This paper presents a novel dead-beat synchronization scheme and applies it to communications in discrete-time chaotic systems. A well-known Henon system is considered as an illustrative example. In addition, a Henon-based image processing application effectively exploits the proposed scheme's effectiveness.

This paper proposes and investigates the adaptive single-user receiver with co-channel interference (CCI) canceller based on orthogonalizing matched filter (OMF) using the multi-dimensional (multi-D) lattice filters for DS/CDMA in a multipath environment. A conventional single-user receiver using OMF cannot correctly cancel CCI in the presence of multipath in a channel, because the desired user's signal component and other users' intersymbol interference (ISI), due to multipath, still remain at the output of OMF, and then a correct replica of CCI cannot be generated. The proposed receiver can solve this problem because a multi-D IIR lattice filter can distinguish the desired user's signal component from the other users' ones and remove the ISI of all users' signals by Gram-Schmidt orthogonalization. And a multi-D FIR lattice filter can selectively regenerate undesired users' signal components which contain neither the desired user's signal component nor ISI. The proposed receiver based on multi-D lattice filters can apply orthogonality property of the OMF to not only a direct wave but also to delayed waves in a multipath channel. Since the proposed receiver does not have to know spreading codes of multiusers except the desired user, it will be applicable at a mobile terminal in the forward link in a multipath environment. Computer simulations show the proposed receiver have capability to cancel the CCI and converges fast in a multipath channel.

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 the radiation characteristics of a circularly polarized conical beam spherical slot array antenna for applying to the mobile satellite communication subscriber. The structure of the antenna is easy to fabricate i. e. , a ring of perpendicular slot pairs cut on an outer surface of a concentric conducting spherical cavity enclosed by the conducting conical surface with the simple feeding structure, and a linear electric probe excited at the center of the inner surface of the cavity. Radiation fields of a spherical slot array antenna are calculated by superposing the patterns of all the slots. From the numerical results of the radiation pattern, in both elevational and azimuthal planes, it is obvious that the conical beam is realized. The elevational beam direction is low, which is suitable for installing in the land mobile subscriber unit located far from the equator. The tracking system is not necessary because the azimuthal pattern is omnidirectional. Directivity of the antenna for various spherical radii and angles of slot positions are illustrated as the guidelines for the design. Experimental results are in good agreement with the predictions.

Hierarchical macrocell/microcell architectures have been proposed for future cellular mobile communication. The performance analysis for the hierarchical cellular system becomes an important issue. In this paper, extending the analytical methods from[1][2][8], assuming that the imperfect power control follows log-normal statistics, and employing different attenuation models for macrocells and microcells, the capacity plane and outage probability of the system are examined and quantified with and without perfect sectorization. From the numerical results of parameters of IS-95 protocol, the high user capacity and lower outage probability may be expected in the case of relatively tight power control and narrower overlap between sectors. These results are compared with the previously published CDMA nonhierarchical cellular system estimation. When we employ the hierarchical cellular system, we can increase the user capacity 2.3 times with the same bandwidth 1.25 MHz than the one of the nonhierarchical cellular system.

This paper proposes a group synchronization mechanism which synchronizes slave destinations with the master destination for stored media in multicast communications. At the master and slave destinations, an intra-stream and an inter-stream synchronization mechanisms which were previously proposed by the authors are employed to output the master media stream and slave media streams synchronously. We achieve group synchronization by adjusting the output timing of the master media stream at each slave destination to that at the master destination. We also deal with control of joining an in-progress multicast group. The paper presents experimental results using an interconnected ATM-Ethernet LAN, which is a kind of heterogeneous network. In our experimental system, stored voice and video streams are multicast from a source to plural destinations distributed among distinct networks, and then they are synchronized and output. Furthermore, the paper demonstrates the effectiveness of the mechanism.

This study is aimed to explore a fast convergence method of blind equalization using higher order statistics (cumulants). The efforts are focused on deriving new theoretical solutions for blind equalizers rather than investigating practical algorithms. Under the common assumptions for this framework, it is found that the condition for blind equalization is directly associated with an eigenproblem, i. e. the lag coefficients of the equalizer can be obtained from the eigenvectors of a higher order statistics matrix. A method of blind phase recovery is also proposed for QAM systems. Computer simulations show that very fast convergence can be achieved based on the approach.

