An integrator is quite a suitable active element for high-speed filters. The effect of its excess phase shifts, however, is severe in the case of high-Q filter realization. The deterioration due to the excess phase shifts cannot be avoided when only integrators are used as frequency-dependent elements like in leapfrog realization. This paper describes a design of second-order high-speed and high-Q filters with low sensitivity to excess phase shifts of integrators by adding a passive RC circuit. The proposed method can drastically reduce the effect due to the undesirable pole of an integrator, which is the cause of the excess phase shifts, compared to conventional filters using only integrators. As an example, a fourth-order bandpass filter with 5-MHz center frequency and Q=25 is implemented by the proposed method on a monolithic chip. The results obtained here show quite good agreement with the theoretical values. This demonstrates effectiveness of the proposed method and feasibility of high-speed and high-Q filters on a monolithic chip.

In order to evaluate multipath signal strengths reflected by mountain, a fundamental equation is derived for both cases where antenna beams are larger and smaller than a reflecting plane, assuming that reflection consists of absoption and scattering at the mountain surface. Absorption loss at a mountain surface was measured on a model propagation path by using sharp beam antennas to separately pick up the mountain-reflected signal.

In this paper, we study the performance of convolutional coding using an error-and-erasure correction Viterbi decoder for π/4-shift QDPSK mobile radio transmission. The receiver uses received signal envelope as channel state information to erase unreliable symbols instead of making explicit decision before decoding. The performance study is carried out over frequency-selective fading channel with additive white Gaussian noise, co-channel interference and propagation delay spread. The results show that decoding with symbol erasure can significantly improve the system transmission performance compared to decoding without symbol erasure.

In this paper, the effects of the grouping and the addressing methods on the accuracy and the response time in a visual search task were investigated. Four grouping conditions (4, 8, 16 and 32 groups) and four addressing methods (random, ordered, cartesian and polar) were selected in the experiment. For each combination of grouping and addressing methods, subjects repeated the search task 30 times. No remarkable differences of the percent correct were observed both among the levels of grouping and among the addressing methods. The mean response time increased with the increase of the number of groups. Moreover, the interaction between addressing methods and grouping for both percent correct and response time was clarified.

Complex filters are used to synthesize real filters in digital signal processing, but few in analog one. In this paper, we propose a leapfrog synthesis of complex analog filters. By shifting frequency response of an LCR network along the ω-axis, we have a complex filter with imaginary resistances, which is called an "LCRRi filter." The complex resonator is then used to simulate series- or parallel-arms of the LCRRi filter. We analyze nonideal properties of the complex resonator due to finite gain-bandwidth product of operational amplifiers and propose a compensation method to put a pole on correct location. Experimental results show good performance of the proposed method.

In this paper, we will define Kleene-Stone logic functions which are functions F: [0, 1]n[0, 1] including the intuitionistic negation into fuzzy logic functions, and they can easily represent the concepts of necessity and possibility which are important concepts of many-valued logic systems. A set of Kleene-Stone logic functions is one of the models of Kleene-Stone algebra, which is both Kleene algebra and Stone algebra, as same as a set of fuzzy logic functions is one of the models of Kleene algebra. This paper, especially, describes some algebraic properties and representation of Kleene-Stone logic functions.

High Tc superconducting (SC) active antennas made from thin films were produced by the magnetron sputtering method. The SC active antennas are found to be good for detecting 50GHz electromagnetic waves. Furthermore, the improvement of the sensitivity of the SC active antennas is demonstrated with the use of a corner reflector.

