The optimal design of complex infinite impulse response (IIR) two-channel quadrature mirror filter (QMF) banks with equiripple frequency response is considered. The design problem is appropriately formulated to result in a simple optimization problem. Therefore, based on a variant of Karmarkar's algorithm, we can efficiently solve the optimization problem through a frequency sampling and iterative approximation method to find the complex coefficients for the IIR QMFs. The effectiveness of the proposed technique is to form an appropriate Chebyshev approximation of a desired response and then find its solution from a linear subspace in several iterations. Finally, simulation results are presented for illustration and comparison.

The scaled down feature size and the increased frequency of today's deep sub-micron region call for fundamental changes in driver-load models. To be more specific, new driver-load models need to take into consideration the nonlinear behavior of the drivers, the inductance effects of the loads, and the slew rates of the output waveforms. Current driver-load models use the conventional single Ceff (one-ramp) approach and treat the interconnect load as lumped RC networks. Neither the nonlinear property nor the inductance effects were considered. The accuracy of these existing models is therefore questionable. This paper introduces a new multi-ramp driver model that represents the interconnect load as a distributed RLC network. The employed two effective capacitance values capture the nonlinear behavior of the driver. The lossy transmission line approach accounts for the impact of inductance when modeling the driving point interconnect load. The new model shows improvements of 9% in the average delay error and 2.2% in the slew rate error compared to SPICE.

Discontinuity such as a bend in a micro-strip line is known as one of major radiation sources. The total radiation from the micro-strip line is, however, being generally investigated because of the difficulties in identifying the radiation from some specific location. In this paper, paying attention to the feature of TDR (Time-Domain Reflectometry) measurement, we made an attempt to extract the radiation only from the bend in a micro-strip line. Such an approach is useful in understanding its radiation mechanism. As a result, we found that the larger the bend angle is, the larger the radiation power becomes. The radiation power achieved 3.5% at maximum when the bending angle was 90at the frequencies below 1 GHz. We also examined the validity of the TDR analysis in comparison with network analyzer measurement. We obtained the radiation power versus frequency from the measured scattering parameters, which exhibited a fair agreement with the TDR result.

This paper proposes a method for estimating the number and locations of multiple targets distributed in the ocean. This is achieved by calculating the cross spectral density matrix (CSDM) generated from individual sound sources and applying them to a minimum variance distortionless response (MVDR), a nonlinear processor. The individual CSDMs are calculated by separating and extracting a Sequence CLEAN-based data vector from the CSDM of the data vector received from multiple targets. Numerical simulations demonstrate that the proposed method improves the MVDR performance in the case of multiple targets.

A DC offset caused by self-mixing is a serious problem for direct-conversion receivers. Local oscillation (LO) leakage via quadrature demodulators (QDEMOD) must be suppressed in order to achieve a low DC offset. An LO buffer which drives QDEMOD mainly causes the LO leakage. We proposed an LO buffer which has a high-pass frequency response with small occupied area and low current consumption. A QDEMOD using the proposed LO buffer is fabricated using a SiGe BiCMOS process. Measured low LO leakage of -70 dBm is achieved, which is 10 dB lower than that of a QDEMOD with a conventional LO buffer. This measured result indicates that the proposed LO buffer is suitable for QDEMODs for direct-conversion receivers.

In this paper we show that an outerplanar graph G with maximum degree at most 3 has a 2-D orthogonal drawing with no bends if and only if G contains no triangles. We also show that an outerplanar graph G with maximum degree at most 6 has a 3-D orthogonal drawing with no bends if and only if G contains no triangles.

Continuous and explosive growth of the Internet has shown that current TCP mechanisms can obstruct efficient use of high-speed, long-delay networks. To address this problem we propose an enhanced transport-layer protocol called gHSTCP, based on HighSpeed TCP proposed by Sally Floyd. It uses two modes in the congestion avoidance phase based on the changing trend of RTT. Simulation results show gHSTCP can significantly improve performance in mixed environments, in terms of throughput and fairness against the traditional TCP Reno flows. However, the performance improvement is limited due to the nature of TailDrop router, and the RED/ARED routers can not alleviate the problem completely. Therefore, we present a modified version of Adaptive RED, called gARED, directed at the problem of simultaneous packet drops by multiple flows in high speed networks. gARED can eliminate weaknesses found in Adaptive RED by monitoring the trend in variation of the average queue length of the router buffer. Our approach, combining gARED and gHSTCP, is quite effective and fair to competing traffic than Adaptive RED with HighSpeed TCP.

