Modern spaceborne precision radar altimeters transmit radio signals of a spectrum bandwidth up to 300 MHz, but the bandwidth should be still increased for precise estimation of the roughness of the sea surface. In this research, the influence of the ionosphere on wideband radar signals is investigated and then it is shown that the signals are strongly influenced by the dispersive distortions in the atmosphere of the Earth even in Ku-band. Finally, the allowable bandwidth of a space borne precision radar altimeter signals is estimated, at which we could ignore the presence of these distortions.

In order to perform the registration of virtual objects in vision-based augmented reality systems, the estimation of the relation between the real and virtual worlds is needed. This paper presents a three-point vision-based registration method for video see-through augmented reality systems using binocular cameras. The proposed registration method is based on a combination of monocular and stereoscopic registration methods. A correction method that performs an optimization of the registration by correcting the 2D positions in the images of the marker feature points is proposed. Also, an extraction strategy based on color information is put forward to allow the system to be robust to fast user's motion. In addition, a quantification method is used in order to evaluate the stability of the produced registration. Timing and stability results are presented. The proposed registration method is proven to be more stable than the standard stereoscopic registration method and to be independent of the distance. Even when the user moves quickly, our developed system succeeds in producing stable three-point based registration. Therefore, our proposed methods can be considered as interesting alternatives to produce the registration in binocular augmented reality systems when only three points are available.

Internet traffic engineering is much important for Internet Service Providers (ISPs) today, since it can be used to fully utilize already deployed network resources. For ISPs, the requirements for traffic engineering should be simple, easy to configure, cost-effective and efficient. Based on these considerations, we propose an algorithm called Web First Adaptive Traffic Engineering (WFATE). Since World Wide Web (WWW) services dominate most of the total Internet traffic and WWW flows are not long-lived, we only apply load balancing to WWW traffic in the algorithm. It can be shown that the number of coexistent WWW flows at an ingress node is almost certainly below a bound, and thus a forward-per-flow mechanism without keeping track of the state of each flow is feasible. This mechanism can balance traffic load at fine granularity and therefore get better performance. Through simulations and performance comparison, it is shown that WFATE is quite efficient, which can improve the network throughput averagely by 26% under the "dense source" traffic pattern and 9% under the "sparse source" traffic pattern.

We proposed a one-way trapdoor permutation f based multi-signature scheme which can keep tighter reduction rate. Assuming the underlying hash functions are ideal, our proposed scheme is not only provably secure, but are so in a tight. An ability to forge multi-signatures with a certain amount of computational resources implies the ability to invert a one-way trapdoor permutation f (on the same size modulus) with about the same computational effort. The proposed scheme provides the exact security against Adaptive-Chosen-Message-Attack and Adaptive-Insider-Attack by . can also attack in key generation phase, and act in collusion with corrupted signers.

The present state of IEC and JIS standards is reviewed on measurement methods of low-loss dielectric and high-tempera-ture superconductor (HTS) materials in the microwave and millimeter wave range. Four resonance methods are discussed actually, that is, a two-dielectric resonator method for dielectric rod measurements, a two-sapphire resonator method for HTS film measurements, a cavity resonator method for microwave measurements of dielectric plates and a cutoff circular waveguide method for millimeter wave measurements of dielectric plates. These methods realize the high accuracy sufficient for measurements of temperature dependence of material properties.

A rigorous analysis for a TM010 mode cylindrical cavity with insertion holes is presented on the basis of the Ritz-Galerkin method to realize accurate measurements of the complex permittivity of liquid. The effects of sample insertion holes, a dielectric tube, and air-gaps between a dielectric tube and sample insertion holes are taken into account in this analysis. The validity of this method is verified from measured results of some kinds of liquid.

A simple method has been proposed for the measurement of the output power and phase characteristics of the 3rd-order inter-modulation distortion (IM3) components appearing in multistage power amplifiers. By adopting a unique definition of the phase for the IM3 components that is independent of the delay time caused by transmission lines and other instrument devices, it is possible to measure the phase, merely by using a vector signal analyzer. It is demonstrated that an accurate estimation of the IM3 characteristics of two-stage cascaded power amplifiers for cellular radio handheld terminals can be made by using the IM3 characteristics of the 1st and 2nd-stage amplifiers as measured by the proposed method. The results indicate that it is possible to reduce the dissipation power by 18% at 28 dBm RF output power with respect to conventional measurement methods. Further studies show that the error in the resultant vector of the estimated IM3 is less than 1 dB, when the asymmetry characteristics of the IM3 sidebands in the 2nd-stage amplifier are less than 7.3%.

