Diseño y simulación de detectores de señales radar utilizando técnicas tiempo-frecuencia

El objetivo de este trabajo fin de grado (TFG) consiste en estudiar algunas técnicas de análisis tiempo-frecuencia y aplicarlas a la detección de señales radar. Estas técnicas se incorporan en los actuales equipos de guerra electrónica radar, tales como los interceptadores digitales. La principal motivación de estos equipos consiste en detectar y localizar las fuentes radiantes enemigas e intentar obtener cierta información de las señales interceptadas, tal como, la dirección de llegada (DOA, Direction Of Arrival), el tiempo de llegada (TOA, Time Of Arrival), amplitud de pulso (PA, Pulse Amplitude), anchura de pulso (PW, Pulse Width), frecuencia instantánea (IF, Instantaneous Frequency) o modulación intrapulso. Se comenzará con un estudio detallado de la Short-Time Fourier Transform (STFT),dado su carácter lineal es la técnica más explotada actualmente. Este algoritmo presenta una mala resolución conjunta tiempo-frecuencia. Este hecho provoca el estudio complementario de una segunda técnica de análisis basada en la distribución de Wigner-Ville (WVD). Mediante este método se logra una resolución optima tiempo-frecuencia. A cambio, se obtienen términos cruzados indeseados debido a su carácter cuadrático. Uno de los objetivos de este TFG reside en calcular la sensibilidad de los sistemas de detección analizados a partir de las técnicas tiempo-frecuencia. Se hará uso del método de Monte Carlo para estimar ciertos parámetros estadísticos del sistema tales como la probabilidad de falsa alarma y de detección. Así mismo, se llevará a cabo el estudio completo de un receptor digital de guerra electrónica a fin de comprender el funcionamiento de todos los subsistemas que componen el conjunto (STFT/WVD, medidor instantáneo de frecuencias, procesamiento no coherente y generación de descriptores de pulso). Por último, se analizará su comportamiento frente a diferentes señales Radar (FM-lineal, BPSK, chirp o Barker). Se utilizará para ello la herramienta Matlab.

Aplicación práctica transceptor BGT24MTR11 : radar Doppler

En los últimos tiempos, los radares han dejado de ser instrumentos utilizados únicamente en aviación, defensa y detección de velocidad. El avance de la tecnología de radiofrecuencia ha permitido la reducción de coste, tamaño y consumo de los componentes radar. Esto ha permitido que cada sea más frecuente el uso del radar en elementos de nuestra vida cotidiana tales como la automoción, la seguridad, la medida de líquidos… Este proyecto se basa en uno de estos nuevos componentes de bajo coste y pequeño tamaño, el transceptor BGT24MTR11. El BGTR24MTR11 integra transmisor, VCO y receptor, los elementos principales para la creación de un radar Doppler en la banda de frecuencia ISM 24-24,25 GHz. A partir de la placa de evaluación de ese transceptor, se aborda el diseño de un prototipo/demostrador de radar Doppler CW en la banda de 24 GHz. Para la generación de frecuencia se utiliza la placa de evaluación del PLL HMC702 y se ha diseñado un PCB a medida cuyas funciones son las de alimentación, programación y amplificación de las señales recibidas por el prototipo. Por último, se comprueba el correcto funcionamiento del prototipo y se verifica su funcionamiento mediante la simulación de dos escenarios de prueba. ABSTRACT. In the recent times, radar systems have changed of being tools used only in aviation, defence and speed detection. Radiofrequency technology improvements have allowed a cost, size and power consumption of the radar components. This is the reason because each time is more frequent the use of radar in elements of our daily life such as automotive, security, liquid measurements… This Project is base don one of this low power and size components, the MMIC transceptor BGT24MTR11. This transceptor integrates the main components needed to make a Doppler radar in the ISM Band (24-24 GHz), the transmitter, the receiver with the low noise amplifier and the VCO. Using the evaluation board of this transceptor, this Project approach the design of a CW Doppler radar prototype/demonstrator in the frequency band of 24 GHz. The frequency generation is based on the use of the HMC702 PLL evaluation board. Moreover, it has been designed a custom PCB whose funcionts are the power supply, programation and amplification of the signals received by the prototype. At the end, the correct operation of the prototype is verified and it is tested simulating two different test scenarios.

