This paper presents a formulation of two-dimensional photonic crystal waveguide devices formed by circular cylinders. The device structures are considered as cascade connections of straight waveguides. Decomposing the structure into layers of the cylinder arrays, the input/output properties of the devices are obtained using an analysis method of multilayer structure. We introduce periodic boundary conditions in the direction perpendicular to the wave propagation, and the Floquet-modes of each layer are calculated by the Fourier series expansion method with the help of the recursive transition-matrix algorithm. Then, the input/output properties of the devices are obtained by recursive calculation of scattering matrix with each layer. The presented formulation is validated by numerical experiments by comparing with the previous works.

We fabricated a p-i-n photodiode (PD) with an integrated microlens, and demonstrated its high performance capabilities including high speed (35 GHz), high responsivity (0.8 A/W), and large misalignment tolerance (26 µm), and an error-free 25-Gbit/s 10-km single-mode fiber transmission by using a 100-Gbit/s Ethernet quadplexer receiver module with the PDs.

When a monochromatic electromagnetic plane wave is incident on an infinitely extending surface with the translation invariance property, a curious phenomenon often takes place at a low grazing angle of incidence, at which the total wave field vanishes and a dark shadow appears. This paper looks for physical and mathematical reasons why such a shadow occurs. Three cases are considered: wave reflection by a flat interface between two media, diffraction by a periodic surface, and scattering from a homogeneous random surface. Then, it is found that, when a translation invariant surface does not support guided waves (eigen functions) propagating with real propagation constants, such the shadow always takes place, because the primary excitation disappears at a low grazing angle of incidence. At the same time, a shadow form of solution is proposed. Further, several open problems are given for future works.

Recently, pairing-based cryptographic application sch-emes have attracted much attentions. In order to make the schemes more efficient, not only pairing algorithm but also arithmetic operations in extension field need to be efficient. For this purpose, the authors have proposed a series of cyclic vector multiplication algorithms (CVMAs) corresponding to the adopted bases such as type-I optimal normal basis (ONB). Note here that every basis adapted for the conventional CVMAs are just special classes of Gauss period normal bases (GNBs). In general, GNB is characterized with a certain positive integer h in addition to characteristic p and extension degree m, namely type-⟨h.m⟩ GNB in extension field Fpm. The parameter h needs to satisfy some conditions and such a positive integer h infinitely exists. From the viewpoint of the calculation cost of CVMA, it is preferred to be small. Thus, the minimal one denoted by hmin will be adapted. This paper focuses on two remaining problems: 1) CVMA has not been expanded for general GNBs yet and 2) the minimal hmin sometimes becomes large and it causes an inefficient case. First, this paper expands CVMA for general GNBs. It will improve some critical cases with large hmin reported in the conventional works. After that, this paper shows a theorem that, for a fixed prime number r, other prime numbers modulo r uniformly distribute between 1 to r-1. Then, based on this theorem, the existence probability of type-⟨hmin,m⟩ GNB in Fpm and also the expected value of hmin are explicitly given.

In a periodic spectrum sensing framework where each frame consists of a sensing block and a data transmitting block, increasing sensing duration decreases the probabilities of both missed opportunity and interference with primary users, but increasing sensing duration also decreases the energy efficiency and the transmitting efficiency of the cognitive network. Therefore, the sensing duration to use is a trade-off between sensing performance and system efficiencies. The relationships between sensing duration and state transition probability are analyzed firstly, when the licensed channel stays in the idle and busy states respectively. Then a state transition probability based sensing duration optimization algorithm is proposed, which can dynamically optimize the sensing duration of each frame in the current idle/busy state by predicting each frame's state transition probability at the beginning of the current state. Analysis and simulation results reveal that the time-varying optimal sensing duration increases as the state transition probability increases and compared to the existing method, the proposed algorithm can use as little sensing duration in each frame as possible to satisfy the sensing performance constraints so as to maximize the energy and transmitting efficiencies of the cognitive networks.

