This paper is concened with the design and implementation of a 2-channel, 2-dimensional filter bank using rectangular (analog/digital) and quincunx (digital/digital) sampling. The associated analog low-pass filters are separable where as the digital low-pass filters are non-separable for a minimum sampling density requirement. The digital low-pass filters are Butterworth type filters, N = 9, realized as LWDFs. They, when itterated, approximate a valid scaling function (raised-consine scaling function). The obtained system can be used to compute a discrete wavelet transform.

In this paper, new wavelet bases are presented. We address problems associated with the proposed matched filter in multirate systems, using an optimum receiver that maximises the SNR at the sampling instant. To satisfy the Nyquist (ISI-free transmission) and matched filter (maximum SNR at the sampling instant) criteria, the overall system filtering strategy requires to split the narrowest filter equally between transmitter and receiver. In data transmission systems a raised-cosine filter is therefore often used to bandlimit signals from which wavelet bases are derived. Sampling in multiresolution subspaces is also discussed.

In this paper we discuss the limiting behavior of the search direction of the steepest descent method in minimizing the Rayleigh quotient. This minimization problem is equivalent to finding the smallest eigenvalue of a matrix. It is shown that the search direction asymptotically alternates between two directions represented by linear combinations of two eigenvectors of the matrix. This is similar to the phenomenon in minimizing the quadratic form. We also show that these eigenvectors correspond to the largest and second-smallest eigenvalues, unlike in the case of the quadratic form.

The convergence characteristics of the adaptive beamformer with the RLS algorithm are analyzed in this paper. In case of the RLS adaptive beamformer, the convergence characteristics are significantly affected by the spatial characteristics of the signals/noises in the environment. The purpose of this paper is to show how these physical parameters affect the convergence characteristics. In this paper, a typical environment where a few directional noises are accompanied by background noise is assumed, and the influence of each component of the environment is analyzed separately using rank analysis of the correlation matrix. For directional components, the convergence speed is faster for a smaller number of noise sources since the effective rank of the input correlation matrix is reduced. In the presence of background noise, the convergence speed is slowed down due to the increase of the effective rank. However, the convergence speed can be improved by controlling the initial matrix of the RLS algorithm. The latter section of this paper focuses on the physical interpretation of this initial matrix, in an attempt to elucidate the mechanism of the convergence characterisitics.

In this paper, we propose a practical and secure electronic voting scheme which meets the requirements of large scale general elections. This scheme involves voters, the administrator or so called the government and some scrutineers. In our scheme, a voter only has to communicate with the administrator three times and it ensures independence among voters without the need of any global computation. This scheme uses the threshold cryptosystem to guarantee the fairness among the candidate's campaign and to provide mechanism for achieving the function that any voter can make an open objection to the tally if his vote has not been published. This scheme preserves the privacy of a voter against the administrator, scrutineers, and other voters. Completeness, robustness, and verifiability of the voting process are ensured and hence no one can produce a false tally, corrupt or disrupt the election.

In-line transceiver chip emitting at 1.3 µm and receiving at 1.55 µm is described regarding the crosstalk occurring between the 1.3-µm laser and the 1.55-µm integrated photodiode. Contribution of optical and electrical crosstalk to the overall crosstalk is measured and discussed. Techniques to overcome the crosstalk are proposed and demonstrated by showing the feasibility of system compatible diplex sensitivities.

A wavelength tunable DBR laser monolithically integrated with an EA-modulator as a WDM system light source was fabricated by selective area MOVPE growth. The lasing wavelength and band-gap energy were simultaneously controlled on the same epitaxial wafer by using a modulated grown thickness of InGaAsP/InGaAsP MQW layers. A wavelength tuning range of 3.5 nm, an output power of 3 mW, and an extinction ratio of 14 dB for 3 V were achieved. The measured 3 dB frequency bandwidth was 2 GHz. No significant change in modulation characteristics were observed when wavelength tuning by injecting the current into the DBR.

