A characteristic-based constrained interpolation profile (CIP) method for solving three-dimensional, time-dependent Maxwell's equations is successfully developed. It is utilized to solve one-dimensional wave equations in the formulation of the Maxwell's equations. Calculation procedure of the CIP method for three-dimensional scattering analysis is described in details. Update equations for boundary conditions of a perfectly conducting (PEC) interface and a dielectric interface are formulated and obtained in explicit forms. Numerical analyses of electromagnetic scatterings of PEC sphere, dielectric sphere and PEC cube are performed and the scattering coefficient is calculated and compared with the Mie's analytic results. As a result, the scattering coefficients show good agreement with the Mie's results, which demonstrates the validity of the CIP method and the formulated update equations. It is also shown that the phase of the scattering coefficients determined by the CIP method are slightly more accurate than that of the FDTD method.

In this paper, a novel feeding technique is proposed to feed a printed rectangular ring patch antenna that attains high gain in two bands simultaneously. The prototype antenna exhibits good impedance bandwidths satisfying ISM 2.45/5.8 GHz achieving maximum gain of 9.56 and 10.17 dBi, respectively, with a stable radiation pattern.

We propose a segment-based voice conversion technique using hidden Markov model (HMM)-based speech synthesis with nonparallel training data. In the proposed technique, the phoneme information with durations and a quantized F0 contour are extracted from the input speech of a source speaker, and are transmitted to a synthesis part. In the synthesis part, the quantized F0 symbols are used as prosodic context. A phonetically and prosodically context-dependent label sequence is generated from the transmitted phoneme and the F0 symbols. Then, converted speech is generated from the label sequence with durations using the target speaker's pre-trained context-dependent HMMs. In the model training, the models of the source and target speakers can be trained separately, hence there is no need to prepare parallel speech data of the source and target speakers. Objective and subjective experimental results show that the segment-based voice conversion with phonetic and prosodic contexts works effectively even if the parallel speech data is not available.

We present the PCA self-cross bilateral filter for denoising multi-modal images. We firstly apply the principal component analysis for input multi-modal images. We next smooth the first principal component with a preliminary filter and use it as a supplementary image for cross bilateral filtering of input images. Among some preliminary filters, the undecimated wavelet transform is useful for effective denoising of various multi-modal images such as color, multi-lighting and medical images.

The IEEE 802.11 MAC standard for wireless ad hoc networks adopts Binary Exponential Back-off (BEB) mechanism to resolve bandwidth contention between stations. BEB mechanism controls the bandwidth allocation for each station by choosing a back-off value from one to CW according to the uniform random distribution, where CW is the contention window size. However, in asymmetric multi-hop networks, some stations are disadvantaged in opportunity of access to the shared channel and may suffer severe throughput degradation when the traffic load is large. Then, the network performance is degraded in terms of throughput and fairness. In this paper, we propose a new cross-layer scheme aiming to solve the per-flow unfairness problem and achieve good throughput performance in IEEE 802.11 multi-hop ad hoc networks. Our cross-layer scheme collects useful information from the physical, MAC and link layers of own station. This information is used to determine the optimal Contention Window (CW) size for per-station fairness. We also use this information to adjust CW size for each flow in the station in order to achieve per-flow fairness. Performance of our cross-layer scheme is examined on various asymmetric multi-hop network topologies by using Network Simulator (NS-2).

The paper presents the state of knowledge about thermal-erosion processes in contacts of low-voltage switching devices for power engineering on switching currents under short-circuit conditions. The graphical models of the short arc and the distribution of arc power introduced into contacts are shown. The method for measurements of a contact temperature during an electric discharge has been elaborated. The obtained test results are presented, i.e. changes of a contact temperature as a function of arc parameters such as current, energy, and integral ∫idt. The tests have shown that a "break point" exists on the curve expressing the relationship between a temperature rise and arc parameters in the range of high currents. The location of this point is dependent on a diameter of contacts and a value of current, and is associated with thermal energy delivered to electrodes. It has been observed that for each diameter of contacts there exists such value of an energetic quantity of arc (current, ∫idt, energy), at which diameters of arc roots are the same as a contact diameter. Above this value, the shape of a curve is changed. The obtained results explain and confirm the discontinuity of a curve expressing a contact arc erosion as a function of current, which was observed earlier by the other research workers.

Novel thermopiles based on modulation doped AlGaAs/InGaAs, AlGaN/GaN, and ZnMgO/ZnO heterostructures are proposed and designed for the first time, for uncooled infrared image sensor application. These devices are expected to offer high performances due to both the superior Seebeck coefficient and the excellently high mobility of 2DEG and 2DHG due to high purity channel layers at the heterojunction interface. The AlGaAs/InGaAs thermopile has the figure-of-merit Z of as large as 1.110-2/K (ZT = 3.3 over unity at T = 300 K), and can be realized with a high responsivity R of 15,200 V/W and a high detectivity D* of 1.8109 cmHz1/2/W with uncooled low-cost potentiality. The AlGaN/GaN and the ZnMgO/ZnO thermopiles have the advantages of high sheet carrier concentration due to their large polarization charge effects (spontaneous and piezo polarization charges) as well as of a high Seebeck coefficient due to their strong phonon-drag effect. The high speed response time τ of 0.9 ms with AlGaN/GaN, and also the lower cost with ZnMgO/ZnO thermopiles can be realized. The modulation-doped heterostructure thermopiles presented here are expected to be used for uncooled infrared image sensor applications, and for monolithic integrations with other photon detectors such as InGaAs, GaN, and ZnO PiN photodiodes, as well as HEMT functional integrated circuit devices.

