In this paper, a new method based on the mode-matching method in the sense of least squares is presented for analyzing the two dimensional scattering problem of TE plane wave incidence to the infinite plane surface with an arbitrary imperfection of finite extent. The semi-infinite upper and lower regions of that surface are a vacuum and a perfect conductor, respectively. Therefore the discussion of this paper is developed about the Dirichlet boundary value problem. In this method, the approximate scattered wave is represented by the integral transform with band-limited spectrum of plane waves. The boundary values of those scattered waves are described by only abscissa z and Fourier spectra are obtained by applying the ordinary Fourier transform. Moreover, new approximate functions are made by inverse Fourier transform of band-limited those spectra. Consequently, the integral equations of Fredholm type of second kind for spectra of approximate scattered wave functions are derived by matching those new functions to exact boundary value in the sense of least squares. Then it is shown analytically and numerically that the sequence of boundary values of approximate wave functions converges to the exact boundary value, namely, the boundary value of the exact scattered wave in the sense of least squares when the profile of imperfection part is described by continuous and piecewise smooth function at least. Moreover, it is shown that this sequence uniformly converges to exact boundary value in arbitrary finite region of the boundary and the sequence of approximate wave functions uniformly converges to the exact scattered field in arbitrary subdomain in the upper vacuum domain of the boundary in wider sense when the uniqueness of the solution of the Helmholtz equation is satisfied with regard to the profile of the imperfection parts of the boundary.

The relative permittivity and permeability are discontinuous at the grating profile, and the electric and magnetic flux densities are continuous. As for the method of analysis for scattering waves by surface relief gratings placed in conical mounting, the spatial harmonic expansion approach of the flux densities are formulated in detail and the validity of the approach is shown numerically. The present method is effective for uniform regions such as air and substrate in addition to grating layer. The matrix formulations are introduced by using numerical calculations of the matrix eigenvalue problem in the grating region and analytical solutions separated for TE and TM waves in the uniform region are described. Some numerical examples for linearly and circularly polarized incidence show the usefulness of the flux densities expansion approach.

An inverse scattering problem of estimating the surface impedance for an inhomogeneous half-space is investigated. By virtue of the fact that the far field representation contains the spectral function of the scattered field, complex values of the function are estimated from a set of absolute values of the far field. An approximate function for the spectral function is reconstructed from the estimated complex values by the least-squares sense. The surface impedance is estimated through calculating the field on the surface of the half-space expressed by the inverse Fourier transform. Numerical examples are given and the accuracy of the estimation is discussed.

Locality in high frequency diffraction is embodied in the Method of Moments (MoM) in view of the method of stationary phase. Local-domain basis functions accompanied with the phase detour, which are not entire domain but are much larger than the segment length in the usual MoM, are newly introduced to enhance the cancellation of mutual coupling over the local-domain; the off-diagonal elements in resultant reaction matrix evanesce rapidly. The Fresnel zone threshold is proposed for simple and effective truncation of the matrix into the sparse band matrix. Numerical examples for the 2-D strip and the 2-D corner reflector demonstrate the feasibility as well as difficulties of the concept; the way mitigating computational load of the MoM in high frequency problems is suggested.

In this paper, we propose a new method for the electromagnetic fields with inhomogeneous media mixed a positive and negative regions by the combination of improved Fourier series expansion method using the extrapolation method which obtains the correct value of the eigenvalue and eigenvectors for the case of TM wave. Numerical results are given for the power reflection and transmission coefficient, the energy absorption, the electromagnetic fields, and the power flow in the inhomogeneous medium mixed the positive and negative regions including the case when the permittivity profiles touches zero for the TM wave. The results of our method are in good agreement with exact solution which is obtained the modified multilayer approximation method.

This paper presents a computational approach to the imaging of a partially immersed conducting cylinder. Both cubic-spline method and trigonometric series for shape description are used and compared. Based on the boundary condition and the recorded scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulated into an optimization problem. The genetic algorithm is employed to find out the global extreme solution of the object function. It is found that the shape described by Fourier series can be reconstructed by cubic-spline. In the opposite case, the shape described by cubic-spline and reconstructed by Fourier series expansion will fail. Even when the initial guess is far away from the exact one, the cubic-spline expansion and genetic algorithm can avoid the local extreme and converge to a global extreme solution. Numerical results are given to show that the shape description by using cubic-spline method is much better than that by the Fourier series. In addition, the effect of Gaussian noise on the reconstruction is investigated.

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.