Mainly, a uniform linear array (ULA) has been used for DOA estimation of coherent signals because we can apply the spatial smoothing preprocessing (SSP) technique. However, estimation by a ULA has ambiguity due to the symmetry, and the estimation accuracy depends on the DOA. Although these problems can be solved by using a uniform circular array (UCA), we cannot estimate the DOA of coherent signals because the SSP technique cannot be applied directly to the UCA. In this paper, we propose to estimate 2-dimensional DOA (polar angles and azimuth angles) estimation of coherent signals using a cylindrical array which is composed of stacked UCAs.

This paper presents a technique for reducing spurious output of balanced modulators used in transmitters and arbitrary waveform generators. Two-step upconversion is a convenient way to produce a desired single-sideband (SSB) radio-frequency (RF) signal--baseband quadrature I and Q signals (which are analog outputs of direct digital frequency synthesizers) are upconverted by mixers and local oscillators (LOs)--but mismatches between the DACs in I and Q paths cause spurious output. We propose a method of dynamically matching the I and Q paths by multiplexing two DACs between I and Q paths in a pseudo-random manner. MATLAB simulation shows that multiplexing the two DACs spreads the spurious output, caused by mismatches between the two DACs, in the frequency domain, and reduces the peak level of spurious signals.

Novel gain monitoring scheme in Remotely-Pumped EDF/DRA hybrid inline amplifier is proposed using Optical Time Domain Reflectometer (OTDR). Signal degradation due to cross gain modulation (XGM) caused by an OTDR pulse in the distributed Raman amplifier (DRA) section and remotely-pumped EDF (RP-EDF) unit is analyzed theoretically. The required conditions for suppressing of XGM in the DRA section are derived. We propose the directional bypass configuration to realize OTDR measurement without XGM in the EDF unit. Transmission experiments using the RP-EDF/DRA hybrid inline amplifier demonstrate the absence of transmission impairement induced by OTDR. An analysis of the OTDR trace for each gain medium is also discussed. The theoretical analysis agrees well with the experimental result.

The widespread use of the Internet raises issues regarding intellectual property. After content is downloaded, no further protection is provided on that content. DRM (Digital Rights Management) technologies were developed to ensure secure management of digital processes and information. In this paper, we present a multilevel content distribution model of which we present formal descriptions.

L-convex functions are nonlinear discrete functions on integer points that are computationally tractable in optimization. In this paper, a discrete Hessian matrix and a local quadratic expansion are defined for L-convex functions. We characterize L-convex functions in terms of the discrete Hessian matrix and the local quadratic expansion.

We proposed a novel structure that improved the linear characteristics of electroabsorption modulator (EAM) with composite quantum-wells as an absorption core layer. We fabricated three types of EAM's whose active cores were 8 nm thick, 12 nm thick and a composite core with 8 nm thick and 12 nm thick quantum-well (QW), respectively. The transfer functions of EAM's were investigated and their third-order inter-modulation distortion (IMD3) was obtained by calculation. The spurious free dynamic range (SFDR) was measured and compared with three types of QW. The linearity of the device with composite quantum-well showed a large enhancement in SFDR by 9.3 dBHz2/3 in TE mode and 7.0 dBHz2/3 in TM mode compared with the conventional EAM.

The XTR public key cryptosystem was introduced in 2000. XTR is suitable for a variety of environments including low-end smart cards, and is regarded as an excellent alternative to RSA and ECC. Moreover, it is remarked that XTR single exponentiation (XTR-SE) is less susceptible than usual exponentiation routines to environmental attacks such as the timing attack and the differential power analysis (DPA). This paper investigates the security of side channel attack (SCA) on XTR. In this paper, we show the immunity of XTR-SE against the simple power analysis if the order of the computation of XTR-SE is carefully considered. In addition, we show that XTR-SE is vulnerable to the data-bit DPA, the address-bit DPA, the doubling attack, the modified refined power analysis, and the modified zero-value attack. Moreover, we propose some countermeasures against these attacks. We also show experimental results of the efficiency of the countermeasures. From our implementation results, if we compare XTR with ECC with countermeasures against "SCAs," we think XTR is as suitable to smart cards as ECC.

