다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Information Theory and Reliable Communication

Random number generators in digital information systems make use of physical entropy sources such as electronic and photonic noise to add unpredictability to deterministically generated pseudo-random sequences1,2. However, there is a large gap between the generation rates achieved with existing physical sources and the high data rates of many computation and communication systems; this is a fundamental weakness of these systems. Here we show that good quality random bit sequences can be generated at very fast bit rates using physical chaos in semiconductor lasers. Streams of bits that pass standard statistical tests for randomness have been generated at rates of up to 1.7 Gbps by sampling the fluctuating optical output of two chaotic lasers. This rate is an order of magnitude faster than that of previously reported devices for physical random bit generators with verified randomness. This means that the performance of random number generators can be greatly improved by using chaotic laser devices as physical entropy sources. Random-number generators are important in digital information systems. However, the speed at which current sources operate is much slower than the typical data rates used in communication and computing. Chaos in semiconductor lasers might help to bridge the gap.

Fast physical random bit generation with chaotic semiconductor lasers

The power consumed by a circuit varies according to the activity of its individual transistors and other components As a result, measurements of the power used by actual computers or microchips contain information about the operations being performed and the data being processed Cryptographic designs have traditionally assumed that secrets are manipulated in environments that expose no information beyond the specified inputs and outputs This paper examines how information leaked through power consumption and other side channels can be analyzed to extract secret keys from a wide range of devices The attacks are practical, non-invasive, and highly effective—even against complex and noisy systems where cryptographic computations account for only a small fraction of the overall power consumption We also introduce approaches for preventing DPA attacks and for building cryptosystems that remain secure even when implemented in hardware that leaks

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Introduction to differential power analysis

Analogue IC Design: the Current Mode Approach

Emerging applications in the radar and communication fields (e.g. 5G cellular communications, automotive radar, etc.) need to use very high frequencies (in particular millimetre waves) and wide bandwidth, in order to achieve high efficiency at relatively short distance at affordable costs. When performing spectrum estimation for different purposes, these systems have to cope with very high frequency signals, whose samples need to be collected at sub-Nyquist rate, as the direct sampling at Nyquist rate would not be advisable. This paper explores the applicability of a new technique, namely the Hybrid Folding Receiver (HFR) and evaluates its performance in spectrum estimation for very high frequency signals. The results obtained by examining typical case studies demonstrate that the implementation of the HFR technique gives good performances in the above mentioned application areas.

Spectrum Estimation for Very High Frequency RF Systems

In this paper, we present a novel topology for a four-quadrant multiplier in GaAs MESFET/HEMT technologies, based on the quadratic relationship between Vgs and Ids. This topology improves the performance of a topology proposed by Song and Kim in 1990, resulting in less sensitivity to common-mode input components and showing better frequency performance. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 277–282, 1999.

A novel topology for four-quadrant GaAs monolithic multipliers

Phase noise models that describe the near-carrier spectrum in an accurate but insightful way are needed, to better optimize the oscillator design. In this paper we present a model to describe the effect of flicker noise sources on the phase noise of an oscillator, that can be applied both to linear oscillators and to nonlinear structures like relaxation and ring oscillators, so extending previous works that considered only the effect of the flicker noise superimposed to the control voltage of a VCO. In the phase noise of an oscillator we can separate the effect of high frequency noise sources, that can be described by a short-time-constant system, and the effect of low frequency noises (mostly flicker sources), described by a system with time constants much slower than the oscillation period. Flicker noise has been considered to cause a change in the circuit bias point; this bias point change can be mapped in a shift of the oscillation frequency by exploiting Barkhausen conditions (for linear oscillators) or obtaining this link by simulations. The power spectral density of the oscillator can then be obtained as the probability distribution of the oscillation frequency, starting from the flicker noise probability distribution. If the effect of high frequency noise sources is also taken into account, the overall oscillator spectrum can be obtained as a convolution of the spectrum due to flicker sources with the Lorentzian-shaped spectrum due to white noise sources, in analogy with the description of inhomogeneous broadening of laser linewidth.

Model of flicker noise effects on phase noise in oscillators

The most popular micromirrors switches, work with a sinusoidal low-frequency carrier obtained by a simple generator with a rude shift-level circuitry. Aiming to the problem for the pulsed rectangulars carrier signals, more and more used in the digital and scanning bonded silicon mirrors, the analog amplifiers arranged to operate in a saturation region, decrease the sharpness of leading and trailing edges of a rectangular pulse envelope (i.e. audio amplifiers). This approach makes unusable a set of features of these actuators. The well-known systems, based on high-voltage logic ports, capable of resulting an output carrier that having the shape substantially a square waveform, require large current and are very expensive. In the proposed architecture, it is possible to reduce both the excessive and unnecessary spectral components resulting from the rapid rise and fall time of the rectangular envelope as also relax the current requirements with a dedicated circuitry arrangement that modifies the output source in a trapezoidal envelope. A new scheme for decreasing power requirements using a source degenerated logic port is introduced. This method, addresses these issues by tracking the output current with a very simple approach that doesn’t require an additional consumption as most solutions do.

Fast Multi-Channel Driver for High-Voltage Micromirrors Switches

In this paper we present a methodology to calibrate and correct frequency-dependent errors in phased-array antennas with large signal bandwidth and large size. If the receivers are not narrow-band, the hypotheses of constant gain and group delay are not valid. If the frequency responses of the receivers are affected by mismatches, this will also impact directivity. Standard Amplitude and Phase Correction (APC) algorithms will not be effective in this case, and a more advanced complex FIR filtering algorithm is used. A transmitted signal is assumed to be known in order to provide a reference and estimate the optimal calibration coefficients of the FIR filters.

Alessandro Trifiletti

Papers

Spectrum Estimation for Very High Frequency RF Systems

A novel topology for four-quadrant GaAs monolithic multipliers

Model of flicker noise effects on phase noise in oscillators

Fast Multi-Channel Driver for High-Voltage Micromirrors Switches

Using feed array networks to control distortions in antenna reflector for astrophysical radio-astronomy