O.A. Peverini

Broadband array element for the SKA low-frequency aperture array

This paper presents a dual-polarization broadband array element for the Aperture Array low-frequency (AA-low) 70–450 MHz subsystem of the Square Kilometer Array (SKA). It is based on the notched Vivaldi antenna and does not require a ground plane. Suitable electromagnetic performance with a reasonable mechanical complexity have been obtained.

Platelet Ortho-mode Transducer (OMT) for millimeter-wave applications

This contribution presents a manufacturing-oriented Ortho-mode Transducer configuration for polarimeter clusters at millimeter-waves. It is based on a turnstile junction with a proper recombination network. All the discontinuities were properly conceived so that the overall geometry can be manufactured in a multi-layer (platelet) fashion, using commercially-available metal layers. All the metal layers can be machined using the spark-erosion technique, which provides high accuracy and high repeatability for a large number of devices. A W-band implementation with standard WR10 output waveguides has been designed in the operative bandwidth 80-108 GHz. The simulated return loss is better than 25 dB in the overall bandwidth for both polarizations. The predicted insertion loss is 0.35 dB at 94 GHz (metal resistivity 10 μΩcm). The isolation between the two polarizations is better than 60 dB owing to the symmetry of the device.

A platelet W-band feed horn-OMT assembly

Future Cosmic Microwave Background polarisation experiments will require large detector arrays to achieve the required sensitivity for precise measurements. New cost- and time-effective techniques are required for mass production of high performance passive components. We present electromagnetic test results on an assembly of feed horn and OMT prototypes, operating in the W-band and fabricated by means of “platelet” technique. The good level of isolation and return loss (respectively >45 dB, >30 dB on 20% bandwidth) for both polarizations are in agreement with numerical simulations, indicating good matching between components. Radiation patterns are also in agreement with simulations, with cross-polarization level <; -30 dB on a 20% bandwidth. These results confirm the good design, manufacturing and assembling of the prototypes.

Passive Microwave Feed-Chains for High-Capacity Satellite Communications Systems

The successful implementation of satellite communication systems requires robust wireless channels providing the up-links and down-links for the communication signals. The frequency operative bands employed depend on the particular application. Navigation and mobile satellite systems are typically operated in the L (1-2 GHz) and S (2-4 GHz) bands, whereas remote-sensing applications are mostly offered in C (4-8 GHz) band. In the commercial communication area, due to the increasing demand of high quality services, the operating frequency bands has evolved towards the Ku (12-18 GHz), K (19-21 GHz) and Ka (27-32 GHz) bands. Although communication systems operating in high frequency bands provide more channel capacity, the effect of free-space attenuation and atmospheric absorption can limit the performances of these systems (e.g. signal-to-noise ratio). In this contest, the employment of efficient transmission algorithms and protocols provide meaningful advantages, but the bottle-neck is however represented by the antenna system that has to satisfy very strict requirements. For these reasons each device composing the antenna-feed chain has to be designed in order to guarantee significant electromagnetic performances and, at the same time, high integration levels (Cecchini et al., 2009). Moreover, when high power levels are employed (also of the order of tens of KW), further problems are related to spurious interferences generated by non-linear devices, as microwave amplifiers, and by metallic contacts that behave as a diode junction due to the oxidation of the metals. Additionally, high-power and low-pressure conditions can cause multipaction discharges in the devices (Addamo et al., 2010). This phenomenon is an exponential growth of electrons emitted by the metallic surfaces due to the synchronism between the applied electromagnetic field and the free electrons inside the components. The final effect consists in the damage and even in the destruction of the RF device.

Design of uniformly radiating slotted coaxial cables

Leaky coaxial cables (LCX) are used as distributed radiators for indoor communications. This kind of structure suffers of low antenna efficiency and not uniform radiated field along the cable length. In this paper a design technique in order to overcome both these problem is presented.

Application of selective laser melting to the manufacturing of antenna-feed chain components

This paper presents the research activity carried out jointly by the CNR-IEIIT and IIT aimed at the design and manufacturing of antenna-feed chain components by additive manufacturing and in particular by the selective laser melting process.

Dual-polarization passive waveguide sub-assemblies for astrophysics

This work will present the research activities ongoing at the CNR-IEIIT institute concerning the development of scientific instrumentation for astrophysical surveys. The presentation will focus both on the analysis, design, manufacturing and measurement techniques and on the layouts conceived for a large class of passive waveguide components.