A hybrid mo-demodulation approach, fully insensitive to the phase noise induced by the sources, is described for CDMA applications at optical frequencies. It is analytically demonstrated that, using bipolar codes in conjunction with polarisation modulation, the considered system can improve the performance of coherent schemes with not negligible laser linewidths, as well as the performance of more conventional noncoherent schemes based on intensity modulation and unipolar codes.

The electric field intensity of the THz radiation from YBCO thin films excited by ultrashort laser pulses has been enhanced by a factor of 3 using a-axis oriented films instead of c-axis oriented ones used previously under the same excitation conditions. This corresponds to the enhancement of a factor of 10 for the radiation power. From the transmittance measurements of the millimeter wave for a-and c-axis oriented films, the origin of the enhancement is attributed to the increased fraction of the THz electromagnetic wave power transmitted from the YBCO film to free space. This result indicates that the utilization of the anisotropic properties of high-Tc superconductors is effective to enhance the radiation power.

In this paper, we will show some significant results of the routability analysis of bit-serial pipeline datapath designs based on Rent's rule and Donath's observation. Our results show that all of the tested bit-serial benchmarks have Rent exponent of below 0.4, indicating that the average wiring length of the circuit is expected to be independent of the circuit size. This study provides some important implications on the silicon utilization and time-area efficiency of bit-serial pipeline circuits on FPGAs and ASICs.

Service interaction resolution is an important study subject to realize a network supporting various advanced communication services. This paper proposes service interaction resolution by service node connected with the communication network via the user-network interface. By executing various advanced services on the service node, service interactions can be efficiently resolved without adding new functions to the existing network. In other words, the service node enables a unified execution control of all the services including those for the originating side and those for the terminating side. This prevents the signalling system and the signalling procedure from being expanded to resolve service interactions. Moreover, the interactions between the services initiated at the conversation active state can be resolved by the service node equipped with function of receiving plural types of in-band signals. This avoids functional expansion of the switching systems in the network. In this paper, feasibility of the proposed resolution scheme is proved by showing a structure of the service node and a detailed procedure to resolve interactions on that service node. In the proposed service node, the application part is divided into basic call processing part and service processing part, and the basic call processing part is represented by three kinds of basic call processing state models. The proposed method for resolving service interactions can control services execution with high flexibility by using feature interaction table.

This paper presents a new generation method of the periodic orthogonal numerical sequences with small maximum amplitude. In the generation method, complex exponential sequences are used as the generating sequences and such periodic orthogonal numerical sequences are constructed from the discrete Fourier transform of the generating sequences. Until now, there has not been found a generation algorithm to derive such sequences with any period. It is shown that the proposed generation method can derive periodic orthogonal real sequences with the maximum amplitude less than 1.5 for the period 1N200 and periodic orthogonal coplex sequences with all the sbsolute amplitude value of 1 for any period.

This paper presents an exact minimization algorithm for AND-OR-EXOR three-level networks, where a single two-input exclusive-OR (EXOR) gate is used. The network realizes an EXOR of two sum-of-products expressions (EX-SOP), where the two sum-of-products expressions (SOP) can share products. The objective is to minimize the total number of different products in the two SOPs. An algorithm for the exact minimization of EX-SOPs with up to five variables are shown. Up to five variables, EX-SOPs for all the representative functions of NP-equivalence classes were minimized. For five-variable functions, we confirmed that minimum EX-SOPs require up to 9 products. For n-variable functions, minimum EX-SOPs require at most 92n-5 (n6) products.

For the completely polarized wave case, this paper presents the explicit formulae of the characteristic polarization states in the co-polarized radar channel, from which one can obtain the CO-POL Max, the CO-POL Saddle and the CO-POL Nulls in the Stokes vector form. Then the problem on the polarimetric contrast optimization is discussed, and the explicit formula of the optimal polarization state for contrast enhancement is presented in the Stokes vector form for the first time. To verify these formulae, we give some numerical examples. The results are completely identical with other authors', which shows the validity of the presented method.

