An optimun design for N(arbitrary)-sheet capacitive Jaumann elctromagnetic (EM) wave absorber, using genetic algorithm will be presented. This algorithm is a random optimization method based on the genetic relation in the human being. We show the bandwidth for two-sheet capacitive Jaumann absorber can be expanded even more than 108% showed by knott, by using this algorithm and without imposing the double-notch design criteria. We also show that our results approaches knott's results when we restrict the characteristic impedances and lengths of the lines to vary within a very short range. We also design one-sheet and three-sheet capacitive Jaumann absorbers. The only restriction used here is about the meaningful range for the design variables. The goal of this algorithm is that we can impose arbitrary restriction about the range of the variation of the variables. So we can see the performance behaviour with the range dimension of the variables, and we can obtain different optimum results for different ranges. Finally we obtain a 20-dB attenuation bandwidth more than 145% for one-sheet, 173% for two-sheet (compare with 108% obtained in [1]) and 193% for three-sheet capacitive Jaumann EM absorbers, with some acceptable short range for the variables. We design the one-sheet and two-sheet capacitive Jaumann absorbers at low frequency and the three-sheet at high frequency. The 20-dB attenuation bandwidth obtained for the one-sheet and two-sheet capacitive Jaumann absorbers are respectively, from 10 to 77 MHz and, from 4 to 61 MHz. For the three-sheet capacitive Jaumann absorber the 20-dB attenuation bandwidth obtained is, from 0.8 GHz to 280 GHz.

We have investigated the operation of a reflection type magnetostatic wave signal-to-noise enhancer in detail. It has good enhancement characteristics, low insertion loss, and low operating power. It is also composed of a transducer using a ceramic substrate having a high dielectric constant and an LaGa-YIG film with low saturation magnetization to enable direct operation in the 400-MHz band (the IF band of current DBS receivers). Enhancement of 8 dB was achieved over a 40-MHz bandwidth. Although its operating frequency range depends critically on device temperature, we can compensate for the temperature dependence by adjusting the bias magnetic field. Experiments showed that the enhancer improved the received carrier-to-noise ratio by 2 to 3 dB, providing good noise reduction in DBS reception.

This paper evaluates the performance of a reliable multicast protocol for bulk-data transfer over unreliable networks via IP-multicast. Bulk-data type reliable multicast appears promising for commercial publishing and large-scale data replication. The proposed reliable multicast transport protocol (RMTP) provides high-performance due to the use of IP multicast while also providing confirmed and error free transfer by end-to-end controls. The protocol includes a multi-round selective repeat scheme dedicated for bulk-data multicast applications. This paper examines the multicast retransmission procedures in RMTP through analysis and tests on an implemented system and clarifies the basic performance behavior of the protocol. Evaluations are conducted with regard to retransmission redundancy, transfer time, and packet processing load with various error conditions and number of receivers. Against the response concentration problem seen in end-to-end communication, the backoff time algorithm is applied to the protocol; the limits it places on system scalability are clarified.

This paper shows the applicability of the integral equation formulation of the measured equation of invariance (IE-MEI) to two-dimensional dielectric scatterers. That is, a relationship between the scattered electric and magnetic fields, which is derived from the new formulation of the IE-MEI, is applicable to lossless dielectric materials as well as perfect electric conductors (PEC). In addition, we show that the IE-MEI does not suffer from internal resonance problems. These two facts are validated by numerical examples for a circular cylinder and a square cylinder illuminated by Transverse Magnetic (TM) plane wave or a TM line source very close to the scatterers. The numerical results calculated by the IE-MEI agree well with the ones by moment methods that employ combined field formulations with exact boundary conditions.

We show by numerical calculations that a chaotic neuron model driven by a weak sinusoid has resonance. This resonance phenomenon has a peak at a drive frequency similar to that of noise-induced stochastic resonance (SR). This neuron model was proposed from biological studies and shows a chaotic response when a parameter is varied. SR is a noise induced effect in driven nonlinear dynamical systems. The basic SR mechanism can be understood through synchronization and resonance in a bistable system driven by a subthreshold sinusoid plus noise. Therefore, background noise can boost a weak signal using SR. This effect is found in biological sensory neurons and obviously has some useful sensory function. The signal-to-noise ratio (SNR) of the driven chaotic neuron model is improved depending on the drive frequency; especially at low frequencies, the SNR is remarkably promoted. The resonance mechanism in the model is different from the noise-induced SR mechanism. This paper considers the mechanism and proposes possible explanations. Also, the meaning of chaos in biological systems based on the resonance phenomenon is considered.

