A novel dual-band internal antenna similar in size to the single-band internal antenna for cellular handsets is proposed. Our approach to realize a small and low-profile dual-band internal antenna is to use the dominant mode (TM10 mode) and the higher-order mode (TM30 mode). In order to use this approach for recent dual-band cellular systems it is necessary to lower the resonant frequency of the higher-order mode (TM30 mode). This motivated our development of a new antenna configuration with a slot on the radiation element of a quarter-wavelength shorted microstrip antenna to lower the resonant frequency of the TM30 mode. In this paper, the experimental and the analytical results for this antenna are presented. In the results, by adjusting the location and the length of the slot, the dual-frequency operation can be achieved with the frequency ratio (TM30 mode/TM10 mode) from 2 to 3. In addition, the enhancement of bandwidth is presented.

We have developed a new type of phase interpolation direct digital synthesizer (DDS) with a symmetrically structured delay generator. The new DDS is similar to a sine output DDS in that it produces lower spurious signals, but it does not require a sine look-up table. The symmetrically structured delay generator reduces the periodic jitter in the most significant bit (MSB) of the DDS accumulator. The symmetrical structure enables the delay generator to produce highly accurate delay timing and eliminates the need to adjust the circuit constants. Experimental results confirm frequency synthesizer operation in which the spurious signal level is reduced to less than that of the accumulator.

This paper presents a technique for miniaturization of microstrip line and coplanar waveguide for microwave integrated circuits by using airbridge technology. A theoretical analysis is given by a combination of the conformal mapping technique and the variational principle. Numerical results demonstrate significant effects on size reduction as well as wide range of the characteristic impedance variation due to the airbridge.

This paper presents a prediction of the millimeter-wave multipath propagation characteristics in the typical urban environment. To analyze the propagation in an outdoor environment, the three dimensional model based on the geometrical optics and the uniform geometrical theory of diffraction is employed. Prediction by the three dimensional ray tracing method needs a detailed map, which records locations and shapes of obstacles surrounding a transmitter and a receiver. It is usually difficult to create a complete map because tremendous data is necessary to describe the area structure. We propose, in this report, a three dimensional propagation model to predict the millimeter wave propagation characteristics by using the information available from only a map on the market. This approach gives us much convenience in the actual design. The modeled results are demonstrated and furthermore comparison are made between the simulated results and the experimental data.

When designing microwave amplifiers, it is the task to select values of the source (input generator) and load reflection coefficients for the transistor, to achieve certain amplifier performance requirements and ensure stability. For unconditionally stable transistors, simultaneous conjugate matching can be achieved using well-known design formulae. Under this condition, the gain is maximised, and the input and output ports are matched. On the other hand when the transistor is conditionally stable, source and load reflection coefficients are selected using graphical design methods, involving gain and stability circles. To eliminate the reliance on graphical techniques, this paper shows the derivation of explicit design formulae that ensure maximum gain for a minimum specified safety margin, with one port matched. In this work, the safety margin is the distance between the chosen source or load reflection coefficient and its respective stability circle. In a production environment, where the circuit and transistor parameters are subject to random variations, the safety margin therefore makes allowance for such variations. This paper shows that the design problem for conditionally stable transistors can be reduced from the selection of values for two complex variables (port terminations) to the selection of the value for just one scalar variable.

In this paper, efficient data transmission methods in wire and wireless interworking environments are studied in the case of handover occurring. To provide efficient mobile data service based on TCP, the wire and wireless interworking module with analysis function of TCP frame header protects the duplicated transmission of TCP frames. Also, by using the forwarding mechanism of status information and buffered data in the interworking module, it is possible to recover frame loss occurring in handover quickly. According to simulation results, proposed method has better performance than conventional method in view of throughput and delay. The reason is due to the fact that duplicated transmission is prevented and data recover is performed very quickly because buffered data is forwarded without loss in the case of handover.

Excitation of magnetostatic surface waves by slot line transducers is analyzed by using the integral kernel expansion method. The Fourier integral for the current density is derived in terms of an unknown normal component of the magnetic flux density in a slot region. The integral kernel is expanded into a series of orthogonal polynomials and then applying Galerkin's method to the resulting equation yields a system of linear equations for the unknown coefficients. Comparison of a numerical result by the present method with an experiment is in good agreement.

