This letter presents a radiation pattern verification system for low-frequency antennas in their operative conditions, e.g., on the ground, next to other elements, etc. It is a far-field setup using a properly equipped micro unmanned aerial vehicle (UAV) as a test source. The micro UAV can perform an autonomous flight. Its absolute position is measured with a remote topographic instrument. By data processing, the received power pattern along the UAV flying path is reconstructed. The proposed setup has been validated on two standard wire antennas at 150 and 408 MHz with an estimated accuracy of 1 dB.

Additive manufacturing (AM) is emerging as a key technology for the minimization and integration of microwave antenna systems. Among the several AM processes, selective laser melting (SLM) is rather convenient for waveguide components, since it allows for all-metal parts with a mechanical accuracy within 30-60 μm and an equivalent surface electrical resistivity in the range of 10-20 μΩcm. This paper reports on the assessment of the SLM applicability to the manufacturing of dual-polarization waveguide components operating in Ka-band, namely, a septum polarizer, a smooth-wall feed horn integrated with the septum polarizer, and an orthomode transducer (OMT). In order to achieve high electromagnetic performance in the Kaband, the architectures have been optimized for the manufacturing process, above all in terms of orientation on the building platform and minimization of supporting structures. As a consequence, the corresponding prototypes exhibit measured performances in significant agreement with the predicted values. As an example, the return loss of all the components has been measured to be as high as 25 dB, while the measured isolation between the rectangular waveguide ports of the OMT is better than 47 dB.

Additive manufacturing technologies have been increasingly applied to the development of radio frequency components in the past few years. Indeed, the free-form capability of these processes allows for the design of novel components, whose actual implementation through conventional machining is rather complex or even not possible. This paper describes a monolithic WR51 component integrating three radio frequency functionalities, namely, bending, twisting, and filtering. Three aluminum prototypes with different bending/twisting radii have been manufactured through the selective laser melting process. They exhibit a measured rejection higher than 60 dB in 17.5 and 21.2 GHz, and a measured return loss better than 20 dB in 12.5 and 15 GHz. Significant mass and envelope reductions (higher than 60% depending on the bending/twisting radius) with respect to the reference subsystem with distinct waveguide components are achieved. These results assess the effectiveness of 3-D metal printing in the miniaturization and integration of waveguide systems.

In this letter, the design and the three-dimensional (3-D) printing of high-performance feed horns operating within Ku- and V-bands are presented. A smooth-wall architecture has been preferred in order to ease the manufacturing and to enhance the 3-D printing quality. A suitable design procedure has been developed for the synthesis of dual-band smooth-wall feeds. Single-band and dual-band all-metal prototypes have been manufactured through the selective laser melting technology. A remarkable agreement between the predicted and measured performances has been achieved also for the higher frequency Q/V-band feed horn with measured return-loss higher than 33 dB, cross-polarization lower than −28 dB, and peak gain of 25 dBi.

In this paper we present the electromagnetic modeling and beam pattern measurements of a 16-elements ultra wideband sparse random test array for the low frequency instrument of the Square Kilometer Array telescope. We discuss the importance of a small array test platform for the development of technologies and techniques towards the final telescope, highlighting the most relevant aspects of its design. We also describe the electromagnetic simulations and modeling work as well as the embedded-element and array pattern measurements using an Unmanned Aerial Vehicle system. The latter are helpful both for the validation of the models and the design as well as for the future instrumental calibration of the telescope thanks to the stable, accurate and strong radio frequency signal transmitted by the UAV. At this stage of the design, these measurements have shown a general agreement between experimental results and numerical data and have revealed the localized effect of un-calibrated cable lengths in the inner side-lobes of the array pattern.