The effects of wall reflection on indoor MIMO channel capacity are statistically investigated with consideration of the average received power, the effective degrees of freedom (EDOF) of multipaths and the eigenvalues of transfer channel covariance matrix. It is found that the stronger wall reflection can lead to higher MIMO channel capacity.

We report on a channel drop filter with a mode gap in the propagating mode of a photonic crystal slab that was fabricated on silicon on an insulator wafer. The results, simulated with the 3-dimensional finite-difference time-domain and plane-wave methods, demonstrated that an index-guiding mode for the line defect waveguide of a photonic crystal slab has a band gap at wave vector k = 0.5 for a mainly TM-like light-wave. The mode gap works as a distributed Bragg grating reflector that propagates the light-wave through the line defect waveguide, and can be used as an optical filter. The filter bandwidth was varied from 1-8 nm with an r/a (r: hole radius, a: lattice constant) variation around the wavelength range of 1550-1600 nm. We fabricated a Bragg reflector with a photonic crystal line-defect waveguide and Si-channel waveguides and by measuring the transmittance spectrum found that the Bragg reflector caused abrupt dips in transmittance. These experimental results are consistent with the results of the theoretical analysis described above. Utilizing the Bragg reflector, we fabricated channel dropping filters with photonic crystal slabs connected between channel waveguides and demonstrated their transmittance characteristics. They were highly drop efficient, with a flat-top drop-out spectrum at a wavelength of 1.56 µm and a drop bandwidth of 5.8 nm. Results showed that an optical add-drop multiplexer with a 2-D photonic crystal will be available for application in WDM devices for photonic networks and for LSIs in the near future.

Molecular aligned naphthacene thins films were fabricated using vacuum evaporation and the rubbing method. The attenuated total reflection (ATR) and emission light properties from surface plasmon (SP) excitation due to molecular luminescence were investigated for these films. The long axis of the rod-like molecule was estimated to align perpendicular to the rubbing direction. The ATR and emission light properties depended on the molecular orientation.

This paper describes a new low-power write driver circuit for mobile hard disk drive preamplifiers. To achieve low power consumption, we developed a write driver circuit with a single-stage MOS transistor as the current driver, which both switches and controls the write current. We also developed a reflection cancellation method to suppress the distortion of the write current waveform during write transition. Fabricated using 0.35-µm SOI-BiCMOS technology, this write driver circuit consumes low power, 380 mW (at 100 MHz).

A rigorous and simple method is proposed for analyzing guided modes of metallic electromagnetic crystal waveguides. The method is a combination of generalized reflection and transmission matrices and the mode-matching technique. Fast convergence, low computer cost, and high calculating precision are main advantages of the proposed method. This method can easily avoid the relative convergence phenomena than a classical mode-matching method, and the proposed formulation is very suitable to analyzing multilayered problems with very low computer cost. The existence of H-polarized modes in metallic electromagnetic crystal waveguides has been verified.

This paper proposes a gonio-spectral imaging system for measuring light reflection on an object surface by using two robot arms, a multi-band lighting system, and a monochrome digital camera. It allows four degrees of freedom in incident and viewing angles necessary for full parametrization of a reflection model function. Spectral images captured for various incident and viewing angles are warped as if they were all captured from the same viewing direction. The intensity of reflected light is thus recorded in a normalized image form for any incident and viewing directions. The normalized images are used to estimate reflection model parameters at each surface point. To ensure point-wise reflection modeling, a calibration method is also proposed based on a geometrical model of the robot arms and camera. The proposed system can deal with objects with surface texture. Experiments are done on system calibration, reflection model, and spectral estimation. The results using colored objects show the feasibility of the proposed imaging system.

High-resolution FMCW reflectometry is often realized by sampling the beat signal with a clock signal generated from an auxiliary interferometer. The drawback of this system is that the measurement range is limited to less than half of the optical path difference of the auxiliary interferometer to satisfy the Sampling theorem. We propose and demonstrate a method to extend the measurement range of the system. The clock signal gerenerated from the auxiliary interferometer is electronically frequency-multipled by using a PLL circuit. The measurement range is experimentally extended by a factor of 20 while keeping high spatial resolution, and is theoretically extended by a factor of 128. The advantage of the proposed system is that the optical path difference of the auxiliary interferometer can be kept short, which is very effective for obtaining the stable and low time-jitter clock signal.

A free-space method is in wide spread use for the reflectivity measurement of electromagnetic wave absorbers (EMA) in VHF and UHF range. In the free-space method, the reflection levels from EMA and from the metal plate with same size as the EMA are measured, and the reflectivity is calculated from their ratio. The incident angle such as normal or oblique must be defined, and the polarization of electromagnetic (EM) wave must be specified to be TE, TM, or circularly-polarized mode. In this paper, a parallel EM wave beam method using dielectric lenses in front of horn antennas was studied experimentally. Electromagnetic wave absorption was measured with the vertical and the oblique incidence by using this parallel EM wave beam. This measurement system has following features:• It is compact because equiphase parallel EM wave beam was obtained in a short distance from the dielectric lens.• It requires no anechoic chamber because of little multi-reflection due to high directivity of parallel EM wave beam.• It allows a large oblique incident measurement by using high directive parallel EM wave beam.

