This study describes an experimental research activity on the manufacturing of passive waveguide components by means of two additive technologies, namely the selective‐laser melting and the stereo‐lithography processes. The former is a power‐bed fusion process, for which aluminium, titanium, and steel powders have been considered in this study. The latter is based on the photopolymerisation of a resin vat. This technology has been applied in conjunction with an acrylonitrile–butadiene–styrene‐like polymer and a subsequent electrolytic copper plating for the metallisation of the internal channels. Wideband filters operating in Ku/K band have been developed as benchmarks, for which detailed comparisons between simulations and measurements are reported.
The measurement of the polarization of the Cosmic Microwave Background (CMB) radiation is one of the current frontiers in cosmology. In particular, the detection of the primordial divergence-free component of the polarization field, the B-mode, could reveal the presence of gravitational waves in the early Universe. The detection of such a component is at the moment the most promising technique to probe the inflationary theory describing the very early evolution of the Universe. We present the updated performance forecast of the Large Scale Polarization Explorer (LSPE), a program dedicated to the measurement of the CMB polarization. LSPE is composed of two instruments: LSPE-Strip, a radiometer-based telescope on the ground in Tenerife-Teide observatory, and LSPE-SWIPE (Short-Wavelength Instrument for the Polarization Explorer) a bolometer-based instrument designed to fly on a winter arctic stratospheric long-duration balloon. The program is among the few dedicated to observation of the Northern Hemisphere, while most of the international effort is focused into ground-based observation in the Southern Hemisphere. Measurements are currently scheduled in Winter 2022/23 for LSPE-SWIPE, with a flight duration up to 15 days, and in Summer 2022 with two years observations for LSPE-Strip. We describe the main features of the two instruments, identifying the most critical aspects of the design, in terms of impact on the performance forecast. We estimate the expected sensitivity of each instrument and propagate their combined observing power to the sensitivity to cosmological parameters, including the effect of scanning strategy, component separation, residual foregrounds and partial sky coverage. We also set requirements on the control of the most critical systematic effects and describe techniques to mitigate their impact. LSPE will reach a sensitivity in tensor-to-scalar ratio of σ r < 0.01, set an upper limit r < 0.015 at 95% confidence level, and improve constraints on other cosmological parameters.
A W-band orthomode transducer has been designed for polarimeter clusters in dense focal planes. Its compact geometry, with aligned output ports, allows for a closely-spaced triangular-lattice arrangement. At these high frequencies, the platelet manufacturing strategy has been applied and verified experimentally on seven prototypes, showing reflection coefficients lower than dB, insertion loss of about 0.25 dB and cross-coupling and isolation levels of dB and 45 dB, respectively, in a 30% bandwidth.Index Terms-Antenna feeds, polarimeter, radio astronomy, waveguide junctions.
1531-1309
In this paper, a Ka/K-band antenna-feeding network in dual-circular polarization is reported. The design of the system was carried out in view of its monolithic manufacturing through selective laser melting in AlSi10Mg alloy. As a proof-of-concept for satellite telecommunication multi-beam applications, the feeding network operates in the K band (19.25, 20.75) GHz and in the Ka band (27.0, 29.0) GHz. The system provides four rectangular-waveguide ports and a common dual-polarized circular-waveguide port to be connected to the feed horn. The prototype exhibits measured values of in-band return loss better than 28 dB and a port-to-port isolation better than 19 dB (in polarization) and 50 dB (in frequency). The cross-polar discrimination is higher than 20 dB. In this regard, an elliptical-waveguide line was specifically designed and manufactured to recover a value higher than 30 dB in both frequency bands. The line can be easily integrated in the feed horn to be connected to the feeding-network thanks the ease of customization provided by 3D printing. The insertion losses are lower than 0.5 and 0.2 dB in the K and Ka bands, respectively. The weight of the prototype is approximately 130 g.
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