Multi-server queueing systems with traffic intensity which vary according to an irreducible Markov chain are considered. We will show that the probability distribution for the number of customers in these systems can be expressed by an algebraic sum of geometric series with appropriate coefficients satisfying some interesting properties. To study these properties a detailed analysis of the denominator of the partial generating functions of the number of customers in the system is presented. These coefficients allow us to explain the behavior of the system under different traffic conditions. First, we derive a general expression for the probability distribution and then compare this result with that of the Zukerman and Rubin's model. One special section is devoted to the case of an arbitrary number of phases. Some numerical results are also provided and discussed to support the theoretical results.

A flexible, Product-structured stchastic process model may be represented by the modified Bessel pdf (probability density function) of the third kind and the Struve cdf (cumulative distribution function) which were formerly represented by a single integral and a double integral respectively. These transcendental functions representation may be used for a rapid and precise computation of the pdf and cdf. The explicit representation of moments by a gamma function is also given.

A high-density cable structure, containing fiber ribbons inserted tightly into slots, is proposed for a high-fiber-count feeder line. This paper describes theoretical and experimental investigations on the residual strain due to inserting ribbons into a helical slot in this cable. The residual strain caused by different insertion methods is clarified and a strain suppression method is discussed. Based on the results, 600-fiber cable is manufactured and the transmission and mechanical performances are confirmed to be excellent.

Waveform moment describes one of the characteristics of the given signal wave. Though basic definitions are quite simple, use of waveform moment and extended waveform moment is shown in numerous areas of DSP. Expressions in both time domain and frequency domain are found and using these, criterion for excluding Nyquist filter possibility, evaluation of frequency characteristics for Elliptic filter, method for determining frequency response for not all points etc. are derived. It is shown that analysis using extended waveform moment method becomes simpler than the direct application of known standard methods.

Switching characteristics of bistable distributed feedback lasers are analyzed theoretically. The results predict that switch-on speed as well as switch-off speed is improved by a factor of two or more by detuning the Bragg wavelength to shorter wavelength from the wavelength at which the gain is the maximum. This improvement is mainly due to enhancement of the differential gain through the detuning effect.

The Josephson triode is a superconducting three terminal device and is used as a heterodyne mixer which has the internal frequency-variable local oscillator. We have fabricated the Josephson triode by integrating the planar-type Josephson junctions and investigated their current-voltage characteristics.

We have defined the number of degrees of freedom of order n (the n-th order NDF) kn(T) of a piece of an ergodic stationary random process X(t) of length T by using the variance of an estimate Zn(T) of the n-th moment of X(t). Zn(T) is here calculated by averaging Xn(t) over a time interval T. The NDF denotes a quantitative measure of the effective number of independent or uncorrelated random variables Xn(ti) included in the time interval T. Correlation times and equivalent bandwidths, which are important in random processes and some fields in physics, are deduced from the NDF's. In this paper, we study the NDF's from the viewpoint of information theory. First, a simple information measure Jn(T) based on the uncertainty (Shannon's entropy) of Zn(T) is defined. It is natural that we introduce such Jn(T) because kn(T) has been defined based on the variance of Zn(T). We show that the relation J1(T)(log k1(T))/2 and the asymptotic relation (log kn(T))/(2Jn(T)) 1(n2, 3, ) as T . Second, a measure In(T) of the information gained about the n-th moment of X(t) by the observation of the Zn(T) is defined in the style of Shannon. The relation I1(T)(log k1(T))/2 and the asymptotic relation I2(T) (log k2(T))/2 as T are deduced. Last, we define a measure Fn(T) as the information in the style of Fisher about the n-th moment contained in the estimate Zn(T) and we show that F1(T)k1(T) and F2(T) approaches asymptotically k2(T) as T . As a result, the n-th order NDF kn(T), which was originally defined by using the variance of Zn(T), is almost equivalent to one defined by using the entropy of Zn(T). Further, the 1st and 2nd order NDF's show the amount of information about the 1st and 2nd moment of X(t) which are contained in Z1(T) and Z2(T) respectively.

This paper describes the first realization of the APSK system with a honeycomb constellation (HC) for high capacity digital radio links. Partial Gray coding method to improve receiver sensitivity is also described. It is shown that the 68 APSK modulation can increase receiver sensitivity by 0.7 dB compared with a 64 QAM. Possibility of the system with the HC using the present state of the art is confirmed by theoretical estimation of tolerances for modem impairments. Techniques necessary to realize a system with the HC are also described. Using the techniques, the 68 APSK modem with the HC was experimentally fabricated. The modem we fabricated has a transmission capacity of 90 Mbps within the FCC-authorized bandwidth of 20 MHz in the 4 GHz band. The BER performance and signature for multipath fading have been measured. It is confirmed that the signature of the 68 APSK is almost the same as that of the conventional 64 QAM. The signature improved using 5 tap transversal equalizer correspons to an outage of 2 seconds per year per hop.

This paper reports a high-speed time division switching system using GaAs ICs. It also describes high-speed switching technologies including the fabrication of a 4-channel time division switch, a multi/ demultiplexer and peripheral circuit ICs, each having more than a 2 Gb/s throughput capability. In addition, such key factors as synchronous LSI operation, optimum circuit board designing and LSI packaging are presented. Finally it reports a great success in High Definition TV (HDTV) time division switching operation.

