Pseudorandom number generators have been widely used in Monte Carlo methods, communication systems, cryptography and so on. For cryptographic applications, pseudorandom number generators are required to generate sequences which have good statistical properties, long period and unpredictability. A Dickson generator is a nonlinear congruential generator whose recurrence function is the Dickson polynomial. Aly and Winterhof obtained a lower bound on the linear complexity profile of a Dickson generator. Moreover Vasiga and Shallit studied the state diagram given by the Dickson polynomial of degree two. However, they do not specify sets of initial values which generate a long period sequence. In this paper, we show conditions for parameters and initial values to generate long period sequences, and asymptotic properties for periods by numerical experiments. We specify sets of initial values which generate a long period sequence. For suitable parameters, every element of this set occurs exactly once as a component of generating sequence in one period. In order to obtain sets of initial values, we consider a logistic generator proposed by Miyazaki, Araki, Uehara and Nogami, which is obtained from a Dickson generator of degree two with a linear transformation. Moreover, we remark on the linear complexity profile of the logistic generator. The sets of initial values are described by values of the Legendre symbol. The main idea is to introduce a structure of a hyperbola to the sets of initial values. Our results ensure that generating sequences of Dickson generator of degree two have long period. As a consequence, the Dickson generator of degree two has some good properties for cryptographic applications.

In general, tunnel diodes exhibit various types of oscillation mode: the sinusoidal mode or the nonsinusoidal mode which is known as the relaxation oscillation (RO) mode. We derive a condition for generating the RO in resonant tunneling diodes (RTDs) with essential components for equivalent circuit model. A conditional equation to obtain sufficient nonlinearity towards the robust RO is clarified. Moreover, its condition also can be applied in case of a bow-tie antenna integrated RTD, thus a design policy to utilize the RO region for the antenna integrated RTD is established by numerical evaluations of time-domain large-signal nonlinear analysis towards a terahertz transmitter for broadband wireless communications.

We propose a wideband reconfigurable circular-polarized single-port antenna to realize high-density linear integration for use in ground penetrating radars. We switch PIN diodes at a T-shaped probe to change its polarization. The forward- and reverse-biased probes work in cooperation to generate circular polarization. Experiments demonstrate the working bandwidths of 20.0% and 18.6% in the left- and right-hand polarization states, respectively, with 7.2 GHz center frequency. They are wider than those of conventional reconfigurable single-port circular-polarized antennas.

Cyclic codes are a subclass of linear codes and have applications in consumer electronics, data storage systems, and communication systems as they have efficient encoding and decoding algorithms. In this letter, a class of four-weight binary cyclic codes are presented. Their weight distributions of these cyclic codes are also settled.

Zero correlation zone (ZCZ) aperiodic complementary sequence (ZACS) sets have potential applications in multi-carriers (MC) CDMA communication systems, which can support more users than traditional complementary sequence sets. In this letter, methods for constructing ZACS sets based on orthogonal matrices are proposed. The new constructions may propose ZACS sets with optimal parameters. The new ZACS sets can be applied in approximately synchronized MC-CDMA to remove interferences.

Periodic interference frequently affects the measurement of small signals and causes problems in clinical diagnostics. Adaptive filters can be used as potential tools for cancelling such interference. However, when the interference has a frequency fluctuation, the ideal adaptive-filter coefficients for cancelling the interference also fluctuate. When the adaptation property of the algorithm is slow compared with the frequency fluctuation, the interference-cancelling performance is degraded. However, if the adaptation is too quick, the performance is degraded owing to the target signal. To overcome this problem, we propose an adaptive filter that suppresses the fluctuation of the ideal coefficients by utilizing a $rac{pi}{2}$ phase-delay device. This method assumes a frequency response that characterizes the transmission path from the interference source to the main input signal to be sufficiently smooth. In the numerical examples, the proposed method exhibits good performance in the presence of a frequency fluctuation when the forgetting factor is large. Moreover, we show that the proposed method reduces the calculation cost.

This paper reports dual-polarization In-phase and Quadrature (DP-IQ) modulators and photodetectors integrated with the 90° hybrid using InP-based monolithic integration technologies for 100/200Gb/s coherent transmission. The DP-IQ modulator was monolithically integrated with the Mach-Zehnder modulator array consisting of deep-ridge waveguides formed through dry etching and benzocyclobutene planarization processes. This DP-IQ modulator exhibited the low half-wavelength voltage (Vπ=1.5V) and the wide 3-dB bandwidth (f3dB > 28GHz). The photodetector monolithically integrated with the 90° hybrid consisting of multimode interference structures was realized by the butt-joint regrowth. A responsivity including total loss of 7.9dB in the waveguide was as high as 0.155A/W at a wavelength of 1550nm, and responsivity imbalance of the In-phase and Quadrature channels was less than ±0.5dB over the C-band. In addition, the low dark current (less than 500pA up to 85°C @ -3.0V) and the stable operation in the accelerated aging test (test condition: -5V at 175°C) over 5,000h were successfully achieved for the p-i-n-photodiode array with a buried heterostructure formed through the selective embedding regrowth. Finally, a receiver responsivity including intrinsic loss of 3dB in the polarization beam splitter was higher than 0.070A/W at a wavelength of 1550nm through the integration of the spot-size converter, and demodulation of 128Gb/s DP-QPSK and 224Gb/s DP-16QAM modulated signals was demonstrated for the compact coherent receiver using this photodetector integrated with the 90° hybrid. Therefore, we indicated that these InP-based monolithically integrated photonic devices are very useful for 100/200Gb/s pluggable coherent transceivers.