For over 40-Gbps optical communication systems, phase coded modulation formats, like differential phase shift keying (DPSK) and quadrature phase shift keying (QPSK), are very important for signal frequency efficiency and long-reach transmission. In such systems, differential receivers which regenerate phase signals are key components. Dual Photo Diodes (dual PDs) are key semiconductor devices which determine the receiver performance. Each PD of the dual PDs should realize high speed performance, high responsibility and high input power operation capability. Highly symmetrical characteristics between the two PDs should be also realized, thus the dual PDs are desired to be monolithically integrated to one chip. In this paper, we describe the design, fabrication, characteristics and reliability of monolithically integrated dual evanescently coupled waveguide photodiodes (EC-WG-PDs) for the purpose described above. The structure of the EC-WG-PDs offers the attractive advantages of high speed performance, high responsivity and high input power operation. Furthermore, their fabrication process is suitable for the integration of two PDs on one ship. First, the optimization was done for high products of 3-dB bandwidth and responsivity for 43-Gbps DPSK receivers. Excellent characteristics (50 GHz bandwidth with a responsivity of 0.95 A/W), and high reliability were demonstrated. The other type of optimization was done for ultra high speed operation up to 100-Gbps. The fabricated PDs exhibited the 3 dB-bandwidth of 80 GHz with a responsivity of 0.25 A/W. Furthermore, 43-Gbps RZ-DPSK receivers including the dual EC-WG-PDs based on the former optimization and differential transimpedance amplifiers (TIAs) newly developed for the purpose were also presented. Clear and symmetrical eye openings were observed for both ports. The OSNR characteristics exhibited 14.3 dB at a bit error rate of 10-3 that is able to be recovery with FEC. These performances are enough for practical use in 43-Gbps RZ-DPSK systems.

This paper investigates primary signal detection by using a quiet period (QP) in cognitive wireless communications. In particular, we provide an analytical model for studying the impact of QPs on the system performance. Our analysis shows that two successive QPs have a significant impact on system performance. Moreover, the analytical results obtained reveal an optimum period of two successive QPs that maximize system performance.

In renewable power generators, because of high initial cost and duty cycle of systems, efficiency parameter has an important place. For this reason, line frequency controlled multilevel inverters are one of most proper choices for renewable power converters. Among these, diode-clamped multilevel inverter structures are one of most important and best efficient inverters. In this paper, a simple diode-clamped equivalent circuit for exploring the efficiency under resistive loads is proposed, and based on this simple circuit, the on-state power dissipation in improved and original diode-clamped multilevel inverter under resistive loads is analyzed. Then, comparative efficiency equations are extracted for inverters that use metal oxide semiconductor field-effect transistors (MOSFETs) and other p-n junction as switches. These equations enable us to have a better idea of conducting power dissipation in diode-clamped and help us to choose appropriate switches for having a lower on-state power dissipation. Some cases are studied and in the end it is proven that the calculated efficiency under resistive load is a boundary for inductive load with the same impedance in diode-clamped inverter with p-n junction switches. This means that calculating the efficiency under resistive loads enables us to approximately predict efficiency under inductive loads.

Binary sequence pairs as a class of mismatched filtering of binary sequences can be applied in radar, sonar, and spread spectrum communication system. Binary sequence pairs with two-level periodic autocorrelation function (BSPT) are considered as the extension of usual binary sequences with two-level periodic autocorrelation function. Each of BSPT consists of two binary sequences of which all out-phase periodic crosscorrelation functions, also called periodic autocorrelation functions of sequence pairs, are the same constant. BSPT have an equivalent relationship with difference set pairs (DSP), a new concept of combinatorial mathematics, which means that difference set pairs can be used to research BSPT as a kind of important tool. Based on the equivalent relationship between BSPT and DSP, several families of BSPT including perfect binary sequence pairs are constructed by recursively constructing DSP on the integer ring. The discrete Fourier transform spectrum property of BSPT reveals a necessary condition of BSPT. By interleaving perfect binary sequence pairs and Hadamard matrix, a new family of binary sequence pairs with zero correlation zone used in quasi-synchronous code multiple division address is constructed, which is close to the upper theoretical bound with sequence length increasing.