This paper presents advantages of sputtering technique using a ceramic target instead of a conventional powder target for preparing ZnS: TbFx emitting layer in electroluminescent devices.

Continuous-time MOSFET-capacitor filters have quite a serious problem, that is, MOS transistors' nonlinearity drastically reduces the filters' dynamic ranges. Czarnul proposed an MOS resistive circuit with high degree of linearity and solved this problem. The method, however, requires two capacitors for each integrator. Consequently, the chip area and manufacturing cost will increase. This paper proposes a new single capacitor integrator which can cancel the nonlinearity of transistors. The integrator is applied to a canonical continuous-time filter synthesis with high linearity. A total harmonic distortion less than 0.33% is obtained by SPICE analysis.

This letter proposes a simulation of an input part of an LCR filter. The proposed method used voltage followers as an active element. As an example, a realization of a 3 MHz third-order maximally-flat filter is presented.

The paper proposes a method of variable-to-fixed length binary data encryption in the class of conventional cryptosystems. An encryption algorithm reduces an interval of the integers that mean candidates of cryptograph according to a key and messages. A decryption algorithm traces the trajectory of reduction of interval according to the key and cryptographs to reproduce the messages. These algorithms are executable with simple arithmetics on several registers. However, wiretappers without knowledge on the key cannot correctly reproduce messages since they cannot trace the trajectory of reduction. The exhaustive cryptanalysis identifies the correct decryption procedure only from cryptographs. The comparing cryptanalysis identifies the correct decryption procedure from some pairs of message and cryptograph. Asymptotic evaluations for the computational complexity of cryptanalysis show a satisfactory endurance against wiretapping.

A rigorous and systematical analysis of the performance of the power inversion adaptive array is shown where the method of moments is applied to analyze the antenna system and the electric field intensity is used as the descriptive parameter of the incident signals. This method can be easily extended to analyze adaptive arrays with arbitrary array structure and with wire antenna elements other than monopoles and dipoles. To show the adavantages of the method, the performance of adaptive arrays with mutual coupling effect among the array elements is considered and the inverted-F antennas (IFA) are used as the elements. The steering vector in the presence of mutual coupling which differs from that in the absence of the mutual coupling is derived. The output signal-to-interference-plus-noise ratio (SINR) of two kinds of adaptive arrays composed of IFA elements is computed and the importance of properly selecting steering vector is demostrated by means of the quiescent array patterns and the output SINR performance.

Potential Controlled (POCO) Laser is a new type of laser which utilizes a character that the lasing gain effectively increases and the threshold current level can be reduced by putting a large number of holes into the active layer. The basic idea of this laser is very close with the so called modulation doping in the multi-quantum-well structure. In this paper, the optimum configuration of the POCO laser is theoretically examined in detail. Possibility to get a very low threshold current lower than 100µA is predicted.

This paper studies the model reduction of separable denominator multi-dimensional (SD M-D, M is used as an integer) linear, shift-invariant systems (systems for short). First, it shows that the controllability, observability and stability of an SD M-D system are completely determined by M 1-D multi-input multi-output systems, which are referred to as the characteristic systems in this paper. Then the balanced realizations of SD M-D systems are defined, and a synthesis method of such realizations is given. Finally, a model reduction method based on the balanced realizations is proposed. Validity of this method is illustrated by a numerical example of a 3-D system.

A method of designing digital FIR transmitter and receiver filter pairs for classes and partial response systems is presented. The truncated ideal impulse response of a specified class is used as an initial response of the filter pair in cascade. For class I filter, the impulse response has an even symmetry, then its transfer function is a linear phase lowpass function of case 1 or case 2. Therefore, the passband zeros occur in mirror image quadruplet (and doublet) and the stopband zeros occur on the unit circle. The initial stopband attenuation slopes gradually up as frequency increases. To get an equiripple stopband attenuation for both filters, the passband zeros inside and outside the unit circle are assigned to transmitter and receiver filters respectively, then the stopband zeros of each filter are redetermined. Both filters form a matched filter pair. Next, the passband zeros of the filter pair are adjusted to give minimum intersymbol interference (ISI) in the overall response. For class filter, the impulse response has an odd symmetry and its transfer function is a linear phase lowpass function of case 3. In this case, the filter pair are designed to have equiripple and nearly the same stopband attenuation. Zero ISI approximation is performed similarly. Two design examples are shown. One is a 57th order class I filter pair having 0.05% ISI. The other is 61st order transmitter and 57th order receiver class filter pair whose ISI is 0.2%.

A traveling-wave semiconductor laser amplifier with a thick, short active layer is optimum for achieving insensitive signal gain to polarization while maintaining high-output power and low-noise characteristics.

A nobel Hilbert transformer is realized by adapting instantenuous spectrum analysis, namely short time discrete Fourier transform (ab. in ST-DFT). The ST-DFT Hilbert transformer is substantiated to be almost ideal in both phase shifting and amplitude characteristics via experiments for unit sample response and analyzing its power spectrum.

Sufficient conditions are given for the transient response of a class of MOS digital circuits composed of inverter-type logic gates, transfer gates and RC ladder networks to vary monotonically with the variations in the characteristics of circuit elements.