In this paper, we present a simple and practical method for determining the front-facing polygons for static, dynamic, and deformable objects. The object space is considered a set of open-frustum regions. A bit string associated with each region records polygons for their extended positive half space intersecting the corresponding region. For a given viewpoint, the bit string of the set of the front facing polygons can be determined in a constant time. While objects continuously keep deforming and/or remain in motion in each frame, we update set of bit strings, determined as minimal as possible by the spatial coherence, making our method still perform efficiently.

This paper reports on the bending loss insensitive single mode fiber suitable for access networks, which is applicable for wide wavelength use. Excellent attenuation stability of the fiber in the full spectrum range has been confirmed even in severe conditions such as fiber handling in mid-span access at aerial closure, cable installation/handling in indoor wirings and so on. Also, applications suitable for FTTH subscribers' use have been introduced.

This paper focuses on the fatigue characteristics of the single crystal silicon (SC-Si) cantilever in relation with the critical design of micro electro-mechanical systems (MEMS). Development of MEMS actuators for optical communication usage is carried out successfully, for example, in optical switches and variable optical attenuators (VOA). In those devices, fatigue characteristics of the MEMS structure are crucial to its practical application. However, fatigue tests using real structures have not been carried out well. In this research, the fatigue life has been inspected at the actual device, under actual usage conditions for the first time. We obtained fracture rate λ from experimental results, and the value of Failure in Time (FIT) λ was about 0.3 FIT. This result indicates that these MEMS devices having enough reliability for practical usage.

An ultra low power CMOS SAW oscillator in the 300-MHz-band that operates on a sub-1 V supply voltage and at sub-1 mW power consumption has been developed. The SAW oscillator is fabricated in a 0.35-µm fully depleted SOI (FD-SOI) process with low voltage operation capability. The SAW oscillator is configured as a type of Colpitts oscillator but consists of 3 cascaded amplifiers instead of a single amplifier. Although the circuit configuration is quite similar to the conventional Colpitts oscillator, this proposed configuration generates an excessively high negative resistance that even exceeds the theoretical limit of the conventional one.

This paper describes a speed-oriented ultralow-voltage and low-power SOI circuit technique based on a differential enhancement- and depletion-mode (ED)-MOS circuit. Combining an ED-MOS circuit block for critical paths and a multi-Vth CMOS circuit block for noncritical paths, that is, the so-called differential ED-CMOS/SOI circuit, makes it possible to achieve low-power and ultrahigh-speed operation of over 1 GHz at a supply voltage of less than 0.5 V. As two applications of the differential ED-CMOS/SOI circuit, a multi-stage frequency divider that uses the ED-MOS circuit in a first-stage frequency divider and a pipelined adder with a CMOS pipeline register are described in detail. To verify the effectiveness of the ED-CMOS/SOI circuit scheme, we fabricated a 1/8 frequency divider and a 32-bit binary look-ahead carry (BLC) adder using the 0.25-µm MTCMOS/SOI process. The frequency divider operates down to 0.3 V with a maximum operating frequency of 3.6 GHz while suppressing power dissipation to 0.3 mW. The 32-bit adder operates at a frequency of 1 GHz at 0.5 V.

A directly modulated AM-VSB CATV erbium-doped fiber amplifier (EDFA)-repeated system that uses push-pull modulated distributed feedback (DFB) laser diodes and half-split-band technique is proposed and demonstrated. Push-pull modulation scheme enhances the frequency response of the laser diode, and thus improves the overall performance of the fiber optical CATV systems. Good performances of carrier-to-noise ratio (CNR), composite second order (CSO), and composite triple beat (CTB) were achieved for the full channel band over a 100-km single-mode fiber (SMF) transport.

We propose a novel approach based on wavelet decomposition for progressive full spectral rendering. In the fourth progressive stage, our method renders an image that is 95% similar to the final non-progressive approach but requires less than 70% of the execution time. The quality of the rendered image is visually plausible that is indistinguishable from that of the non-progressive method. Our approach is graceful, efficient, progressive, and flexible for full spectral rendering.

This paper presents 160-Gbit/s full channel time-division demultiplexing using a semiconductor optical amplifier hybrid integrated demultiplexer on a planer lightwave circuit. Error-free demultiplexing from a 160-Gbit/s signal to 8 channel 20 Gbit/s signals is successfully demonstrated. Results of a 160-Gbit/s optical time-division-multiplexed full channel OTDM signal transmission experiment using the circuit and successful 80-km transmission are presented.

