27 research outputs found
RFID multiantenna systems for wireless communications and sensing
Many scientific, industrial and medical applications require the measurement of different physical parameters in order to collect information about the spatially distributed status of some process. Very often this information needs to be collected remotely, either due to the spatial dispersion of the measurement points or due to their inaccessibility. A wireless embedded self-powered sensor may be a convenient solution to be placed at these inaccessible locations. This thesis is devoted to study the analytical relation governing the electromagnetic coupling between a reader and a embeddable self-powered sensor, based on radio frequency identification (RFID) technology, which is capable of wirelessly retrieving the status of physical parameters at a remote and inaccessible location. The physical parameter to be sensed may be the electromagnetic (EM) field existing at that location (primary measurement) or the indirect measurement of other parameters such as the temperature, humidity, etc. (secondary measurement). Given the simplicity of the RFID solution (highly embeddable properties, scavenging capabilities, penetration and radio coverage characteristics, etc.) the measurement can be done at a single location, or it can be extended to a set of measuring locations (an array or grid of sensors). The analytical relation is based on a reciprocity formulation studying the modulation of the scattered field by the embedded sensor in relation with the incident field, and allows to define a set of quality parameters of interest for the optimum design of the sensors. Particular attention is given to the scavenging circuitry as well as to the antenna design relevant to the sensing objective. In RFID tags, the existence of an RF harvesting section is an improvement with respect to conventional scattering field probes since it removes the need of DC biasing lines or optical fibers to modulate the sensor. However, this harvesting section introduces non-linearities in the response of the sensor, which requires a proper correction to use them as EM-field probes, although the characterization of the non-linearities of the RFID tag cannot be directly done using a conventional vector network analyzer (VNA), due to the requirements of an RFID protocol excitation. Due to this, this thesis proposes an alternative measurement approach that allows to characterize the different scattering states used for the modulation, in particular its non-linear behavior. In addittion, and taking this characterization as the starting point, this thesis proposes a new measurement setup for EM-field measurements based on the use of multiple tones to enlarge the available dynamic range, which is experimentally demonstrated in the measurement of a radiation pattern, as well as in imaging applications.
The RFID-based sensor response is electromagnetically sensitive to the dielectric properties of its close environment. However, the governing formulation for the response of the probe mixes together a set of different contributions, the path-loss, the antenna impedance, the loads impedance, etc. As a consequence, it is not possible to isolate each contribution from the others using the information available with a conventional RFID sensor. This thesis mathematically proposes and experimentally develops a modification of the modulation scheme to introduce a new set of multi-load scattering states that increases the information available in the response and properly isolate each term. Moreover, this thesis goes a step forward and introduces a new scattering state of the probe sensitive to temperature variations that do not depend on the environment characteristics. This new configuration enables robust environmental sensing in addition to EM-field measurements, and sensing variations of the dielectric properties of the environment
ATS-4 study program, volume 7 Final report
Direct phase reading X-band radio interferometer for attitude control of Applications Technology Satellite-
Diode mixers with optical local oscillator injection
The results of an investigation into the use of diodes
as mixers with optical local oscillator injection are
presented. Such 'optically pumped mixers' might be
employed in complex microwave systems where the optical
distribution of the local oscillator is attractive.
The photocurrent generation, through which the optical
local oscillator is coupled into the device, the frequency
conversion and noise mechanisms in optically pumped mixers
are all investigated. Computer models of optically pumped
mixing have been developed, and are shown to give very
good agreement with experimental measurements.
A novel optically pumped mixer structure using the
tunnelling nonlinearity in a metal contact to heavily
doped gallium arsenide has been investigated theoretically
and experimentally. The prototype device has been found to
be limited to relatively low frequencies (\simeq 100MHz) as an
optically pumped mixer, although for a device of smaller
area low conversion loss may be achieved at frequencies up
to 1GHz. The structure is limited by the large capacitance
per unit area, the generally poor responsivity, and the
dependence of the responsivity on relatively slow,
minority-carrier diffusion, current transport mechanisms.
The results from the above investigation have enabled
an improved, Mott diode structure to be proposed for
optically pumped mixers. Predictions from the accurate
computer model indicate efficient operation should be
achievable at X-band frequencies and beyond using gallium
arsenide lasers of moderate output power (\geqslant 3mW average).
Similar performance at lower power levels should be
achievable with shorter wavelength illumination.
Due to the simplicity of using a single device, it is
shown that optically pumped mixers may be more attractive
than photodetector-mixer combinations in many complex
microwave systems
Analysis and correction of the helium speech effect by autoregressive signal processing
SIGLELD:D48902/84 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Shuttle synthetic aperture radar implementation study, volume 1
Results of an implementation study for a synthetic aperture radar for the space shuttle orbiter are described. The overall effort was directed toward the determination of the feasibility and usefulness of a multifrequency, multipolarization imaging radar for the shuttle orbiter. The radar is intended for earth resource monitoring as well as oceanographic and marine studies
Advanced Computational Methods for Oncological Image Analysis
[Cancer is the second most common cause of death worldwide and encompasses highly variable clinical and biological scenarios. Some of the current clinical challenges are (i) early diagnosis of the disease and (ii) precision medicine, which allows for treatments targeted to specific clinical cases. The ultimate goal is to optimize the clinical workflow by combining accurate diagnosis with the most suitable therapies. Toward this, large-scale machine learning research can define associations among clinical, imaging, and multi-omics studies, making it possible to provide reliable diagnostic and prognostic biomarkers for precision oncology. Such reliable computer-assisted methods (i.e., artificial intelligence) together with clinicians’ unique knowledge can be used to properly handle typical issues in evaluation/quantification procedures (i.e., operator dependence and time-consuming tasks). These technical advances can significantly improve result repeatability in disease diagnosis and guide toward appropriate cancer care. Indeed, the need to apply machine learning and computational intelligence techniques has steadily increased to effectively perform image processing operations—such as segmentation, co-registration, classification, and dimensionality reduction—and multi-omics data integration.
Susceptibility and magnetoresistance measurements on ferro- and antiferro- magnetic materials
Imperial Users onl
Removal of cardiovascular obstructions by spark erosion
Coronary atherosclerosis, leading to coronary
artery stenosis, is the main cause for ischemic
health disease in the Westem countries. Stenoses
manifest themselves by limiting blood supply to
the myocardium thus causing complaints. A long
history of degenerative atherosclerotic disease of
the intimal wall of the coronary vessels has usually
preceded these events. Probably because of
this long term process the composition of the accumulated
obstructive tissue is quite heterogeneous
and consists of a variety of cells and extra
cellular material like lipid containing macrophages,
smooth muscle cells, Illonocytes, collagen.
cholesterol crystals and calcium. In addition,
fresh or organized thrombi may have been deposited
on these plaques. Regression of these lesions
may be obtained by lifestyle changes or
lipid lowering therapy. The acute invasive removal
of such complex lesions, however, cannot
be achieved by applying simple mechanical or
chemical means
1957-1958 CATALOG ISSUE- BULLETIN
Course catalog for 1957-1958https://digitalrepository.unm.edu/course_catalogs/1063/thumbnail.jp