We have designed a torque magnetometer using a 60-kG split-type superconducting magnet. A balance torque compensates the torque acting on a sample in the magnetic field. The feedback circuit for a sample direction consists of an optical position sensor, a moving coil, and a PID controller. We measured the coil current to know a sample torque. The whole torque machinery is directly rotated by a stepping motor of angular resolution 0.0036. An advantage of the torque apparatus is a wide dynamic range up to 1000 dyncm. The sample temperature can be controlled between 4 K and 300 K.

Scaled models for an anatomical head model and a simple head model are used to investigate the effects of head size on SAR characteristics for a cellular phone exposure at 835 MHz. From the results, we can see that a larger head produces a higher localized SAR and a lower whole-head averaged SAR.

We have designed the Half Adder (HA) circuit and the Carry Save Serial Adder (CSSA) circuit based on pipeline architecture. Our HA has the structure of a two-stage pipeline and consists of 160 Josephson Junctions (JJs). Our CSSA has the structure of a four-stage pipeline with a feedback loop and consists of 360 JJs. These circuits were fabricated by the NEC standard process. There are two issues which should be considered in the design. One is parameter spreads generated by the fabrication process and the other is leakage currents between the gates. We have introduced a parameter optimization method to deal with the parameter spreads. We have also inserted three stages of JTLs to reduce leakage currents. We have experimentally confirmed the correct operations of these circuits. The obtained bias margins were 33.1% for the HA and 24.6% for the CSSA.

We present measurements of kilohertz and megahertz sine waves synthesized using a Josephson arbitrary waveform synthesizer. A 4.8 kHz sine wave synthesized using an ac-coupled bias technique is shown to have a stable 121 mV peak voltage and harmonic distortion 101 dB below the fundamental (-101 dBc (carrier)). We also present results of our first phase-noise measurement. A 5.0 MHz sine wave was found to have distortion 33 dB lower than the same signal synthesized using a semiconductor digital code generator. The white-noise floor of the Josephson synthesized signal is -132 dBc/Hz and is limited by the noise floor of the preamplifier.

We propose a new solvable Markov random field model for Bayesian image processing and give the exact expressions of the marginal likelihood and the restored image by using the multi-dimensional Gaussian formula and the discrete Fourier transform. The proposed Markov random field model includes the conditional autoregressive model and the simultaneous autoregressive model as a special case. The estimates of hyperparameters are obtained by maximizing the marginal likelihood. We study some statistical properties of the solvable Markov random field model. In some numerical experiments for standard images, we show that the proposed Markov random field model is useful for practical applications in image restorations. The investigation of probabilistic information processing by means of a solvable probabilistic model is recently in progress not only for image processing but also for error correcting codes and so on. The solvable probabilistic model gives us some important aspects for the availability of probabilistic computational systems.

An approach to the enhancement of speech signals corrupted by additive colored noise is proposed and the system architecture to implement the proposed idea in real-time communication is introduced in this paper. A combination of a bandpass FIR filtering technique with wiener filtering is used to improve the SNR for speech signals. The average SNR improvement (between input and output SNR) is 22.48 dB. The additive noises are the sound from a turbo prop aircraft. The system, which shows excellent performance, is designed based on a 16 bits fixed point DSP (ADSP-2181) from Analog Devices. Experiment results demonstrate that the FIR filter leads to a significant gain in SNR, thus visibly improvement for the quality and the intelligibility of the speech.

Transmitter diversity is a powerful technique to improve the transmission quality of downlink in microcellular mobile communications systems. Under cochannel interference (CCI) at the base station (BS), the transmitter diversity is not necessarily effective, because the desired-plus-interference signal power used as a criterion of downlink branch selection is not always relative to the downlink propagation condition. This paper proposes the theoretical derivation of bit error rate (BER) performance in the transmitter diversity under CCI occurring at BS, as parameters of average SIR at BS, normalized Doppler frequency, and so on. It is confirmed from the correspondence of theoretical results with simulation results that the proposed theoretical approach is applicable to the CCI environments at BS.

