In this paper, an eight-legged resonant element is proposed for a multiband and dual-polarized frequency selective surface (FSS). The FSS element has two resonant frequencies for constructing two reflection bands, of which the separation can be easily controlled by adjusting the shape of the element. The flexibility is demonstrated by the simulated results of transmission responses for various geometrical parameters. And it is shown that introducing resonant-grid and closely-packing techniques can improve the reflection bandwidth. Finally, the good agreement between the measured and the calculated results proves that the eight-legged element is useful for the design of a multiband FSS.

In conventional OFDM systems, the effect of inter-block-interference (IBI) can be completely removed by inserting sufficient redundant symbols between successive transmission blocks. In this paper, based on the reformulated received block symbols of the discrete multirate filterbanks model, a new transceiver model for the cyclic prefix (CP) OFDM systems is proposed, associated with the oblique projector technique (view as the pre-processor for achieving IBI-free). Consequently, a novel ISI-free receiver with the zero-order FIR zero-forcing (ZF) filterbanks equalizer can be devised, under noise-free environment. For performance comparison the bit-error-rate (BER) is investigated for the cases of noisy and noise-free channels. In all cases, viz., the length of CP is shorter or longer than the order of the channel impulse response, we show that the same BER performance compared with the one suggested in [3] can be achieved, under the same assumptions and conditions. Since a simple cascade configuration of the IBI cancellation using the oblique projector followed by the ISI cancellation using the zero-order FIR ZF filterbanks equalizer can be realized for OFDM systems with sufficient or insufficient CP, the complexity of transceiver design can be reduced.

A high quality-factor of active inductor has been implemented by using the 0.18 µm 1P6M CMOS technologies in this work. By adding a feedback resistance and a regulated gain stage transistor into the conventional cascade-grounded approach, the quality-factor and performance of CMOS active inductor can be improved. This novel active inductor demonstrated a maximum quality-factor of 540 and a 3.2 nH inductance at 4.3 GHz, where the self-resonant frequency was 5.4 GHz. An active CMOS bandpass filter was also fabricated including this tunable high quality factor active inductor, performing an insertion loss of 0.2 dB and a return loss more than 32 dB with a tuning range from 3.45 GHz to 3.6 GHz. The input IP3 was -2.4 dBm, and the noise figure was 14.1 dB with a 28 mW dc power consumption.

We propose utilizing subband-based blind source separation (BSS) for convolutive mixtures of speech. This is motivated by the drawback of frequency-domain BSS, i.e., when a long frame with a fixed long frame-shift is used to cover reverberation, the number of samples in each frequency decreases and the separation performance is degraded. In subband BSS, (1) by using a moderate number of subbands, a sufficient number of samples can be held in each subband, and (2) by using FIR filters in each subband, we can manage long reverberation. We confirm that subband BSS achieves better performance than frequency-domain BSS. Moreover, subband BSS allows us to select a separation method suited to each subband. Using this advantage, we propose efficient separation procedures that consider the frequency characteristics of room reverberation and speech signals (3) by using longer unmixing filters in low frequency bands and (4) by adopting an overlap-blockshift in BSS's batch adaptation in low frequency bands. Consequently, frequency-dependent subband processing is successfully realized with the proposed subband BSS.