49-GHz operation for a state-of-the-art static frequency divider using FETs is achieved with high-performance 0.1-µm-gate InAlAs/InGaAs/InP HEMTs and high-speed double-layer interconnections with a thick low-permittivity BCB inter-layer dielectric film. An experiment shows that the propagation delay for the upper-layer line in the double-layer interconnections is less than half of that for the conventional single-layer interconnections directly on InP-substrate. The frequency divider with the double-layer interconnections is about 20% faster than the conventional one with the single-layer interconnections. A delay time analysis reveals that this speed increase is due to the decrease in interconnection propagation delay.

We propose a novel planar filter design for narrow-band applications. The filter consists of half-wavelength ring resonators with open gaps. This design has three advantages over conventional planar designs: a smaller size despite narrow bandwidth, a sharper skirt response at the passband edge without notch, an excellent out-band attenuation. We demonstrated these advantages by fabricating an 8-poles filter centered at 1.95 GHz with a 5 MHz bandwidth using YBCO films on a 2 inch diameter MgO substrate.

This article clarifies the requirements of VHE (Virtual Home Environment), issues and resolution for realization of VHE, when the environment will use Intelligent Network (IN) within IMT-2000 networks that is targeted to start in the year 2000. The IN aims the applicability of it's architecture to any kind of network. However, the following subjects need to be considered when IN will be used in the IMT-2000 network; The approach of the service related capabilities' extraction and specification; security management; cooperation between the service switching function within a core network and the IN function(s); cooperation between the mobility management function and the IN function(s); and consideration of mobile and fixed network convergence/integration. This article mainly focuses on these subjects. Some open issues like service/feature interaction and their tentative solutions are identified. Main results are; expandability of current IN to supporting IMT-2000 requirements, identification of key issues in providing VHE in IMT-2000, identification of candidate relationships, and associated issues for VHE. The currently available scenarios for VHE are evaluated from these points, and it is proposed that the specification to be common both for mobile and fixed network.

This paper presents two man-machine reliability models. A system consists of one machine unit, one operator, and one event detecting monitor. The machine unit has three states, normal, abnormal, and failed. The event detecting monitor may fail in two ways. If a machine unit becomes abnormal, the event detecting monitor sends a signal, and the operator takes necessary actions. If the operator fails in the action in the cause of human error, the machine unit goes down. The condition of the operator is classified into two types, good and bad. The time to repair, and the human error rate both depend on the condition of the operator. The MTTF is obtained by using a Markov model and numerical computation. Furthermore, the optimal operating period which minimizes the overall cost is decided by using computer methods. Some numerical examples are shown.

In this paper, we consider the Integrate-and-Fire Model (ab. IFM) with two periodic inputs. The IFM outputs a pulse-train which is governed by a one dimensional return map. Using the return map, the relationship between the inputs and the output is clarified: the first input determines the global shape of the return map and the IFM outputs various periodic and chaotic pulse-trains; the second input quantizes the state of the return map and the IFM outputs various periodic pulse-trains. Using a computer aided analysis method, the quantized return map can be analyzed rigorously. Also, some typical phenomena are confirmed in the laboratory.

In wireless ATM networks, the condition of the transmission channel fluctuates significantly as a result of many causes such as multipath, shadow phasing, and so forth. Several schemes have been proposed to take care of transmission errors. Some schemes are suitable for favorable channel conditions, while others are more suitable for unfavorable channel conditions. Thus, using a fixed error control scheme regardless of channel conditions is destined to be inefficient. This paper presents a dynamic error control scheme that dynamically selects an appropriate error control scheme according to the conditions of the transmission channel. Using this method, we can decrease both errors and the overhead of redundancy.

This paper proposes a new design method of nonlinear filtering and fixed-point smoothing algorithms in discrete-time stochastic systems. The observed value consists of nonlinearly modulated signal and additive white Gaussian observation noise. The filtering and fixed-point smoothing algorithms are designed based on the same idea as the extended Kalman filter derived based on the recursive least-squares Kalman filter in linear discrete-time stochastic systems. The proposed filter and fixed-point smoother necessitate the information of the autocovariance function of the signal, the variance of the observation noise, the nonlinear observation function and its differentiated one with respect to the signal. The estimation accuracy of the proposed extended filter is compared with the extended maximum a posteriori (MAP) filter theoretically. Also, the current estimators are compared in estimation accuracy with the extended MAP estimators, the extended Kalman estimators and the Kalman neuro computing method numerically.