This paper examines polarimetric scattering characteristics caused by a dihedral corner reflector of finite size. The dihedral corner reflector is a basic model of double-bounce structure in urban area. The detailed scattering information serves the interpretation of Polarimetric Synthetic Aperture Radar (POLSAR) data analysis. The Finite-Difference Time-Domain (FDTD) method is utilized for the scattering calculation because of its simplicity and flexibility in the target shape modeling. This paper points out that there exists a stable double-bounce squint angle region both for perfect electric conductor (PEC) and dielectric corner reflectors. Beyond this stable squint angular region, the scattering characteristics become completely different from the assumed response. A criterion on the double-bounce scattering is proposed based on the physical optics (PO) approximation. The detailed analyses on the polarimetric index (co-polarization ratio) with respect to squint angle and an experimental result measured in an anechoic chamber are shown.

Based on the concept of Equivalent Transformation Method of Material Constant (ETMMC), a thin and light weight EM-wave absorber is newly proposed. It becomes possible to merge both the competing characteristics of changing the matching frequency toward a higher frequency region by means of punching out small holes in the magnetic absorber and of changing the matching frequency toward a lower frequency region by attaching periodical conductive patterns to the surface of it. First, the ETMMC idea is introduced in this paper. The detailed matching characteristics of the present absorber are investigated based on FDTD analysis. The matching mechanism is clarified from input admittance chart viewpoints. The matching characteristics can be changed from 2.4 GHz to above 6.0 GHz using carbonyl iron with the thickness of 2 mm and improved below -20 dB.

When a large-size car exists on the ETC lane (Electronic Toll Collection System), there is the possibility that the interference on the adjacent lane occurs by the scattering waves from one. In this paper, we propose a new improvement method which the transparent EM wave absorber is placed between the ETC lane and the adjacent one in order to suppress the scattering waves from a large-size car. Therefore, we design the transparent EM wave absorber which consists of the transparent resistive and conductive films. Then, this absorber is produced, and its reflection and transmission coefficients are evaluated. In addition, its transmittance in optics is evaluated. As the results, the reflectivity of this absorber is obtained lower than -20 dB in the oblique incident angle from 0to 30at 5.8 GHz circular polarized wave, abbreviated as CP wave, and also the transmittivity is obtain lower than -27 dB in the oblique incident angle from 0to 70, respectively. On the other hand, the transmittance in optics is obtained higher than 60%. Moreover, we study experimentally on the ETC system with placing this absorber between the ETC lane and the adjacent one. We measured the distribution of receiving power on the adjacent lane, when a water sprinkler existed on the ETC lane. As a result, it is confirmed that the receiving power on the adjacent lane could be realized lower than -70.5 dBm, and then a new improvement method has proven to be very useful in the ETC system.

A design of a linearly-polarized non-resonant waveguide broad-wall transverse slot linear array with suppressed grating lobes is presented. Each unit element in the array consists of a transverse slot, an inductive post and a parasitic dipole-pair at a height of half of the free space wavelength. It is designed as an isolated unit without considering mutual coupling by using the Method of Moments (MoM) for radiation suppression in grating beam direction and reflection cancellation at the input. The elements thus designed are used in a travelling wave array environment. It is predicted that the reflection is less than -20 dB at 11.95 GHz while the grating lobes are suppressed by more than 15 dB. The design and the characteristics of the array are confirmed by measurements.

Deflection routing is one of the promising approaches to resolve contention in the optical burst switching networks. In the conventional deflection routing scheme, optical bursts may be unable to traverse the route evaluated to select an outgoing link because of the contention at succeeding downstream transit nodes. As a result, the optical bursts may traverse a different route resulting in a long distance or decreased performance. This paper proposes a deflection routing scheme that considers the possibility of the contention at downstream nodes. This scheme utilizes the "expected route distance" instead of the static route distance toward a destination node. The expected route distance considers the possibility of contention at each downstream transit node and is calculated using measured link blocking probabilities at each downstream transit node. The selection priority of each outgoing link is given dynamically based on its expected route distance toward a destination node. By considering the possibility of contention at downstream nodes, a routing scheme with high performance can be realized. The loss rate of optical bursts is improved when an imbalanced load is applied to the network, and the loss rate of optical bursts is also improved when the network includes links with extremely different distances.

