Broadening the frequency bandwidth of antennas has been one of the major subjects concerning antenna design technologies. Two of the major subjects for microstrip antennas, which appeared in the 1970s, have also been the broadening of the frequency bandwidth and the sharing of multifrequency bands. In this paper, we describe the broadband and multiband techniques of printed antennas, and show the configurations of realized broadband and multiband antennas and their characteristics. Here, resonant-type microstrip antennas, planar monopole antennas, fractal antennas and ultra-wideband printed antennas are introduced. The optimum design techniques using a genetic algorithm are introduced for developing broadband and multiband printed antennas. The usefulness of this method is verified by the simulation and experimental results of the fabricated planar monopole antenna which has ultrawide-band characteristics.

In the next-generation networks, ultra high-speed data transmission will become necessary to support a variety of advanced point-to-point and multipoint multimedia services with stringent quality-of-service (QoS) constraints. Such a requirement desires the realization of optical WDM networks. Researches on multicast in optical WDM networks have become active for the purpose of efficient use of wavelength resources. Since multiple channels are more likely to share the same links in WDM multicast, effective routing and wavelength assignment (RWA) technology becomes very important. The introduction of the wavelength conversion technology leads to more efficient use of wavelength resources. This technology, however, has problems to be solved, and the number of wavelength converters will be restricted in the network. In this paper, we propose an effective WDM multicast design method on condition that wavelength converters on each switching node are restricted, which consists of three separate steps: routing, wavelength converter allocation, and wavelength assignment. In our proposal, preferentially available waveband is classified according to the scale of multicast group. Assuming that the number of wavelength converters on each switching node is limited, we evaluate its performance from a viewpoint of the call blocking probability.

Propagation characteristics of acoustic waves in photonic crystal fibers (PCFs) have been theoretically investigated in details. In order to evaluate acoustic band structures and guided modes for out-of-plane propagation in PCFs, analysis methods based on the finite element method are newly formulated. It is shown through numerical results that complete acoustic band-gaps (ABGs) exist in the cladding region of PCFs and that acoustic guided modes could be localized in the defect region of PCFs by the ABG effect. Furthermore, it is shown that acoustic guided modes could also be localized in the defect region of PCFs by the total internal reflection. These confinement mechanisms of acoustic waves propagating along the fiber length are completely different to those of lightwaves.

Press-induced long-period fiber gratings exhibiting strong core-to-cladding mode coupling were formed in photonic crystal fiber. Only one resonance peak was observed over a 600 nm spectral range and the resonant wavelength was tuned over the whole range by tilting a groove plate before pressing the fiber. The resonant wavelength decreased with increasing periodicity of the grating, which was opposite to the trend of the step-index conventional optical fiber. Meanwhile, the resonant wavelength increased with increasing the ambient refractive index, which was also opposite to that of the conventional optical fiber.

In this paper, a Dynamic Voltage and Frequency Management (DVFM) scheme introduced in a microprocessor for handheld devices with wideband embedded DRAM is reported. Our DVFM scheme reduces the power consumption effectively by cooperation of the autonomous clock frequency control and the adaptive supply voltage control. The clock frequency is controlled using hardware activity information to determine the minimum value required by the current processor load. This clock frequency control is realized without special power management software. The supply voltage is controlled according to the delay information provided from a delay synthesizer circuit, which consists of three programmable delay components, gate delay, RC delay and a rise/fall delay. The delay synthesizer circuit emulates the critical-path delay within 4% voltage accuracy over the full range of process deviation and voltage. This accurate tracking ability realizes the supply voltage scaling according to the fluctuation of the LSI's characteristic caused by the temperature and process deviation. The DVFM contributes not only the dynamic power reduction, but also the leakage power reduction. This microprocessor, fabricated in 0.18 µm CMOS embedded DRAM technology achieves 82% power reduction in a Personal Information Management scheduler (PIM) application and 40% power reduction in a MPEG4 movie playback application. As process technology shrinks, the DVFM scheme with leakage power compensation effect will become more important realizing in high-performance and low-power mobile consumer applications.

This work proposes an 8b 220 MS/s 230 mW 3-stage pipeline CMOS ADC with on-chip filters for temperature- and power supply- insensitive voltage references. The proposed RC low-pass filters reduce reference settling time at heavy R&C loads and improve switching noise performance without conventional off-chip bypass capacitors. The prototype ADC fabricated in a 0.25 µm CMOS occupies the active die area of 2.25 mm2 and shows the measured DNL and INL of maximum 0.43 LSB and 0.82 LSB, respectively. The ADC maintains the SNDR of 43 dB and 41 dB up to the 110 MHz input at 200 MS/s and 220 MS/s, respectively, while the SNDR at the 500 MHz input is degraded as much as only 3 dB than the SNDR at the 110 MHz input.