A unipolar n-n heterostrucuture diode is developed in the InP material system. The electronic barrier is formed by a saw tooth type of conduction band bending which consists of a quaternary In0.52(AlyGa1-y)0.48As layer with 0 < y < ymax. This barrier is lattice matched for all y to InP and is embedded between two n+-InGaAs layers. By varying the maximum Al-content from ymax,1 = 0.7 to ymax,2 = 1 a variable barrier height is formed which enables a diode-type I-V characteristic by epitaxial design with an adjustable current density within 3 orders of magnitude. The high current density of the diode with the lower barrier height (ymax,1 = 0.7) makes it suitable for high frequency applications at low signal levels. RF measurements reveal a speed index of 52 ps/V at VD = 0.15 V. The device is investigated for RF-to-DC power conversion in UHF RFID transponders with low-amplitude RF signals.

A novel construction of complementary sequences with multi-width zero cross-correlation zone (ZCCZ) is presented based on the interleaving iteration of a basic kernel set. The presented multi-width ZCCZ complementary (MWZC) sequences can be divided into multiple sequence groups, the correlation functions of which possess one-width intragroup ZCCZ and multi-width intergroup ZCCZ. When an arbitrary orthogonal sequence set with set size equal to sequence length is used as a basic kernel set, the constructed MWZC sequence set and the combination sets of specific subsets with each subset including several groups can be optimal with respect to the theoretical bound on set size. In addition, the MWZC sequence set includes complementary sequence sets with one-width or two-width ZCCZ as special subsets, and allows a more flexible choice of sequence parameters.

In this paper, a coexistence mechanism between IEEE 802.15.4 and IEEE 802.11b, Active Channel Reservation for cOexiStence (ACROS), is proposed. The key idea underlining ACROS is to reserve the channel for IEEE 802.15.4 transmission, where IEEE 802.11 transmissions are forbidden. The request-to-send (RTS)/clear-to send (CTS) mechanism within IEEE 802.11 is used to reserve a channel. The proposed ACROS mechanism is implemented into a PC based prototype. The embedded version of ACROS is also developed to mitigate the timing drift problem in the PC-based ACROS. The efficiency of ACROS is shown using the throughput and packet error rate achieved in actual experiments.

In order to quickly discharge the electrostatic discharge (ESD) energy, an unassisted low-voltage-trigger ESD protection structure is proposed in this work. Under transmission line pulsing (TLP) stress, the trigger voltage, turn-on speed and second breakdown current can be obviously improved, as compared with the traditional protection structure. Moreover there is no need to add any extra mask or do any process modification for the new structure. The proposed structure has been verified in foundry's 0.18-µm CMOS process.

A high directivity microstrip coupler suppressing leak coupling with a cancellation circuit of a Wilkinson divider is presented. The presented coupler utilizes a cancellation circuit between a coupling port and an isolation port of the conventional microstrip coupler to enhance the isolation. The cancellation circuit consists of the Wilkinson divider, the multistage attenuator, and the phase offset line. The frequency to enhance the isolation is controlled by the attenuators. As the directivity is improved without the modification of the conventional coupler, the cancellation circuit can be applied to the fabricated conventional couplers. The measured directivity of the presented 1/18 λ coupler is improved from 4.8 dB to 43.0 dB at 2.6 GHz, compared with the conventional 1/4 λ coupler with -20 dB coupling. Simultaneously, the 27.4% relative bandwidth with the 20 dB directivity is achieved.

In this paper, the transmission and reflection properties of the microstrip line with bends are investigated using the Fourier transform and a mode-matching technique. Based on the waveguide model, the microstrip bends are modeled as the rectangular waveguides with perfect electric conducting top and bottom walls and perfect magnetic conducting side walls. Analytical closed-form expressions for transmission and reflection coefficients are developed using the residue calculus. To verify the proposed method, numerical computations are performed for comparison with 3D full-wave simulations and measurements. A quarter-wavelength transmission line scheme is also proposed to improve the signal integrity of double bend discontinuity.

Electrostatic discharge (ESD) events due to metal objects electrified with low voltages give a fatal electromagnetic interference to high-tech information equipment. In order to elucidate the mechanism, with a 6-GHz digital oscilloscope, we previously measured the discharge current due to collision of a hand-held metal piece from a charged human body, and gave a current calculation model. In this study, based on the calculation model, a method was presented for deriving a gap potential gradient from the measured discharge current. Measurements of the discharge currents were made for charge voltages from 200 V to 1000 V. The corresponding potential gradients were estimated, which were validated in comparison with an empirical formula based on the Paschen's law together with other researcher's experimental results.