Ambient light sensors have been used to reduce power consumption of Active Matrix Liquid Crystal Displays (AMLCD) adjusting display brightness depending on ambient illumination. Discrete sensors have been commonly used for this purpose. They make module design complex. Therefore it has been required to integrate the sensors on the display panels for solving the issue. So far, many kinds of integrated sensors have been developed using Amorphous Silicon (a-Si) technology or Low Temperature Polycrystalline Silicon (LTPS) technology. These conventional integrated sensors have two problems. One is that LTPS sensors have less dynamic range due to the less photosensitivity of LTPS photodiodes. The other is that both the LTPS and a-Si sensors are susceptible to display driving noises. In this paper, we introduce a novel integrated sensor using both LTPS and a-Si technologies, which can solve these problems. It consists of vertical a-Si Schottky photodiodes and an LTPS differential converter circuit. The a-Si photodiodes have much higher photosensitivity than LTPS ones, and this contributes to wide dynamic range and high accuracy. The LTPS differential converter circuit converts photocurrent of the photodiodes to a robust digital signal. In addition it has a function of canceling the influences of the display driving noises. With the circuit, the sensor can stably and accurately work even under the noises. The performance of the sensor introduced in this paper was measured to verify the advantages of the novel design. The measurement result showed that it worked in a wide ambient illuminance range of 5-55,000 lux with small errors of below 5%. It was also verified that it stably and accurately worked even under the display driving noise. Thus the sensor introduced in this paper achieved the wide dynamic range and noise robustness.

In this paper, a novel pseudo-random noise complementary pair (PNCP) is proposed and adopted as the guard intervals in the time-domain synchronous OFDM (TDS-OFDM) system. The proposed PNCP has nearly ideal aperiodic auto-correlation property and inherits the differential property of the PN sequence. Simulations demonstrate the proposed TDS-OFDM system padded with PNCP could achieve better performance in both synchronization and channel estimation than the conventional TDS-OFDM system.

A band diagram is fundamental for investigating the electromagnetic properties of periodic structures such as photonic and/or electromagnetic crystals and electromagnetic bandgap structures. In this paper, computer resources and the accuracy of the Finite Difference Frequency Domain and the Finite Difference Time Domain methods are studied. The periodic structure treated here consists of two-dimensional dielectric cylinders.

In order to evaluate the goodness of frequency hopping sequence design, the aperiodic Hamming correlation function is used as an important measure. In this letter, the aperiodic Hamming correlation lower bounds for frequency hopping sequences with low hit zone which have not yet been reported previously are established.

A third order harmonic oscillator has been proposed based on the resonant tunneling diode pair oscillators. This oscillator has significant advantages, good stability of the oscillation frequency against the load impedance change together with capability to output higher frequencies. Proper circuit operation has been demonstrated using circuit simulations. It has been also shown that the output frequency is stable against the load impedance change.

A unipolar n-n heterostrucuture diode is developed in the InP material system. The electronic barrier is formed by a saw tooth type of conduction band bending which consists of a quaternary In0.52(AlyGa1-y)0.48As layer with 0 < y < ymax. This barrier is lattice matched for all y to InP and is embedded between two n+-InGaAs layers. By varying the maximum Al-content from ymax,1 = 0.7 to ymax,2 = 1 a variable barrier height is formed which enables a diode-type I-V characteristic by epitaxial design with an adjustable current density within 3 orders of magnitude. The high current density of the diode with the lower barrier height (ymax,1 = 0.7) makes it suitable for high frequency applications at low signal levels. RF measurements reveal a speed index of 52 ps/V at VD = 0.15 V. The device is investigated for RF-to-DC power conversion in UHF RFID transponders with low-amplitude RF signals.

