A new beam tilt dipole array antenna in a simple structuer has been developed for indoor base stations in the 1.9 GHz band. The antenna comprises a radiator and skewed off-center parasitic elements placed around the radiator. With this stucture, the main beam of the array antenna can be tilted for mobile terminals reception by the effect of mutual coupling. Studies on tilt characteristics for antenna dimensions and tilt mechanism by precise current measurements have clarified the operating principle. The antennas with a fan beam and an omnidirectional pattern have been designed. The measured tilt angle was varied in the range of 0 to 26 with little alteration of the horizontal radiation patterns.

A simplified equivalent circuit, which is useful in L-band, of switching MOSFET is presented. The MOSFET model accounts for the relatively low resistivity of Si substrate. By using this circuits, the relationship between the MOSFET equivalent circuit parameters and a series-shunt FET connected SPDT switch characteristics has been revealed. In order to evaluate the relationship mentioned above, enhancement type NMOSFETs and a SPDT switch with the FETs are fabricated. The MOSFET equivalent circuit parameters at L-band were extracted from measured small-signal S-parameters of the FETs. The measured switch characteristics are fairly good agreement with the simulated results which has been accomplished by using the MOSFET model. This good agreements shows the effectiveness of the MOSFET model which is presented here.

An extended configuration of a stepped impedance comb-line filter is presented. The parallel stripline sections of stepped impedance resonators are coupled electromagnetically and a coupling capacitor is introduced. The creation of an attenuation pole near the passband was detailed. A design procedure for the two-pole extended filter is derived from an analysis using even-and odd-mode impedances. Experimental filters were constructed by ceramic lamination technique. They exhibited excellent performances suitable for portable telephones.

A new postprocessing method using interpolated n-gram model for Japanese documents is proposed. The method has the advantages over conventional approaches in enabling high-speed, knowledge-free processing. In parameter estimation of an n-gram model for a large size of vocabulary, it is difficult to obtain sufficient training samples. To overcome poverty of samples, two smoothing methods for Japanese character trigram model are evaluated, and the superiority of deleted interpolation method is shown by using perplexity. A document recognition system based on the trigram model is constructed, which finds maximum likelihood solutions through Viterbi algorithm. Experimental results for three kinds of documents show that the performance is high when using deleted interpolation method for smoothing. 90% of OCR errors are corrected for the documents similar to training text data, and 75% of errors are corrected for the documents not so similar to training text data.

A refection type and loaded-line type phase shifter switching multi phase-states has been described. This novel phase shifter circuit is constructed by adding switching FETs to a conventional 2-phase-state phase shifter. A conventional 3 bit phase shifter can be replaced by this type of phase shifter. The total chip size is reduced to 2/3. This paper reports on the design, fabrication, and performance of the novel reflection-type and loaded-line-type phase shifter MMICs.

The E-polarized plane wave diffraction by a perfectly conducting strip located at the plane interface between two different media is analyzed by the Wiener-Hopf technique. Applying the boundary conditions to the integral representations for the unknown scattered field, the problem is formulated in terms of the modified Wiener-Hopf equation(MWHE), which is reduced to a pair of simultaneous integral equations via the factorization and decomposition procedure. The integral equations are solved asymptotically for large strip width via the method of successive approximations leading to the first, second and third order solutions, which are valid at high frequencies. The scattered far field expression is derived by taking the inverse Fourier transform and applying the saddle point method. It is shown that the high-frequency scattered far field comprises the geometrical optics field, the singly, doubly and triply diffracted fields and the lateral waves. Numerical examples of the radar cross section(RCS) and the lateral waves are presented, and the far field scattering characteristics discussed in detail.

We proposed a new thchnique using saw wave modulation light to measure the thermal diffusivity of a transparent adhesive by photoacoustic microscope. In this technique, the time required for the measurement of it can be reduced by one-fifth compared with that of a conventional method.

In ths letter, we suggest a collision resolution algorithm when the packet length is random, and analyze its throughput and delay performance. Here, three different packet length distributions and two feedback schemes (ternary and binary success/failure feedback) are considered.

Most conventional methods used in character recognition extract geometrical features, such as stroke direction and connectivity, and compare them with reference patterns in a stored dictionary. Unfortunately, geometrical features are easily degraded by blurs and stains, and by the graphical designs such as used in Japanese newspaper headlines. This noise must be removed before recognition commences, but no preprocessing method is perfectly accurate. This paper proposes a method for recognizing degraded characters as well as characters printed on graphical designs. This method extracts features from binary images, and a new similarity measure, the complementary similarity measure, is used as a discriminant function; it compares the similarity and dissimilarity of binary patterns with reference dictionary patterns. Experiments are conducted using the standard character database ETL-2, which consists of machine-printed Kanji, Hiragana, Katakana, alphanumeric, and special characters. The results show that our method is much more robust against noise than the conventional geometrical-feature method. It also achieves high recognition rates of over 97% for characters with textured foregrounds, over 99% for characters with textured backgrounds, over 98% for outline fonts and over 99% for reverse contrast characters. The experiments for recognizing both the fontstyles and character category show that it also achieves high recognition rates against noise.

