In this paper, a quite general systematic procedure is presented for defining incremental field contributions, that may provide effective tools for describing a wide class of scattering and diffraction phenomena at any aspect, whthin a unitary, self-consistent framework. This is based on a generalization of the localization process for cylindrical canonical problems with elementary source illumination and arbitrary observation aspects. In particular, it is shown that the spectral integral formulation of the exact solution may also be represented as a spatial integral convolution along the axis of the cylinder. Its integrand is then directly used to define the relevant incremental field contribution. This procedure, that will be referred to as a ITD (Incremental Theory of Diffraction) Fourier transform convolution localization process, is explicitly applied to both wedge and circular cylinder canonical configurations, to define incremental diffiraction and scattering contributions, respectively. These formulations are asymptotically approximated to find closed form high-frequency expression for the incremental field contributions. This generalization of the ITD lacalization process may provide a quite general, systematic procedure to find incremental field contributions that explicitly satisfy reciprocity and naturally lead to the UTD ray field representation, when it is applicable.

A rigorous radar cross section (RCS) analysis is carried out for two-dimensional rectangular and circular cavities with double-layer material loading by means of the Wiener-Hopf (WH) technique and the Riemann-Hilbert problem (RHP) technique, respectively. Both E and H polarizations are treated. The WH solution for the rectangular cavity and the RHP solution for the circular cavity involve numerical inversion of matrix equations. Since both methods take into account the edge condition explicitly, the convergence of the WH and RHP solutions is rapid and the final results are valid over a broad frequency range. Illustrative numerical examples on the monostatic and bistatic RCS are presented for various physical parameters and the far field scattering characteristics are discussed in detail. It is shown that the double-layer lossy meterial loading inside the cavities leads to the significant RCS reduction.

The H-polarized diffraction by a wedge consisting of perfect conductor and lossless dielectric is investigated by employing the dual integral equations. Its physical optics diffraction coefficients are expressed in a finite series of cotangent functions weighted by the Fresnel reflection coefficients. A correction rule is extracted from the difference between the diffraction coefficients of the physical optics field and those of the exact solution to a perfectly conducting wedge. The angular period of the cotangent functions is changed to satisfy the edge condition at the tip of the wedge, and the poles of the cotangent functions are relocated to cancel out the incident field in the artificially complementary region. Numerical results assure that the presented correction is highly effective for reducing the error posed in the physical optics solution.

The purpose of this report is to predict far-field EMI spectrum emitted from a signal line on a digital PCB based on near-field EMI measurement. The relation between near magnetic field and far electric field is shown. A method of predicting far electric field from near magnetic field is proposed. Current flowing along a signal line is calculated from measured near magnetic field. Far electric field is estimated from the current. Measurement and prediction of EM emission are carried out using a simple PCB. The result of prediction and measurement of far-field EMI spectrum coincide within the error of 3 dB.

This paper deals with a probabilistic formulation of the diffraction and scattering of a plane wave from a periodic surface randomly deformed by a binary sequence. The scattered wave is shown to have a stochastic Floquet's form, that is a product of a periodic stationary random function and an exponential phase factor. Such a periodic stationary random function is then represented in terms of a harmonic series representation similar to Fourier series, where `Fourier coefficients' are mutually correlated stationary processes rather than constants. The mutually correlated stationary processes are written by binary orthogonal functionals with unknown binary kernels. When the surface deformations are small compared with wavelength, an approximate solution is obtained for low-order binary kernels, from which the scattering cross section, coherently diffracted power and the optical theorem are numerically calculated and are illustrated in figures.

Recently, the low earth orbit satellite communications has been attracting much attention. These communications have many strong features, however, the communication performances are influenced by carrier frequency offset (CFO) and, particularly, it is hard to acquire the synchronization. A large number of publications have so far been made on the synchronization acquisition of DS/SS systems under CFO and most of them make use of the maximum likelihood decision in finding the maximum values of Fourier transform outputs. However, the implementations of Fourier transforms usually require high cost and large space. In this paper, we propose a new simple acquisition scheme using half-symbol differential decoding technique for DS/SS systems under CFO. This scheme makes use of the addition and subtraction of baseband signals and their delayed versions, (omitting Fourier transforms), together with integrations by recursive integrators, and thus resulting in much simpler implementation. In general, it is shown that the proposed scheme can acquire the code synchronization under carrier frequency offset with much smaller computational complexities and the sacrifice of longer acquisition time.

A bicomplex representation for time-harmonic electromagnetic fields appearing in scattering and diffraction problems is given using two imaginary units i and j. Fieldsolution integral-expressions obtained in the high-frequency and low-frequency limits are shown to provide the new relation between high-frequency diffraction and low-frequency scattering. Simple examples for direct scattering problems are illustrated. It may also be possible to characterize electric or magnetic currents induced on the obstacle in terms of geometrical optics far-fields. This paper outlines some algebraic rules of bicomplex mathematics for diffraction or scattering fields and describes mathematical evidence of the solutions. Major discussions on the relationship between high-frequency and low-frequency fields are relegated to the companion paper which will be published in another journal.