This paper presents an improved spectral subtraction method for speech enhancement. A new noise estimation method is derived in which the noise is assumed to be white. By using the property that a white noise spectrum is flat, high frequency components of a noisy speech spectrum are averaged and the standard deviation of the noise is estimated. This operation is performed in the analysis segment, thus the spectral subtraction method combined with the new noise estimation method does not need non-speech segments and as a result can adapt to non-stationary noise conditions. The effectiveness of the proposed spectral subtraction method is confirmed by experiments.

This paper presents some new protocols for (M+1)st-price auction, a style of auction in which the highest M bidders win and pay a uniform price, determined by the (M+1)st price. A set of distributed servers collaborates to resolve the (M+1)st price without revealing any information in terms of bids including the winners' bids. A new trick to jointly and securely compute the highest value as a degree of distributed polynomials is introduced. The building block requires just one round for bidders to cast bids and one round for auctioneers to determine the winners.

A method for fast calibration of digital-beam-forming (DBF) receiving array antennas by means of digital signal processing is described. It uses plane wave arriving from a known direction that contains a known reference sequence. Non-uniformities of the amplitude and phase in the branches are detected and calibrated in real time by the complex correlation of a replica of the known reference sequence with the received signal obtained from the output signals of each element. No special circuit for calibration is required, and the non-uniformities can quickly be compensated for by digital signal processing even for an array antenna with many antenna elements. This method enables highly accurate calibration of large-scale array antennas operating at a high frequency even under a low signal-to-noise power ratio (SNR).

As a new type of a linear decorrelating receiver, the Pseudo-Decorrelator was presented for asynchronous code division multiple access systems in [6]. In this paper, the concept of the Pseudo-Decorrelator is extended to derive a suboptimal receiver for WCDMA uplink systems in a Rayleigh fading environment. Starting with the analysis of the multiple access components of the decision statistics, a non-square cross-correlation matrix for each bit is obtained. This cross-correlation matrix is then inverted and the inverted matrix is applied to the decision statistics obtained from a conventional receiver. Simulation results are presented for K-user systems over a Rayleigh fading channel. The effects of the synchronization errors, such as time delays and carrier phase errors, are also examined through simulations in this paper.

Iterative schemes for demodulating M-ary orthogonal signaling formats in direct-sequence code-division multiple access (DS-CDMA) systems are proposed and compared with the standard noncoherent matched filter receiver. Interference cancellation, i.e., (approximative) removal of the multiple access interference (MAI) by means of subtraction is studied. The considered system is similar to the uplink (reverse link) of an IS-95 system. Hence, the received signals from the concurrent users are asynchronous, and no pilot signals are available for channel estimation. A decision-directed algorithm is proposed for estimating the time-varying complex channel gains of a multipath channel. The receivers are evaluated on Rayleigh-fading channels and are shown to provide large capacity gains compared with the conventional receiver.

Femtosecond optical pulses were irradiated into a YBa2Cu3O7-δ strip-line of 400 µm in width in order to investigate the relationship between the laser beam power profile and the distribution of the optically generated magnetic fluxes. To homogenize the current distribution in the strip-line, a half of the strip-line was patterned into the ordered array structure of holes of 2 µm in diameter at an interval of 4 µm, and several experimental conditions were examined by changing the focal size of the pulsed laser beam at the sample surface. As a result, it was found out that the generated optical magnetic fluxes strongly depend on the power profile of the femtosecond optical pulses, and showed a possibility for the application to a laser beam profiler and the other optical devices.

The FDTD method needs Fourier analysis to obtain the fields of a single frequency. Furthermore, the frequency spectra of the fields used in the FDTD method ordinarily have wide bands, and all the fields in FDTD are treated as real numbers. Therefore, if the permittivity ε and the permeability µ of the medium depend on frequency, or if the surface impedance used for the surface impedance boundary condition (SIBC) depends on the frequency, the FDTD method becomes very complicated because of convolution integral. In the electromagnetic theory, we usually assume that the fields oscillate sinusoidally, and that the fields and ε and µ are complex numbers. The benefit of introduction of the complex numbers is very extensive. As we do in the usual electromagnetic theory, the authors assume that the fields in FDTD oscillate sinusoidally. In the proposed FDTD, the fields, ε, µ and the surface impedances for SIBC are all treated as the complex numbers. The proposed FDTD method can remove the above-mentioned weak points of the conventional FDTD method.