We analyze the average bit error probability (BER) performances of BPSK with pilot tone in the frequency-selective Rayleigh fading channel, which can be characterized by the delay power spectrum due to multipath fading. The analysis is based on the error probability conditioned on the receiver input envelope in order to investigate the diversity effects. With taking into consideration of predetection receiving filter characteristic, the average BER is evaluated by treating the normalized standard deviation (rms delay spread), τ0/T (T: digital symbol period), of the delay power spectrum, BT product of predetection filter and power distribution between BPSK signal and pilot tone as parameters. The results show that the optimum power distribution (kopt) can be determined mainly according to the ratio (α) of tone extracting filter bandwidth to predetection filter bandwidth provided that α is small. For fixed α, τ0/T and kopt corresponding to α, optimum BT product, which minimizes the error rate, exists and the value is dependent on signal energy per bit to noise power spectral density ratio (SNR), and is affected slightly by the delay power spectrum shapes. In this paper, one-sided exponential, Gaussian and double spike shapes are treated as delay power spectrum shapes. On the average BER characteristics due to delay spread with fixed α, BT and kopt corresponding to α, the delay power spectrum shape is of no importance for τ0/T0.06. For τ0/T0.06, in the case of double spike delay power spectrum, BER is less than that for the other two spectral shapes. By making use of the selection diversity with 2-branch and predetection filter with optimum BT product, SNR can be improved by 16dB at the average BER of 10-4.

This paper presents the successful performance of an optical waveguide phase controller for microwave signals generated by heterodyne photodetection. A 22 optical waveguide structure with four optical phase shifters was fabricated on a LiNbO3 substrate. As a result of heterodyne photodetection of two optical signals from wavelength-tunable laser diodes, two microwave signals at 585 MHz were generated and phase shifted in the manner of electro-optical phase retardation. The monolithic waveguide structure allowed linear phase shifting more than 1800 degrees. Similar phase shifting performances were also confirmed over a wide microwave frequency range from 300 MHz to 1.3 GHz. The optical waveguide structure demonstrated here will be applicable to fiber-optic fed microwave systems such as a phased array antenna.

An information retrieval system based on a dynamic thesaurus was developed utilizing the connectionist approach. The dynamic thesaurus consists of nodes, which represent each term of a thesaurus, and links, which represent the connections between nodes. Term information that is automatically extracted from user's relevant documents is used to change node weights and generate links. Thus, node weights and links reflect a user's interest. A document retrieval experiment using the dynamic thesaurus was conducted in which both a high recall rate and a high precision rate were achieved.

We propose a new type of Graph Rewriting Systems (GRS) that provide a theoretical foundation for using the reduction method which plays an important role on analyze network reliability. By introducing this GRS, several facts were obtained as follows: (1) We clarified the reduction methods of network reliability analysis in the theoretical framework of GRS. (2) In the framework of GRS, we clarified the significance of the completeness in the reduction methods. (3) A procedure of recognizing complete systems from only given rewriting rules was shown. Specially the procedure (3) is given by introducing a boundary graph (B-Graph). Finally an application of GRS to network reliability analysis is shown.

Theoretical prediction of propagation is required for the future urban mobile communications, in order to make possible precise and universal prediction for arbitrary conditions. The necessity and the fundamental concept of theoretical prediction are introduced, and the theoretical prediction of mean field strength in urban areas is reviewed and discussed. Theoretical method is important particularly in prediction of multipath delay characteristics, in relation to the prediction of error rates in digital mobile radio communications.

For a method to control the microwave coupled lines with optically induced plasma effectively, we propose the selective mode-control method, which restricts controlled modes to a selected one. We analyzed the basic characteristics of coupled microstrip lines theoretically by using the spectral domain technique and indicated the effectiveness of this method with the aid of numerical results. Further, we designed an optically controlled change-over switch as an application of this method.

This paper reports the influence of optical reflection induced noise and distortion for optical fiber feeder systems for microcellular mobile communication systems. Since the optical feeder requires very wide dynamic range, noise and distortion must be suppressed to an extremely low level. From optical transmission experiments and theoretical analysis, the basic characteristics of the reflection induced noise and distortion were investigated. By using these results, it was estimated that, for currently used analog mobile telephone systems, the number of connectors with 35 dB reflectance must be limited to less than 17, in order to suppress the noise caused by the connector reflections. Moreover, it was confirmed that the reflection induced distortion drastically decreases according to the increase of the length between reflectors. Therefore, the distortion can be suppressed by expanding the connector spacing to more than 7 meters.