Optical signal processing is one of essential technologies for improving the flexibility of all-optical network. Above all, recently there have been a lot of studies regarding all-optical 2R/3R regeneration technology. However, there are few studies about all-optical 2R/3R technologies that are carried out in field environment. In this paper, we report the successful results of field trials of an all-optical 2R regeneration system based on an electro-absorption modulator for 40-Gbit/s WDM transmission systems with optical add/drop multiplexing. It was made sure that by applying the all-optical 2R regeneration system to the optical add/drop multiplexer in the 320-km-long transmission systems the transmission characteristics of the express signal after 320-km transmission and those of the dropped signal at 160-km can be made nearly the same. It is quite important that the transmission characteristics are equal for both the dropped and express channel from a point of view of the system design, and the results in this paper suggests one possible solution for this matter.

The wavelength-division multiplexing (WDM) technology has been popular in communication societies for providing very large communication bands by multiple lightpaths with different wavelengths on a single optical fiber. Particularly, a double-ring optical network architecture based on the packet-over-WDM technology such as the HORNET architecture, has been extensively studied as a next generation platform for metropolitan area networks (MANs). Each node in this architecture is equipped with a wavelength-fixed optical-drop and a fast tunable transmitter so that a lightpath can be established between any pair of nodes without wavelength conversions. In this paper, we formulate the optical-drop wavelength assignment problem (ODWAP) for efficient wavelength reuse under heterogeneous traffic in this network, and prove the NP-completeness of its decision problem. Then, we propose a simple heuristic algorithm for the basic case of ODWAP. Through extensive simulations, we demonstrate the effectiveness of our approach in reducing waiting times for packet transmissions when a small number of wavelengths are available to retain the network cost for MANs.

RF MOSFET's are usually measured in common source configuration by a 2-port network analyzer, and the common gate and common drain S-parameters cannot be directly measured from a conventional 2-port test structure. In this work, a 4-port test structure for on-wafer measurement of RF MOSFET's is proposed. Four-port measurements for RF MOSFET's in different dimensions and the de-embedded procedures are performed up to 20 GHz. The S-parameters of the RF MOSFET in common source (CS), common gate (CG), and common drain (CD) configurations are obtained from a single DUT and one measurement procedure. The dependence of common source S-parameters of the device on substrate bias are also shown.

This paper reports on the bending loss insensitive single mode fiber suitable for access networks, which is applicable for wide wavelength use. Excellent attenuation stability of the fiber in the full spectrum range has been confirmed even in severe conditions such as fiber handling in mid-span access at aerial closure, cable installation/handling in indoor wirings and so on. Also, applications suitable for FTTH subscribers' use have been introduced.

This paper proposes a new angular measurement system to a moving target in the presence of clutter. We apply MUSIC (MUltiple SIgnal Classification) to the outputs of a Doppler filter bank consisting of quadrature mirror filter (QMF). The comparison between QMF and the short time Fourier transform (STFT) as a preprocessor of MUSIC is also discussed. DOA estimation performance by QMF-MUSIC is nearly equal to that of STFT-MUSIC. On the other hand, QMF-MUSIC overcomes STFT-MUSIC in the aspect of computational cost. In a specific example in this paper, the proposal QMF bank by Daubechies (4th order) wavelet requires 80% fewer the number of multiplications and 25% fewer the number of additions than the FFT-based STFT filter bank.

In this paper a novel dielectric resonator (DR) bandpass filter (BPF) with flexible arrangement of attenuation poles is proposed. This DR filter is similar to a conventional DR filter except adding a microstrip line below a DR, which not only shifts the location of attenuation poles, but also improves skirt characteristics. The duplexer with the proposed DR BPF has been yielded better isolation and sharper skirt behavior than that with a conventional DR filter. The implemented duplexer has shown a good performance and been well agreed with the simulation.