This paper deals with the scattering and diffraction of a plane wave by a randomly rough half-plane by three tools: the small perturbation method, the Wiener-Hopf technique and a group theoretic consideration based on the shift-invariance of a homogeneous random surface. For a slightly rough case, the scattered wavefield is obtained up to the second-order perturbation with respect to the small roughness parameter and represented by a sum of the Fresnel integrals with complex arguments, integrals along the steepest descent path and branch-cut integrals, which are evaluated numerically. For a Gaussian roughness spectrum, intensities of the coherent and incoherent waves are calculated in the region near the edge and illustrated in figures, in terms of which several characteristics of scattering and diffraction are discussed.

Investigated is a guided-wave device for dividing optical power into three equal parts. The device fundamentally consists of a three-waveguide tapered-velocity coupler which is designed to operate under the adiabatic condition. Field distributions of the local normal modes along the coupler explain basic principles of the device. Its performance is confirmed through numerical simulations by means of finite difference beam propagation method.

Electromagnetic field diffracted by conducting circular disk and circular hole in the conducting plate is formulated by the method of Kobayashi potential. The field is expressed by linear combination of functions which satisfy the required boundary conditions except on the disk or hole. Thus the functions may be regarded as eigen functions of the configuration. By imposing the remaining boundary conditions, we can derive the matrix equations for the expansion coefficients. It may be verified readily that each eigen function satisfies edge conditions for induced current on the disk and for aperture field distribution on the hole. It may also be verified that the solutions for the disk and the hole satisfy Babinet's principle. Matrix elements of the equations for the expansion coefficients are given by two kinds of infinite integrals and the series solutions for these integrals are derived. The validity of these expressions are verified numerically by comparing with the results obtained from direct numerical integrations.

We present theoretical results on the convergence of iterative methods for the solution of linear differential-algebraic equations arising form circuit simulation. The iterative methods considered include the continuous-time and discretetime waveform relaxation methods and the Krylov subspace methods in function space. The waveform generalized minimal residual method for solving linear differential-algebraic equations in function space is developed, which is one of the waveform Krylov subspace methods. Some new criteria for convergence of these iterative methods are derived. Examples are given to verify the convergence conditions.

For mobile communication systems with code division multiple access (CDMA), a new modulation scheme, π/2-shift BPSK, is proposed. The performance has been evaluated in terms of relative out-of-band power, bit-error rate (BER), and spectral efficiency. As the result, it is shown that the proposed scheme has an advantage over conventional BPSK, conventional QPSK, and π/4-shift QPSK under nonlinear amplification.

This paper proposes a novel FEC (forward error correction) scheme for high-speed wireless systems aiming at mobile computing applications. The proposed scheme combines inner nonredundant error correction with outer parallel encoding random FEC for differentially detected QPSK (quadrature phase shift keying) signals. This paper, first, examines error patterns after the differential detection with nonredundant error correction and reveals that particular double symbol errors occur with relatively high probability. To improve the outer FEC performance degradation due to the double symbol errors, the proposed scheme uses I and Q channel serial to parallel conversion in the transmission side and parallel to serial conversion in the receiving side. As a result, it enables to use simple FEC for the outer parallel encoding random FEC without interleaving. Computer simulation results show the proposed scheme employing one bit correction BCH coding obtains a required Eb/No improvement of 1.2 dB at a Pe of 10-5 compared to that with the same memory size interleaving in an AWGN environment. Moreover, in a Rician fading environment where directional beam antennas are assumed to be used to improve the degradation due to severe multipath signals, an overall Eb/No improvement at Pe of 10-5 of 3.0 dB is achieved compared to simple differential detection when the condition of delay spread of 5 nsec, carrier to multipath signal power ratio of 20 dB and Doppler frequency at 20 GHz band of 150 Hz.

The key concept of Physical Optics (PO), originally developed for a perfectly electric conductor (PEC), consists in that the high frequency fields on the scatterer surface are approximated by those which would exist on the infinite flat surface tangent to the scatterer. The scattered fields at arbitrary observation points are then calculated by integrating these fields on the scatterer. This general concept can be extended to arbitrary impedance surfaces. The asymptotic evaluation of this surface integration in terms of diffraction coefficients gives us the fields in analytical forms. In this paper, uniform PO diffraction coefficients for the impedance surfaces are presented and their high accuracy is verified numerically. These coefficients are providing us with the tool for the mechanism extraction of various high frequency methods such as aperture field integration method and Kirchhoff's method.