A simple extension to treat evanescent modal excitation at the aperture of a parallel plane waveguide is shown here by GTD diffracted rays with complex propagation angles. Numerical comparison with other solution confirmed that our simple solution can be used for modal excitation estimation below the cut-off frequency.

This paper describes a novel quasi-transmission-line variable-reactance circuit that extends the variable-phase range of phase shifters. It consists of a transmission line and two shunt varactors. By appropriately choosing the characteristic impedance and electrical length of the transmission line, the variable-phase range can be significantly increased. Since the proposed circuit can be fabricated by the conventional MESFET process, a phase shifter can be integrated with other functional circuits. This enables fully monolithic integration of RF circuits as a one-chip multi-functional MMIC in radio communication systems. The variable-phase range of the prototype X-band monolithic phase shifter is 208 degrees, which is approximately four times as large as that of conventional one.

Key aspects and technologies of future satellite communications are discussed toward multimedia era. Onboard processing called the switchboard in the sky and networking taking full advantage of features peculiar to satellite communications are pointed out as essential technologies to overcome a variety of big challenges for realizing future satellite communications. Several experimental and commercial systems are introduced as the first step toward multimedia era.

A very simple but general scheme has been developed to calculate burst error occurrences due to cycle slip in clock recovery on frequency-selective Nakagami-Rice fading channels. The scheme, which we call the "Equivalent Transmission-Path Model," plays a role in connecting "wave propagation" with "digital transmission characteristics" in a general manner. First computer simulations assuming various types of delay profiles identify the "key parameters in Nakagami-Rice fading" that principally dominate the occurrence of cycle slips. Following this a simple method is developed to calculate the occurrence frequency of cycle slips utilizing the nature of the key parameters. Then, the accuracy of the scheme is confirmed through comparison between calculated values and simulation results. Finally, based on the scheme, calculated results on cycleslip occurrences are presented in line-of-sight fading environments.

In this paper, a new spectral subtraction technique with two microphone inputs is proposed. In conventional spectral subtraction using a single microphone, the averaged noise spectrum is subtracted from the observed short-time input spectrum. This results in reduction of mean value of noise spectrum only, the component varying around the mean value remaining intact. In the method proposed in this paper, the short-time noise spectrum excluding the speech component is estimated by introducing the blocking matrix used in the Griffiths-Jim-type adaptive beamformer with two microphone inputs, combined with the spectral compensation technique. By subtracting the estimated short-time noise spectrum from the input spectrum, not only the mean value of the noise spectrum but also the component varying around the mean value can be reduced. This method can be interpreted as a partial construction of the adaptive beamformer where only the amplitude of the short-time noise spectrum is estimated, while the adaptive beamformer is equivalent to the estimator of the complex short-time noise spectrum. By limiting the estimation to the amplitude spectrum, the proposed system achieves better performance than the adaptive beamformer in the case when the number of sound sources exceeds the number of microphones.

This paper deals with performance evaluation of CDMA based on DS/SS/GMSK signaling with the differential detection over multipath Rayleigh fading channels. To demodulate DS/SS/GMSK signals, we consider differential detection, which does not need a carrier recovery. The bit-error-rate performance is evaluated in the presence of thermal noise and multipleaccess interferences under the multipath Rayleigh fading environment. To improve the performance, we also consider adoption of a RAKE receiver.

In this contribution an algorithm for joint detection in fast frequency hopping/multiple frequency shift keying (FFH/MFSK) multiple access (MA) systems is presented. The new algorithm - referred to as REC algorithm - evaluates ambiguities which occur during the decision process and iteratively reduces the number of candidate symbols. The REC algorithm is of low complexity, suitable for every addressing scheme, and effective for both an interference-only channel and a fading channel. For the interference-only channel the REC algorithm enables maximum likelihood (ML) joint detection with low computational effort.