An optical detection system using a DFB laser with a very small aperture is theoretically proposed. The threshold gain level in DFB laser is sensitively varied with combined reflections by the facet and the corrugation as well as with the optical injection reflected at the surface of the optical disk. Variation of the threshold gain level is counted as the voltage change on electrodes of the laser. It is found that sensitivity of the optical detection with a well-designed DFB laser becomes six times larger than that with conventional Fabry-Perot ones. Field distribution around the small aperture is analyzed taking into account both the near-field and the radiation field. Numerical data on the voltage change are given as examples of the detection system.

In this paper, we propose a turbo equalization scheme for GMSK signals with frequency detection. Although the channel is AWGN, there exists severe ISI (Inter-Symbol Interference) in the received signal due to the premodulation Gaussian baseband filter in the transmitter as well as the narrowband IF filter in the receiver. We regard these two filters as a real number inner convolutional encoder. The ISI equalizer for this inner encoder and the outer decoder for a RSC (Recursive Systematic Convolutional) code, are connected through a random (de-)interleaver. These inner and outer decoders generate the reliability values in terms of LLR (Log Likelihood Ratio), using MAP or SOVA algorithm with SISO (soft input and soft output). Moreover iterative decoding with the limitation of LLR values are employed between two decoders to achieve a turbo equalization for GMSK frequency detection. Through computer simulations, the proposed system shows the BER=10-5 at Eb/N0=8.8 dB, when we take BT=0.6 (IF filter bandwidth multiplied by symbol duration) with the iteration number of 3. This means 3.1 dB improvement compared with the conventional scheme where the inner ISI equalizer is concatenated with the outer hard decision Viterbi decoder.

This paper deals with security issues in a mobile agent system, especially protecting agent data from malicious servers. For this purpose, one-time key generation system, OKGS in short, is proposed. In OKGS, we integrate notions of an one-way hash function and a coupler. A one-way function plays a major role in ensuring confidentiality and integrity of agent data. And the notion of a coupler is used to establish inter-relationship among consecutive encryption keys for agent data, i.e,. all agent keys form a unidirectional chain. With these two features of OKGS, therefore, only the agent owner, who creates the agent bearing data, can decrypt and protect all agent data which are gathered in its itinerary.

We are developing a superconducting analog-to-digital converter (ADC) as a readout for high-resolution X-ray detectors based on a superconducting tunnel junction (STJ). The ADC has a sensitive front end which consists of a DC superconducting quantum interference device (SQUID). A signal current is digitized by this front end without using any preamplifiers. A single-flux-quantum (SFQ) pulse train whose frequency is proportional to the input current is launched by the front end, and integrated by a digital counter. The counter has a 10-bit resolution, and the integrated value is scanned and transferred to room-temperature processing modules with a frequency of 40 MHz. In this paper, the design of the ADC is described, and the preliminary results of the ADC performance test are shown. The performance of the STJ accompanied by the ADC is discussed in terms of the X-ray energy resolution.

The electronically steerable passive array radiator (ESPAR) antenna performs analog aerial beamforming that has only a single-port output and none of the signals on its passive elements can be observed. This fact and one that is more important--the highly nonlinear dependence of the output of the antenna from adjustable reactances--makes the problem substantially new and not resolvable by means of conventional adaptive array beamforming techniques. A novel approach based on stochastic approximation theory is proposed for the adaptive beamforming of the ESPAR antenna as a nonlinear spatial filter by variable parameters, thus forming both beam and nulls. Our theoretic study, simulation results and performance analysis show that the ESPAR antenna can be controlled effectively, has strong potential for use in mobile terminals and seems to be very perspective.

This contribution discusses which information can be derived from estimated directions of arrival (DOAs) and directions of departure (DODs) from a multiple-input multiple-output (MIMO) radio system, and establishes two new parameters describing the multipath spread at both link ends. We find that the multipath component separation, MCS, combines delay, (double-) angular and Doppler dispersion, as appropriate. MCS provides a system-independent radio characterization of propagation environments and aids in selecting optimum positions for smart-antenna deployment. Evaluation of double-directional measurements (antenna arrays at both link ends) in indoor environments show the usefulness and the limits of the multipath component separation concept.