Most of actual environmental systems show a complicated fluctuation pattern of non-Gaussian type, owing to various kinds of factors. In the actual measurement, the fluctuation of random signal is usually contaminated by an external noise. Furthermore, it is very often that the reliable observation value can be obtained only within a definite fluctuating amplitude domain, because many of measuring equipments have their proper dynamic range and original random wave form is unreliable at the end of amplitude fluctuation. It becomes very important to establish a new signal detection method applicable to such an actual situation. This paper newly describes a dynamical state estimation algorithm for a successive observation contaminated by the external noise of an arbitrary distribution type, when the observation value is measured through a finite dynamic range of measurement. On the basis of the Bayes' theorem, this method is derived in the form of a wide sense digital filter, which is applicable to the non-Gaussian properties of the fluctuations, the actual observation in a finite amplitude domain and the existence of external noise. Differing from the well-known Kalman's filter and its improvement, the proposed state estimation method is newly derived especially by paying our attention to the statistical information on the observation value behind the saturation function instead of that on the resultant noisy observation. Finally, the proposed method is experimentally confirmed too by applying it to the actual problem for a reverberation time measurement from saturated noisy observations in room acoustics.

A new Viterbi algorithm with adaptive path reduction method is presented. The proposed system consists of the pre-decoder and reduced path Virerbi decoder. The predecoder separates the mixed channel noise from the received sequence. The number of errors in the pre-decoded error sequence is counted and the path reduction is implemented by the number of errors in pre-decoded error sequence. The path reduction is implemented as a function of channel condition because the errors in the pre-decoded error sequence can be considered as the channel error sequence. Due to the reduction of the path, the number of ACS (add compare select) operations can be reduced, which occupies the dominant part in Viterbi decoding. The ACS reduction ratio for the proposed system achieves up to 30% for the case of (2, 1, 2) Ungerboeck code without degradation of the error performance.

Asymptotic bounds are considered for unidirectional byte error-correcting codes. Upper bounds are developed from the concepts of the Singleton, Plotkin, and Hamming bounds. Lower bounds are also derived from a combination of the generalized concatenated code construction and the Varshamov-Gilbert bound. As the result, we find that there exist codes of low rate better than those on the basis of Hamming distance with respect to unidirectional byte error-correction.

This paper proposes new design methods for single b-bit (b2) byte error correcting and double bit error detecting code, called SbEC-DED code, suitable for high-speed memory systems using byte organized RAM chips. This new type of byte error control code is practical from the viewpoint of having less redundancy and stronger error control capability than the existing ones. A code design method using elements from a coset of subfield under addition gives the practical SbEC-DED code with 64 information bits and 4-bit byte length which has the same check-bit length, 12 bits, as that of the Hamming single byte error correcting code. This also has very high error detection capabilities of random double byte errors and of random triple bit errors.

Recently, the small set of nonbinary Kasami sequences was presented and their correlation properties were clarified by Liu and Komo. The family of nonbinary Kasami sequences has the same periodic maximum nontrivial correlation as the family of Kumar-Moreno sequences, but smaller family size. In this paper, first it is shown that each of the nonbinary Kasami sequences is unbalanced. Secondly, a new family of nonbinary sequences obtained from modified Kasami sequences is proposed, and it is shown that the new family has the same maximum nontrivial correlation as the family of nonbinary Kasami sequences and consists of the balanced nonbinary sequences.

A model for a large network with an unidirectional linear respone (ULR) is proposed in this letter. This deterministic system has powerful computing properties in very close correspondence with earlier stochastic model based on McCulloch-Pitts neurons and graded neuron model based on sigmoid input-output relation. The exclusive OR problems and other digital computation properties of the earlier models also are present in the ULR model. Furthermore, many analog and continuous signal processing can also be performed using the simple ULR neural network. Several examples of the ULR neural networks for analog and continuous signal processing are presented and show extemely promising results in terms of performance, density and potential for analog and continuous signal processing. An algorithm for the ULR neural network is also developed and used to train the ULR network for many digital and analog as well as continuous problems successfully.

