named the phenomena as "phase-inversion waves." In this study, phase-inversion waves which exist in the state of in-and-anti-phase synchronization have been found. We observe the phenomena by circuit experiments and computer calculations, and investigate them.

Efficient mixing of microwave signals is an important issue for new radio over fiber telecommunications systems. In this paper, we propose a novel device based on two cascaded semiconductor optical amplifiers working in a non-linear regime and a loss section in between Results show potential performance improvement as compared to other technological approaches for photonic microwave mixers.

We developed compact high-power photonic millimeter-wave emitter (PME) modules for 60-GHz fiber radio links. The PME chip is a monolithic integration of a uni-traveling-carrier photodiode (UTC-PD) and an antenna. One module was fabricated by attaching the chip and a plastic housing to a metal substrate, and the equivalent-isotropic radiated power (EIRP) of over 8 dBm was obtained with weak directivity of the radiated pattern. This module is suitable for point-to-multi-point communication. It is very compact, 29 24 6 mm. A module whose antenna gain was increased by attaching a dielectric lens to it was also fabricated, and the estimated EIRP of 18 dBm was obtained. This type of module is suitable for point-to-point communication and it too is compact, 29 24 17.5 mm. We achieved high-speed error-free data transmission of 1.25- and 2.5-Gbit/s phase-shift keyed (PSK) signal. The maximum distances of free-space propagation were estimated to be 18.2 and 8.9 m at bit rates of 1.25 and 2.5 Gbit/s, respectively.

A new CMOS 1/x circuit is presented in this letter. The output amplitude of the proposed circuit can be adjusted by a bias current. The proposed circuit can be used to realize a current-to-voltage converter and a current-mode divider. The proposed circuits have been fabricated in a 0.5 µm CMOS process. Experimental results show that under the linear error less than 1%, the input range of the proposed 1/x circuit can be up to 1.5 V for the supply voltages of 1.5 V and the power dissipation is 0.24 mW. The experimental results are given to demonstrate the proposed circuits.