An Acoustic echo canceller has problems adaptating under noisy or double-talk conditions. The adaptation process requires a precise identification of the temporarily changed room impulse response. To do this, both minimizing the step size parameter of the Least Mean Square (LMS) method to be as small as possible and giving up on updating the adaptive filter coefficients have been considered. This paper describes an adaptive cross-spectral technique that is robust to adaptive filtering under noisy or double-talk conditions and for colored signals such a speech signal. The cross-spectral technique was originally developed to measure the impulse response in a linear system. Here we apply in the adaptive cross-spectral technique to solve the acoustic echo cancelling problem. This cross-spectral technique takes the ensemble average of the cross spectrum between input and error signals and the averaged cross spectrum is divided by the averaged power spectrum of the input signal to update the filter coefficients. We have confirmed that the echo signal is suppressed by about 15 dB even under double-talk conditions. We also explain that this method has a systematic error due to using a short time block for estimating the room impulse response. Then we investigate overlapping every last half block by the following first half block in order to reduce the effect of the systematic error. Finally, we compare our method with the Frequency-domain Block LMS (FBLMS) method because both methods are implemented in the frequency domain using a short time block.

This paper proposes a newly developed dual-frequency antenna for 800 MHz and 1500 MHz band use. A uniformly spaced array configuration, originally designed for a 800 MHz analog system, is extended to yield dual frequencies operations. An important characteristic of a base station antenna is low sidelobe level in order to suppress inter-cell interference. In the case of a uniformly spaced array configuration, sidelobe levels are increased by the emergence of grating lobes at higher frequencies. Electrical beam tilt also degrades the sidelobe level. As does the change in the excitation coefficients of the array elements at higher frequencies. These three factors are studied theoretically to yield practical sidelobe levels. One more important beam characteristic is the sector beam in the horizontal plane. The same beam width in two frequency bands is achieved by designing the novel reflector shape and determining the proper array element positions in front of the reflector. Practical antenna characteristics are confirmed by designing, manufacturing, and testing a base station antenna.

As TCP/IP networks develop, various type of applications or services are appearing. Especially, many people want to use real time multicast applications over TCP/IP networks like a TV conference system. Most of the current TCP/IP networks, however, still do not support QoS guarantees using RSVP, so that they provide only a best-effort service. Therefore, such real time applications must control data transmitting rate by the network or receiver's condition. However, it is difficult to control data rate over a multicast session, since every receiver on a multicast network does not necessarily have the same environment. To solve this problem, the authors proposed a locally adaptive control intermediate system. This paper describes a rate-adaptive real-time multicast system with locally adaptive packet flow control.

A new method of designing a microphone array with two outputs preserving binaural information is proposed in this paper. This system employs adaptive beamforming using multiple constraints. The binaural cues may be preserved in the two outputs by use of these multiple constraints with simultaneous beamforming to enhance target signals is also available. A computer simulation was conducted to examine the performance of the beamforming. The results showed that the proposed array can perform both the generation of the binaural cues and the beamforming as intended. In particular, beamforming with double-constraints exhibits the best performance; DI is around 7 dB and good interchannel (interaural) time/phase and level differences are generated within a target region in front. With triple-constraints, however, the performance of the beamforming becomes poorer while the binaural information is better realized. Setting of the desired responses to give proper binaural information seems to become critical as the number of the constraints increases.

In order to reduce state explosion problem, techniques such as symbolic state space traversal and partial order reduction have been proposed. Combining these two techniques, however, seems difficult, and only a few research projects related to this topic have been reported. In this paper, we propose handling single place zero reachability problem of Petri nets by using both partial order reduction and symbolic state space traversal based on ZBDDs. We also show experimental results of several examples.

This paper is consisting of the two novel EMC technologies that we have been developed in our laboratory. The first is the technology for measuring the RF (Radio Frequency) nearby magnetic field and estimation of the RF current in the printed circuit board (PCB) by using the small loop antenna with multi-layer PCB structure developed by our laboratory. I introduce the application of our small loop antenna with its physical structure and the analysis of the nearby magnetic field distribution of the printed circuit board applying the discrete Wavelet analysis. We can understand the behavior of the digital circuit in detail, and we can also take measures to meet the specification about the electromagnetic radiation from the digital circuit from the higher order of priority by using these technologies. The second is our proposing novel technology for reducing the electromagnetic radiation from the digital equipment by taking notice of the improvement of the de-coupling in the PCB. We confirmed the remarkable effect of this technology by redesigning the motherboard of the small-sized computer.