This paper presents recursive algorithms for the least mean-squared error linear filtering and fixed-interval smoothing estimators, from uncertain observations for the case of white and white plus coloured observation noises. The estimators are obtained by an innovation approach and do not use the state-space model, but only covariance information about the signal and the observation noises, as well as the probability that the signal exists in the observed values. Therefore the algorithms are applicable not only to signal processes that can be estimated by the conventional formulation using the state-space model but also to those for which a realization of the state-space model is not available. It is assumed that both the signal and the coloured noise autocovariance functions are expressed in a semi-degenerate kernel form. Since the semi-degenerate kernel is suitable for expressing autocovariance functions of non-stationary or stationary signal processes, the proposed estimators provide estimates of general signal processes.

The artifacts of low-bit rate quantization in images cannot be removed satisfactorily by known methods. We propose decomposition of images as HSI and LSI (higher- and lower- significance images), followed by subsampling and reconstruction methods for LSI. Experiments show significant improvement in image quality, as compared to other methods.

In this paper, a simple blind algorithm for a beamforming antenna is proposed. This algorithm exploits the property of cyclostationary signals whose cyclic autocorrelation function depends on delay as well as frequency. The cost function is the mean square error between the delay product of the beamformer output and a complex exponential. Exploiting the delay greatly reduces the possibility of capturing undesired signals. Through analysis of the minima of the non-quadratic cost function, conditions to extract a single signal are derived. Application of this algorithm to code-division multiple-access systems is considered, and it is shown through simulation that the desired signal can be extracted by appropriately choosing the delay as well as the frequency.

A traffic engineering problem in a network consists of setting up paths between the edge nodes of the network to meet traffic demands while optimizing network performance. It is known that total traffic throughput in a network, or resource utilization, can be maximized if a traffic demand is split over multiple paths. However, the problem formulation and practical algorithms, which calculate the paths and the load-splitting ratios by taking bandwidth, the route constraints or policies into consideration, have not been much touched. In this paper, we formulate the constrained multipath-routing problems with the objective of minimizing the maximum of link utilization, while satisfying bandwidth, the maximum hop count, and the not-preferred node/link list in Linear Programming (LP). Optimal solutions of paths and load-splitting ratios found by an LP solver are shown to be superior to the conventional shortest path algorithm in terms of maximum link utilization, total traffic volume, and number of required paths. Then, we propose a heuristic algorithm with low computational complexity that finds near optimal paths and load-splitting ratios satisfying the given constraints. The proposed algorithm is applied to Multi-Protocol Label Switching (MPLS) that can permit explicit path setup, and it is tested in a fictitious backbone network. The experiment results show that the heuristic algorithm finds near optimal solutions.

A novel method for measuring microwave reflection coefficients without the open and load standards is proposed. In this method, a single probe is inserted into an air line and the output wave is detected by a vector detector. Offset shorts are used for the calibration. The measurement system is constructed using 7 mm coaxial line and APC7 connectors. The result of the measurement in the frequency range 1-9 GHz shows the possibility of the proposed method. All the major systematic errors can be estimated from the data that is easily obtainable.

Recent advances in measurement techniques for microwave active devices and circuits are reviewed in this paper. The R&D activities have been devoted aggressively how to characterize nonlinear performance of high power devices and circuits. They are pulsed I-V, a variety of load-pull measurements, probing, sampling, and sensing techniques, supported by the recent significant advances in DSP (Digital Signal Processing), RF components, semiconductor devices, etc. The recent advances in vector network analyzers are of our great interest. They are (a) multi-port vector network analyzers for characterizing mixers, differential devices, packaged components, electronic package characterization, and multi-layer transmission lines, and (b) EO (Electro-Optic) modulated vector network analyzers for characterizing electronic performance of EO devices with the aid of EO modulators and photonic probes. In addition, probing, sampling, and sensing techniques have made great progress to directly measure electromagnetic field, time-domain voltage waveform, and temperature in small spot areas. In this paper, some topics related to these measurement techniques are briefly reviewed. Then the existing and future issues for characterization and measurement techniques of microwave active devices and circuits are discussed.

