In this paper, a novel method of clock feedthrough reduction in CMOS autozeroed operational amplifiers with three-phase clock operation is presented. The operational amplifiers in the method are configured by two autozeroed-gain stages. The differential input stage and the second output gain stage are autozeroed individually by a three-phase clock for autozeroing. The three-phase clock is provided so as to finish the compensation period of the input stage earlier than the end of the second stage compensation period. This operation makes it possible to absorb affection of clock feedthrough in the input stage with the second stage. As a result, residual error of offset compensation is much reduced by the voltage gain of the first stage. The effect of the two-stage autozeroing has been confirmed with SPICE simulation and fabricated CMOS circuit. The results of SPICE simulation showed that the two-stage autozeroed operational amplifier has significant advantage as compared to conventional configuration. Affection of clock feedthrough is reduced to about 1/50 in the two-stage configuration. Fabricated CMOS circuit also showed high potential of the two-stage autozeroed operational amplifier for feedthrough reduction. It has been proven experimentally that the two-stage autozeroing is an effective design approach to reduce clock feedthrough error in CMOS autozeroed operational amplifiers.

A novel common emitter common collector transistor pair (CECCTP) mixer is presented. A LO pumped CECCTP enables even harmonic mixing operation, and a balanced CECCTP mixer configuration enables the suppression of both 2fLO and fIM2 which are undesirable component for direct conversion mixer. A 2 GHz-band balanced CECCTP mixer is fabricated in SiGe HBT process, and the direct conversion characteristics are measured. It performs conversion gain of 8.8 dB, NF of 14.9 dB and IIP2 of 42.3 dBm when LO power is -6 dBm, supplied voltage is 3 V and current is 5 mA.

In this paper, we present a new approach to the construction of a set of binary sequences with a zero-correlation zone. The set consists of n pairs of binary sequences and the length of each binary sequence is n2(m+2) for some integers m and n. The Hadamard sequences with length n are used to construct the set. Any sequence in the set has 2(m+1) subsequences, each of length 2n. The author proves that any two subsequences are orthogonal if they belong to different pairs of binary sequences in the set.

In this paper, we propose a new consolidation algorithm called the Selective Backward Resource Management (BRM) cell Feedback (SBF) algorithm. It achieves a fast response and low consolidation noise by selectively forwarding BRM cell from the most congested branch to the source instead of waiting from all branches. Mathematical models are derived to quantitatively characterize the performance, i.e. the response time and ACR of the source, of SBF and previously proposed algorithms. The interoperation of consolidation algorithms in point-to-multipoint available bit rate (ABR) is investigated. We address response time, consolidation noise and the effect of asymmetrical round trip delay (RTD) from branch point to destinations aspects. All combinations of four different consolidation algorithms are interoperated in both local/metropolitan area network (LAN/MAN) and wide area network (WAN) configuration. By a simulation method, we found that the consolidation algorithm used at the uppermost stream branch point, especially in WAN configuration, plays an important role in determining the performance of the network. However, consolidation algorithm used at the lower stream branch point affects the network performance insignificantly. Hence, in order to achieve a good and effective performance of the consolidation algorithms interoperated network, a fast response with low consolidation noise algorithm should be used at the uppermost stream branch point and a simple and easy to implement algorithm should be used at the lower stream branch point.

We propose a set of Fabry-Perot etalons integrated in a planar lightwave circuit (PLC-FPE) designed for a unified system for broadcasting and communication. A PLC-FPE containing four etalons having different cavity lengths is fabricated and their loss and frequency characteristics are investigated. The total loss and the maximum finesse were found to be 8 dB and 34, respectively.

A wavelet based algorithm for scalable video compression is described, with the main focus put on memory bandwidth reduction and efficient VLSI implementation. The proposed algorithm adopts a modified 2-D subband decomposition scheme in conjunction with a partial zerotree search for efficient Embedded Zerotree Wavelet coding. The experiment with the performance of the proposed algorithm in comparison with that of conventional DWT, MPEG-2, and JPEG demonstrates that the image quality of the proposed algorithm is consistently superior to that of JPEG, and our scheme can even outperform MPEG-2 in some cases, although it does not exploit the inter-frame redundancy. In spite of the performance inferiority to the conventional DWT, the proposed algorithm attains significant reduction of DWT memory requirements, enhancing a reasonable balance between implementation cost and image quality.

