Receptor de banda ultraancha para vigilancia y control del espectro radioeléctrico

Un receptor de banda ultraancha es aquel que pretende sintonizar señales presentes en el espectro radioeléctrico con la suficiente selectividad y dentro de un amplio margen de frecuencias, que significa siempre varias octavas, con unos criterios de calidad, como rechazo elevado a los espurios, factor de ruido bajo, rechazo elevado de la frecuencia imagen o relación señal a intermodulación elevada. En este proyecto fin de carrera se presentan inicialmente los aspectos críticos del diseño de un receptor de este tipo, teniendo en cuenta que los parámetros básicos de un receptor de banda estrecha deben ser extrapolados a uno de banda ancha, con un aumento en la complejidad. En consecuencia, se repasan los parámetros básicos en receptores pero siempre con la visión de la banda ancha. Por otra parte, la propia naturaleza de un receptor de banda ultraancha hace surgir nuevos problemas, como los espurios o la necesidad de precanalización. En consecuencia, se realizan los análisis teóricos oportunos que permitan aclarar aspectos concretos problemáticos de este tipo de receptores. También se incluye la descripción de ciertas herramientas software que optimizan y analizan aspectos concretos de estos receptores, analizados con anterioridad. Se describen las herramientas de cálculo frecuencial y de rechazo de espurios, de análisis de cadenas genéricas de receptores y de optimización de estructuras con precanalización. Se presentan tres alternativas para la arquitectura de un receptor de banda ultraancha y se dedican capítulos concretos para el análisis de cada una de ellas y el diseño de soluciones realistas, haciendo siempre énfasis en las ventajas e inconvenientes de las mismas. Finalmente, se extraen las conclusiones oportunas de todo el trabajo realizado a lo largo del proyecto

Enfocado de imágenes de radar de apertura sintética inversa. Nuevas técnicas y aplicaciones

ISAR es una técnica radar coherente capaz de generar imágenes distancia-Doppler de blancos no-cooperativos. Tales imágenes pueden ser útiles para posteriores esquemas de reconocimiento y/o identificación. La técnica ISAR complementa la labor de otros sensores generadores de imágenes, como cámaras pasivas o sistemas láser radar, los cuales pueden ver reducidas sus prestaciones en condiciones atmosféricas adversas. El movimiento del blanco se descompone en movimiento de traslación y de rotación. El primero se divide a su vez en componente radial y tangencial, mientras que el segundo tiene tres componentes de actitud: guiñada, cabeceo y balanceo. La componente radial del movimiento de traslación es indeseada, pues no produce gradiente Doppler entre dispersores del blanco y además genera importantes efectos de desenfocado. El resto de componentes del movimiento del blanco pueden generar el deseado gradiente Doppler entre dispersores situados en la misma celda de distancia, con lo que se obtiene información bidimensional. Sin embargo, estas componentes también pueden producir efectos de desenfocado en la imagen ISAR obtenida: migración a través de las celdas de resolución. En esta Tesis Doctoral se presentan técnicas de enfocado de imágenes ISAR que mitigan los efectos de desenfocado debidos al movimiento. Por un lado, se presentan técnicas de compensación del movimiento de traslación. Estos métodos trabajan en dos etapas: alineamiento de los perfiles de distancia y ajuste fino de la fase. Por otro lado, se desarrollan también técnicas de compensación del movimiento de rotación, donde se considera tanto tasa de rotación uniforme como no-uniforme. Finalmente, se presentan otras técnicas de enfocado que hacen uso de transformadas tiempo-frecuencia y algoritmos de superresolución. Las técnicas de enfocado ISAR son útiles para aplicaciones de vigilancia de tráfico. En los últimos capítulos se muestra la utilización de tales métodos para la obtención de imágenes ISAR enfocadas de blancos reales marítimos. En el caso de la aplicación de vigilancia de tráfico rodado, se explotan los datos capturados para la estimación de la dinámica y la longitud de los vehículos simultáneamente iluminados en un tramo de carretera por un radar de alta resolución. Finalmente, en lo que respecta a la vigilancia de tráfico aéreo, se estudian las posibilidades de clasificación de helicópteros en base al eco de las aspas cuando se utiliza un radar LFMCW de alta resolución