In the traditional note symbol extraction processes, extracted candidates of note elements were identified using complex if-then rules based on the note formation rules and they needed subtle adjustment of parameters through many experiments. The purpose of our system is to avoid the tedious tasks and to present an accurate and high-speed extraction of note heads, stems and flags according to the following procedure. (1) We extract head and flag candidates based on the stem positions. (2) To identify heads and flags from the candidates, we use a couple of three-layer neural networks. To make the networks learn, we give the position informations and reliability factors of candidates to the input units. (3) With the weights learned by the net, the head and flag candidates are recognized. As an experimental result, we obtained a high extraction rate of more than 99% for thirteen printed piano scores on A4 sheet which have various difficulties. Using a workstation (SPARC Station 10), it took about 90 seconds to do on the average. It means that our system can analyze piano scores 5 times or more as fast as the manual work. Therefore, our system can execute the task without the traditional tedious works, and can recognize them quickly and accurately.

This paper describes advances in the study of handwritten Kanji character recognition mainly performed in Japan. The research focus has shifted from the investigation of the possibility of recognition by the stroke structure analysis method to the study of the feasibility of recognition by the feature matching methods. A great number of features and their extraction methods have been proposed according to this approach. On the other hand, studies on pattern matching methods of recognizing Kanji characters using the character pattern itself have been made. The research efforts based on these two approaches have led to the empirical fact that handwritten Kanji character recognition would become more effective by paying greater attention to the feature of directionality. Furthermore, in an effort to achieve recognition with higher precision, active research work has been carried out on pre-processing techniques, such as the forced reshaping of input pattern, the development of more effective features, and nonlinear flexible matching algorithms. In spite of these efforts, the current character recognition techniques represent only a skill of guessing characters" and are still on an insufficient technical level. Subsequent studies on character recognition must address the question of how to understand characters".

Handwritten character recognition has been increasing its importance and has been expanding its application areas such as office automation, postal service automation, automatic data entry to computers, etc. It is challenging to develop a handwritten character recognition system with high processing speed, high performance, and high portability, because there is a trade-off among them. In current technology, it is difficult to attain high performance and high processing speed at the same time with single algorithms, and therefore, we need to find an efficient way of combination of multiple algorithms. We present an engineering solution to this problem. The system is based on multi-stage strategy as a whole: The first stage is a simple, fast, and reliable recognition algorithm with low substitution-error rate, and data of high quality are recognized in this stage, whereas sloppily written or degraded data are rejected and sent out to the second stage. The second stage is composed of a sophisticated structural pattern classifier and a pattern matching classifier, and these two complementary algorithms run in parallel (multiple expert approach). We demonstrate the performance of the completed system by experiments using real data.

In this paper, authors propose a linear array antenna using two bifilar helical antenna elements placed along the helix axis to reduce beam direction movement according to frequency change. The beam direction movement of this proposed array antenna is smaller than that of a conventional bifilar helical antenna. Also, the gain of this proposed array antenna is higher than that of the conventional helical antenna for a cross point angle of radiation patterns at the different transmit and receive(Tx and Rx) frequencies. The conventional helical antenna is suitable for vehicle antennas in mobile satellite communication systems such as the MSAT system because it owns circularly polarized omni-directional radiation pattern and its thin pole form. However, this antenna has a disadvantage that the beam direction in an elevation plane moves according to frequency change. In the proposed array antenna, the beam direction movement is about 9 smaller than that of the conventional bifilar helical antenna on condition that antenna total length is 4.83 λ0, antenna diameter is 0.12 λ0, and frequency change is from 0.957f0 to 1.043f0(f0 is center frequency and λ0 is free space wavelength at f0). Also, the Tx and Rx gains of this proposed array antenna at the cross point angle between Tx and Rx beams are about 2 dB higher than that of the conventional bifilar helical antenna on the same condition.

AlGaAs/GaAs power HBTs for digital cellular phones have been developed. A three-dimensional thermal analysis taking the local-temperature dependence of the collector current into account was applied to the thermal design of the HBTs. The HBTs were fabricated using the hetero-guardring fully selfaligned transistor technique. The HBT with 220µm2 60 emitters produced a 31.7 dBm CW-output power and 46% poweradded efficiency with an adjacent channel leakage power of -49 dBc at the 50kHz offset bands for a 948 MHz π/4-shifted QPSK modulated signal at a low collector-emitter voltage of 3V. Through comparison with the conventional GaAs power FETs, it has been shown that AlGaAs/GaAs power HBTs have a great advantage in reducing the chip size.