In this paper, a novel type of the step-up high frequency transformer linked full-bridge soft-switching phase-shift PWM DC-DC power converter with ZVS and ZCS bridge legs is proposed for small scale fuel cell power generation systems, automotive AC power supplies. A tapped inductor filter with a freewheeling diode is implemented in the proposed soft-switching DC-DC power converter to minimize the circulating current in the high-frequency step-up transformer primary side and high-frequency inverter stage. Using a tapped inductor filter with a freewheeling diode makes possible to reduce the circulating current without any active switches and theirs gate-drive circuits. The operating principle of the proposed DC-DC power converter with each operation mode during a half cycle of the steady state operation is explained. The optimum design of the tapped inductor turns ratio is described on the basis of the circuit simulation results. Developing 1 kW 100 kHz prototype with power MOSFETs and 36 V DC source verifies the practical effectiveness of the proposed soft-switching DC-DC power converter. The actual efficiency of the proposed DC-DC power converter is obtained 94% for the wide load and output voltage variation ranges.

A full-duplex radio-on-fiber (ROF) transport system based on optical single sideband (SSB) modulation, wavelength-division-multiplexing (WDM) and optical add-drop multiplexing techniques is proposed and demonstrated. A 1.5-dB RF power degradation due to the chromatic dispersion was achieved by employing optical SSB modulation scheme in the system, in which resulting in low bit error rate (BER) and third order intermodulation distortion to carrier ratio (IMD3/C) values. Such a proposed full-duplex ROF transport system is suitable for the long-haul microwave optical link.

Scattering of the two dimensional electromagnetic waves is studied by the infinite sequences of zeros arising on the complex plane, which just correspond to the null points of the far field pattern given as a function of the azimuthal angle θ. The convergent sequences of zeros around the point of infinity are evaluated when the scattering objects are assumed to be N-polygonal cylinders. Every edge condition can be satisfied if the locations of zeros are determined appropriately. The parameters, which allow us to calculate the exact positions of zeros, are given by the asymptotic analysis. It is also shown that there are N-directions of convergence, which tend to infinity. An illustrative example is presented.

A novel method is presented to the symbolic computation of Noise Figure (NF) of transistor circuits. Several computationally efficient macromodels of BJTs and MOSFETs by using nullors, are introduced. To demonstrate the suitability of the proposed method, the fully-symbolic expression of NF of a CMOS current-mirror is computed, and the total output noise-voltage is compared with HSPICE simulations. The calculated NF and the simulated noise are in good agreement. Finally, the method is extended to compute NF of a CMOS translinear circuit biased in weak inversion.

In this letter, we show the effects of the chip waveform selection on the detection performance of the energy detector in DS/SS communications. Three chip waveforms such as rectangular, half-sine and raised-cosine are examined as the DS/SS chip waveform. It is demonstrated that the partial-band detection can enhance the detection performance of the energy detector approximately 50-70% compared with the full-band detection. When the chip rate is identical, the raised-cosine waveform shows lower detection probability due to its wider spreading bandwidth. However, when the spreading bandwidth is identical, the rectangular waveform shows lower detection probability due to its lower partial-band energy factor.

Classical designs of maximally flat finite impulse response digital filters need to perform inverse discrete Fourier transformation of the frequency responses, in order to calculate the impulse response coefficients. Several attempts have been made to simplify the designs by obtaining explicit formulas for the impulse response coefficients. Such formulas have been derived for digital differentiators having maximal linearity at zero frequency, using different techniques including interpolating polynomials and the Taylor series etc. We show that these formulas can be obtained directly by application of maximal linearity constraints on the frequency response. The design problem is formulated as a system of linear equations, which can be solved to achieve maximal linearity at an arbitrary frequency. Certain special characteristics of the determinant of the coefficients matrix of these equations are explored for designs centered at zero frequency, and are used in derivation of explicit formulas for the impulse response coefficients of digital differentiators of both odd and even lengths.

Novel designs of multiple-valued logic (quaternary) half adder, full adder, and carry-lookahead adder are introduced. The proposed circuits are static and operate in voltage-mode. Moreover, there is no current flow in steady states, and thus, no static power dissipation. Although the comparison in transistor count shows that the proposed quaternary circuits are larger than two respective binary ones, benefits in parallel addition arise from the use of multiple-valued logic. Firstly, the ripple-carry additions are faster because the number of carries is half compared to binary ones and the propagation delay from the input carry through the output carry is relatively small. Secondly, the carry-lookahead scheme exhibits less complexity, which leads to overall reduction in transistor count for addition with large number of bits.