Optimisation-based design of transversal signal-interference microwave bandpass and lowpass filters with extended stopband

Generalised bi-path stepped-impedance-line signal-interference bandpass and lowpass transversal filtering sections (TFSs) with increased stopband bandwidth above the main transmission band are presented. They are realised by partitioning the two in-parallel transmission-line paths in their related classic spectrally periodic TFS approach into a plurality of line sub-segments, whose characteristic-impedance and electrical-length values are derived through optimisation. It is demonstrated that the stopband range above the transmission band in these generalised non-frequency-periodic TFSs can be remarkably broadened with regard to those intrinsic to their conventional bandpass and lowpass TFS counterparts. Furthermore, as added benefits, this is achieved for shorter transmission-line paths and a sharper cut-off slope between the transmission band and the extended stopband. For experimental-validation purposes, three proof-of-concept microstrip prototypes are manufactured and characterised. They correspond to a 1-GHz bandpass TFS, a 1-GHz two-TFS-in-series-cascade-based bandpass filter (BPF) with augmented selectivity and out-of-band power-rejection levels, and one lowpass TFS with a designed 3-dB cut-off frequency of 1.25 GHz.Agencia Estatal de InvestigaciónEuropean Commissio

Balanced quasi-elliptic-type combline diplexer with multiextracted-pole junction/output sections

A class of coupled-multiline quasi-elliptic-type balanced diplexer device with closely spaced channels and its balanced coupling-routing-diagram formalism to simultaneously model its differential- and common-mode operation are reported. It employs third-order combline-type bandpass filters (BPFs) in its filtering channels, whose resonating lines are connected at one of their extremes to the symmetry plane of the balanced-circuit structure (i.e., virtual grounds for the differential mode), along with a multiextracted-pole/coupled-multiline dual-band BPF junction and single-band BPF output cells. In differential-mode operation, the dual-band BPF junction adds one in-band pole to each diplexer channel and three transmission zeros (TZs) to both channels, whereas the single-band BPF output cells incorporate one in-band pole and two TZs in their corresponding channels. In this manner, increased-selectivity differential-mode BPF transfer functions for the diplexer channels when compared to those of its third-order combline-type BPFs are obtained. Grounded resistors are connected at the symmetry plane of the balanced diplexer for all the resonating lines of the combline-type BPFs, which become detuned with regard to the poles associated with the dual-band BPF junction and the single-band BPF output cells under common-mode excitation. This allows for high common-mode suppression levels in wide spectral ranges to be realized for both channels while maintaining the same TZs as in differential-mode operation. For practical-validation purposes, a 1.6-GHz/1.8-GHz microstrip prototype is manufactured and tested.Ministerio de Economía, Industria y CompetitividadEuropean Commissio

Estimación de la Reflectividad del Multitrayecto en Entornos Urbanos en Radares de Apertura Sintética

Synthetic Aperture Radar (SAR) images a target region reflectivity function in the multi-dimensional spatial domain of range and cross-range. SAR synthesizes a large aperture radar in order to achieve finer azimuth resolution than the one provided by any on-board real antenna. Conventional SAR techniques assume a single reflection of transmitted waveforms from targets. Nevertheless, today¿s new scenes force SAR systems to work in urban environments. Consequently, multiple-bounce returns are added to direct-scatter echoes. We refer to these as ghost images, since they obscure true target image and lead to poor resolution. By analyzing the quadratic phase error (QPE), this paper demonstrates that Earth¿s curvature influences the defocusing degree of multipath returns. In addition to the QPE, other parameters such as integrated sidelobe ratio (ISLR), peak sidelobe ratio (PSLR), contrast and entropy provide us with the tools to identify direct-scatter echoes in images containing undesired returns coming from multipath

Técnica de Inversión Temporal para la Mejora del Enfocado de Imágenes SAR en Entornos Urbanos