Organic optical materials are possible to sense light because of its high photosensitivity and large absorption only 100 nm thick films. These characteristics can be applied to an optoelectronic device, such as an organic photodiode. In our previous report, we studied blue and green organic photodiode respectively. In this report, we investigated a tandem photodiode which was vertically stacked blue and green OPDs inserting intermediate semitransparent electrode. Individual photoresponse was confirmed in each blue/green unit.

In this paper, a new class of low-hit-zone (LHZ) frequency-hopping sequence sets (LHZ FHS sets) is constructed based upon the Cartesian product, and the periodic partial Hamming correlation within its LHZ are studied. Studies have shown that the new LHZ FHS sets are optimal according to the periodic partial Hamming correlation bounds of FHS set, and some known FHS sets are the special cases of this new construction.

In this paper, a periodic perfect conductor is used to investigate the solution for the metallic scatterer problem in soil. We analyzed the pulse reflection responses from the periodic perfect conductor in two dispersion media by varying the parameters for the permittivity properties of the complex dielectric constants, and also investigated the influence of both the dielectric and conductor using a combination of the fast inversion Laplace transform (FILT) method and the point matching method (PMM). In addition, we verified the accuracy of the present method with exact solutions for the transient scattering problem for a perfect conductor plate in the dispersion media.

This paper deals with the diffraction of a monochromatic plane wave by a periodic grating. We discuss a problem how to obtain a numerical diffraction efficiency (NDE) satisfying the reciprocity theorem for diffraction efficiencies, because diffraction efficiencies are the subject of the diffraction theories. First, this paper introduces a new formula that decomposes an NDE into two components: the even component and the odd one. The former satisfies the reciprocity theorem for diffraction efficiencies, but the latter does not. Therefore, the even component of an NDE becomes an answer to our problem. On the other hand, the odd component of an NDE represents an unwanted error. Using such the decomposition formula, we then obtain another new formula that decomposes the conventional energy error into two components. One is the energy error made by even components of NDE's. The other is the energy error constructed by unwanted odd ones and it may be used as a reciprocity criterion of a numerical solution. This decomposition formula shows a drawback of the conventional energy balance. The total energy error is newly introduced as a more strict condition for a desirable solution. We point out theoretically that the reciprocal wave solution, an approximate solution satisfying the reciprocity for wave fields, gives another solution to our problem. Numerical examples are given for the diffraction of a TM plane wave by a very rough periodic surface with perfect conductivity. In the case of a numerical solution by the image integral equation of the second kind, we found that the energy error is much reduced by use of the even component of an NDE as an approximate diffraction efficiency or by use of a reciprocal wave solution.

nMOS-type and pMOS-type silicon avalanche photodiodes (APDs) were fabricated by standard 0.18µm CMOS process, and the current-voltage characteristic and the frequency response of the APDs with and without guard ring structure were measured. The role of the guard ring is cancellation of photo-generated carriers in a deep layer and a substrate. The bandwidth of the APD is enhanced with the guard ring structure at a sacrifice of the responsivity. Based on comparison of nMOS-type and pMOS-type APDs, the nMOS-type APD is more suitable for high-speed operation. The bandwidth is enhanced with decreasing the spacing of interdigital electrodes due to decreased carrier transit time and with decreasing the detection area and the PAD size for RF probing due to decreased device capacitance. The maximum bandwidth was achieved with the avalanche gain of about 10. Finally, we fabricated a nMOS-type APD with the electrode spacing of 0.84µm, the detection area of 10×10µm2, the PAD size for RF probing of 30×30µm2, and with the guard ring structure. The maximum bandwidth of 8.4GHz was achieved along with the gain-bandwidth product of 280GHz.

We propose a highly sensitive carrier-recovery system for in-line amplification for binary phase shift keying (BPSK) signals in a periodically poled LiNbO3 based phase sensitive amplifier (PSA). We applied a discrete two-stage second harmonic generation/difference frequency generation (SHG/DFG) parametric conversion scheme to enhance the sensitivity of the carrier recovery. Owing to this two-stage SHG/DFG scheme, the conversion efficiency of the seed light for the injection locking needed for the pump generation can be improved compared to that of the cascaded SHG/DFG scheme. The new discrete scheme might also prevent the SNR degradation of the seed light caused by the ASE from the booster EDFA compared with the previous system that used the cascaded scheme. This novel carrier-recovery system exhibits high sensitivity with the SNR of over 7.8dB of the seed light, while tapped signal power is as low as -50dBm, which is low enough for injection locking. The new in-line PSA with this carrier-recovery system exhibits high gain of over 11dB. Since we successfully obtained the high gain property, we tried multistage amplification taking into account practical use and achieved it with both a high gain of 20dB and a noise figure that is almost as low as the standard quantum limit of a PSA.

