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Radiació i Propagació (RP-2B). Bloc Bàsic graus ETSETB. Enunciat de les pràctiques de laboratori i dels estudis previs.

This paper presents a method for compensating the elevation angle fluctuations occurring in airborne radiometry due to aircraft roll and pitch. The correction is based on a radiative transfer model, and is demonstrated by real data from conical scans over the ocean, showing good results.

Current spaceborne radiometers do not achieve the required spatial resolution demanded by the scientific community due to antenna-size technological limitations. In recent years, several space agencies have been studying aperture synthesis interferometric radiometers as a way of overcoming these limitations, which are more evident at low microwave frequencies (e.g., at L-band), where sea surface salinity and soil moisture can be monitored. Interference is an important issue in any remote sensing instrument, but it is crucial in microwave radiometers, since the signal being measured is the spontaneous thermal noise emission. Interference analyses already exist for classic radiometers. The objective of this paper is the analysis of RF interference on interferometric radiometers. The study involves the analysis of possible interference sources that may affect the performance of such systems at L-band: (1) nearby emissions from radars, non-Geo-Stationary Orbit (GSO) and Mobile Satellite Services (GSO-MSS), (2) harmonics of lower frequency emissions, and (3) possible jamming.

Desde medi ados de los años 80, di versas Agencias Espaciales han prestado una atención a los ll amados radiómetros interferométricos por síntesis de apertura. Estos in strumentos ofrecen por primera vez un salto cuantitativo importante en resolución espac ial como para permitir monitorizar la superfi cie terrestre a frecuencias bajas de microondas (banda L). En esta banda de frecuencias (1.4 GHz) existe la máxima sensibilidad de la temperatura de brillo tanto a la humedad del terreno, como a la salinidad del océano. En los radiómetros clásicos, la resolución espacial viene dada por el ancho de haz de la antena que, al ser escaneada, forma la imagen de temperatura de brillo. Por ello, para alcanzar la resolución espacial deseada (30-50 km como máximo, 10-20 km ideal) 'desde un satélite en órbita baja, las antenas requeridas tienen unas dimensiones inaceptablemente grandes: entre 10 y 20 metros de diámetro. Durante los años 90, la Agencia Europea del Espacio (ESA) llevó a cabo una serie de estudios tecnológicos con vistas a desarrollar un radiómetro por síntesis de apertura bidimensional en banda L. A este proyecto se le llamó MIRAS (Microwave Imaging Radiometer by Aperture Synthesis). En Noviembre de 1998, la mi sión SMOS (Soil Moisture and Ocean Salinity) basada en el concepto derivado de los estudios del proyecto MIRAS, fue propuesta como respuesta a un anuncio de «Misiones de Oportunidad Earth Exploren) lanzado por la ESA [1). En Mayo de 1999, después de un proceso de selección de 27 propuestas, la ESA aprobó la mi sión SMOS en segundo lugar para una fase A extendida. Este artículo describe brevemente la moti vación de esta misión , los principios de funcionamiento de dicho in strumento y las actividades en las que ha participado y participa un grupo de profesores del Departament de Teoria del Senyal i Comunicacions, de la Universitat Politecnica de Catalunya.

Sea surface salinity (SSS) has been recognized as a key parameter in climatological studies. SSS can be measured by passive microwave remote sensing at L band, where the sensitivity of the brightness temperatures shows a maximum and the atmosphere is almost transparent. To provide global coverage of this basic parameter with a 3-day revisit time, the SMOS mission was recently selected by ESA within the frame of the Earth Explorer Opportunity Missions. The SMOS mission will carry the MIRAS instrument, the first 2D L-band aperture synthesis interferometric radiometer. To address new challenges that this mission presents, such as incidence angle variation with pixel, polarization mixing, effect of wind and foam and others, a measurement campaign has been sponsored by ESA under the name of WISE 2000 and it is scheduled for October-November 2000. Two L-band radiometers, a video, a IR and a stereo-camera and four oceanographic and meteorological buoys will be installed in the oil platform 'Casablanca' located at 40 Km off the coast of Tarragona, where the sea conditions are representative of the Mediterranean open sea with periodic influence of the Ebro river fresh water plume.

This paper starts with a summary and classification of errors of any kind that corrupt the fundamental measurement performed by an InR (interferometric radiometer), the so-called visibilities. This summary is based on prior works from the authors concerning end-to-end rnodeling of the instrument. The paper follows with a trade-off analysis of the capability of different calibration approaches to remove those errors and, at the end, to recover a map of brightness temperatures. In order to perform the trade-off analysis, extensive simulations have been undertaken to analyze the approaches found in the literature: the redundant space method, used in radio astronomy, the G-matrix method, used in ESTAR, and the Noise injection method. both centralized and distributed, proposed for MIRAS. A short description is made of each one and a comparative table is presented. The trade off is presented in terms of what kind of errors can be removed by each method, hardware requirements, robustness and on-ground/on-board input data required to perform such error correction.

