UAV-Based Antenna Measurements: Improvement of the Test Source Frequency Behavior

Drone-based radiation pattern measurements require the knowledge of the whole test-source radiation pattern in order to reach the expected measurement accuracy. However, the radiation pattern of the onboard antenna can be highly distorted by the metal frame of the vehicle, particularly in the VHF and UHF bands, showing highly resonant behaviors. This paper presents a preliminary analysis aimed to highlight such behavior and adopt compatible solutions to minimize or avoid the pattern distortion in the frequency of interest

3D Printing of a Monolithic K/Ka-Band Dual-Circular Polarization Antenna-Feeding Network

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

Large Horizontal Near-field Scanner based on a Non-tethered Unmanned Aerial Vehicle

A horizontal planar scanner with an approximate size of 40 m x 40 m has been implemented using the Unmanned Aerial Vehicle (UAV) technology. The UAV is not wired to the ground to maintain the flexibility and short setup time of a non-tethered flight. In this configuration, the UAV-mounted continuous-wave source is not phase-locked to the on-the-ground receiver. A dual-polarized reference antenna placed on the ground is hence used to retrieve the relevant phase information. The presented approach has been applied on the Pre - Aperture Array Verification System (Pre -AAVS1) of the Square Kilometre Array, which is a digital beamformed array with 16 active elements. An inverse source technique has been applied on measured Near-Field (NF) data acquired on two different sets of points (one for each electric field component) from all the receiver channels. In this way, Embedded Element Patterns (EEPs), array calibration coefficients and pattern have been determined from NF data only. The achieved results have been validated using a complementary set of Far-Field (FF) measurements and simulations

Effect of the UAV orientation in antenna pattern measurements

A novel radiation pattern measurement system for VHF and UHF antennas has been recently developed using the Unmanned Aerial Vehicle (UAV) technology. This paper discusses the effect of the UAV orientation and the applicable corrections on the pattern extraction procedure, in order to increase the accuracy and repeatability of the measurements

The STRIP instrument of the Large Scale Polarization Explorer: microwave eyes to map the Galactic polarized foregrounds

In this paper we discuss the latest developments of the STRIP instrument of the "Large Scale Polarization Explorer" (LSPE) experiment. LSPE is a novel project that combines ground-based (STRIP) and balloon-borne (SWIPE) polarization measurements of the microwave sky on large angular scales to attempt a detection of the "B-modes" of the Cosmic Microwave Background polarization. STRIP will observe approximately 25% of the Northern sky from the "Observatorio del Teide" in Tenerife, using an array of forty-nine coherent polarimeters at 43 GHz, coupled to a 1.5 m fully rotating crossed-Dragone telescope. A second frequency channel with six-elements at 95 GHz will be exploited as an atmospheric monitor. At present, most of the hardware of the STRIP instrument has been developed and tested at sub-system level. System-level characterization, starting in July 2018, will lead STRIP to be shipped and installed at the observation site within the end of the year. The on-site verification and calibration of the whole instrument will prepare STRIP for a 2-years campaign for the observation of the CMB polarization.Comment: 17 pages, 15 figures, proceedings of the SPIE Astronomical Telescopes + Instrumentation conference "Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX", on June 15th, 2018, Austin (TX

Full-Wave Design of Broad-Band Compact Waveguide Step-Twists

Rectangular waveguide twists are components that provide an on-axis rotation of the transverse waveguide section. In this letter, a step twist configuration, obtained by the direct connection of rotated rectangular waveguide lengths, is considered. The advantages of this configuration are the easy manufacturing with tight control on the relative rotation angles and the reduction of the overall dimensions. By means of a full-wave synthesis approach various wide-band devices were designed and reported in the letter. In particular, a couple of 45 twists was manufactured and integrated in the Ka-band OMT realized for the SPOrt project. The experimental results match the excellent predicted data

A mortar-element method for the analysis of periodic structures

In this work a mortar-element method aimed at analyzing 2D periodic structures is introduced. The mathematical formulation of a single-domain problem involving periodicity conditions is derived; then, the multi-domain feature of this numerical scheme is exploited, in order to separate regions with media with different refraction indices. Finally, a comparison with results obtained by mode-matching is performed

3D-Printing of Antenna-Feed Components for Space Applications

This paper reports an overview on the on-going research activity aimed at the exploitation of 3D-printing technologies to the development of dual-band and dual-polarization components for SatCom antenna feed chains. In particular, architectures optimized for 3D-printing are discussed, and the results of a preliminary study on the application of perforations along the internal channels is reported

New RF data on ECCOSORB CR/MF absorber

ECCOSORBTM CR/MF is a widely used absorber at radio and millimeter wavelengths. It is used both at room and at cryogenic temperature to realize loads and calibrators both for laboratory and for space-borne instruments. Data on its RF properties are available from the data sheet at room temperature. But it is also widely used outside the design wavelength range and at cryogenic temperature, where specific measurement of electromagnetic and thermal properties are needed. Scarce information is available in the literature and inconsistencies are frequent. We report here new RF data in Ka and W-band at room temperature obtained with waveguide measurements with different setups