High-Tc SQUID was applied to the detection of magnetized fine particle moving at high speed. Two types of SQUIDs were used. One was a large washer type and the other was a flux transformer type. Their Josephson junctions were step edge type. The iron particle was attached on a nylon wire and scanned under the SQUID. High-Tc SQUID detected an iron particle of 50 µm diameter running at 800 m/min. It was shown that the magnetic field measured by the SQUID was proportional to the volumer of the particle and is inversely proportional to the distance between the SQUID and the particle. This technique using high-Tc SQUID is hopeful not only to wire production line but also for the processing of food and medicine, etc.

This study shows the results of evaluating the flux noises at low frequency when the alternating current(AC) bias direct offset integrated technique(DOIT) with additional positive feedback (APF) is used in a high-Tc dc superconducting quantum interference device (SQUID). The AC-bias DOIT can reduce low-frequency noise without increasing the level of white noise because each operating point in the two voltage-flux characteristics with AC bias can always be optimum on the magnetometer in the high-Tc dc-SQUID. APF can improve the effective flux-to-voltage transfer function so that it can reduce the equivalent flux noise due to the voltage noise of the preamplifier in the magnetometer. The use of APF combined with the AC-bias DOIT reduced the noise of the magnetometer by factors of 1.5 (33µΦ0/Hz vs. 50 µΦ0/Hz) at100 Hz, 3.5 (43 µΦ0/Hz vs. 150 µΦ0/Hz) at 10 Hz, and 5.2 (67 µΦ0/Hz vs. 351 µΦ0/Hz) at 1 Hz as compared with the noise levels that were obtained with the static-current-bias DOIT. The contribution of the factors at 1 Hz is about 2 by APF and 2.6 by AC bias. The performance of improving the flux noise in the AC -bias DOIT with APF is almost equal to that of the flux locked loop (FLL) circuits in which the flux modulation uses a coupling system with a transformer and with the AC bias.

We report on progress in the development of high-current-density all-NbN tunnel junctions for application as submillimeter wave SIS mixers. A very high current density up to 54 kA/cm2, roughly an order of magnitude larger than any reported results for all-NbN tunnel junctions, was achieved in the junctions with a thin aluminum nitride (AIN) tunnel barrier. Even though the junctions have a very high current density, they showed high-quality junction characteristics with a large gap voltage, sharp quasipartical current rise, and small subgap leakage current. The junctions also exhibited good Josephson tunneling behavior, excellent terahertz response, and sensitive heterodyne mixing properties. NbN/AIN/NbN tunnel junctions were integrated with a NbN thin-film antenna to investigate the terahertz responses and the heterodyne mixing properties in a quasioptical mixer testing system. Photon-assisted tunneling steps were clearly observed on the I-V curve with irradiation up to 1 THz, and low-noise heterodyne mixing was demonstrated in the 300-GHz band.

The problem of restoring binary (black and white) images degraded by color-dependent flip-flap noises is considered. The real image is modeled by a Markov Random Field (MRF). The Iterated Conditional Modes (ICM) algorithm is adopted. It is shown that under certain conditions the ICM algorithm is insensitive to the MRF image model and noise parameters. Using this property, we propose a parameter-free restoration algorithm which does not require the estimations of the image model and noise parameters and thus can be implemented fully in parallel. The effectiveness of the proposed algorithm is shown through applying the algorithm to degraded hand-drawn and synthetic images.

We report the strong microwave Josephson radiation from an array of high-Tc junctions on a MgO bicrystal substrate from centimeter- to millimeter-wave ranges. The dc bias current was fed to the junction array having parallel geometry with the pair of junctions shunted by superconducting loops. The configuration of bias leads was a series of interlocking dc SQUID's geometry which guaranteed the oscillation of all junctions at the same frequency. For a five-junctions array, we observed the coherent output power of about 13 pW at receiving frequency fREC22GHz without an external magnetic flux, which was nearly five times higher than that of a single bicrystal junction. We observed the Josephson linewidth of the selfradiation in coherent state less than 1 GHz by the adjustment of the external flux. The phase differences between adjacent junctions with different IcRn products could be controlled by an external small magnetic field. Submillimeter-wave detector response of the five-junction array was also studied experimentally at frequency f478 GHz.