Multipath propagation of radio signal introduces frequency selectivity. OFDMA systems greatly suffer from frequency selective fading. It is an important limit factor of performance of OFDMA systems, especially in subband based multiple user access scehems. In this paper, we propose the method of subband selection and handover to improve the system performance over the frequency selective channel. Two subband selection algorithms are presented to accurately select the subband with high channel gain and avoid the channel notch. The random access procedure employing subband selection is presented as an example. The effects of the subband selection are also given. The selection effectively improves the performances of frame synchronization, frequency synchronization, channel estimation, and bit error rate (BER). The investigations show that the proposed scheme is promising to reliable communications over frequency selective fading channel.

Conventional WDM systems multiplex channels with different signal bandwidths using fixed and equal channel spacing. As a result, their spectral efficiency is rather poor. If the wavelength and the bandwidth of each channel in a WDM system could be freely changed as needed, a variety of services with different signal bandwidths could be accommodated efficiently. This is expected to yield high spectral efficiency. For this purpose, this paper proposes a WDM optically amplified system that combines optical power splitting with homodyne detection; its use in three configurations, point to point, ring (center to remote nodes), and peer to peer, is described. Coherent optical systems generally need a frequency stable local light source in addition to a sending light source in each WDM channel. We improve cost effectiveness by proposing that the output of one light source be divided to yield the local light for frequency selection by homodyne detection and the sending light source whose output is externally modulated by transmission signal. In this configuration, the local light level is low to permit high levels of sending power. The key problem is how to get high SNR with limited low-level local lights. This paper derives the optimum receiving loss condition that can maximize the SNR with local light levels as low as -20 dBm for the point to point configuration. For the ring configuration, the system overcomes the optical power loss created by splitting numbers over 1,000 even if the local lights are as low as 0 dBm. The ring configuration can, therefore, flexibly accommodate many users and services. We also elucidate the relation between SNR and BER for DPSK homodyne detection in a bandwidth-flexible system.

In this paper a novel dielectric resonator (DR) bandpass filter (BPF) with flexible arrangement of attenuation poles is proposed. This DR filter is similar to a conventional DR filter except adding a microstrip line below a DR, which not only shifts the location of attenuation poles, but also improves skirt characteristics. The duplexer with the proposed DR BPF has been yielded better isolation and sharper skirt behavior than that with a conventional DR filter. The implemented duplexer has shown a good performance and been well agreed with the simulation.

We propose an aperture coupling E-bend with step structure as a robust post-wall waveguide interface to an external standard waveguide in which the posts are separated from the aperture. A 61.25 GHz model transformer gives 11.4% bandwidth for the reflection below -25 dB by using a 1.2 mm-height dielectric substrate. We have compared the mechanical tolerances of both the conventional straight structure and the proposed step structure. The step structure is more robust against mechanical errors than the conventional one. Another advantage is that the accuracy of the analysis model for the post-wall to metal-wall replacement is enhanced for the step structure.

Recently, wideband speech communication using 7 kHz-wideband speech coding, as described in ITU-T Recommendations G.722, G.722.1, and G.722.2, has become increasingly necessary for use in advanced IP telephony using PCs, since, for this application, hands-free communication using separate microphones and loudspeakers is indispensable, and in this situation wideband speech is particularly helpful in enhancing the naturalness of communication. An objective quality measurement methodology for wideband-speech coding has been studied, its essential components being an objective quality measure and an input test signal. This paper describes Wideband-PESQ conforming to the draft Annex to ITU-T Recommendation P.862, "Perceptual Evaluation of Speech Quality (PESQ)," as the objective quality measure, by evaluating the consistency between the subjectively evaluated MOS (Mean Opinion Score) and objectively estimated MOS. This paper also describes the verification of artificial voice conforming to Recommendation P.50 "Artificial Voices," as the input test signal for such measurements, by evaluating the consistency between the objectively estimated MOS using a real voice and that obtained using an artificial voice.

We report tunable optical devices based on fiber Bragg gratings (FBGs), whose filtering characteristics are controlled by strain distributions. These devices include a widely wavelength tunable filter, a tunable group-velocity dispersion (GVD) compensator, a tunable dispersion slope (DS) compensator, and a variable-bandwidth optical add/drop multiplexer (OADM), which will play important roles for next-generation reconfigurable optical networks.

