Magíster en Ciencias de la Ingeniería, Mención Ingeniería Eléctrica / Polarization is a key measurement within radio astronomy because its state can give insight as to the physical conditions of the source and the medium the radiation has traveled through. In radio astronomy receivers, the device used to separate the polarization is known as an Ortho-Mode Transducer (OMT). The OMT is a passive component that separates signals into two orthogonal components. Using available millimeter-wave analog technology, wideband heterodyne receiver systems generally obtain polarization isolation ratios of 15dB to 20dB, insufficient for modern astronomical applications. That low polarization isolation ratio is due to the presence of leakage from one polarization contaminating the other, which is known as cross-polarization. In order to improve polarization isolation and reduce cross-polarization, a new approach called Digital OMT has been proposed, based on passing one given functionality from the analog domain to the digital domain using digital signal processing techniques. Digital techniques were studied to improve OMT performance, which led to the design of a polarimeter based on the Fast Fourier Transform (FFT). The polarimeter was implemented on a Field Programmable Gate Array (FPGA), including the implementation of a Ku-band analog front-end to characterize the design and measure the synthesized polarization. This thesis introduces a prototype of a DOMT created for real-time processing and continuous integration, suitable for radio astronomy observations. The configuration used is based on the architecture of a compact four-port OMT. The outputs are downconverted using mixers and then directly digitalized using four 8bit ADC sampling at 1.2 GSPS. A 180° hybrid was implemented on the FPGA together with a set of calibration vectors, with the purpose of compensating the amplitude and phase imbalance typical of analog radio astronomy front-ends. This calibrated Digital OMT exhibits a polarization isolation ratio of more than 40 dB for the entire RF bandwidth, representing an improvement factor of 100 over its analog counterpart. / Este trabajo ha sido parcialmente financiado por Centro de Astrofísica y Tecnologías Afines (CATA-BASAL-PBF 06), FONDECYT 11140428 y 1121051, y ALMA-CONICYT 31150012. Agradecemos a Xilinx Inc. por la donación de circuitos integrados y licencias de software y a la comunidad de CASPER por el apoyo brindado.

[pt] O presente trabalho trata da caracterização da vazão mássica do refrigerante R404a através de orifícios calibrados de diferentes diâmetros, em função das condições de operação. Um aparato experimental, que representa os fenômenos que ocorrem em um sistema de refrigeração real, foi utilizado para o controle das condições de operação. Os dados experimentais apresentados neste trabalho cobrem a faixa de pressão a montante de 1549 kPa (210 psig) 1618 kPa (220 psig) e 1756 kPa (240 psig) e pressão a jusante de 818 kPa (104 psig) a 1377 kPa (185 psig), tendo o grau de sub- resfriamento se situado entre 1,3 ºC e 18,02 ºC. A revisão bibliográfica realizada mostrou que até a presente data não há, na literatura aberta, dados experimentais para este refrigerante, um dos prováveis substitutos dos CFC s e HCFC s. Os resultados obtidos constituem um fato original para o escoamento do refrigerante R404a através de orifícios calibrados, representando uma importante contribuição tecnológica. É apresentada ainda, uma correlação para dados experimentais obtidos, podendo ser utilizada em futuras simulações de orifícios calibrados. / [en] The present work describes the experimental analysis of flow of refrigerant R404a through short tube orifices, for different diameters and operating conditions. An experimental apparatus was constructed to provide the desired operating conditions. The experimental data covers upstream pressures from 210 psig to 240 psig, downstream pressures from 104 psig to 185 psig and inlet subcooling from 1,30 o C to 18,02 o C. A literature review revealed, at the time of publication, the absence of works on the flow of R404a through short tube orifices. A correlation of the experimental data, to be used in future simulations of short tube orifices, is presented. The results constitute an original contribution to the study of flow of R404a through short tube orifices. / [es] Este trabajo aborda la caracterización de la salida másica del refrigenerante R404a a través de orificios calibrados de diferentes diámetros, en función de las condiciones de operación. Un aparato experimental, que representa los fenómenos que ocurren en un sistema de refrigeneración real, fue utilizado para el control de las condiciones de operación. Los datos experimentales presentados en este trabajo cubren una banda de presión de 1549 kPa (210 psig) 1618 kPa (220 psig) y 1756 kPa (240 psig) y presión aguas abajo de 818 kPa (104 psig) a 1377 kPa (185 psig), con grado de subrefriamiento situado entre 1,3 ºC y 18,02 ºC. La revisión bibliográfica realizada mostró que hasta la presente fecha no hay, en la literatura abierta, datos experimentales para este refrigerante, uno de los probables substitutos de los CFC s y HCFC s. Los resultados obtenidos constituyen un hecho original para el flujo del refrigenerante R404a a través de orificios calibrados, representando una importante contribución tecnológica. Se presentada la correlación para datos experimentales obtenidos, pudiendo ser utilizada en futuras simulaciones de orificios calibrados.