New THz radiation devices made of high-Tc superconductors are fabricated and their characteristics are studied in detail. Ultrashort electromagnetic pulses with 0.5 ps width have been radiated into free space from current biased devices made of superconducting YBa2Cu3O7 (YBCO) films by exciting with femtosecond laser pulses. The Fourier spectrum of them extends up to 3 THz. The radiation mechanism is ascribed to the ultrafast supercurrent modulation by the optical pulses. The THz waveform is analyzed using rate equations describing the relaxation of photoexcited quasiparticles. By the improvement of the device structure and the collecting optics, the radiation power can be increased up to 0.5 µW. A new type THz radiation from YBCO films under an external magnetic field without a transport current is also reported.

We have developed a network architecture that achieves ATM multicast communication services with receiver-specified quality of service (QoS) guarantee which depends on the dynamic resource environment of the receivers (e.g. CPU capability, memory capability, and network capability). We propose two receiver-initiated QoS guarantee methods and concentrate on the functions required to achieve them. Moreover, on our ATM testbed, we also evaluate the performance of an experimental implementation of the proposed methods.

Nonuniform transmission lines are crucial in integrated circuits and printed circuit boards, because these circuits have complex geometries and layout between the multi layers, and most of the transmission lines possess nonuniform characteristics. In this article, an efficient numerical method for analyzing nonuniform transmission lines has been presented by using the Chebyshev expansion method and moment techniques. Efficiency on computational cost is demonstrated by numerical example.

In this paper, we present CB-Power, a hierarchical power analysis and characterization environment of cell-based CMOS circuits. The environment includes two parts, a cell characterization system for timing, input capacitance as well as power and a cell-based power estimation system. The characterization system can characterize basic, complex and transmission gates. During the characterization, input slew rate, output loading, capacitive feedthrough effect and the logic state dependence of nodes in a cell are all taken into account. The characterization methodology separates the power consumption of a cell into three components, e.g., capacitive feedthrough power, short-circuit power and dynamic power. With the characterization data, a cell-based power estimator (CBPE) embedded in Verilog-XL is used for estimating the power consumption of the gates in a circuit. CBPE is also a hierarchical power estimator. Macrocells such as flip-flops and adders are partitioned into primitive gates during power estimation. Experimental results on a set of MCNC benchmark circuits show that the power estimation based on our power modeling and characterization provides within 6% error of SPICE simulation on average while the CPU time consumed is more than two orders of magnitude less.

Field Programmable Gate Arrays (FPGA's) are important devices for rapid system prototyping. Roth-Karp decomposition is one of the most popular decomposition techniques for Look-Up Table (LUT) -based FPGA technology mapping. In this paper, we propose a novel algorithm based on Binary Decision Diagrams (BDD's) for selecting good lambda set variables in Roth-Karp decomposition to minimize the number of consumed configurable logic blocks (CLB's) in FPGA's. The experimental results on a set of benchmarks show that our algorithm can produce much better results than the similar works of the previous approaches.

We propose a top-down approach for cosimulation of hardware/software co-designs for embedded systems and introduce a component logical bus architecture as an interface between software components implemented by processors and hardware components implemented by custom logic circuits. Co-simulation using a component logical bus architecture is possible is the same environment from the stage at which the processor is not yet finalized to the stage at which the processor is modeled in register transfer language. Models based upon a component logical bus architecture can be circulated and reused. We further describe experimental results of our approach.

The analysis of an architecture may provide statistic information on the use of the resources and on the execution time. Some of these information need just a static analysis. Others, such as the execution time, may need dynamic analysis. Moreover as the computation time of behavioral descriptions (control step time unit) and RTL ones (cycle based) may differ a lot, unexpected architectures may be generated by behavioral synthesis. Therefore means to debug the results of behavioral synthesis are required. This paper introduces a new approach to integrate an interactive simulator within a behavioral synthesis tool, thereby allowing concurrent synthesis and simulation. The simulator and the behavioral synthesis are based on the same model. This model allows to link the behavioral description and the architecture produced by synthesis. This paper also discusses an implementation of this concept resulting in a simulator, called AMIS. This tool assists the designer for understanding the results of behavioral synthesis and for architecture exploration. It may also be used to debug the behavioral specification.

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.