Human Motion Analysis Based on Sequential Modeling of Radar Signal and Stereo Image Features

Falls are one of the greatest threats to elderly health in their daily living routines and activities. Therefore, it is very important to detect falls of an elderly in a timely and accurate manner, so that immediate response and proper care can be provided, by sending fall alarms to caregivers. Radar is an effective non-intrusive sensing modality which is well suited for this purpose, which can detect human motions in all types of environments, penetrate walls and fabrics, preserve privacy, and is insensitive to lighting conditions. Micro-Doppler features are utilized in radar signal corresponding to human body motions and gait to detect falls using a narrowband pulse-Doppler radar. Human motions cause time-varying Doppler signatures, which are analyzed using time-frequency representations and matching pursuit decomposition (MPD) for feature extraction and fall detection. The extracted features include MPD features and the principal components of the time-frequency signal representations. To analyze the sequential characteristics of typical falls, the extracted features are used for training and testing hidden Markov models (HMM) in different falling scenarios. Experimental results demonstrate that the proposed algorithm and method achieve fast and accurate fall detections. The risk of falls increases sharply when the elderly or patients try to exit beds. Thus, if a bed exit can be detected at an early stage of this motion, the related injuries can be prevented with a high probability. To detect bed exit for fall prevention, the trajectory of head movements is used for recognize such human motion. A head detector is trained using the histogram of oriented gradient (HOG) features of the head and shoulder areas from recorded bed exit images. A data association algorithm is applied on the head detection results to eliminate head detection false alarms. Then the three dimensional (3D) head trajectories are constructed by matching scale-invariant feature transform (SIFT) keypoints in the detected head areas from both the left and right stereo images. The extracted 3D head trajectories are used for training and testing an HMM based classifier for recognizing bed exit activities. The results of the classifier are presented and discussed in the thesis, which demonstrates the effectiveness of the proposed stereo vision based bed exit detection approach.

Mean sea surface modelling from multi-satellite altimetry utilising frequency domain techniques

A technique is presented for the development of a high precision and resolution Mean Sea Surface (MSS) model. The model utilises Radar altimetric sea surface heights extracted from the geodetic phase of the ESA ERS-1 mission. The methodology uses a modified Le Traon et al. (1995) cubic-spline fit of dual ERS-1 and TOPEX/Poseidon crossovers for the minimisation of radial orbit error. The procedure then uses Fourier domain processing techniques for spectral optimal interpolation of the mean sea surface in order to reduce residual errors within the model. Additionally, a multi-satellite mean sea surface integration technique is investigated to supplement the first model with additional enhanced data from the GEOSAT geodetic mission.The methodology employs a novel technique that combines the Stokes' and Vening-Meinsz' transformations, again in the spectral domain. This allows the presentation of a new enhanced GEOSAT gravity anomaly field.

Effect of ray and speed perturbations on ionospheric tomography by over-the-horizon radar: A new method

International audience

Understanding the CO Preoxidation and the Intrinsic Catalytic Activity of Step Sites in Stepped Pt Surfaces in Acidic Medium

In order to deepen the knowledge about the origin of the CO preoxidation process and the intrinsic catalytic activity of Pt superficial steps toward CO oxidation, a series of CO stripping experiments were performed on stepped Pt electrodes in acidic medium. For the occurrence of CO preoxidation, it was found that it arises (reproducibly) whenever four interconnected conditions are simultaneously fulfilled: (1) CO adsorption at potentials lower than about 0.2 V; (2) on surfaces saturated with COads; (3) in the presence of traces of CO in solution; (4) in the presence of surface steps. If any of these four conditions is not satisfied, the CO preoxidation pathway does not appear, even though the steps on the electrode surface are completely covered by CO. By controlling the removal of the CO adlayer (voltammetrically), we show that once the CO adlayer has been partially oxidized, the (111) terrace sites of stepped surfaces are released earlier than the (110) step sites. Moreover, if (110) steps are selectively decorated with CO, its oxidation occurs only at potentials ∼150 mV higher than the CO preoxidation peak. Our results systematically demonstrate that step sites are less active to oxidize CO than those ones responsible for the CO preoxidation process. Once the sites responsible for the CO preoxidation are made free, there is no apparent motion of the remaining adsorbed CO layer, suggesting that the activation of the surface controls the whole process, rather than the diffusion of COads toward hypothetically “most active sites”. Voltammetric and chronoamperometric experiments performed on partially covered CO adlayers suggest that adsorbed CO behave as a motionless species during its oxidation, in which the CO adlayer is removed piece by piece. By means of in situ FTIR experiments, the stretching frequency of CO selectively adsorbed on (110) step sites was examined. Band frequency results confirm that those molecules adsorbed on steps are fully coupled with the adsorbed CO on (111) terraces when the surface reaches full coverage.