In this paper, the performance of some communication systems using chaos synchronization is evaluated and compared. A new channel model taking the attenuation, impedance mismatch and noise into account, is proposed for the performance evaluation. The evaluation of bit error rate is done for both ideal and non-ideal conditions using the channel model. It is confirmed that some chaos-based communication systems have a good performance compared with conventional analog communication schemes.

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.

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.

Design of circularly polarized active antennas of dual-fed square patch type is given, and spatial power combining and phased array operation of the antennas have been successfully achieved. In a phased array experiment of the arrays with two and three active antennas by the method of varying their free-running oscillation frequencies, we obtained the scan angles from -12 to +13 and those from -13 to +13, respectively, and good axial ratios together with high spatial power-combining efficiencies.

A cavity-backed two-element rectangular loop slot antenna for circular polarization is presented and investigated by using the generalized network formulation based on the equivalence principle. By applying the method of moments, the magnetic current including the effect of the cavity is obtained for a thin rectangular loop slot. Two short-circuiting points are introduced on the slots to get circular polarization and symmetrical radiation pattern. The axial ratio bandwidth (3 dB) with VSWR (2) reaches 7.6%. The measured and computed results are in good agreement.

This paper presents a novel full-band optoelectronic system extending the capabilities of vector network measurements to the millimeter-wave regime both in small and large signal analysis. The design of the measurement system is made with an emphasis on its practicability for real-world applications using all 1.55-µm-wavelength-based photonic technology. We demonstrate the performance of this network analyzer by measuring the 2-port S-parameters of a HEMT device. The accuracy of the results is also shown by comparing them with conventional 50-GHz electronic measurements. The transit frequency of the active device of over 100 GHz is directly measured for the first time to our knowledge.

One effective way to make a large-capacity mobile communication system is to use a microcellular system. One way to do this is to place the base station antennas lower than the surrounding buildings. This result in what is called a street microcellular system. We previously presented basic simulation results evaluating the performance of a different-sized cell combination algorithm (DCC) designed to avoid the problems due to an unbalanced distribution of traffic in street microcellular systems. In this paper, we present the results of simulations evaluating the performance of an improved active different-sized cell combination method (ADCC) that controls the transmission power of each base station.

The transfer function or impulse response of propagation path is one of the most fundamental and most important quantities for equalizing the distortions cased by multipath propagation. In this paper, precise identification of the transfer function of the propagation path under multipath condition is presented. By use of the least-square method, uncertainty due to white noise is sufficiently eliminated.

We propose a learning algorithm for self-organizing neural networks to form a topology preserving map from an input manifold whose topology may dynamically change. Experimental results show that the network using the proposed algorithm can rapidly adjust itself to represent the topology of nonstationary input distributions.

In order to investigate the dynamic behavior of quantized interconnection neural networks on neuro-chips, we have designed and fabricated hardware neural networks according to design rule of a 1.2 µm CMOS technology. To this end, we have developed programmable synaptic weights for the interconnection with three values of 1 and 0. We have tested the chip and verified the dynamic behavior of the networks in a circuit level. As a result of our study, we can provide the most straightforward application of networks for a dynamic pattern classifier. The proposed network is advantageous in that it does not need extra exemplar to classify shifted or reversed patterns.

An upper bound on frame error rate (FER) for generalized concatenated convolutional codes (GCCC's) with iterative decoding is presented. The GCCC is a generalized concatenated code which consists of an inner binary convolutional code and outer Reed-Solomon codes. The FER bound is derived from the average weight enumerator of the inner code. We can optimize the configuration of the outer code since the FER bound can be easily computed. Some optimum outer code profiles will be shown. The results show that combination of GCCC and iterative decoding attains fairly small frame error probability (PB 10-13, Eb/N0 = 6 dB) with relatively simple component code (16-state convolutional code and Reed-Solomon code of length 32).

With the progress of LSI technology, the electronic device size is presently scaling down to the nano-meter region. In such an ultrasmall device, it is indispensable to take quantum mechanical effects into account in device modeling. In this paper, we first review the approaches to the quantum mechanical modeling of carrier transport in ultrasmall semiconductor devices. Then, we propose a novel quantum device model based upon a direct solution of the Boltzmann equation for multi-dimensional practical use. In this model, the quantum effects are represented in terms of quantum mechanically corrected potential in the classical Boltzmann equation.