We derive physics-based formula of current-voltage characteristic for resonant tunneling diodes (RTDs) by using the Voigt function. The Voigt function describes the mixing condition of homogeneous and inhomogeneous broadenings of peak energy width in transmission probability, which is sensitively reflected to nonlinear negative differential resistance of RTDs. The obtained formula is applicable to the SPICE model of RTD without performing numerical integrals. We indicate validity of the formula by comparing to measured data for double-barrier and triple-barrier RTDs.

Multilayered volumetric composite right/left handed metamaterial structures are investigated. The present structure is composed of conducting mesh plates and dielectric layers including dielectric resonators. The 2-D composite right/left handed metamaterial structure is designed for the in-plane propagation. Propagation mode analysis was made for the volumetric structure under the periodic boundary condition along the normal to the layers as well as for finite number of layered type for comparison. The negative-refractive-index planar lenses were designed and fabricated for the demonstration. It is found from the numerical simulation that the beam focusing through the planar lens with large number of layers is clearly confirmed in both magnitude and phase distribution of the fields. On the other hand, for small number of layers, the beam spot is not found in the magnitude distribution due to the effect of discontinuities between air and designed structure at the top and bottom surfaces, but is still found in the phase distribution. The effect of number of stacked layers on the propagation characteristics is discussed by comparing the numerical simulation results with the measurement.

Beam steering of leaky wave radiation from a nonreciprocal composite right/left handed transmission line with a ferrite substrate is proposed. The nonreciprocal phase constants of the line were tuned by changing the applied DC magnetic field normal to the ferrite substrate. In the numerical simulation and the experiment, the nonreciprocal phase characteristics and leaky wave radiation are investigated for the ferrite substrate with the magnetization not only in the saturated region, but also in the unsaturated region. The numerical simulation results are in good agreement with the measurement. It is confirmed that the beam directions of the obliquely unidirectional leaky wave radiation for two different power directions are continuously tunable.

A composite right/left-handed transmission line (CRLH-TL) using substrate integrated waveguide (SIW) with floating-conductor (SIW-type CRLH-TL) for microwave and millimeter wave frequencies has been proposed by the authors. This paper proposes a new configuration that is shield type of the SIW-type CRLH-TL, which can suppress the radiation from the exposed floating-conductors, and shows that even if the shielded structure is used, the SIW-type CRLH-TL supports the LH mode as well as the prototype. Proposed CRLH-TL consists of a SIW with slot apertures (part 1), a dielectric film with floating-conductors (part 2) and a SIW without lower conductor (part 3). A shielded SIW-type CRLH-TL for X--K band (with wide LH mode bandwidth of 6 GHz and transition frequency of 16 GHz) that satisfies the balance condition is designed. Dispersion diagram and S-parameters are derived numerically, and typical field distributions of RH and LH transmission and the zeroth-order resonance are shown. Measured result agrees well with theoretical result, by considering the accuracy performance and loss factors of the fabricated CRLH-TL. Proposed CRLH-TL has advantage of simple manufacturing, because the parts 1--3 are composed of simple planar periodic structure. It is expected to be one of the basic structure of CRLH-TL or components such as LH coupler above 10 GHz or millimeter wave frequency.

Multi-dimensional (MD) periodic complementary array sets (CASs) with impulse-like MD periodic autocorrelation function are naturally generalized to (one dimensional) periodic complementary sequence sets, and such array sets are widely applied to communication, radar, sonar, coded aperture imaging, and so forth. In this letter, based on multi-dimensional perfect arrays (MD PAs), a method for constructing MD periodic CASs is presented, which is carried out by sampling MD PAs. It is particularly worth mentioning that the numbers and sizes of sub-arrays in the proposed MD periodic CASs can be freely changed within the range of possibilities. In particular, for arbitrarily given positive integers M and L, two-dimensional periodic polyphase CASs with the number M2 and size L L of sub-arrays can be produced by the proposed method. And analogously, pseudo-random MD periodic CASs can be given when pseudo-random MD arrays are sampled. Finally, the proposed method's validity is made sure by a given example.