In this paper, we describe effects of oddcorrelation functions and band-limitation filters for direct-wave reception systems using broadband spread-spectrum (B-SS) techniques. The receiver of this system is synchronized to the direct-wave. First, the effects of odd-correlation functions are investigated by using M-sequences and random sequences. The effects of even-correlation functions for those sequences can be easily obtained by using results of effects of odd-correlation functions for random sequences. Here we derive a novel function of odd-correlation variance for M-sequence, which is obtained theoretically. Consequently, we show the advantage of M-sequence which is used as spreading sequence. As a reason, in the odd-correlation function of M-sequence, small values are taken near the synchronous phase where harmful scattered-waves exist, strongly. Next, the effects of both odd-correlation function and band-limitation filter are studied by using several kinds of filters. Here we discuss the difference of characteristics in case that despreading sequence of bandlimited pulse or that of rectangular pulse is used in the correlator of the receiver. The technique despreading by rectangular pulse can be achieved a high speed signal processing and equipment miniaturizing because of utilization of switching circuit. We show the advantage of despreading sequence of rectangular pulse, when the limitation bandwidth of transmitting signal takes a small value. Because the characteristics of the correlation function between transmitting sequence of bandlimited pulse and despreading sequence of rectangular pulse can be kept better than that between the transmitting sequence and despreading sequence of bandlimited pulse. As these results, in severe bandlimited direct-wave reception systems using B-SS techniques, M-sequence of rectangular pulse as despreading sequence is most suitable.

In logic programming or functional programming languages, data objects, such as terms and lists, are immutable. In a basic implementation of such language, updating one element of an aggregate (contiguous data structure, such as an array) involves making a new copy of the whole aggregate. However, such copying can be expensive, and can be avoided by using a destructive update. We introduce the concept of a wrapper which enables destructive operation on an immutable object. Based on this concept, we designed the reversible functor as a solution to the aggregate update problem. We implemented the reversible functor in the existing SB-Prolog system and carried out several benchmarks. These benchmark results show its effectiveness. When using a large functor and updating it many times, the performance is improved dramatically by implementing the reversible functor. It incurs some overhead at runtime, but the amount is small and acceptable.

Preliminary experiments on non-destructive quantitative analysis of water vapor density in halogen lamps have been carried out. A working curve showing a relation between absorbance and water vapor density was successfully obtained by using frequency-stabilized InGaAsP/InP semiconductor laser spectrometric system.

In outdoor fields such as construction, mining and agriculture, there is an increasing demand for autonomous vehicles to reduce labor costs. Also, a positioning system is one key technology required for autonomous vehicle systems. For the purpose of expanding the potential of millimeter-wave applications, we have developed a positioning system in the 77-79 GHz frequency band, using the hyperbolic radio navigation method. This system operates in a restricted area with a radius of about a few hundred meters. A spread spectrum with a PN code is used as the ranging signals. We realized about 0.1 m in positioning accuracy.

In this paper stochastic aradient adaptive filters using the Sign or Sign-Sign Algorithm are analyzed based upon general assumptions on the reference signal, additive noise and particularly jointly distributed tap errors. A set of difference equations for calculating the convergence process of the mean and covariance of the tap errors is derived with integrals involving characteristic function and its derivative of the tap error distribution. Examples of echo canceller convergence with jointly Gaussian distributed tap errors show an excellent agreement between the empirical results and the theory.

The polymer matrix for the number of N in-puts/outputs, N stages and 2x2-switches is denoted as the 1-D Spanke-Benes (SB) network. Throughout the paper, the 1-D SB-network, which equals the diamond cellular array, is extended to arbitrary dimensions by a mathematical transformation (a 1-D network provides the interconnection of 1-D data). This transformation determines the multistage architecture completely by providing size, location, geometry and wiring of the switches as well as it preserves properties of the networks, e.g., the capability of sorting. The SB-networks of dimension 3 are analysed and sorting is applied.