The use of a two-point modulator with variable PLL loop bandwidth as a GFSK signal generator is proposed. Delta-sigma modulation is adopted for the modulator. Through the combination of a variable PLL feedback loop and delta-sigma modulation, both a fast settling time and very clear eye opening are achieved for the modulator. We fabricate it in 0.35-µm BiCMOS process technology. The two-point modulator has a center-frequency drift of only 14.9 kHz, much lower than the 178-kHz result for a single time slot in the case of direct VCO modulation. This is due to the PLL feedback loop. Evaluation also confirmed that the circuit satisfies the various characteristics required of a Bluetooth transmitter. The two-point modulator is also applicable to other transceivers which use FSK or PSK modulation, i.e. forms of modulation where a constant signal level is transmitted, and thus contributes to the simplification of a range of wireless transmitters.

This letter presents a method to simulate a phase-included UWB channel impulse responses for a given indoor channel. In this method we decompose a UWB pulse into a finite number of spectral components. This enables the received signal to be determined by the sum of the convolutions between each spectral component and a corresponding frequency-dependent UWB channel impulse response. The ray-tracing algorithm is applied to calculate the amplitude and the phase of each frequency-dependent channel impulse response. Based on the calculated results, we finally show the simulation of the UWB channel impulse response.

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.

In this paper an analog-digital signal processing scheme for multichannel signal reception with low-IF receivers is proposed and its performance is investigated. In the low-IF receivers, the signal in the mirror frequency causes interference to the desired signal. In the proposed analog-digital signal processing scheme, the interference signal is extracted with the analog filter and the interference to the desired signal is reconstructed by LMS algorithm.

This paper describes a polarimetric feature extraction method from urban areas using the POLSAR (Polarimetric Synthetic Aperture Radar) data. The scattering characteristic of urban areas is different from that of natural distributed areas. The main point of difference is polarimetric correlation coefficient, because urban areas do not satisfy property of azimuth symmetry, Shh = Shv = 0. The decomposition technique based on azimuth symmetry can not be applied to urban areas. We propose a new model fit suitable for urban areas. The proposed model fit consists of odd-bounce, even-bounce and cross scattering models. These scattering models can represent the polarimetric backscatter from urban areas, and satisfy Shh 0 and Shv 0. In addition, the combination with the proposed model fit and the three component scattering model suited for natural distributed areas is examined. It is possible to apply the combined technique to POLSAR data which includes both urban areas and natural distributed areas. The combined technique is used for feature extraction of actual X-band POLSAR data acquired by Pi-SAR. It is shown that the proposed model fit is useful to extract polarimetric features from urban areas.

Electromagnetic noise radiated from microwave ovens may cause serious interference problems in wireless systems using the 2.4-GHz band. Since oven noise waveforms show strong dependence on the frequency selectivity of the receiver filters, the effect of band limitation on the interfering oven noise is an important issue for evaluating or comparing the performance degradation of wireless systems subject to interference. To understand these effects, theoretical and experimental investigations of the waveform, peak amplitude, and pulse width of band-limited oven noise are carried out. It is found that the peak amplitude of the received noise changes with the bandwidth in a way very similar to the case of a simple RF tone-burst input. The pulse width of the received noise also changes with the receiver bandwidth but takes a minimum value at a certain receiver bandwidth, which is an essential feature of band-limited microwave oven noise. In addition, an appropriate resolution bandwidth is determined for using a spectrum analyzer to obtain accurate oven noise parameters.

A one-dimensional finite-difference time-domain (FDTD) simulator for ultrafast optical switches based on intersubband transition (ISBT) in GaN/AlN waveguide is described. Influences of the inhomogeneous broadening and the 2D mode profile have been taken into consideration. The ultrafast optical response (τ 185 fs) measured in a GaN/AlN waveguide was successfully reproduced by the simulator. At present, however, the saturation characteristics of the fabricated device are mainly limited by the excess TM loss caused by the dislocation in MBE-grown nitride layers. When the dislocation density is reduced and the structure is optimized, the switching pulse energy will be improved to about 10 pJ. Further reduction ( 1 pJ) will be possible when low-loss submicron waveguides with spot-size converters are developed.

Bandpass sampling algorithm is effectively adopted to obtain the digital signal with significantly reduced sampling rate for a single radio frequency(RF) signal. In order to apply the concept to multiple RF signals, we propose bandpass sampling algorithms with the normal and the inverse placements since we are interested in uniform order of the spectrum in digital domain after bandpass sampling. In addition, we verify the propose algorithms with generalized equation forms for the multiple RF signals.