We demonstrate the C-band wavelength conversion unit having functions of automatic wavelength recognition, power equalization, and elimination of original signal and pumping light for the first time, which is based on four-wave mixing (FWM) in semiconductor optical amplifiers (SOA's). The constructed unit automatically detects signal wavelength, sweeps wavelength of a pumping light, and adjusts center wavelengths of band pass filters and gain values of erbium-doped fiber amplifiers (EDFA's), in order to convert the wavelength of the signal to the arbitrary wavelength we set, and eliminate the original signal and pumping light after conversion. Amplification of the signal, pumping, and wavelength-converted lights compensates the detuning dependence of conversion efficiency and its asymmetry in the quantum-well (QW) SOA, to keep the power of the wavelength-converted light constant within the whole C-band region. The switching time of wavelength conversion by the unit is about a second, which is dominated by mechanical movement of the tunable filters. Wavelength-converted 2.5 and 10 Gb/s NRZ signals show clear eye-openings when the detuning is positive (ωp > ωs), and a 2-ps pulse train is also successfully wavelength-converted. To overcome the problem of the asymmetric conversion efficiency in the QW-SOA, we adopted quantum-dot (QD) SOA's. Although the 1.5 µm QD-SOA still shows its asymmetry, which will be improved by optimization of quantum dot structure, wavelength conversion of a 160 Gb/s RZ signal is demonstrated by the QD-SOA's. More improvement of the performance of the wavelength conversion unit should be possible by making switching time faster and installing the optimized QD-SOA's.

We propose a method of dimensioning and managing the bandwidth of a link on which flows with heterogeneous access-link bandwidths are aggregated. We use a processor-sharing queue model to develop a formula approximating the mean TCP file-transfer time of flows on an access link in such a situation. This only requires the bandwidth of the access link carrying the flows on which we are focusing and the bandwidth and utilization of the aggregation link, each of which is easy to set or measure. We then extend the approximation to handle various factors affecting actual TCP behavior, such as the round-trip time and restrictions other than the access-link bandwidth and the congestion of the aggregation link. To do this, we define the virtual access-link bandwidth as the file-transfer speed of a flow when the utilization of the aggregation link is negligibly small. We apply the virtual access-link bandwidth in our approximation to estimate the TCP performance of a flow with increasing utilization of the aggregation link. This method of estimation is used as the basis for a method of dimensioning the bandwidth of a link such that the TCP performance is maintained, and for a method of managing the bandwidth by comparing the measured link utilization with an estimated threshold indicating degradation of the TCP performance. The accuracy of the estimates produced by our method is estimated through both computer simulation and actual measurement.

By inserting a slot and metallic strips at the widened stub in a single layer and fed by coplanar waveguide (CPW) transmission line, novel dual-band and broadband operations are presented. The proposed antennas are designed to have dual-band operation suitable for applications in DCS (1720-1880 MHz), PCS (1850-1990 MHz), IMT-2000 (1920-2170 MHz), and IEEE 802.11 WLAN standards in the 2.4 GHz (2400-2484 MHz) and 5.2 GHz (5150-5350 MHz) bands. The dual-band antennas are simple in design, and the two operating modes of the proposed antennas are associated with perimeter of slots and loading metallic strips, in which the lower operating band can be controlled by varying the perimeters of the outer square slot and the higher band depend on the inner slot of the widened stub. The experimental results of the proposed antennas show the impedance bandwidths of the two operating bands, determined from 10-dB return loss, larger than 61% and 27% of the center frequencies, respectively.

This paper describes a multiband vector quantization (VQ) technique based on inner product for wideband speech coding at 16 kb/s. Our approach consists of splitting the input speech into two separate bands and then applying an independent coding scheme for each band. A code excited linear prediction (CELP) coder is used in the lower band while a transform based coding strategy is applied in the higher band. The spectral components in the higher frequency band are represented by a set of modulated lapped transform (MLT) coefficients. The higher frequency band is divided into three subbands, and the MLT coefficients construct a vector for each subband. Specifically, for the VQ of these vectors, an inner product-based distance measure is proposed as a new strategy. The proposed 16 kb/s coder with the inner-product based distortion measure achieves better performance than the 48 kb/s ITU-T G.722 in subjective quality tests.

In this paper, we discuss the role of physical (PHY) layer in realization of energy-aware wireless communication systems. With an energy consumption model for a wireless link between a transmitter and a receiver, we discuss a dominant factor to reduce energy consumption and show that, to reduce energy consumption, we should adopt an energy-efficient circuit architecture and modulation/detection scheme, even allowing a little degradation of packet error rate. Finally, we show that wide band signal transmission has a potential to realize not only high data rate transmission but also low energy consumption in wireless communication systems.