When computing the radiometric resolution of an interferometric radiometer the correlation among the errors of different baselines is usually assumed negligible. ln this way: a) the radiometric sensitivity turns out to be pixel independent (except for antenna pattern effects), and b) the error of the average of P redundant baselines is reduced by a factor of (P)1/2. While this may be the case in radioastronomy applications, for an on-board instrument where all the baselines are measured at the same time interval the errors will actually be correlated. This has two effects: a) The radiometric resolution changes from pixel to pixel and b) the radiometric resolution improvement introduced by redundance is reduced as compared with the case of independent errors. In this paper this correlation is computed and the results obtained are applied, first, to a fully redundant (all possible baselines are actually measured) filled linear array to analyze the actual radiometric improvement, and, next, to the same array without redundance to investigate the dependence of sensitivity on pixel information.

The AMR Group has an automatized bench for the measurement of DC-characteristics, [S] parameters (45 MHz- 40 GHz) and noise parameters (2-26.5 GHz) of microwave on-wafer transistors. The hardware configuration is described, as well as the software applications developed. The measurement procedures are commented in detail, in particular those concerning the noise-parameters extraction techniques. Experimental results show the bench performances.

This communication describes the design of an Automatic Level Control (ALC) for the transmiter of a CODE (Co-operative Olympus Data Experiment) earth station. The goal of the ALC system is to keep constant the transmited the RF output signal (28 GHz). The results show that the ALC has optimal behavior in Ka band transmiter chains.

A digital radio-relay link in the band 10.7- 11.7 GHz developed for the remote control system of ENHER is presented. The objectives were the construction of a reliable and yet low-cost transmitter-receiver. To accomplish this, the RF unit has been constructed in microstrip on plastic substrate, and the FI from commercially available TV subsystems. The version herein presented has a 200 kbits/s capacity (susceptible of being increased) and can operate on vanes of at least 5 km.

An end-to-end simulator for the assessment of the performances of a spaceborne interferometric radiometer measuring the brightness temperature of Earth’s surface (ground and sea) is presented. The tool covers the complete simulation of the input brightness temperature map, the full instrument modeling, the instrumental error correction, and the inversion algorithm to recover the brightness temperature. The output maps are presented in a graphical format including most of the standard cartographic projections. The simulator has been developed with two main objectives: (1) to provide the engineers a tool to predict system performance, and (2) to provide the scientific and end users a tool to help them in the implementation and improvement of algorithms for the Soil Moisture and Ocean Salinity (SMOS) retrieval for the SMOS Earth Explorer Opportunity Mission of the European Space Agency.

Radiation and Propagation. List of Exercises. Engineering Degree. Basic Block. TelecomBCN

This paper presents a general analysis of correlation measurements in an interferometer or a radiometer based on noise injection and/or switching and measurement of normalized correlations (e.g., imaging synthetic aperture or polarimetric radiometers). A compact unifying notation for denormalizing the measured normalized correlations in the presence of noise injection in one or both of the receiving channels is presented. Technological limitations are also assessed by evaluating the effect of associated approximations. Finally, the approach is validated by experimental results of the measurement and calibration of related front-end nonidealities, namely, the finite isolation of the front-end switch. The methods presented in this paper are illustrated by a thorough analysis of the so-called mixed baselines of microwave imaging radiometer using aperture synthesis, which refer to those baselines which are formed between the regular receivers (light-weight cost-efficient front-end) and the reference radiometers. These baselines require special attention, since the reference radiometers are noise-injection radiometers, which inject noise to the measured signal, whereas the regular receivers are total power receivers.

In this paper the analysis and design of an oscillator in V band is presented. Taking advantage of a coaxial oscillation, sorne results related with frequency stability have been obtained. A special attention has been paid in the design of the RF choke.

To design microwave transistor oscillators or power amplifiers a good non-linear characterization of the transistor is needed. This characterization can be obtained by measuring it on large signa! operation in a load-pull setup. This is a very time consuming method and dificult to implement, especially at millimeter wave frequencies, where good test fixtures are difficult to build. This paper describes a method to determine a non-linear model of MESFET transistors, based on experimental results. Using this non-linear model and by means of numerical methods, based on the harmonic balance mcthod, large signa! measurements can be simulated, thus allowing to easily obtain valuable design data.

Los circuitos integrados monolíticos de microondas presentan ventajas potenciales respecto de los circuitos híbridos habituales en cuanto a fiabilidad, reducido tamaño y peso, banda ancha y bajo coste. Se describe el estado actual y desarrollo en los últimos años, los aspectos tecnológicos de diseño y fabricación, las aplicaciones y los productos comerciales existentes.

Microstrip coupled lines technology has been used to design and built low noise amplifiers in 20 and 30 GHz bands. Active devices are GaAs MESFET and HEMT in chip form. The amplifiers have input and output waveguide interfaces, probe transitions between microstrip line and rectangular waveguide are described. Two three-stage low noise amplifiers, at 20 and 30 GHz respectively, are presented.

A classification of system errors in aperture synthesis radiometry applied to Earth obervation is presented. A general procedure to quantify th eimpact of antenna errors on the radiometric accuracy is developed and is then particularized to an L-band Y-shaped interferometer called MIRAS (microwave imaging radiometer by aperture synthesis) currently under study at the European Space Agency. This work analyze in detail the impact of antenna errors on the radiometric accuracy of the instrument. These antenna errors are grouped into amplitude and phase antenna pattern errors, antenna position errors and antenna cros polarization errors. Special attention is paid to antenna coupling effects because of their importance in the selection of a suitable inversion algorithm for large aperture synthesis interferometers: the G-matrix techniques or the Fourier techniques proposed for MIRAS.