Apodised chirped gratings based on InGaAsP/InP deep-ridge waveguides with vertical-groove surface gratings were fabricated. Reflectivity ripple and group delay ripple were reduced from around 4 dB to 1 dB and from around 5 ps to 2 ps, respectively, by apodisation over a wavelength range of around 20 nm.

The reflection characteristics of large alternating-phase fed single-layer waveguide arrays with center-feeds are investigated to identify the mechanism for bandwidth narrowing effects. Firstly, the overall reflection for the whole array is analyzed by FEM and fine agreement with measurements is demonstrated. It is deviating from the conventional prediction based upon a simple sum of reflections from components in the array, such as the multiple-way power divider, the slot waveguides and the aperture at the antenna input. Careful diagnosis reveals that the mutual coupling between the alternating phase waveguides via external half-space is the key factor in reflection accumulation. Amongst all, the slot with strong excitation whose position depends upon the aperture illumination design produces the dominant contribution in the mutual coupling.

This paper attempts to use the polarimetric correlation coefficient for extraction of the polarimetric features of the urban areas and the natural distributed areas from Polarimetric Synthetic Aperture Radar (POLSAR) data. There is a possibility that the polarimetric correlation coefficient can reveal various scattering mechanisms of terrains based on the reflection symmetry property. In order to verify the capability of polarimetric correlation coefficient, we examined the behavior of this coefficient of the urban areas and the natural distributed areas with respect to the several polarimetric scattering models in the linear and circular polarization bases, and the difference of the polarimetric scattering characteristics between these two areas was derived. It was confirmed that the polarimetric correlation coefficient is useful to extract the polarimetric features from the actual L-band and X-band POLSAR data.

A GaInAs/InP multiple quantum well (MQW)-based wavelength demultiplexer composed of a waveguide array in which the refractive index varies across the array yielded successful results of wavelength demultiplexing and optical deflection. Since optical path length differences between waveguides in the array are achieved through refractive-index differences controlled by the SiO2 mask design in selective metal-organic vapor phase epitaxy (MOVPE), a straight waveguide grating can be formed with reduced optical propagation losses. A straight waveguide array device with a 1.4% refractive-index difference was fabricated. The fabrication of a preliminary wavelength demultiplexer was also achieved, for which a wavelength separation with an approximately 25 nm spacing and free spectral range (FSR) of approximately 100 nm were obtained. Moreover, an optical deflector was investigated and primitive deflection was achieved at 1460 and 1490 nm incident wavelengths.

We have implemented a distributed sensor system based on an array of fiber Bragg gratings (FBGs), which can measure up to 1000 points with a single piece of fiber. The system consists of FBGs having the same resonant wavelengths and small reflectivities (0.1 dB), and a wavelength tunable optical time-domain reflectometer (OTDR). To interrogate the distributed grating sensors and to address the event locations simultaneously, we have utilized the tunable OTDR. A thermoelectric temperature controller was used to tune the emission wavelength of the OTDR. The operating temperature of the laser diode was changed. By tuning the pulse wavelength of the OTDR, we could identify the FBGs whose resonant wavelengths were under change within the operating wavelength range of the DFB LD. A novel sensor cable with dry core structure and tensile cable was fabricated to realize significant construction savings at an industrial field and in-door and out-door applications. For experiments, a sensor cable having 52 gratings with 10 m separations was fabricated. To prevent confusion with unexpected signals from the front-panel connector zone of the OTDR, a 1 km buffer cable was installed in front of the OTDR. The proposed system could distinguish and locate the gratings that were under temperature variation from 20 to 70.

In this paper we analyze the characteristics of tapered multimode interference (MMI)-based coherent lightwave combiners, and theoretically confirm that the stable and clear multimode interference images exist in the tapered MMI combiners. We present the output characteristics of 21 tapered MMI-based coherent lightwave combiners under various structures, which are useful to optimally design the combiners. In order to extend the combiner to a multi-port (N1, N > 2) configuration, a new structure with the border shapes of two tangent arcs is proposed, by which we show an output power imbalance of about 0.5 dB between different input ports of an 81 tapered coherent lightwave combiner. Due to the advantages of no end-facet reflection, easy extension to a multi-port configuration, high tolerance for fabrication errors and a compact size, the tapered MMI structure is a good candidate as a coherent lightwave combiner used in large-scale photonic integrated circuits.

This paper deals with a TE plane wave reflection and transmission from a one-dimensional random slab by means of the stochastic functional approach. The relative permittivity of the random slab is written by a Gaussian random field in the vertical direction with finite thickness, and is uniform in the horizontal direction with infinite extent. An explicit form of the random wavefield is obtained in terms of a Wiener-Hermite expansion with approximate expansion coefficients (Wiener kernels) under a small fluctuation case. By using the first three terms of the random wavefield representation, the optical theorem is illustrated in figures for several physical parameters. It is then found that the optical theorem holds with good accuracy.