This work presents a further development of the approach to modelling thermal (i.e. carrier-velocity-fluctuation) noise in semiconductor devices proposed in papers by the present authors. The basic idea of the approach is to apply classical theory of Ito's stochastic differential equations (SDEs) and stochastic diffusion processes to describe noise in devices and circuits. This innovative combination enables to form consistent mathematical basis of the noise research and involve a great variety of results and methods of the well-known mathematical theory in device/circuit design. The above combination also makes our approach completely different, on the one hand, from standard engineering formulae which are not associated with any consistent mathematical modelling and, on the other hand, from the treatments in theoretical physics which are not aimed at device/circuit models and design. (Both these directions are discussed in more detail in Sect. 1). The present work considers the bipolar transistor compact model derived in Ref. [2] according to theory of Ito's SDEs and stochastic diffusion processes (including celebrated Kolmogorov's equations). It is shown that the compact model is transformed into the Ito SDE system. An iterative method to determine noisy currents as entries of the stationary stochastic process corresponding to the above Ito system is proposed.

New functional surface tunnel transistors (STTs) with multiple interband-tunnel-junctions in a symmetric source-to-drain structure are proposed to reduce the number of fabrication steps and to increase functionality. These devices have p+/n+ interband tunnel junctions in series between a p+ source and a p+ drain through n+ channels. We successfully fabricated GaAs-based multiple-junction STTs (MJ-STTs) using molecular-beam epitaxy regrowth. This fabrication method eliminates the need for two of the photo-masks in the conventional process for asymmetric planar STTs. In the preliminary experiments using multiple-junction p+/n+ diodes, we found that the peak-voltage increment in negative-differential-resistance (NDR) characteristics due to the reverse-biased tunnel junction in negligible, while the first-peak voltage is roughly proportional to the number of forward-biased tunnel junctions. Moreover, the number of NDR characteristics are completely determined by the number of tunnel junctions. The fabricated STTs with multiple junctions, up to eight junctions, exhibited clear transistor operation with multiple NDR characteristics, which were symmetric with the drain bias. These results indicate that any number of gate-controlled NDR characteristics can be realized in MJ-STTs by using an appropriate number of tunnel junctions in series. In addition, as an example of a functional circuit using MJ-STTs, we implemented a tri-stable circuit with a four-junction STT and a load resistor connected in series. The tri-stable operation was confirmed by applying a combination of a reset pulse and a set pulse for each stable point.

A new multiple-valued current-mode (MVCM) integrated circuit using a switched current-source control technique is proposed for a 1.5 V-supply high-speed arithmetic circuit with low-power dissipation. The use of a differential logic circuit (DLC) with a pair of dual-rail inputs makes the input voltage swing small, which results in a high driving capability at a lower supply voltage, while having large static power dissipation. In the proposed DLC using a switched current control technique, the static power dissipation can be greatly reduced because current sources in non-active circuit blocks are turned off. Since the gate of each current source is directly controlled by using a multiphase clock whose technique has been already used in dynamic circuit design, no additional transistors are required for currentsource control. As a typical example of arithmetic circuits, a new 1.5 V-supply 5454-bit multiplier based on a 0.8µm standard CMOS technology is also designed. Its performance is about 1.3 times faster than that of a binary fastest multiplier under the normalized power dissipation. A prototype chip is also fabricated to confirm the basic operation of the proposed MVCM integrated circuit.

In this article, a new type of diffusion template and an analogic CNN algorithm using this diffusion template for detecting some lung cancer symptoms in X-ray films are proposed. The performance of the diffusion template is investigated and our CNN algorithm is verified to detect some key lung cancer symptoms, successfully.

A new linearization technique of a transconductor is presented. The linearization is realized by using a differential current amplifier with an emitter-coupled pair. A specific value of the linearization parameter gives a maximally flat or an equiripple characteristic. Deviations from the theoretical characteristic can be adjusted by tuning the tail current of the emitter-coupled pair. The proposed technique is demonstrated by PSPICE simulation.

This paper describes the analysis of integrated optical waveguides using Finite-Difference Time-Domain (FDTD) method, and proposes the design methodology for low loss waveguide components: corner bends and branches. In order to integrate optical waveguides with Si VLSI technologies on a chip, the compact bends or branches are necessary. Since the optical power radiation from a bend or a branch point depends on the waveguide shapes, an accurate analysis of guided wave behavior is required. For the purpose we adopted the FDTD method which can analyze optical waveguides with a large variation of refractive index and arbitrary shape. Proposed design concept is to have all waveguides transmit only the fundamental mode and to design whole waveguides based on the fundamental mode transfer characteristics. For this design concept, waveguide components are required to have not only low radiation loss but also a little mode shift from the fundamental mode. The bend using the double-reflection mirrors and the branch using a slit are proposed for suppressing the mode shift and improving radiation loss. By the FDTD analysis, the following results have been obtained. The radiation loss and mode shift of double reflection bend are 1% and 4%, and those of the slit branch are 2% and 5%, respectively, in 2 µm width waveguide.