Infrared thermograms applied to near-field testing

Electromagnetic fields close to radiant structures can be measured quickly using an infrared camera. Examples of induced fields by wire antennas over a detection screen at distances shorter than one wavelength are presented. The measured thermograms agree with simulations that take into account heat propagation on the detection screenPeer ReviewedPostprint (published version

Vectorial waveguide reflectometer for dielectric characterisation of materials under power microwaves

The temperature rise in a material modifies its physical properties, particularly its dielectric permittivity. In many applications involving relatively high levels of power the electrical behavior of the different materials will change as they are heated by the radiation. For instance, the numerical codes that simulates the behavior of microwave heating processes in order to improve the design of the feeding antennas must take into account the load variations with temperature. The measurement of the changing dielectric characteristics of materials is of great interest for the industry. Previous works used completely filled waveguides near a shorting plate. The method supplied excellent results at low power levels, while the sample was not heated. When the power is risen, the field distribution of the TE/sub 10/ mode causes a non-uniform heating of the sample and the measured permittivity corresponds to an average value. In order to reduce this problem a method using a partially filled waveguide is presented. The reduced sample dimensions and its positioning into the waveguide assures a near homogeneous power distribution implying a uniform heating.Peer ReviewedPostprint (published version

Atmospheric phase drift analysis and compensation in permanent Gb-Sar monitoring of crop fields

In the framework of a feasibility study in support of the Hydroterra mission, a high resolution radar has been setup to monitor continuously a crop field with high resolution synthetic aperture radar images. In parallel, ground-truth data is acquired such as soil roughness, soil moisture and crop biological parameters. From this experimental data set the possibility to monitor soil moisture and crop biological parameters from back-scattering radar measurements will be assessed. To use the phase information of SAR images it is interesting to compensate the atmospheric phase screen induced by tropospheric refractive index. The paper presents a study of the atmosphetric phase drift prediction and compensation based on the local measurement of meteorological parameters.Peer ReviewedPostprint (author's final draft

Infrared thermograms applied to near-field testing

Electromagnetic fields close to radiant structures can be measured quickly using an infrared camera. Examples of induced fields by wire antennas over a detection screen at distances shorter than one wavelength are presented. The measured thermograms agree with simulations that take into account heat propagation on the detection screen.Peer ReviewedPostprint (published version

A pulsed carrier recovery using a discrete conception of the PLL

A bistatic radar system requires accurate synchronization between the transmitter and the remote receiver in order to achieve a correct coherent target detection and positioning. An unlinked receiver carrier phase/frequency synchronization method, from the radiated pulsed signal of a remote radar transmitter when its antenna beam illuminates the receiver, is presented. A modified discrete conception of the phase locked loop (PLL) technique is used, based on the special properties of the signal to be recoveredPeer ReviewedPostprint (published version

Active zone self-similarity of fractal sierpinski antenna verified using infra-red thermograms

The surface current distribution of a Sierpinski fractal antenna shows a self-similar behaviour determined by the self-similar properties of its geometry. The application of infra-red thermography to electromagnetic near field detection allows the experimental verification of the active region scaling of a fractal antenna operating at different bands.Peer ReviewedPostprint (published version

Infrared thermograms applied to near-field testing

Electromagnetic fields close to radiant structures can be measured quickly using an infrared camera. Examples of induced fields by wire antennas over a detection screen at distances shorter than one wavelength are presented. The measured thermograms agree with simulations that take into account heat propagation on the detection screen.Peer Reviewe

Optimum design of a scavenging antenna system

This paper presents some guidelines for the design procedure of an optimum scavenging antenna system. Based on these guidelines, a scavenging antenna has been fabricated and characterized, achieving very good results in comparison to the traditional designs.Postprint (published version

Receptor biestático sin enlace dedicado con el transmisor

This paper presents an introduction to the study and development of a new concept of Bistatic Radar Receiver, which eliminates any kind of direct microwave or optical fiber link between them. It is based on discret phase-lock techniques to acquire and maintain all the signal parameters when the transmitter illuminates directly the receiver system.Peer ReviewedPostprint (published version

Impact of wind-induced scatterers motion on GB-SAR imaging

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Ground-based synthetic aperture radar (GB-SAR) sensors represent a cost-effective solution for change detection and ground displacement assessment of small-scale areas in real-time early warning applications. GB-SAR systems based on stepped linear frequency modulated continuous wave signals have led to several improvements such as a significant reduction of the acquisition time. Nevertheless, the acquisition time is still long enough to force a degradation of the quality of the reconstructed images because of possible short-term variable reflectivity of the scenario. This reduction of the quality may degrade the differential interferometric detection process. In scenarios where interesting targets are surrounded by vegetation, this is normally related to atmospheric conditions, in particular, the wind. The present paper characterizes the effect of the short-term variable reflectivity in the GB-SAR image reconstruction and evaluates its equivalent blurring effect, the decorrelation introduced in the SAR images, and the degradation of the extracted parameters. In order to validate the results, the study assesses different GB-SAR images obtained with the RISKSAR-X sensor, which has been developed by the Universitat Politècnica de Catalunya.Peer ReviewedPostprint (published version