A 1.9GHz direct conversion receiver(DCR) chip which integrates an LNA, I/Q mixers(MIX), active lowpass filters(LDF) and variable gain amplifiers(VGA) was fabricated. Because the DCR for QPSK modulation systems is sensitive to the 2nd-order nonlinearity, linearization techniques are adopted in MIX and LPF. The DCR chip was fabricated using a BiCMOS process, and the die size is 5.1 mm by 5.1mm. The chip can operate from 2.7 V supply voltage and consumes 165mW when all the functions are activated. Suppression of local signal radiation and the 2nd-order distortion indicate the feasibility of Si-based DCR for QPSK modulation systems such as PHS.

A multi-terminal serial optical link(MSOL) achieves very simple and cost effective radio cell configurations because only one pair of fibers is needed. In addition, low cost Fabry-Perot laser diodes(FP-LDs) can be employed. MSOL has a substantial problem in that the beat noise degrades the C/N in the up-link. To reduce this noise, we propose using an automatic wavelength-offset control(AWOC) circuit. The AWOC circuit offsets the LD wavelength by controlling the laser bias current to minimise the RF band beat noise which is inherent in MSOL systems, and enables high C/N optical-microwave transmission. An experimental MSOL consisting of 5 radio access stations, each equipped with AWOC, is constructed to estimate the noise free dynamic range for 800-MHz 20-carrier signal transmission. The up-link comprises a single mode fiber connecting five 1.3-µm FP-LDs operating at 0.2 mW. The down-link consists of a single mode fiber and one 1.3-µm Distributed Feedback type Laser Diode(DFB-LD) emitting at 4.0 mW. The experimental device achieves over 15 dB noise reduction compared to MSOL without AWOC in the temperature range of 0 to 40. By using the proposed AWOC, MSOL can achive low cost optical fiber RF microcell systems that are easy to install. Additionally, when we install MSOL in the radio base station, the links become more cost effective than coaxial cable links; they offer a wide dynamic range and higher transmission quality.

We present a new method for the identification of time-invariant multichannel autoregressive (AR) processes corrupted by additive white observation noise. The method is based on the Yule-Walker equations and identifies the autoregressive parameters from a finite set of measured data. The input signals to the underlying process are assumed to be unknown. An inverse filtering technique is used to estimate the AR parameters and the observation noise variance, simultaneously. The procedure is iterative. Computer simulation results that demonstrate the performance of the identification method are presented.

A new adaptive AR spectral estimation method is proposed. While conventional least-squares methods use a single windowing function to analyze the linear prediction error, the proposed method uses a different window for each frequency band of the linear prediction error to define a cost function to be meinemized. With this approach, since time and frequency resolutions can be traded off throughout the frequency spectrum, an improvement on the precision of the estimates is achieved. In this paper, a wavelet-like time-frequency resolution grid is used so that low-frequency components of the linear prediction error are analyzed through long windows and high-frequency components are analyzed through short ones. To solve the optimization problem for the new cost function, special properties of the correlation matrix are used to derive an RLS algorithm on the order of M2, where M is the number of parameters of the AR model. Computer simulations comparing the performance of conventional RLS and the proposed methods are shown. In particular, it can be observed that the wavelet-based spectral estimation method gives fine frequency resolution at low frequencies and sharp time resolution at high frequencies, while with conventional methods it is possible to obtain only one of these characteristics.

This paper is described on the realization of simulated inductance cercuit with parallel negative conductance and its application for an oscillator. The design's condition for realizing the circuit needs stability, narrow expance of elements, larger dynamic-range and lower sensitivity. A new floating simulated inductance circuit with parallel nagative conductance with two operational amplifiers, four resistors, and four capacitors is created by using the design's algorithm. And the elements sensitivity of the simulated circuit is superior to that of the conventional circuits. By experimenting with a resonance circuit, the author tested the sinusoidal oscillator's circuit of a parallel -GLC as an application in order to confirm the operation of the simulated inductance circuit with parallel negative conductance.

This paper examines the feasibility of a high frequency (moro than 1 GHz) ring-oscillator-type CMOS VCO, able to maintain a good linearity between the oscillator output frequency and control voltage, while preserving low voltage and low power operation capabilities. A CMOS VCO circuit, with a newly developed corrent-controlled delay cell and an architecture combining the transitions of each delay cell output, with high-frequency operation, was designed and simulated using the CMOS 0.6 µm device paramenters. We analyzed the generation of unnecessary harmonics and sub-harmonics when a delay cell's propagation delay time varied. The simulation indicated that a CMOS VCO with a frequency range of 200 MHz to 1.4 GHz, a power dissipation of 8.5 mW at 900 MHz from a 3 V power supply, and an operation voltage of 1 V to 3 V can be implemented on a chip.