This paper analyzes the performance of the capacity controlled radio system under a frequency selective fading environment. This system controls the number of modulation levels according to the number of active subscribers. In the analysis, we consider the capacity controlled system either with or without adaptive equalizer. As the results of analysis, it is clarified that the system is superior to the conventional fixed capacity system, and can be considered as a good countermeasure for multi-path fading. And it is found that there exists a synergistic effect due to capacity controlling and adaptive equalizing.

A theoretical method is required for prediction of mean field strength in land mobile radio systems, instead of the conventional empirical methods. Feasibility study of theoretical prediction using the ray-tracing method, was made in a 1.2GHz band for a model of a small-cell system. Theoretical values showed better agreement with the measured, when diffraction around the side edges of a building is taken into account. Comparison between mean field strengths in summer and winter suggested the seasonal variations in attenuation due to trees.

Kleene-Stone algebra is both Kleene algebra and Stone algebra. The set of Kleene-Stone logic functions discussed in this paper is one of the models of Kleene-Stone algebra, and they can easily represent the concepts of necessity and possibility which are important concepts for many-valued logic systems. Main results of this paper are that the followings are clarified: a necessary and sufficient condition for a function to be a Kleene-Stone logic function and a formula representing the number of n-variable Kleene-Stone logic functions.

Given an integer N, it is easy to determine whether or not N is prime, because a set of primes is in LPP. Then given a composite number N, is it easy to determine whether or not N is of a specified form? In this paper, we consider a subset of odd composite numbers +1MOD4 (resp. +3MOD4), which is a subset of odd composite numbers consisting of prime factors congruent to 1 (resp. 3) modulo 4, and show that (1) there exists a four move (blackbox simulation) perfect ZKIP for the complement of +1MOD4 without any unproven assumption; (2) there exists a five move (blackbox simulation) perfect ZKIP for +1MOD4 without any unproven assumption; (3) there exists a four move (blackbox simulation) perfect ZKIP for +3MOD4 without any unproven assumption; and (4) there exists a five move (blackbox simulation) statistical ZKIP for the complement of +3MOD4 without any unproven assumption. To the best of our knowledge, these are the first results for a language L that seems to be not random self-reducible but has a constant move blackbox simulation perfect or statistical ZKIP for L and without any unproven assumption.

This paper describes a general interface system for speech input and output and a dialog management system, MASCOTS, which is a component of the interface system. The authors designed this interface system, paying attention to its generality; that is, it is not dependent on the problem-solving system it is connected to. The previous version of MASCOTS dealt with the dialog processing only for the speech input based on the SR-plans. We extend MASCOTS to cover the speech output to the user. The revised version of MASCOTS, named MASCOTS II, makes use of topic information given by the topic packet network (TPN) which models the topic transitions in dialogs. Input and output messages are described with the concept representation based on the case structure. For the speech input, prediction of user's utterance is focused and enhanced by using the TPN. The TPN compensates for the shortages of the SR-plan and improves the accuracy of prediction as to stimulus utterances of the user. As the dialog processing in the speech output, MASCOTS II extracts emphatic words and restores missing words to the output message if necessary, e.g., in order to notify the results of speech recognition. The basic mechanisms of the SR-plan and the TPN are shared between the speech input and output processes in MASCOTS II.

The diffraction of a plane electromagnetic wave by a parallel-plate waveguide cavity with a thick planar termination is rigorously analyzed for both the E and the H polarization using the Wiener-Hopf technique. Introducing the Fourier transform for the unknown scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are solved exactly in a formal sense via the factorization and decomposition procedure. Since the formal solution involves an infinite number of unknowns and branch-cut integrals with unknown integrands, approximation procedures based on rigorous asymptotics are further presented to yield the approximate solution convenient for numerical computations. The scattered field inside and outside the cavity is evaluated by taking the inverse Fourier transform and applying the saddle point method. Representative numerical examples of the monostatic and bistatic radar cross sections are presented for various physical parameters, and the scattering characteristics of the cavity are discussed in detail.