Recent advances in measurement techniques for microwave active devices and circuits are reviewed in this paper. The R&D activities have been devoted aggressively how to characterize nonlinear performance of high power devices and circuits. They are pulsed I-V, a variety of load-pull measurements, probing, sampling, and sensing techniques, supported by the recent significant advances in DSP (Digital Signal Processing), RF components, semiconductor devices, etc. The recent advances in vector network analyzers are of our great interest. They are (a) multi-port vector network analyzers for characterizing mixers, differential devices, packaged components, electronic package characterization, and multi-layer transmission lines, and (b) EO (Electro-Optic) modulated vector network analyzers for characterizing electronic performance of EO devices with the aid of EO modulators and photonic probes. In addition, probing, sampling, and sensing techniques have made great progress to directly measure electromagnetic field, time-domain voltage waveform, and temperature in small spot areas. In this paper, some topics related to these measurement techniques are briefly reviewed. Then the existing and future issues for characterization and measurement techniques of microwave active devices and circuits are discussed.

We propose a novel optical signal processing using an optically pumped vertical-cavity surface-emitting laser (VCSEL) with an external light input. The mode transition between a fundamental and a 1st-high-order transverse mode is induced by an external light injection. Since a single mode fiber (SMF) spatially selects a fundamental transverse mode as an output signal, we are able to realize a nonlinear transfer function, which will be useful in future photonic networks. The mode transition characteristic of a 1.55 µm optically pumped two-mode VCSEL has been simulated by using a two-mode rate equation, which includes the effects of spatial hole burning and spectral hole burning as gain saturation coefficients. We focus on the detuning effect in the injection locking. When the wavelength of an input light with a fundamental mode is slightly longer than that of a VCSEL operating in a 1st-high-order transverse mode, the transverse mode of the VCSEL is switched to a fundamental mode at a critical input power level. This gives us an ideal transfer function for 2R (reamplification and reshaping) regeneration. Also, the proposed scheme may enable polarization insensitive signal processing, which is a unique feature in surface emitting lasers.

In this paper, a simple adaptive notch filter (ANF) scheme for reducing RFI over CAP/QAM-based VDSL systems is proposed. To alleviate the spectral null caused by notch filtering, a null reshaping scheme is introduced between the normal ANF and the decision feedback equalizer (DFE). The proposed filter scheme can control the width and depth of the null. The shallow and narrow null obtained by null reshaping reduces the loss of signal components and consequently improves the mean square error (MSE) at the output of the equalizer. The proposed null reshaping scheme also enables the infinite impulse response (IIR) type constrained ANF to have a smaller pole contraction factor α. This results in a fast convergence property in RFI frequency estimation with a recursive prediction error (RPE) algorithm. The performance variations of the proposed null reshaping are investigated with varying filter parameters. Compared to the conventional ANF, simulation results show that, at the expense of small system complexity, the proposed structure yields a 2-3 dB MSE gain and a fast convergence property for RFI estimation.

In this letter, we propose (1) a new sub-optimum minimum distance search (sub-MDS), whose search complexity is reduced considerably compared with optimum MDSs and (2) a termination criterion, called near optimality condition, to reduce the average number of decoding iterations with little degradation of error performance for the proposed decoding using sub-MDS iteratively. Consequently, the decoding algorithm can be applied to longer codes with feasible complexity. Simulation results for several Reed-Muller (RM) codes of lengths 256 and 512 are given.

Information service provision and utilization is an important infrastructure in the high-assurance distributed information service system. In order to cope with the rapidly evolving situations of providers' and users' heterogeneous requirements, one autonomous information service system has been proposed, called Faded Information Field (FIF). FIF is a distributed information service system architecture, sustained by push/pull mobile agents, through a recursive demand-oriented provision of the most popular information closer to the users to make a tradeoff between the cost of service allocation and access. In this system, users' requests are autonomously driven by pull mobile agents in charge of finding the relevant service. In the case of a mono-service request, the system is designed to reduce the time needed for users to access the information and to preserve the consistency of the replicas. However, when the user requests joint selection of multiple services, synchronization of atomic actions and timeliness have to be assured by the system. In this paper, the relationship that exists among the contents, properties and access ratios of information services is clarified. Based on these factors, the ratio of correlation and degree of satisfaction are defined and the autonomous integration and optimal allocation of information services for heterogeneous FIFs to provide one-stop service for users' multi-service requirements are proposed. The effectiveness of the proposed technology is shown through evaluation and the results show that the integrated services can reduce the total users access time and increase services consumption compared with separate systems.