Waveguide-type optical amplifiers doped with Ytterbium and Erbium ions are theoretically studied. Sensitization of Er-doped amplifiers with Yb ion doping have many advantages such as the possibility of using broader pumping wavelength range and efficient pumping with smaller pumping power. Transient amplification characteristics of optical short pulses are numerically analyzed using FDTD method. The amplification characteristics are compared with the result of the steady state analysis using the rate equations.

The Modified edge representation (MER) is the concept to be used in the line integral approximation for computing the surface radiation integrals of diffraction. The MER as applied to the physical optics (PO-MER), has remarkable accuracy in the surface-to-line integral reduction even for the curved surfaces and for sources very close to the scatterer. In the discussion of the mathematical foundation for this accuracy, the evaluation of the singularities in the integrand of the PO-MER line integration was left for further study.

In this paper, we presented a beam adjustable antenna made up of a slit waveguide and a dielectric slab. In order to change the radiation main-beam angle, we changed the phase constant of the waveguide mode by inserting a dielectric slab for perturbing its field distribution. The direction of radiation main-beam can be steered by dynamically changing the position of the dielectric slab. For the theoretical analysis, the dispersion relation, including the phase and attenuation constants, was determined by solving the transverse resonance equation. An agreement between the theoretical and experimental radiation pattern verifies the beam-steering mechanism. Up to 23beam-steering angle can be achieved using this approach.

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.

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.

The authors propose the simple and efficient method based on the shooting and bouncing rays (SBR) method in order to evaluate multi-reflection effects inside a radome. In this paper, we show the analysis procedure of the proposed method. Next, we compare calculated data with some measured data in order to verify the proposed method. We confirmed that the proposed method is effective for the objects with radome except the areas where strong edge diffraction appears.

We propose an adaptive plastic-landmine visualizing radar system employing a complex-valued self-organizing map (CSOM) dealing with a feature vector that focuses on variance of spatial- and frequency-domain inner products (V-CSOM) in combination with aperture synthesis. The dimension of the new feature vector is greatly reduced in comparison with that of our previous texture feature-vector CSOM (T-CSOM). In experiments, we first examine the effect of aperture synthesis on the complex-amplitude texture in space and frequency domains. We also compare the calculation cost and the visualization performance of V- and T-CSOMs. Then we discuss merits and drawbacks of the two types of CSOMs with/without the aperture synthesis in the adaptive plastic-landmine visualization task. The V-CSOM with aperture synthesis is found promising to realize a useful plastic-landmine detection system.

Target reconstruction algorithm from its monostatic radar cross section (RCS) has been proposed for polygonal cylinders with curved surfaces. This algorithm is based on our previous finding that the main contribution to the back scattering is due to edge diffracted fields excited at a facet of nearly specular reflection direction. Dimension of this constitutive facet of the target is estimated from the local maxima and its lobe width in the angular RCS variation. Half and quarter circular cylinders are used as canonical scattering objects, and their measured and numerically simulated monostatic RCS values have been studied extensively to find scattering pattern characteristic difference between flat and circularly curved surfaces. Thus estimated constitutive facets are connected in order, and this procedure will be continued until the distance between the first and the final edges would be minimized. Our algorithm has been tested for other targets, and it is found that it works well for predicting metal convex targets with flat and curved facets.

Coupling between resonators are analyzed theoretically on basis of the coupled mode theory. New and basic equations for the coupling coefficient are derived and compared with those of waveguides. They should be useful for understanding the physical background of coupling and designing a new coupling scheme.

Characteristics of a class of stepped-impedance resonators (SIRs) which is loaded with two dielectric rods, are investigated by a Finite-Difference Time-Domain (FDTD) method. Dielectric rods to be inserted between a strip conductor and the ground plane have higher relative permittivity than that of the substrate. When a tapped half-wavelength (λ/2) microstrip resonator is loaded with two dielectric rods, the electric length of a loaded λ/2 resonator becomes longer than λ/2, which makes its fundamental resonant frequency () to be generated on the region lower than that of an unloaded λ/2 resonator (f_r) and its first spurious response (f_sp1) is generated on the region higher than 2. Therefore, to shift back to f_r, the resonator's length is to be reduced, and this, in turns, suppress the spurious responses. Then, the resonant characteristics of an SIR employing the proposed method has also been investigated, and it is found that this is capable of suppressing the spurious responses in wideband together with an attenuation pole in the stopband, and of further reducing the resonator's length. Therefore, wide exploitation of the presented method can be expected in the filter design based on the LTCC technique.