In this era of System-On-a-Chip (SOC) technology, a designable initial state is required. Thus, embedding low voltage and low power Power-On-Reset (POR) circuit on the SOC chip is important for the portable device. This paper proposes a new POR circuit with process and temperature compensations. A band-gap reference is used in this circuit to reduce the effect of the temperature and process variations. With 200 mV hysteretic design provides robust noise immunity against voltage fluctuations on the power supply. The POR circuit has been designed, simulated, and implemented. A test chip has been fabricated by using 0.18 µm single-poly triple-metal CMOS logical process. Measurement results show the rise threshold voltage Vrr has only a 3% variation under the temperature range from -40 to 125. The power consumption is 39 mW at the 1.8 V power supply. The chip size of the POR is 62 mm280 mm. Thus, this POR circuit has a great potential to apply to a low power supply system.

This paper proposes a sensing and a precharge circuit schemes suitable for low-voltage and high-speed DRAM design. The proposed offset-compensated direct sensing scheme improves refresh characteristics as well as speed performance. To minimize the number of control switches for the offset compensation, only the output branches of differential amplifiers are implemented in each bit-line pair with a semi-global bias branch, which also reduces 50-percent of bias current. The addition of the direct sensing feature to the offset-compensated pre-sensing dramatically increases the differential current output. For the fast bit-line equalization, a charge-recycled precharge scheme is proposed to reuse VPP discharging current for the generation of a boosted bias without additional charge pumping. The two circuit schemes were verified by the implementation of a 256 Mb SDRAM with a 0.1 µm dual-doped poly-silicon technology.

In this paper, we propose a simple and accurate transfer function model of the power amplifiers for mobile communications. Detail analysis yields a generalized model for AM/AM characteristics in classes AB, B, and C. The analysis includes the effect of drain current variation with input level variation. This model introduces a loadline variation ratio to indicate the change of drain current and to represent the operation classes in a small signal region. Further discussion leads to simplified approximate equations for the AM/AM characteristics, and the estimation procedures for the simplified model parameters. Using the derived procedures, an efficient power amplifier employing pseudomorphic high electron mobility transistor (PHEMT) is fabricated for the 2 GHz band. Finally, the various characteristics given by the model, simulator and measurements are compared and found to agree well in the range of 20 dB below the saturated output level. The model is very effective for characterizing the power amplifiers that are used in linear compensation techniques such as predistortion methods, due to its severe nonlinearity of AM/AM and AM/PM characteristics.

High-frequency characteristics of SiGe heterojunction bipolar transistors with different emitter sizes are studied based on pulsed measurements. Because the self-heating effect in transistors will enhance the Kirk effect, as the devices operate in high current region, the measured cutoff frequency and maximum oscillation frequency decrease with measurement time in the pulsed duration. By analyzing the equivalent small-signal device parameters, we know the reduction of cutoff frequency and maximum oscillation frequency is attributed to the reduction of transconductance and the increase of junction capacitances for fixed base-emitter voltage, while it is only attributed to the degradation of transconductance for fixed collector current. Besides, the degradation of high-frequency performance due to self-heating effect would be improved with the layout design combining narrow emitter finger and parallel-interconnected subcells structure.

This paper investigates some fundamental properties of one-way alternating pushdown automata with sublinear space. We first show that one-way nondeterministic pushdown automata are incomparale with one-way alternating pushdown automata with only universal states, for spaces between log log n and log n, and also for spaces between log n and n/log n. We then show that there exists an infinite space hierarchy among one-way alternating pushdown automata with only universal states which have sublinear space.

Finite-ground microstrip line (FGMSL) open-end discontinuities are characterized via a self-calibrated method of moments (MoM) as a unified circuit model with a fringing capacitance and radiation conductance. By integrating the short-open calibration (SOC) procedure into a determinant MoM, the model parameters are extracted without needing the alternative port impedance. Regardless of non-ideal voltage sources, extracted parameters are observed to achieve a stable convergence as the feeding line is sufficiently extended. After extracted capacitance of a FGMSL open-end with equal strip and finite-ground widths are validated against its traditional MSL counterpart with infinite ground, extensive results are given to originally demonstrate that the capacitance increases as a decelerated function of the finite-ground width and length while the conductance is negligibly small as compared with its imaginary part.

In this paper, we derive expressions for the bit error probability of QPSK/OFDM on frequency-selective Rayleigh fading channels. In the OFDM system, ICI (interchannel interference) caused by Doppler spread of the channel degrades the error performance of the system and introduces the error floor even for coherent detection. Analysis results show that the error performance of QPSK/OFDM can be degraded as the normalized maximum Doppler frequency fD /Bsub is increased where fD is the maximum Doppler frequency and Bsub is the subchannel bandwidth. Computer simulations confirm the theoretical analysis results for BPSK and QPSK signals.