We report the measurements on the ramp-edge type Josephson and quasiparticle tunnel junctions with the different interface angle geometry using high-Tc YBa2Cu3O7-y (YBCO) electrodes. The YBCO/I/Ag tunnel junctions with different crystal-interface boundary angles are fabricated for the investigation of zero bias conductance peak. The angle dependent zero bias conductance peak typical to a dx2-y2-wave superconductor is observable. For Josephson junctions, YBCO ramp-edge junctions with different ab-plane electrodes relatively rotated by 45are fabricated using a CeO2 seed-layer technique. The temperature dependence of the maximum Josephson current for YBCO/PBCO/YBCO junctions (PBCO: PrBa2Cu3O7-y) exhibits angle-dependent behavior, qualitatively different from the Ambegaokar-Baratoff prediction. Under microwave irradiation of 9 GHz, the Shapiro steps appear at integer and/or half integer multiples of the voltage satisfying Josephson voltage-frequency relation, whose behavior depends on the sample angle geometry. The results are reasonably interpreted by the dx2-y2-wave theory by taking the zero energy state into account.

We have fabricated a novel type of intrinsic Josephson junctions with superconducting Bi2Sr2CaCu2O8+y (Bi-2212)/YBa2Cu3O7-x(YBCO) bilayer thin films deposited on MgO(100) substrates. We used the 4th harmonics of a Nd:YAG pulsed laser ablation. Furthermore, we studied the transport properties of a 25 µm 25 µm Bi-2212/YBCO mesa-type junction. The zero resistance temperature was around 50 K. The current-voltage characteristics showed flux-flow-like behavior and a supercurrent of about 2 mA at 4.2 K. Shapiro steps were observed when microwave was irradiated to the mesa junction. These Shapiro steps are attributed to the Josephson junction formed at the interface between the Bi-2212 and YBCO layers in the mesa structure and not to the intrinsic Josephson junctions in the Bi-2212 layer or the micro-grains within the films.

Previous device models for Hot Electron Bolometers (HEB) apply a lumped element approach to calculate the small signal parameters. In this work, large signal parameters are calculated using a nonlinear one-dimensional heat balance equation including critical current effects. Small signal equivalents are obtained by solving a linearized heat balance for the small signal beat term in the HEB. In this model, the absorbed bias power density is treated as a profile along the HEB bridge and the electrothermal feedback acts differently on different parts of the bridge. This model predicts more realistic conversion gain figures being about 10 dB lower than in previous ones.

In this paper, we review the progress in BiSrCaCuO-2212 Intrinsic Josephson junctions (IJJs) by summarizing our recent results in fabrication and high frequency experiments. Using a double-side fabrication process, a well defined number of intrinsic Josephson junctions in a well defined geometry can be fabricated. The junctions in the stack are quite homogeneous, and the power distribution of external irradiation among the junctions is even. Shapiro steps are clearly observed up to 2.5 THz, and the general condition for the occurrence of Shapiro steps at frequency frf is that it should be much greater than the plasma frequency fpl. Under certain conditions the Shapiro steps are zero-crossing, making some applications possible, such as quantum voltage standard etc.

We present analytical and numerical results on the flux-quantum transitions in a three-junction superconducting quantum interference device (3J-SQUID) controlled by two RF signals. The 3J-SQUID has two superconducting loops, and the RF signals are magnetically coupled to the loops. Flux-quantum transitions in the 3J-SQUID loops can be controlled by utilizing the phase difference of the two RF signals. Under proper conditions, we can obtain a situation where one flux quantum passes through the 3J-SQUID per one cycle of the RF signals without DC current biasing, which results in a zero-crossing step on the current-voltage characteristics. In this paper, we first explain the operation principle by using a quantum state diagram of a 3J-SQUID. Next, we numerically simulate RF-induced transitions of the quantum states. A zero-crossing step on the current-voltage characteristics is demonstrated. We also investigate dependence of zero-crossing steps upon parameters of the 3J-SQUID and RF signals.

We present a simple framework for multicasting video in an active network, in which we overcome heterogeneity in the quality requests by filtering the video stream at some properly located active nodes. The framework includes the requirements for the underlying active network and outlines the video multicast application. We then introduce a heuristic algorithm for electing the filtering nodes to conform a multicast distribution tree, in which we use an objective function to, for example, minimize the required bandwidth. We evaluate the performance of our algorithm comparing it with simulcast and layered encoded transmission through simulation experiments, showing some advantages of using active filtering.

In this paper, we review recent developments in the field of optical regeneration for both ultra long-haul transmission and terrestrial networking applications. Different techniques (2R/3R) using nonlinear properties of materials and/or devices are proposed such as saturable absorber or InP based interferometer structures showing regenerative capabilities. Principles of operation as well as system experiments are described.