This paper investigates intermodultation distortion in ferroelectric phase shifters depending on bias voltage. Two analog phase shifters based on barium-strontium-titantate (BST) coated sapphire substrates have been fabricated with interdigital capacitors (IDCs) which have 2 and 4 µm spacing between adjacent fingers. In case of the phase shifter with 4 µm-spaced IDCs, a phase shift of more than 121was obtained with a maximum insertion loss of 1.8 dB from 2.4 to 2.5 GHz over a bias voltage range of 0-140 V. The phase shifter with 2 µm-spaced IDCs exhibited a phase shift of more than 135with a maximum insertion loss of 2.37 dB in the same frequency range. In this case, a bias voltage of 80 V was used. Using 2 and 4 µm-spaced phase shifters, a third-order intermodulation (IM3) measurement was carried out with a two-tone cancellation setup to investigate nonlinearity, resulting in an input third-order intercept point (IIP3) of about 30.5 dBm and 38.5 dBm, respectively.

This paper presents a high performance wideband CMOS direct down-conversion mixer for UWB based on 0.18 µm CMOS technology. The proposed mixer uses the current bleeding technique and an extra resonant inductor to improve the conversion gain, noise figure (NF) and linearity. Also, with an extra inductor and the careful choosing of transistor sizes, the mixer has a very low flicker noise. The shunt resistor matching is applied to have a 528 MHz bandwidth matching at 50 Ohm. The simulation results show the voltage conversion gain of 20.5 dB, the double-side band NF of 5.6 dB. Two-tone test result indicates 11.25 dBm of IIP3 and higher than 70 dBm of IIP2. The circuit operates at the supply voltage of 1.8 V, and dissipates 11.5 mW.

This paper presents a frequency-controllable image rejection mixer in heterodyne architecture for 2 GHz applications based on TSMC 0.18 µm CMOS technology. The designed mixer uses a notch filter to suppress the image signal and allows precise tuning the image frequencies. An image rejection of 20-70 dB is obtained in a 200 MHz of bandwidth. The simulation results show single-side band (SSB) NF is improved 3.7 dB, the voltage conversion gain of 14.7 dB, improved by more than 4 dB. The circuit operates at the supply voltage of 1.8 V, and dissipates 11.34 mW.

In [1], an algorithm based on phase variations of received pilot symbols was proposed to estimate one of the most important channel parameters, maximum Doppler shift, f_d. However, AWGN (Additive white gauss noise) will cause large estimation error in some cases. In order to analyze the influence of noise, we extended the phase probability density function (pdf) in [1] to the scenario with both fading and AWGN, then the estimation error is characterized in closed-form expression. By this error expression, we found that power control will affect the estimator of [1] and we proposed a modification method based on SNR estimation to obtain accurate Doppler shift estimation in moderate low SNRs (signal-to-noise ratio). Simulation results show high accuracy in wide range of velocities and SNRs.

A multi-user space-time block coding (STBCa) system is a multi-access system where co-channel users employ space-time block codes (STBC). In this paper, we aimed at the design of efficient zero-forcing (ZF) receivers, especially ZF iterative interference cancellation (IC) receivers, for multi-user {G₂, G₃, G₄} STBC systems with an arbitrary number of users, based on the identification of algebraic properties existing in the systems. First, we identify some algebraic properties for {G₂, G₃, G₄} STBC systems. Then, utilizing these algebraic properties, we further expose two significative properties, called "ZF output uncorrelated property" and "ZF output equal Post-detection SNR property" respectively, for least-squares (LS) ZF receivers in multi-user {G₂, G₃, G₄} STBC systems by detailed proofs. Based on the two properties, a novel LS ZF user-ordered successive interference cancellation (ZF UOSIC) detection algorithm is proposed subsequently. Finally, simulation results show that ZF UOSIC is superior to the conventional ZF IC and maximum-likelihood (ML) algorithms and the non-ordered ZF user-based SIC (ZF USIC) algorithm due to adopting iterative IC and optimal ordering among users, and has very close performance to the ZF symbol-ordered SIC but with lower complexity due to the fewer iterative times.

We propose an efficient and practical seamless handoff scheme for 4G mobile systems based on IP and OFDM. The seamless handoff scheme obtains the physical channel for handoff in a contention-free manner with pre-synchronization and pre-forwarding IP contexts. As a result, it thoroughly decreases the physical channel blocking time as well as IP layer context-switching time to minimize total handoff delay.

