Logic gate | EPFL Graph Search

A logic gate is an idealized or physical device that performs a Boolean function, a logical operation performed on one or more binary inputs that produces a single binary output. Depending on the context, the term may refer to an ideal logic gate, one that has, for instance, zero rise time and unlimited fan-out, or it may refer to a non-ideal physical device (see ideal and real op-amps for comparison). In the real world, the primary way of building logic gates uses diodes or transistors acting as electronic switches. Today, most logic gates are made from MOSFETs (metal–oxide–semiconductor field-effect transistors). They can also be constructed using vacuum tubes, electromagnetic relays with relay logic, fluidic logic, pneumatic logic, optics, molecules, or even mechanical elements. With amplification, logic gates can be cascaded in the same way that Boolean functions can be composed, allowing the construction of a physical model of all of Boolean logic, and therefore, all of the

Computer Algebraic Approach to Verification and Debugging of Galois Field Multipliers

Maciej Jerzy Ciesielski, Cunxi Yu

The paper presents a novel method to verify and debug gate-level arithmetic circuits implemented in Galois Field arithmetic. The method is based on forward reduction of the specification polynomials of the circuit in GF(2(m)) using GF(2) models of its logic gates. We define a forward variable order "FO >" and the rules of forward reduction that enable verification, bug detection, and automatic bug correction in the circuit. By analyzing the remainder generated by forward reduction, the method can determine whether the circuit is buggy, and finds the location and the type of the bug. The experiments performed on Mastrovito and Montgomery multipliers show that our debugging method is independent of the location of the bug(s) and the debugging time is comparable to the time needed to verify the bug-free circuit.

IEEE2018

Magnonic crystals with reconfigurable magnetic defects for spin-based microwave electronics

Korbinian Baumgärtl

Collective spin excitations can propagate in magnetically ordered materials in the form of waves. These so-called spin waves (SWs) or magnons are promising for low-power beyond-CMOS information processing, which does not rely anymore on the lossy movement of electric charges. SWs in the few GHz frequency regime possess nanoscale wavelengths about five orders of magnitude smaller than electromagnetic waves of the same frequency. This property makes SWs ideally suited for application in microwave technology, essential for on-chip processing of wireless telecommunication signals. In this thesis, three crucial challenges relevant for the technological application of SWs are addressed: First, to functionalize SWs and exploit their small wavelengths, it is necessary to control them at the nanoscale. Here, periodically nanostructured materials, denoted magnonic crystals, are promising, as they allow to tailor the band structure of SWs. We report on SWs propagating in a prototypical one-dimensional magnonic crystal consisting of dipolarly coupled magnetic nanostripes. The remanent magnetization of individual stripes was designed to be bistable along the long axis. By magnetizing an individual stripe in opposite direction to the others, we created a magnetic defect. We measured by means of all-electrical spin wave spectroscopy and Brillouin light scattering microscopy phase and amplitude of SWs trespassing the defect. We found that SW phases and amplitudes were modified at the nanoscale, and phase shifts could be tuned by an applied bias magnetic field. Using micromagnetic simulations, we identified specific bias fields for which phase shifts of Pi are achieved without suppressing SW amplitudes. This result is highly relevant for the implementation of logic gates based on interference of phase-controlled SWs. We further measured propagation of short-waved SWs in an antiferromagnetically ordered one-dimensional magnonic crystal, where every second stripe was magnetized in opposite direction. We found a band gap closing at the Brillouin zone boundary when no magnetic bias field was applied. Our observations are promising for reprogrammable microwave filters capable of adjusting stop- and passband. Second, we address how long-waved electromagnetic waves can be coupled efficiently to nanoscale SWs. We demonstrate by space- and time-resolved scanning X-ray transmission measurements, that excited nanogratings allow to transfer their reciprocal lattice vector and multiple of it to an underlying magnetic thin film, in which nanoscale propagating SWs are launched. Additionally, we discovered a second method for short-waved SW generation based on magnetic microwave guides. This approach is easy to fabricate and relies on the adaption of the SW wavelength to a changing effective magnetic field. Efficient coupling of electromagnetic waves to nanoscale SWs promises an unprecedented miniaturization of microwave components. Third, we found that the magnetization direction of bistable nanomagnets can be switched by propagating SWs in an underlying magnetic thin film when a threshold amplitude is reached. This discovery is promising for the realization of a non-volatile magnonic memory, which stores SW amplitudes. A possible application are SW logic gates, which encode the outcome of a logic operation in the output SW amplitude. Magnonic memory would allow for storing these amplitudes directly, without requiring lossy conversion into the electrical domain.

EPFL2021

Design and Energy Management Optimizations for Wireless Sensor Networks

Mitko Tanevski

Real-time monitoring of the temperature in supermarket refrigerators, testing air quality, detecting presence or position of a person indoors, monitoring the structural integrity of bridges, and measuring soil humidity for precision agriculture are only a few applications of wireless sensor networks. A wireless sensor network (WSN) is a system of spatially distributed autonomously powered embedded devices that are used to measure and collect one or more magnitudes, detect events, or both. Those devices are called wireless sensor nodes and can perform measurement or detection either independently or in cooperation with other sensor nodes of the network. WSN systems are used in applications that require distributed measurement points or mobility of the measurement points during operation. The subject of this thesis is the design of energy-efficient wireless sensor nodes and wireless sensor networks for the sub-GHz industrial scientific and medical (ISM) band, focusing on the hardware, firmware and communication protocol. Hence, the contributions span several different aspects of wireless sensor network design. A new robust wireless sensor node platform is presented; it was fully characterized and used to build a demonstration WSN that is in operation providing field results for more than two and a half years. The development, production and testing of the new wireless sensor node named RoSe (Round Sensor) is presented. Details are given on the choices of components, design priorities, production, and testing of a small prototype series. The node features a robust overmolded antenna-housing and two battery configurations. The parameters of the node are compared with those of an existing commercial sensor node that inspired the new development. During development of the low-level routines, a new technique was introduced that enables debugging and troubleshooting of an operating sensor node by using the supply current waveform measurement and a logic output. The second part of the thesis presents per-task charge consumption measurements of the RoSe node both in test conditions and while operating in the demo WSN. These measurements serve as a base for estimating the battery lifetime for a known application and communication protocol. The battery lifetimes of the nodes operating as a part of the demo WSN are reported, and by analyzing those results, battery lifetime estimations for different measurement intervals are calculated. Furthermore, a generalized overview of the ensemble of WSN parameters is given. Those parameters are then classified in groups and their interconnections are explained. Then, the network capacity limitations in terms of the number of sensor nodes and measurement intervals are derived based on radio frequency regulations and parameter interconnections. Recognizing that compliance with radio frequency regulations in Europe is one of the key constraints in single channel sub-GHz WSN development at present, we propose a new approach to regulatory compliance by introducing a firmware module for ensuring real-time regulatory compliance. The proposed firmware module was implemented and its memory and energy footprints were evaluated. Finally, we identified the need for a hardware module that will serve as an energy usage optimization block between the battery and the rest of the sensor node. The implementation of such a module requires both hardware and firmware development. To demonstrate the concept, a simplified hardware module was designed using a commercial off-the-shelf DC-DC converter and supercapacitors. The module was implemented and characterized in a new design iteration of the RoSe node and showed a possible battery autonomy extension of 19–28 %. Practical aspects of designing and building sensor nodes and a WSN are interwoven into the chapters of the thesis for completeness.

EPFL2013