This paper presents the technologies for over-40-Gbit/s operation of InP-based HEMT ICs for future optical communication systems. High-speed interconnection using low-permittivity benzocyclobutene (BCB) film as an inter-layer insulator decreases interconnection delay and results in high-speed operation of digital circuits. A static frequency divider and a 2 : 1 multiplexer using this novel interconnection demonstrate 49-GHz and 80-Gbit/s operation, respectively. Ultrahigh-speed digital/analog ICs fabricated using the HEMTs were used in 40 Gbit/s optical transmission experiment and showed good bit-error-rate performance. A novel two-step recess process for gate recess etching considerably improves the performance of InP-based HEMTs and is found to be promising for future ultrashort-gate devices.

Computational sensor (smart sensor, vision chip in other words) is a very small integrated system, in which processing and sensing are unified on a single VLSI chip. It is designed for a specific targeted application. Research activities of computational sensor are described in this paper. There have been quite a few proposals and implementations in computational sensors. Firstly, their approaches are summarized from several points of view, such as advantage vs. disadvantage, neural vs. functional, architecture, analog vs. digital, local vs. global processing, imaging vs. processing, new processing paradigms. Then, several examples are introduced which are spatial processings, temporal processings, A/D conversions, programmable computational sensors. Finally, the paper is concluded.

This paper describes a flip-flop circuit using a directly controlled emitter-follower with a diode-feedback level stabilizer (DC-DF) and a resistor-feedback level stabilizer (DC-RF) for low-power multi-GHz prescalers. The new flip-flop circuit reduces the emitter-follower current and gains both high-frequency operation and low-power. A dual modulus (4/5) prescaler using this circuit technology was fabricated with a 0.35 µm BiCMOS process. The current draw of the prescaler using the DC-RF is 34% smaller than conventional LCML circuits. The DC-RF prescaler operates at 2.11 GHz with a total current consumption of 1.03 mA. In addition, the circuit operates with a supply voltage of down to 2.4 V by using the resistor level-shift clock-driver.

A trinary-phased array, in which a phase quantization unit of phase shifters is 120 degrees is examined. The phase quantization unit of 120 degrees is the roughest value in practical phased array applications. Despite its rough phase quantization, the sidelobe level of less than -9 dB is attained by a genetic algorithm approach.

Feedback of class memberships is incorporated into multimodal pattern classifiers and their unsupervised learning algorithm is presented. Classification decision at low levels is revised by the feedback information which also enables the reconstruction of patterns at low levels. The effects of the feedback are examined for the McGurk effect by using a simple model.

This letter introduces a new digital halftoning technique based on error diffusion along a random space-filling curve. The purpose of introducing randomness is to erase regular patterns which tend to arise in an image area of uniform intensity. A simple algorithm for generating a random space-filling curve is proposed based on a random spanning tree and maze traversal. Some experimental results are also given.

This paper describes a 2.5-Gb/s optical receiver and transmitter chipset consisting of a preamplifier, a main amplifier, a clock and data recovery (CDR) circuit, and a laser-diode (LD) driver. Low-voltage and adjustment-free circuit techniques are introduced in order to achieve low cost and low power circuits. Circuit adjustments are eliminated by using a multi-stage automatic offset canceling technique in the main amplifier, and by using a PLL structure with a sample-and-hold technique in the CDR circuit. For power reduction, ICs are operated at a power supply voltage of -3 V. Fabricating the ICs by a 0.5-µm Si bipolar process makes it possible to achieve 2.5-Gb/s receiver and transmitter operation with a total power dissipation of 1.04 W. Especially significant is that the receiver ICs need no external devices and adjustments.

This paper proposes a novel sequential coherent preambleless demodulator that uses phase signals instead of complex signals in the automatic frequency control (AFC) and carrier recovery circuits. The proposed demodulator employs a phase-combined frequency error detection circuit and dual loop AFC circuit to achieve fast frequency acquisition and low frequency jitter. It also adopts an open loop carrier recovery scheme with a sample hold circuit after the carrier filter to ensure carrier signal stability within a packet. It is shown that the frame error rate performance of the proposed demodulator is superior, by 30%, to that offered by differential detection in a frequency selective Rayleigh fading channel. The hardware size of the proposed demodulator is about only 1/10 that of a conventional coherent demodulator employing complex signals.

An optical receiver with a saturated electrical amplifier is studied for signal light that is distorted due to the use of a gain-saturated semiconductor optical amplifier or homowavelength crosstalk light. It is shown that less penalty is induced in a receiver with a DC-coupled saturated amplifier than in one with a linear amplifier, in a practical situation where the decision threshold is fixed at a value optimized for a back-to-back signal. The result suggests that a receiver with a saturated amplifier or a limitter is preferable to an automatic gain control circuit for detecting distorted signal lights.