Programa del congreso

The “radio blackout” phenomenon is the communications loss between a spacecraft and the Earth during the re-entry in the atmosphere. The intense heating of the air around the spacecraft ionizes it creating a plasma layer that prevents the propagation of electromagnetic waves. Several techniques have been proposed to mitigate this phenomenon, such as the use of higher frequencies, the aerodynamic shape of the reentry capsule, the cooling of the thermal shield itself, or the creation of an intense magnetic field. However, none of them is completely effective. This paper describes the underlying Physics, presents the simulation results of the plasma properties around an ARD-like reentry capsule in terms of electron density, temperature, and pressure, and the attenuation in [dB/m] at three different heights. It is shown that the presence of an intense magnetic field significantly reduces the cut-off frequency and the attenuation above it favoring the propagation of radio waves.

This work presents preliminary results on a measurement campaign at mmW between 26 and 40 GHz in an indoor environment in line-of-sight conditions. 2D-virtual arrays and 3D-directional sounding were tested in the same identical positions to investigate the accuracy of both approaches by comparing the directional characteristics of the double directional radio channel. The radio channels and corresponding characteristics were also simulated with an in-house 3D ray tracer. The results show that both approaches are different by nature, due to the fact that different antennas are used in each approach. URA and 3D rotor share the same large-scale characteristics. The capacity of the 3D rotor to sound the channel in the elevation plane is better than that of the more complex planar URA due to its limited aperture and the use of an omnidirectional antenna. This comes at the expense of longer measurements as the number of positions is much larger

En los últimos años, los sistemas RFID se han utilizado para numerosas aplicaciones, incluyendo la apicultura. Por tanto, es necesario estudiar el entorno en el que se usan estos sistemas. En este trabajo, se modela el panal de una colmena y un sistema RFID UHF (lector y etiqueta) utilizando el software CST Studio, y se compara con medidas empíricas. El panal (44,5x23,5x2cm) está compuesto por un marco de madera con alambres y cera de abejas. La antena del lector se coloca en un lateral del panal y la etiqueta se posiciona en diferentes puntos sobre él, considerando entre y sobre los alambres. Los resultados muestran un comportamiento periódico en la potencia recibida de la etiqueta, tanto en las medidas como en la simulación. Además, cuando el tag se coloca sobre los alambres del panal, la potencia recibida es mayor que en el caso de colocarlo entre dos alambres.

Usually the analysis of intra-wagon environments is performed considering empty scenarios, without any person inside the wagon. Only some works have addressed the influence of passengers in the wireless channel in this kind of scenarios. Moreover, the analysis in these works is limited to the computation of the signal strength and the path loss values. In this work we have simulated the wireless channel in two sub-bands of the millimeter wave band using a ray tracing tool. The path loss and the root-mean-squared delay spread have been calculated from the simulations, allowing a deeper insight than previous works. The computed parameters have been compared with measured and simulated values.

El factor K es una medida de la calidad del canal radio, cuyo conocimiento es importante en el diseño de técnicas de transmisión y recepción orientadas a mitigar el efecto de selectividad en tiempo, espacio y frecuencia introducido por el canal. En esta comunicación se realiza un estudio experimental de la distribución del factor K en un escenario de laboratorio caracterizado por la existencia de un elevado número de contribuciones multicamino. Los valores del factor K han sido estimados a partir de medidas de banda ancha realizadas en el margen de frecuencias de 24 a 40 GHz. La estimación se ha realizado a partir de la función de transferencia compleja del canal, utilizando el método de los momentos como si de canales de banda estrecha se tratase. Los valores del factor K estimados se han utilizado para evaluar la capacidad de sistemas MIMO en este tipo de entornos, demostrando que es posible su implementación incluso en condiciones de visión directa sin una degradación importante con respecto al canal ideal tipo Rayleigh.

This paper presents a frequency modulation

continuous wave (FMCW) C-band radar system with high

sensitivity and 2D detection capacity to detect low-radar cross

section targets and to measure their range and velocity. A low

jitter high signal-to-noise and distortion ratio (SINAD) S band

signal is directly generated by an SDR system which greatly

increases the quality of the obtained and measured signals. Up

conversion to C-Band by x2 frequency multiplication is

performed. Proper amplification and filtering of emitted and

detected signals are implemented to achieve 70dB dynamic range

in the final system. The transmitter antenna is a single 60º

aperture whereas multi-long baseline interferometer (MLBI)

concept is implemented in the receiver antenna for a low cost, low

dimension, and high angle resolution in the 2D position of the

targets. Measurements in terms of the range and the velocity of a

small drone have been carried out to evaluate the proposed radar

system. Micro-Doppler signature is also measured and evaluated.

The results show that we can clearly detect, identify and track

the small drone within a 350 m range, which demonstrates the

high performance of the radar and its potential use for

unmanned aerial vehicles (UAV) tracking and identification.