Conventional SAR (Synthetic Aperture Radar) techniques only consider a single reflection of transmitted waveforms from targets. Nevertheless, today?s new applications force SAR systems to work in much more complex scenes such as urban environments. As a result, multiple-bounce returns are additionally superposed to direct echoes. We refer to these as ghost images, since they obscure true target image and lead to poor resolution. By applying Time Reversal concept to SAR imaging (TR-SAR), it is possible to reduce considerably ?or almost mitigate? ghosting artifacts, recovering the lost resolution due to multipath effects. Furthermore, some focusing indicators such as entropy (E), contrast (C) and Rényi entropy (RE) provide us a good focusing criterion when using TR-SAR

Input-reflectionless low-pass filter on multilayered diplexer-based topology

A class of two-layered input-reflectionless diplexer-based LPF is reported in this letter. By using a resistively-terminated wideband microstrip vertical transition by the first time for this application, an input-reflectionless response for the conceived LPF device is realized. The RF operational foundations and theoretical examples of this input-reflectionless LPF design approach have been shown and experimentally verified with the development and characterization of a two-LPF-unit microstrip prototype with extended reflectionless stopband.Ministerio de Economía, Industria y CompetitividadEuropean Commissio

Balanced quasi-elliptic-type dual-passband filters using planar transversal coupled-line sections and their digital modeling

A class of balanced dual-band bandpass filters (BPFs) with planar transversal-signal-interference coupled-line sections is reported. In their building balanced dual-band BPF stage under differential-mode excitation, a second-order quasi-elliptic-type dual-band bandpass filtering transfer function is obtained. Specifically, from the transversal interaction among their two open-ended and virtually-short-ended half-wavelength coupled-line paths, sharp-rejection differential-mode dual passbands with several out-of-band transmission zeros at both sides are realized. To attain high common-mode suppression levels within the differential-mode passbands, two open-ended line segments are connected at the symmetry plane of the devised balanced dual-band BPF stage. Moreover, higher-order schemes based on in-series-cascaded multi-stage designs to further increase differential-mode selectivity and in-band common-mode rejection are illustrated. The operational principles and parametric-analysis design rules of the engineered transversal-coupled-line-based balanced dual-band BPF approach are detailed. Additionally, for a rigorous interpretation of their zero/pole characteristics, a digital-modeling framework is applied to them to connect RF balanced filters with their discrete-time versions. For practical-validation purposes, a microstrip prototype of two-stage/fourth-order balanced dual-band BPF is built and tested. It exhibits measured differential-mode dual passbands with center frequencies of 1.464 GHz and 2.294 GHz, 3-dB fractional bandwidths of 8.74% and 9.68%, and in-band common-mode rejection levels above 23.16 dB and 31.36 dB, respectively.European CommissionAgencia Estatal de Investigació

Planar high-order broad-band bandpass filters based on two-stage quadrature couplers and their digital modeling

2022 24th International Microwave and Radar Conference (MIKON), 12-14 September 2022, Gdansk, Poland.Planar two-stage branch-line directional power couplers are applied in this paper to the design of transversalsignal-interference high-order wide-band bandpass filters (BPFs) with very-sharp-rejection characteristics. In comparison with the previously-reported experimental BPF demonstrators of their precursors—i.e., those using transversal filtering sections (TFSs) with one-stage branch-line couplers loaded by longer dissimilar stubs—, an enlarged-bandwidth passband with a higher number of in-band reflection zeros and lower amplitude variation can be obtained. Moreover, multiple transmission zeros (TZs) can be created in the out-of-band region owing to the intrinsic signal-energy cancelation phenomena of the transversal signal-interference philosophy, which result in highselectivity filtering capabilities. As further conceptual understanding of the devised two-stage-coupler signal-interference BPFs, a digital-modeling interpretation for various illustrative synthesis examples is provided. In addition, for experimentalvalidation purposes, single- and two-TFS-based microstrip prototypes of wide-band BPFs centered at 2 GHz are manufactured and characterized. In these circuits, inter-digital-type input/output feeding sections are co-integrated. They allow to extend the lower/upper stopband bandwidths with regard to those inherent to their isolated two-stage-coupler-based TFSs.Agencia Estatal de InvestigaciónEuropean Commissio