Analysis and Design of Microwave and Millimeter-wave Passive Devices for Scientific Instrumentation

In the recent astrophysical experiments i.e. QUIET, QUIJOTE, STRIP-LSPE, arrays of polarimeters are used in order to measure the linearly polarized component of the Cosmic Microwave Background Radiation (CMBR). Since the signal of interest is very faint, the sensitivity of the scientific instrumentation should be very high. This goal can be achieved by accommodating a large number of high-performance polarimeters in the focal plane of the antenna. In this perspective, a novel layout of Ortho-Mode-Transducer (OMT) and polarizer, which are key passive waveguide elements of dual-circular polarization polarimeters, have been designed. The polarizer is based on a Dual-Fold-Stub (DFS) design having 20% bandwidth centered at 94.5GHz, whereas the broadband OMT exploits a turnstile junction with 30% bandwidth centered at 94 GHz. The components are realized using the multi-layer technology, where each metallic plate is manufactured by wire spark erosion technique. Using this design methodology, several identical devices can be manufactured in a single machining process. The exploitation of multi-layer technology in conjunction with wire spark erosion technique provides high level of manufacturing repeatability and accuracy along with low cost, making this solution well suitable for the realization of polarimetric arrays consisting of tens/hundreds of chains. The propriety SEM (Spectral Element Method) tool of IEIIT-CNR and commercial EM (Electromagnetic) tools (CST-MWS & HFSS) have been exploited in an effective manner to achieve the required performances. In order to integrate MATLAB with EM tools, COM EM Automation Tool (COM-EM-AT) has been developed and exploited in various manner to attain the final design. The simulation acceleration through distributed computing have also been employed efficiently for tolerance analysis using the SEM tool.