Since the impact of the recent rapid penetration of Information Technologies into the society is so tremendous, it is said that IT revolution is coming. Recognizing the above new waves, the Japanese Government is now promoting e-Government programs, and most enterprises are going to depend on the Internet to do their various activities. However, computer criminals, and other threats to security are increasing and becoming serious. Therefore, 'security' is the key for the Internet to be infrastructure of the future society in a true sense. There are many products for security controls, which are not necessarily compatible or interoperable. Interoperability is the basic requirement for infrastructures. In April, 2000, JNSA was organized by about a hundred IT companies. On the other hand, in October, 2000, LINCS was set up in Kogakuin University. The two organizations set up a Consortium to make experimental studies on IPSec interoperability. This is the first report of the activities and intermediate (the first) results obtained.

A Fourier-optics based imaging system for electromagnetic interference (EMI) sources is presented. It is necessary to decrease undesired emissions in order to meet EMI requirements. To investigate this problem, a visualization of electromagnetic (EM) emitting fields is very useful. In this paper, we propose a passive imaging system of EM emitting fields based on Fourier optics. Amplitude and phase values of diffracted fields on an entrance pupil are acquired by using a six-port interferometer. The measured EM fields are then processed on a computer, and an image is retrieved using an inverse Fresnel transform. Experiments are presented, which demonstrate the potential of the proposed method. The proposed system is useful not only in the field of electromagnetic compatibility (EMC), but also for scientific elucidation to discuss the optics and microwave theory of the same viewpoint.

Synthetic aperture radar interferometry have been established in the past two decades, and used extensively for many applications including topographic mapping of terrain and surface deformation. Vegetation analysis is also a growing area of its application. In this paper, we propose an polarimetric SAR interferometry technique for interferometric phase extraction of each local scatterer. The estimated position of local scattering centers has an important information for effective tree height estimation of forest. The proposed method formulated for local scattering center extraction is based on the ESPRIT algorithm which is known for high-resolution capability of closely located incident waves. The method shows high-resolution performance when local scattered waves are uncorrelated and have different polarization characteristics. Using the method, the number of dominant local scattering centers and interferometric phases in each image pixel can be estimated directly. Validity of the algorithm is demonstrated by using examples derived from SIR-C data.

The scatterometer is a real aperture radar capable to perform a set of normalized radar cross section measurements under different azimuth angles for each resolution cell. The main field of application of a wind scatterometer regards the sea surface wind field determination. As a matter of fact, once such measurements have been performed it is possible to determine the sea surface wind field by means of an inversion procedure. In this paper we present a novel inversion scheme which is an evolution of the procedure nowday used by the Italian Space Agency (ASI) under the Italian Processing and Archiving Facility (I-PAF). A full comparative study shows that the novel inversion scheme better behaves whenever light wind regimes are in question.

In this paper, we examine the polarimetric characteristics and the potential of the coherent decomposition in polarimetric synthetic aperture radar (SAR) interferometry. Coherent scattering decomposition based on the coherence optimization can separate effective phase center of different scattering mechanisms and can be used to generate canopy digital elevation model (DEM). This decomposition is applied to a simplified stochastic scattering model such as forest canopy. However, since the polarimetric characteristics are not well understood when the decomposition is carried out, we investigate its characteristics and potential using polarimetric entropy-alpha and three-component scattering matrix decomposition. The results show that the first and third components correspond to the lower and upper layer, respectively, in ideal case. In this investigation, SIR-C/X-SAR data of the Tien Shan flight-pass are used.

Wavelet based image compression is getting popular due to its promising compaction properties at low bitrate. Zerotree wavelet image coding scheme efficiently exploits multi-level redundancy present in transformed data to minimize coding bits. In this paper, a new technique is proposed to achieve high compression by adding new zerotree and significant symbols to original EZW coder. Contrary to four symbols present in basic EZW scheme, the modified algorithm uses eight symbols to generate fewer bits for a given data. Subordinate pass of EZW is eliminated and replaced with fixed residual value transmission for easy implementation. This modification simplifies the coding technique as well and speeds up the process, retaining the property of embeddedness.

We describe a simple all-optical wavelength converter based on a Fabry-Perot semiconductor optical amplifier (FPSOA). We measure its static characteristics in detail and successfully demonstrate its dynamic wavelength-conversion operation (both inverted and non-inverted) at 2.5 Gbit/s. This is the first demonstration of FPSOA-based wavelength conversion. Quasi-digital response is also observed. Low input power, ease of fabrication and good compatibility with WDM networks are important advantages of FPSOA.