FDTD (Finite-Difference Time-Domain) method has been widely used for the analysis of photonic devices consisting of sub-wavelength structures. In recent years, increasing efforts have been made to implement the FDTD on GPGPUs (General-Purpose Graphic Processing Units), to shorten simulation time. On the other hand, it is widely recognized that most of the middle- and low-end GPGPUs have difference of computational performance, between single-precision and double-precision type arithmetics. Therefore the type selection of single/double precision for electromagnetic field variables in FDTD becomes a key issue from the viewpoint of the total simulation performance. In this study we investigated the difference of results between the use of single-precision and double-precision. As a most fundamental sub-wavelength photonic structure, we focused on an alternating multilayer (one dimensional periodic structure). Obtained results indicate that significant difference appears for the amplitudes of higher order spatial harmonic waves.

Biphase periodic sequences having elements +1 or -1 with the two-level autocorrelation function are desirable in communications and radars. However, in case of the biphase orthogonal periodic sequences, Turyn has conjectured that there exist only sequences with period 4, i.e., there exist the circulant Hadamard matrices for order 4 only. In this paper, it is described that the conjecture is proved to be true by means of the isomorphic mapping, the Chinese remainder theorem, the linear algebra, etc.

In this paper, we have investigated a new structure which combines dielectric cylinders with air-hole cylinders array, and analyzed the guiding problem for periodically dielectric waveguides by arbitrary shape of dielectric constants in the middle layer. In the numerical analysis, we examined an influence of the dielectric circular cylinder along a middle layer by using the energy distribution and complex propagation constants at the first stop band region compared with hollow dielectric cylinder. In addition, we also investigated the influence of dielectric structure with equivalence cross section compared with dielectric cylinders, and clarified an influence of dielectric structures in the middle layer by energy distribution analysis for TE0 mode.

In this study we investigate the synchronization of relaxation oscillators having individual differences by using non-periodic signal injection. When a common non-periodic signal is injected into the relaxation oscillators, the oscillators exhibit synchronization phenomena. Such synchronization phenomena can be classified as injection locking. We also consider the relation between the synchronization state and the individual difference. Further, we pay attention to the effect of the fluctuation range of the non-periodic injected signal. When the fluctuation range is wide, we confirm that the synchronization range increases if the individual difference is small.

Coordinate interleaved orthogonal design (CIOD) using four transmit antennas provides full diversity, full rate (FDFR) properties with low decoding complexity. However, the constellation expansion due to the coordinate interleaving of the rotated constellation results in peak to average power ratio (PAPR) increase. In this paper, we propose two signal constellation design methods which have low PAPR. In the first method we propose a signal constellation by properly selecting the signal points among the expanded square QAM constellation points, based on the co-prime interleaving of the first coordinate signal. We design a regular interleaving pattern so that the coordinate distance product (CPD) after the interleaving becomes large to get the additional coding gain. In the other method we propose a novel constellation with low PAPR based on the clipping of the rotated square QAM constellation. Our proposed signal constellations show much lower PAPR than the ordinary rotated QAM constellations for CIOD.

In this study, we investigated Si(100), Si(110) and Si(111) surface flattening process utilizing sacrificial oxidation method, and its effect on Metal-Insulator-Semiconductor (MIS) diode characteristics. By the etching of the 100 nm-thick sacrificial oxide formed by thermal oxidation at 1100°C, the surface roughness of Si(100), Si(110) and Si(111) substrates were reduced. The obtained Root-Mean-Square (RMS) roughness of Si(100) was reduced from 0.22 nm (as-cleaned) to 0.07 nm (after etching), while it was reduced from 0.23 nm to 0.12 nm in the case of Si(110), and from 0.23 nm to 0.11 nm in the case of Si(111), respectively. Furthermore, it was found that time-dependent dielectric breakdown (TDDB) characteristics of MIS diodes for p-Si(100), p-Si(110) and p-Si(111) were improved with the reduction of Si surface RMS roughness.

Novel constructions of inter-group complementary (IGC) sequences are proposed based on Z-periodic complementary (ZPC) sequences and uncorrelated sequence set by taking advantages of interleaved operation. The presented methods can get IGC sequences from interleaving ZPC sequence set. The proposed methods not only can get polyphase IGC sequence set, but also can obtain binary and ternary IGC sequence set. In particular, with the aid of uncorrelated sequence, the number of available groups of IGC sequences from interleaving ZPC sequence set can be chosen with flexibility compared to the existed IGC sequences. The IGC sequences based code division multiple access (CDMA) systems may perform better on bit error rates than conventional sequences based interference-limited CDMA systems. Moreover, the novel IGC sequences may work well in both synchronous and asynchronous operational modes.