A novel wideband orthomode transducer (OMT) featuring a folded-arm turnstile junction covering a 2:1 frequency band is employed to achieve an effective structure while meeting the strict OMT requirements for radio astronomy applications. The turnstile junction is designed with two symmetry planes to ensure separation between perpendicular polarizations and the effective management of higher order modes. Within the throat of the turnstile junction, stepped cylinders serve as scattering elements and matching stubs to ensure efficient impedance matching between the quad-ridge circular waveguide at the input and the single-ridge rectangular waveguides at the output. The folded arms play a pivotal role in achieving excellent matching while significantly reducing the overall size. Considering the significance of developing wideband radio astronomy receivers with minimal noise, this design demonstrates a precisely engineered compact OMT, with tuned bends, junctions, and delivers simulated return loss better than 20 dB while maintaining cross-polarization performance well below 65 dB within the specified 20-40 GHz frequency range.
In the effort to push the boundaries of radio astronomy observations, technological innovations are essential for future generations of observatories. This paper introduces an innovative design for future radio receivers in major observatories like ngVLA, ALMA, and SKA. The concept centers around an Octave Band Quad Ridge Feed Horn and Vacuum Window, designed to operate within the 25 to 50 GHz (2:1) frequency range. This cutting-edge feed model uses dielectric loading to enhance phase and polarization efficiency, thereby significantly increasing the overall aperture efficiency across the bandwidth. The dielectric rod, features a solid construction with comb-shaped ridges located in the throat of the feed horn. To complete the entire optic model an HDPE vacuum window with three custom designed antireflection layers to minimize the signal reflections, is designed and presented. To confirm the performance of the proposed model, we use two different 3D full-wave electromagnetic simulators, CST Studio Suite and HFSS. The results showcase a return loss exceeding 25dB with exceptional beam symmetry across the entire bandwidth.
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