Surface wave distribution over electromagnetic bandgap (EBG) plate is measured and suppression of surface wave propagation over the EBG is investigated. We used a micro current probe that detects H-field strength of the propagating transverse magnetic (TM) microwave up to 6 GHz. By scanning with the probe over the EBG, we visualized surface wave distribution at various frequencies. This visualized map shows that the EBG plate suppresses the surface wave propagation within the bandgap frequency. We utilized this effect for the antenna reflective shield. By combining the EBG with a microstrip patch antenna, this EBG works as a reflective shield and the front-to-backward radiation ratio of antenna is increased. In this experiment, we fabricated three types of shield board; mushroom type of EBG that has hexagonal textured patches connected with via-holes, textured surface without via-holes, and plane metal. By comparing the surface wave distributions and beam patterns of antenna with various shields, we found that the visualized map of TM surface wave gives us direct and intuitive information and helpful tips in designing the EBG reflective shield for patch antenna.

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.

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 (ω_p > ω_s), 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.

This paper introduces a new approach to realize a multi-state operation on the microwave isolator using ferrite edge-mode. The voltage control of total transmission on the isolator is realized. The operation is based on the unique property of ferrite edge-mode and the variable resistance of PIN diodes. On the isolator, the frequency response is investigated both experimentally and numerically. The numerical analysis is performed by the FDTD method. Both numerical and experimental results have shown that the transmission between two ports can be totally controlled by the applied voltage for the diodes. The experimental results indicate that the transmission direction can be controlled at 11 GHz, and the isolation ratio can be controlled for more than 30 dB.

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.

Generalized impedance boundary conditions are employed to simulate the effects of the parallel-stratified media on electromagnetic fields. Sommerfeld type integral contained in Hertz potential is expressed as the sum of two parts: zeroth order Hankel function and an absolutely convergent series expansion of spherical Hankel functions.

A reconfigurable CMOS mixer for multi-standard application is presented. The mixer can be tuned and adjusted to multi-frequency bands using a flexible matching network which is a kind of variable reactance transformer. The flexible matching network consists of a few switched inductors and capacitors. The mixer has acceptable conversion gain, IIP3 and NF. It operates with a return loss of less than -10 dB through 2-6 GHz except for a few narrow frequency bands.

In this letter, the validity of lumped element class-F amplifier circuit design approaches, which were previously proposed by the same authors, has been demonstrated experimentally using microwave InGaP/GaAs HBT. By means of the proposed class-F amplifier design method, more than 4th order higher harmonic frequencies can be taken into account in class-F microwave amplifier design using only lumped element components. In this approach, miniaturization of class-F amplifier circuit has also been realized. A collector efficiency of 71.2% and a power-added efficiency of 69.2% have been measured at an operating fundamental frequency of 1 GHz considering up to the 4th order higher harmonic frequency.

In this paper, we propose a voltage controlled oscillator (VCO) with up mode type Miller-integrator. The controlled voltage of this VCO can continuously change 0 V center in the positive and negative bidirection. Also, the relationship between control voltage and oscillating frequency shows the good linearity, and the calculated and the measured values agree well.

In the letter we extend our previous work, which applies genetic programming to passive filter synthesis tasks. The extended method deals with the tolerance design considerations. Experimental results show that our method can effectively generate filters which outperform those generated by traditional methods. In addition, it provides filter designers with an effective CAD tool to manage the trade-off between manufacturing yield and circuit cost.

In this letter, a new asynchronous Re-Order Buffer (ROB) with fully distributed control is proposed for an asynchronous on-chip bus. Due to the fully distributed control by each dedicated controller, the proposed ROB has high modularity and scalability. Simulation results show that the proposed asynchronous ROB can operate on an asynchronous on-chip bus of 2.01 Gbit/s throughput and 0.232 nJ power consumption per bus transaction.

A multiple-issue on-chip bus of a layered architecture in a Globally Asynchronous Locally Synchronous (GALS) design style, supporting in-order/out-of-order completion, is proposed in this letter. The throughput of the proposed on-chip bus is increased by 31.3% and 34.3%, while power consumption overhead is only 6.76% and 3.98%, respectively, as compared to an asynchronous single-issue on-chip bus.

A new dual-slope ramp (DSR) reset waveform is proposed to improve the dark room contrast ratio in AC-PDPs. The proposed reset waveform has two different voltage slopes during a ramp-up period. The first voltage slope lower than the conventional ramp voltage slope plays a role in producing the priming particles under the low background luminance, which is considered to be a kind of pre-reset discharge. On the other hand, the second voltage slope higher than the conventional ramp voltage slope produces a stable reset discharge due to the presence of the priming particles, but gives rise to a slight increase in the background luminance. Thus, a bias voltage is also applied during a part of the second voltage-slope period to adjust the background luminance and address discharge characteristics. As a result, the proposed dual-slope reset waveform can lower the background luminance without causing the discharge instability, thereby improving the high dark room contrast ratio of an AC-PDP without reducing the address voltage margin.