We discuss delay times derived from the current gain cutoff frequency of a heterostructure field effect transistor and describe three types of novel channel structures for millimeter-wave InP-based HFETs. The first structure discussed is a lattice-matched InGaAs HEMT with high state-of-the art performance. The second structure is an InAs-inserted InGaAs HEMT which harnesses the superior transport properties of InAs. Fabricated devices show high electron mobility of 12,800 cm2/Vs and high transconductance over 1.4 S/mm for a 0.6-µm-gate length. The effective saturation velocity in the device derived from the current gain cutoff frequency in 3.0107 cm/s. The third one is an InGaAs/InP double-channel HFET that utilizes the superior transport properties of InP at a high electric field. Fabricated double-channel devices show kink-free characteristics, high carrier density of 4.51012 cm-2 and high transconductance of 1.3 S/mm for a 0.6-µm-gate length. The estimated effective saturation velocity in these devices is 4.2107 cm/s. Also included is a discussion of the current gain cutoff frequency of ultra-short channel devices.

The Cooper pairing interaction in high Tc oxide superconductor is discussed in terms of an empirical expression; TcDexp[1/g], gcωo which was derived in our previous investigation. The dual character of this expression consisting of the phonon Debye temperature D and electronic excitation ωo in the mid-infrared region can be interpreted on the basis of the phonon-assisted mechanism on carrier conduction and the electronic excitation. A tunneling spectrum here presented shows certain evidence of the phonon contribution. The characteristics of the long range superconductive proximity phenomena recently reported are also may be interpreted by this mechanism.

It is concluded from numerical examples for the well-known linear PN sequence families of a large range of periods that the mean-square cross-correlation value between sequences is the dominating parameter to the average signal-to-noise power ratio performance of an asynchronous direct-sequence (DS) code-division multiple-access (CDMA) system. The performance parameters derived by Pursley and Sarwate are used for numerical evaluation and the validity of conclusion is supported by reviewing the other related works. The mean-square periodic cross-correlation takes the equal value p (code period) for the known CDMA code families. The equal mean-square cross-correlation performance results from the basic results of coding theory.

A new method of multipath diversity combination is proposed for Direct Sequence Spread Spectrum (DS-SS) mobile communications. In this method, the transmitted signal from the base staion is the sum of a number of the same spread signal, each one delayed and scaled according to the delay and the strength of the multipaths of the transmission channel. As a result the received signal at the mobile unit will already be a Rake combination of the multipath signals. This new method is called Pre-Rake diversity combination because the Rake diversity combination process is performed before transmission By this method the size and complexity of the mobile unit can be minimized, and the unit is made as simple as a non-combining single path receiver. A theoretical examination of the Signal to Noise Ratio (SNR) and the Bit Error Rate (BER) results for the traditional Rake and the Pre-Rake combiners as well as computer simulations show that the performance of the Pre-Rake combiner is equivalent to that of the Rake combiner.

A simple method is given for obtaining new families of pseudonoise (PN) sequences based on chaotic non-linear maps. Such families are worse than the Gold and the Kasami families in terms of maximum correlation values. Nevertheless, such a method has several advantages: the generation is easy, and various families with an arbitrary family size and sequence period can be obtained primarily because non-linear maps have several parameters to be secret keys for communications security. Hence these sequences are good candidates of spreading sequences for CDMA.

The capacity of a cellular direct sequence code division multiple access system is investigated in situations with and without power control for both the reverse link (from mobile to base station) and the forward link (from base station to mobile). The capacity is defined as the number of simultaneous users per cell with a prespecified performance. A theoretical analysis of the effect of imperfect power control on the reverse link capacity is presented using an analytical model. To investigate the reverse link capacity without any form of power control, a general spatial user distribution is developed which is very suitable for analytical study of any multiple access system with the near-far effect problem. The performance of the reverse link of a CDMA system is also evaluated considering the users located in surrounding cells. Finally, the forward link capacity is studied considering multiple cells. Two possible forward power control schemes, namely carrier-to-interference ratio driven and distance driven systems, are discussed.

In this paper, we propose an adaptive RAKE receiver, which does not need to send the sounding signals and can track the fluctuations caused by fading. The channel estimation can be done by using a least squares method of the first and second equations suppressing additive noise and tracking the channel fluctuations. It is confirmed by computer simulations that the result has good agreement with theory and the performance is almost same as that of the conventional RAKE with the sounding signals.

Amorphous films of YBCO and BSCCO (2212) sputtered on MgO substrate were crystallized using zonemelt technique. For YBCO films, thin Ag intermediate layer was found to be effective in enhancing crystal growth and preferred orientation. Zone-melted BSCCO films included both (2201) phase and Cu(Sr, Ca)O2 in a form of dendritic crystallites. Tc's obtained for YBCO and BSCCO films were 70 and 75 K, respectively.