In this paper, a general formula of disparity estimation based on Bayesian Maximum A Posteriori (MAP) algorithm is derived and implemented with simplified probabilistic models. The formula is the generalized probabilistic diffusion equation based on Bayesian model, and can be implemented into some different forms corresponding to the probabilistic models in the disparity neighborhood system or configuration. The probabilistic models are independence and similarity among the neighboring disparities in the configuration. The independence probabilistic model guarantees the discontinuity at the object boundary region, and the similarity model does the continuity or the high correlation of the disparity distribution. According to the experimental results, the proposed algorithm had good estimation performance. This result showes that the derived formula generalizes the probabilistic diffusion based on Bayesian MAP algorithm for disparity estimation. Also, the proposed probabilistic models are reasonable and approximate the pure joint probability distribution very well with decreasing the computations to O(n()) from O(n()4) of the generalized formula.

Newton based adaptive algorithms are among the algorithms which are known to exhibit a higher convergence speed in comparison to the least mean square (LMS) algorithms. In this paper we propose a simplified Newton based adaptive algorithm for an adaptive infinite impulse response (IIR) filter implemented using cascades of second order allpass filters and a finite impulse response (FIR) filter. The proposed Newton based algorithm avoids the complexity that may arise in the direct differentiation of the mean square error. The analysis and simulation results presented for the algorithm, show that the property of convergence of the poles of the IIR ADF to those of the unknown system will be maintained for both white and colored input signal. Computer simulation results confirm an increase in convergence speed in comparison to the LMS algorithm.

The feasibility of a dynamic zone configuration technique has been investigated. To make it easy to implement this technique in wireless communication systems, a simplified method for determining a suitable weight vector by using the least squares (LS) methods was developed. Simulations showed that the developed system is more effective than the present omni-directional zone system. Moreover, combining dynamic zone configuration technique with dynamic channel assignment strategy reduced blocking rate, forced call termination ratio, and required transmission power.

By integrating three networks, namely, Public Switched Telephone Network (PSTN), Personal Handy-Phone System (PHS) and Intelligent Network (IN) to work together as a Personal Communication Telephone (PCT) service to be offered in the Bangkok metropolis area, the PCT service enables the advent of three new concepts, first, using the same telephone number as that of the fixed line to become a "Personal Number," second, a cell coverage designed to cover larger areas than that of the PHS (by changing hand-out threshold level from 33 dBµV to 30 dBµV and hand-in threshold level from 30 dBµV to 25 dBµV) in order to reduce the muting time during the handover process and provide higher mobility at up to 60 kilometers per hour, and third, a technique of "2 carriers per area" to reduce "call drop." All these techniques will be described in this paper.

The conductor-backed asymmetrical coplanar waveguide or micro-coplanar strip (MCS) line has been analyzed. The conformal mapping method is used to calculate the quasi-static effective permittivity εeff and characteristic impedance Z0. The computed results of the present work are found to be in good agreement when compared with the results obtained using the method reported by Yamashita et al. [1] and experimental values reported in [2]. A novel MCS end-coupled half-wavelength long resonator filter is designed to illustrate an application of the present work. The designed filter has 4% bandwidth at a center frequency of 10.5 GHz. The measured insertion loss is approximately 3.4 dB. One of the main advantages of the MCS filter compared to the CPW filter is that bond wires do not have to be used to maintain both coplanar ground at the same potential. The MCS filter is also easily integrable with other planar components and does not require a complicated transition to microstrip.

The world of mobile communications has undergone dramatic changes in recent years. Since the Personal Digital Cellular (PDC) system of digital mobile communications became commercially available in Japan in 1993, the number of subscribers has increased to the extent that almost 30% of the Japanese population are subscribed. Furthermore, the increasing sophistication of communications, such as the growing popularity of the Internet and expansion of our spheres of existence, have led to demand for new applications, such as use on a global scale. Many new technologies are also being introduced, such as the IMT-2000 system and the IN system which are slated to be introduced at the end of 2000. Based on the above and in view of the increasing scale and sophistication of mobile communications networks, the time has come to reexamine the configuration within networks of SCPs, which perform subscriber data management and service control. This paper focuses on the functions of subscriber data management and service control, classifies data necessary for mobile networks and using the signal number of common networks as a guide considers the optimum arrangement of data and control nodes. The paper also examines reliability measures for SCPs to ensure the reliability of increasingly large-scale networks.