Subjects in Electromagnetic Compatibility (EMC) research that have been presented at meetings of the IEICE Technical Committee on Electromagnetic Compatibility (EMCJ) are overviewed and categorized. The temporal changes in the proportions of the categorized subjects among the total number of presentations each year is also shown. Finally, speculative opinions are presented on what EMC subjects will be studied in the near future.

A new type of the wide-band BPF made up of an inter-digital resonator and parallel-coupled lines was proposed. The bandwidth of the inter-digital resonator becomes wider by increasing the number of fingers. The design of the parallel-coupled line was performed by optimazing the structural parameters so that the bandwidth is the same as that of the inter-digital resonator. The measured results of the combination of above elements for the BPF agreed well with the simulated ones such that the insertion loss is less than 0.67 dB and that the sharp skirt characteristics are realized by attenuation poles near the edges of the passband.

The design of microstrip bandpass filters using stepped-impedance resonators (SIRs) is examined. The passband center frequency for the WCDMA-FDD (uplink band) Japanese cellular system is 1950 MHz with a 60-MHz bandwidth. The SIR physical characteristic can be designed using a SIR characteristic chart based on second harmonic suppression. In our filter design, passband design charts were obtained through the design procedure. Tchebycheff and maximally flat bandpass filters of any bandwidth and any number of steps can be designed using these passband design charts. In addition, sharp skirt characteristics in the passband can be realized by having two transmission zeros at both adjacent frequency bands by using open-ended quarter-wavelength stubs at input and output ports. A new even-mode harmonics suppression technique is proposed to enable a wide rejection band having a high suppression level. The unloaded quality factor of the resonator used in the proposed filters is greater than 240.

With the big success of 802.11 wireless networks, there have been many proposals addressing end-to-end QoS guarantees in 802.11 WLAN. However, we have found that current end-to-end QoS architectures lack of one or more important properties such as cross-layer interaction, end-to-end integration, reconfigurability and modularity. In this work, we present an end-to-end reference QoS architecture for 802.11 WLAN that encapsulates in an unifying fashion software-based QoS components (mechanisms, algorithms, services), proposed in the literature. To show the usefulness and correctness of the reference architecture, we present three case studies of end-to-end QoS architectures addressing different QoS requirements such as bandwidth and delay with different approaches such as differentiated services and integrated services. We will give an architectural comparison and performance evaluation of these architectures. We believe the reference QoS architectures can help QoS designers to understand the importance and the complexity of various QoS components during the design phase and thus choose these QoS components appropriately.

This paper proposes a cross-layer packet scheduling scheme for QoS support in audio-video transmission with IEEE 802.11e HCCA and assesses application-level QoS and QoE of the scheduling scheme under lossy channel conditions. In the proposed scheme, the access point (AP) basically allocates transmission opportunity (TXOP) for each station in a service interval (SI) like the reference scheduler of the IEEE 802.11e standard, which is referred to as the TGe scheme in this paper. In the proposed scheme, however, the AP calculates the number of MAC service data units (MSDUs) arrived in an SI, considering the inter-arrival time of audio samples and that of video frames, which are referred to as media units (MUs), at the application layer. The AP then gives additional TXOP duration in the SI to stations which had audio or video MAC protocol data units (MPDUs) in their source buffers at the end of the previous TXOP. In addition, utilizing video frame information from the application layer, we propose video frame skipping at the MAC-level of a source station. If a station fails to transmit a video MPDU, it drops all the following video MPDUs in the source buffer until the next intra-coded frame comes to the head of the buffer. We compare the reference scheduler (TGe scheme), the proposed packet scheduling scheme with and without the video frame skipping at the source in terms of application-level QoS and QoE. We discuss the effectiveness of the proposed packet scheduling scheme from a viewpoint of QoE as well as QoS. Numerical results reveal that the proposed packet scheduling scheme can achieve higher quality than the TGe scheme under lossy channel conditions. We also show that the proposed scheduling scheme can improve the QoS and QoE by using the video frame skipping at the source. Furthermore, we also examine the effect of SI on the QoS and QoE of the proposed packet scheduling scheme and obtain that the appropriate value of SI is equal to the inter-arrival time of video frame.

An on-chip Charged Device Model (CDM) ESD protection method for RF ICs is proposed in a 0.13 µm RF process and evaluated by using very fast Transmission Line Pulse (vf-TLP) system. Key design parameters such as triggering voltage (Vt1) and the oxide breakdown voltage from the vf-TLP measurement are used to design input ESD protection circuits for a RF test chip. The characterization and the behavior of a Low Voltage Triggered Silicon Controlled Rectifier (SCR) which used for ESD protection clamp under vf-TLP measurements are also reported. The results measured by vf-TLP system showed that the triggering voltage decreased and the second breakdown current increased in comparison with the results measured by a standard 100 ns TLP system. From the HBM/ CDM testing, the RF test chip successfully met the requested RF ESD withstand level, HBM 1 kV, MM 100 V and CDM 500 V.