Bi2Sr2CuOx (Bi(2201)) thin films have been fabricated by atomic layer-by-layer deposition using ion beam sputtering (IBS) method. During the deposition, 14 wt%-ozone/oxygen mixture gas of typical pressure of 5.010-5 Torr is supplied with ultraviolet light irradiation for oxidation. XRD and RHEED investigations reveal that a buffer layer with compositions different from Bi(2201) is formed at the early deposition stage of less than 10 units cell and then Bi(2201) oriented along the c-axis is grown.

Structure and resistivity of BaBiOy were compared with those of Ba1-xLaxBiO3. Decrease in an average Bi valence from 3.91 to 3.03 for BaBiOy leads to an increase in the lattice parameter c from 4.37 to 4.53 , in the unit cell volume from 81 3 to 87 3, and in the resistivity from 10 Ωcm to 2105 Ωcm. It was found that the increase in the unit cell volume and the resistivity was due to change in the average Bi valence. The resistivity of BaBi1-xLaxO3 was compared with that of BaBiOy and Ba1-xLaxBiO3. We also found that pseudocubic Ba1-xLaxBiO3 remains semiconducting as well as pseudotetragonal BaBiOy. The high resistivity in the Ba1-xLaxBiO3 and the BaBi1-xLaxO3 will be useful to the application for the SIS junction.

A YBCO/CeO2/Au MIS structure (YBCO:YBa2Cu3O7y) is fabricated on a MgO(100) substrate with the help of the all-in-situ electron-beam and heater coevaperation system. The current-voltage (I-V) characteristics of the deposited YBCO film under various gate voltages are examined. Small modulation of the I-V characteristics by gate voltages can be observed. Meanwhile, the surface morphology is also studied by means of an atomic force microscope (AFM). The relation between the field effect and the surface morphology of a thin YBCO film is discussed.

In order to explain the temperature and frequency characteristics of high-Tc superconductors, a new model is proposed, which will be called the improved three-fluid model, where the momentum relaxation time τ is assumed to depend on temperature in the superconducting and normal states, respectively, although τ has been assumed to be independent of temperature for the conventional three-fluid model. According to this model, the complex conductivity σ1jσ2 and the surface impedance ZsRsjXs, where Rs is the surface resistance and Xs is the surface reactance, are expressed as a function of temperature. The temperature dependences of Zs and for a YBCO bulk estimated using this model agree very well with ones measured by the dielectric-loaded cavity method in room to cryogenic temperature. In particular, a peak of σ1 observed just below the critical temperature Tc in experiments, appeared in the calculated results based on this model. This phenomenon has been already known in the BCS theory. Thus, it is verified that this model is useful to explain the microwave characteristics of high-Tc superconductors in room to cryogenic temperature. On the other hand, the residual normal electron density nres4.2541023 m-3 and the total electron density nt7.3081024 m-3 are obtained by calculation. The ratio nres/nt0.058 can be used as figure of merit to evaluate material quality of high-Tc superconductors; thus it means that there is 5.8% nonpairing electron in this YBCO bulk.

Nojima and Fujita have found a universal relation, irrespective of temperatures T, between the reduced field hH/Hir(T) and the reduced quantity of magnetization hysteresis mΔM (T, H)/ΔM (T, H0), where Hir is the irreversibility field and ΔM(T, H) is the hysteresis of magnetization for YBa2Cu3Ox and Bi2Sr2CaCu2Ox films. We could explain this universal relation based on a scaling theory in a three-dimensional superconducting vortex-glass phase. The exponent ν derived by this relation coincides with that obtained by nonlinear I-V characteristics for YBa2Cu3Ox films.

This paper investigates a multihopping scheme for MFSK (Multilevel Frequency Shift Keying) /FH-SSMA (Frequency Hopping-Spread Spectrum Multiple Access) system. Moreover, we propose and investigate a modified decoding scheme for the coded MFSK/FH-SSMA system. In this multi-hopped MFSK/FH-SSMA system, several hopping frequencies per chip are assigned and transmitted in parallel in order to improve its frequency diversity capability for a fading channel. We theoretically analyze the performance of the multihopped MFSK/FH-SSMA system in a Rayleigh fading channel. Moreover, in the coded MFSK/FH-SSMA system, we propose a modified scheme of the error and erasure decoding of an error-correcting code. The modified decoding scheme utilizes the information of rows having the largest number of entries in the decoded time-frequency matrix. Their BER (Bit Error Rate) performance is evaluated by theoretical analysis in order to show the improvement in user capacity.