A novel scheme for a multi-band power amplifier (PA) that employs a low-loss reconfigurable matching network is presented and discussed. The matching network basically consists of a cascade of single-stub tuning circuits, in which each stub is connected to a transmission line via a Single-Pole-Single-Throw (SPST) switch. By controlling the on/off status of each switch, the matching network works as a band-switchable matching network. Based on a detailed analysis of the influence of non-ideal switches in the matching network, we conceived a new design perspective for the reconfigurable matching network that achieves low loss. A 900/1900-MHz dual-band, 1 W class PA is newly designed following the new design perspective, and fabricated with microelectro mechanical system (MEMS) SPST switches. Owing to the new design and sufficient characteristics of the MEMS switches, the dual-band PA achieves over 60% of the maximum power-added efficiency with an output power for each band exceeding 30 dBm. These results are comparable to the estimated results for a single-band PA. This shows that the proposed scheme provides a band-switchable highly efficient PA that has superior performance compared to the conventional multi-band PA that has a complex structure.

A new sub-1-V CMOS bandgap voltage reference without using low-threshold-voltage device is presented in this paper. The new proposed sub-1-V bandgap reference with startup circuit has been successfully verified in a standard 0.25-µm CMOS process, where the occupied silicon area is only 177 µm106 µm. The experimental results have shown that, with the minimum supply voltage of 0.85 V, the output reference voltage is 238.2 mV at room temperature, and the temperature coefficient is 58.1 ppm/ from -10 to 120 without laser trimming. Under the supply voltage of 0.85 V, the average power supply rejection ratio (PSRR) is -33.2 dB at 10 kHz.

A CMOS low noise amplifier (LNA) for low-power ultra-wideband (UWB) wireless applications is presented. To achieve low power consumption and wide operating bandwidth, the proposed LNA employing stagger tuning technique consists of two stacked common-source stages with different resonant frequencies. This work is implemented in 0.18-µm CMOS process and shows a 2.4-9.4-GHz bandwidth. The amplifier provides a maximum forward gain (S21) of 10.9 dB while drawing 7.1 mW from a 1.8-V supply. A noise figure as low as 4.1 dB and an IIP3 of -3.5 dBm have been demonstrated.

This letter introduces a modified multiband orthogonal frequency division multiplexing (MB-OFDM) signal with low peak-to-average power ratio (PAPR). From the presented results, we can see that the modified MB-OFDM signal can be implemented with low PAPR. When MB-OFDM signals is equipped with a partial transmit sequence (PTS) approach, the PAPR of the modified MB-OFDM signals using two partial transmit sequences is almost the same to that of the ordinary MB-OFDM signals using four partial transmit sequences.

In this paper, three new ultra wideband (UWB) communication systems with quadrature-phase shift keying (QPSK) impulse modulation are proposed. First, direct-sequence (DS) multiple-access scheme is applied. The second proposed system is based on time-hopping (TH) multiple-access scheme. The last proposed system applies TH multiple-access scheme with QPSK impulse modulation and pulse position modulation (PPM). The conventional UWB communications as TH scheme with PPM modulation and DS scheme with binary-phase shift keying (BPSK) are used to compare. The simulation results show that all proposed UWB communication systems can provide obviously better performances compared with the conventional TH-PPM and DS-BPSK UWB communication systems. The comparisons in aspects of transmission bit rate and the number of users are also investigated.

A novel microstrip dual-mode bandpass filter with ultra-broad stopband is proposed using the aperture-backed stepped-impedance ring resonator (SIRR). This SIRR consists of low-impedance strips in the four bended corners and high-impedance strips in the four straight sides. With the cross-shaped aperture placed on the ground underneath the SIRR, the upper stopband is significantly broadened. In particular, the 2nd resonant frequency of this proposed SIRR is confirmed to exceed the four times of its 1st counterpart. The dual-mode filter with the passband of 7.5% at 1.59 GHz is then designed and implemented, demonstrating the measured stopband of 1.70-5.80 GHz and size reduction of 56.0%.

