SAW Sensor for Fastener Failure Detection

The proof of concept for using surface acoustic wave (SAW) strain sensors in the detection of aircraft fastener failures is demonstrated. SAW sensors were investigated because they have the potential for the development of passive wireless systems. The SAW devices employed four orthogonal frequency coding (OFC) spread spectrum reflectors in two banks on a high temperature piezoelectric substrate. Three SAW devices were attached to a cantilever panel with removable side stiffeners. Damage in the form of fastener failure was simulated by removal of bolts from the side stiffeners. During testing, three different force conditions were used to simulate static aircraft structural response under loads. The design of the sensor, the panel arrangement and the panel testing results are reported. The results show that the sensors successfully detected single fastener failure at distances up to 54.6 cm from the failure site under loaded conditions

SunPy - Python for Solar Physics

This paper presents SunPy (version 0.5), a community-developed Python package for solar physics. Python, a free, cross-platform, general-purpose, high-level programming language, has seen widespread adoption among the scientific community, resulting in the availability of a large number of software packages, from numerical computation (NumPy, SciPy) and machine learning (scikit-learn) to visualisation and plotting (matplotlib). SunPy is a data-analysis environment specialising in providing the software necessary to analyse solar and heliospheric data in Python. SunPy is open-source software (BSD licence) and has an open and transparent development workflow that anyone can contribute to. SunPy provides access to solar data through integration with the Virtual Solar Observatory (VSO), the Heliophysics Event Knowledgebase (HEK), and the HELiophysics Integrated Observatory (HELIO) webservices. It currently supports image data from major solar missions (e.g., SDO, SOHO, STEREO, and IRIS), time-series data from missions such as GOES, SDO/EVE, and PROBA2/LYRA, and radio spectra from e-Callisto and STEREO/SWAVES. We describe SunPy's functionality, provide examples of solar data analysis in SunPy, and show how Python-based solar data-analysis can leverage the many existing tools already available in Python. We discuss the future goals of the project and encourage interested users to become involved in the planning and development of SunPy

Chipless Rfid Saw Sensor System-Level Simulator

Chipless RFID SAW technology has been identified as a possible solution for NASA\u27s long term needs for ground, space-flight, and space-exploration sensor requirements. SAW has many unique advantages over possible competing technologies, which include the following properties: passive, radiation hard, operable over wide temperature ranges, small, rugged, inexpensive, and identifiable. The purpose of this paper is to define a system simulation environment for SAW sensors; not on any particular sensor. For remote sensing, it is beneficial to be able to simulate effectively the sensor environment prior to fabrication. This paper will use previously presented orthogonal frequency coded (OFC) sensor tags. The parameters of interest are the transmitter, channel characteristics, target, and the receiver output. The simulations utilize a SAW device coupling of modes (COM) model and combined with the RF system parameters. This provides an accurate simulation tool for the overall system when performing analysis on important parameters, such as signal to noise ratio (SNR), SAW coding type, and range effects. Theoretical system performance of a multi-frequency SAW RFID sensor system utilizing multiple targets will be discussed. ©2010 IEEE

Coherent Correlator Multi-Sensor Receiver

The focus of this paper is to discuss theoretical and practical applications of a coherent correlator transceiver (CCT) system approach for SAW RFID sensors, with the vision toward low cost sensing. For high volume applications, it appears achievable to meet the ultimate system goals and costs with RF device integration. As with most technologies, the sensor device and system volumes will drive the cost down, and it seems reasonable to expect a similar product cycle as with SAW filters. Theoretical predictions of range, SNR, and correlation properties will be shown for differing system parameters, such as bandwidth, power, coherent integration, and ADC parameters. A comparison of SAW device resonant, CDMA and OFC type signal formats will be given and an approach for signal detection and extraction discussed. Recent measurement results for a 915 MHZ, 64 MHz bandwidth, CCT system using OFC SAW temperature sensors will be given and compared to predictions, which demonstrates the practicality and implementation of the system architecture. © 2012 IEEE

Saw Multi-Sensor System With Temperature And Range

This paper explores the effect of time overlapping multiple Bragg reflectors on the waveform of a coded, passive SAW sensor. Typical SAW sensors utilize serial reflectors, or chips, with a constant waveform shape; however, by using a multi-track SAW configuration the overlap of chips can be optimized for a desired waveform independent of bandwidth. Theoretical results for common signal envelopes are discussed and fabricated results on YZ-LiNbO3 are presented. By properly designing the chip overlap an arbitrary envelope and weight can be achieved. These techniques are used to design a new type of orthogonal frequency coded (OFC) SAW sensor. The updated coding technique decreases device response length while preserving code diversity and bandwidth as compared to a traditional, serial OFC layout. Results of these devices in a multi-sensor system show the ability to simultaneously track temperature and range, with 4 concurrent devices tracked at distances between 5-14 meters. Single sensor operation at a range of 14 meters is highlighted with a range determination accuracy of 0.25 meters (at +/-3°C). © 2012 IEEE

Characteristics of ZnO/diamond/Si SAW resonators

The surface acoustic wave (SAW) resonator response of ZnO/diamond/Si layered structures are calculated and discussed including velocity dispersion. Smith\u27s second equivalent circuit including energy storage effects is used to calculate the resonator response. The effect of velocity dispersion appears for the shift of resonant frequency to the expected center frequency, and appears for the band width of resonator becomes narrower than that of non dispersive case. The coupling of modes equation is modified for the velocity dispersion to explain these effects. The reflection coefficients of gratings are calculated for velocity dispersive case and the non velocity dispersive case. These results agree with the response calculated by the equivalent circuit model. With assuming the deviation of velocity dispersive be small neighboring the resonance area, the effect of velocity dispersion is explained in theoretically. The ZnO/diamond/Si SAW resonators provide high frequency operation and the high quality factor (Q) SAW resonators due to the velocity dispersion

A First Generation Cad Compiler For Surface Acoustic Wave Filters Using Bidirectional Transducers

An automation system has been developed for the design and analysis of SAW (surface acoustic wave) bidirectional transducers and filters and has been implemented on a personal-computer-class workstation. All dominant SAW acoustic and electrical effects have been modeled for nonreflecting transducers in a modular architecture. These synthesis and analysis tools form the core of the design-automation system. An automation shell used with the design tools forms the basis of a SAW compiler that is capable of noninteractive filter design. The first-generation set of SAW-filter design rules is implemented in a declarative language that provides logical-decision control of the automation system. The highest level of design choices, such as synthesis technique, transducer weighting, and substrate material, has been implemented in the design-rule system. The design-automation system controls the execution and iteratively evaluates options, corrects errors, and decides on an optimum design choice within the set of design rules. The system accepts user input of a frequency-domain specification and noninteractively outputs a filter meeting these specifications. A design automation system example is shown and experimental results using the CAD (computer-aided design) tools are presented

Time Domain Diffraction Analysis For Saw Transducers

A time domain diffraction analysis for surface acoustic wave (SAW) transducers was previously developed based on Huygen\u27s principle. The analysis was performed using an approximation to the scalar two dimensional impulse response of an ideal point source which allowed for fast computation of diffraction effects in the time domain. Because the diffraction analysis was performed in the time domain a broadband frequency prediction of diffraction effects via the Fourier transform was possible. This paper will present a more rigorous derivation of the time domain impulse response from the angular spectrum of waves (ASoW) approach for the case of isotropic velocity. The extension of the analysis to include the velocity and electromechanical coupling anisotropy found in typical SAW substrates will also be presented. Predictions of broadband diffraction effects will be shown for several representative SAW transducers