In this paper, we address how to efficiently support differentiated services with the optimized bandwidth reservation in a polling-based generalized TDMA network like E-PON (Ethernet Passive Optical Network). In E-PON, performances of service differentiation for QoS (Quality of Service) guaranteed multiples services are directly affected by the bandwidth reservation algorithm of ONU (Optical Network Unit) in addition to the priority-based packet scheduling. Our proposed Service Quality Pre-engagement (SQP) algorithm reduces the system buffer size, the light-load penalty problem and the service interference among classes effectively by partially introducing the dynamic forward recurrence reservation scheme for QoS guaranteed classes. We also introduce the FRC(Forward Reservation Class) Selection algorithm that preserves the optimized reservation bandwidth to minimize the unnecessary reservation contentions. These algorithms do not mandate the basic concept of DBA and request the similar amount of REPORT bandwidth. The analytic and simulation results are performed to evaluate the performances of the proposed algorithms.

This paper deals with the use of neural network rule extraction techniques based on the Genetic Programming (GP) to build intelligent and explanatory evaluation systems. Recent development in algorithms that extract rules from trained neural networks enable us to generate classification rules in spite of their intrinsically black-box nature. However, in the original decompositional method looking at the internal structure of the networks, the comprehensive methods combining the output to the inputs using parameters are complicated. Then, in our paper, we utilized the GP to automatize the rule extraction process in the trained neural networks where the statements changed into a binary classification. Even though the production (classification) rule generation based on the GP alone are applicable straightforward to the underlying problems for decision making, but in the original GP method production rules include many statements described by arithmetic expressions as well as basic logical expressions, and it makes the rule generation process very complicated. Therefore, we utilize the neural network and binary classification to obtain simple and relevant classification rules in real applications by avoiding straightforward applications of the GP procedure to the arithmetic expressions. At first, the pruning process of weight among neurons is applied to obtain simple but substantial binary expressions which are used as statements is classification rules. Then, the GP is applied to generate ultimate rules. As applications, we generate rules to prediction of bankruptcy and creditworthiness for binary classifications, and the apply the method to multi-level classification of corporate bonds (rating) by using the financial indicators.

This paper introduces a state-of-art on an ultra-wideband (UWB) technology in intelligent transport systems (ITS). To examine the detection performance of a UWB short-range radar for vehicular applications, we developed a 26-GHz band short-range UWB radar system with an embedded compact MMIC-based RF module. In this paper, we briefly comment on the current regulatory environment for UWB radar systems by outlining the structure of an international organization involved in examining the regulatory status of these systems. We then describe the principles of detection and system design for impulse radar, the radar system that we developed, and a MMIC-based RF module as well as the performance of these devices. We measured their performance in a series of laboratory experiments and also measured UWB radar cross sections of an automobile. The results of our experiments suggest that our radar system is capable of detecting targets with a range resolution of around 9 cm.

This paper is devoted to the problem of force sensorless disturbance rejection in robot manipulators. In the proposed approach, the control system uses position sensor signals and estimated values of external forces, instead of force sensor signals. The estimation process is performed via an adaptive force estimator. Then the estimated force vector is utilized to compensate for the force disturbance effect in order to achieve a better trajectory tracking performance. The force estimation is carried out directly using no environment model. Asymptotical stability of the proposed control system is analyzed by the invariant set and Lyapunov direct method establishing an appropriate theorem. Finally, the performance of the proposed control system is verified using numerical simulation.

In this paper, we propose a broadband 3-dB rat-race ring coupler that uses tightly coupled lines. An aperture compensation technique that can simplify the fabrication of tightly coupled lines, is also discussed here. The effective bandwidth of the proposed rat-race coupler with a return loss better than -20 dB can be increased by 14.3%, in comparison with that of March's. Its isolation is always below -20 dB and the phase shift errors less than 6.