Beam Scanning Capabilities of a 3D-Printed Perforated Dielectric Transmitarray

In this paper, the design of a beam scanning, 3D-printed dielectric Transmitarray (TA) working in Ka-band is discussed. Thanks to the use of an innovative three-layer dielectric unit-cell that exploits tapered sections to enhance the bandwidth, a 50 × 50 elements transmitarray with improved scanning capabilities and wideband behavior has been designed and experimentally validated. The measured radiation performances over a scanning coverage of ±27° shown a variation of the gain lower than 2.9 dB and a 1-dB bandwidth in any case higher than 23%. The promising results suggest that the proposed TA technology is a valid alternative to realize a passive multibeam antenna, with the additional advantage that it can be easily manufactured using 3D-printing technique

Dual Circularly Polarized Antennas with Low Cross-Polarization for GNSS-R Applications

Global Navigation Satellite System-Reflectometry (GNSS-R), has gained increasing interests as an efficient tool for remote sensing. It is based on the concept of utilizing the received signals reflected from the Earth’s surface. Several GNSS-R system configurations were proposed depending on different retrieval algorithms. In a GNSS-R system, the antenna plays a key role as a receiving component. In this paper, in-situ measurements using a commercial dual circular polarized antenna receiving both the left-hand and right-hand circular polarization reflected from the ground are analyzed. A low cost and compact dual-port circular polarized patch antenna is designed and realized to overcome the limitations of the previous configuration. The prototype shows a low level of cross polarization suitable for GNSS-R application

Design and experimental validation of Convex Conformal Reflectarray Antennas

In this work the design, the numerical analysis and the experimental characterization of a Convex conformal Reflectarray (CRA) has been carried out, with the aim of investigating the feasibility of reflectarrays bent on convex curved surfaces. A medium-size offset CRA in Ka-band has been designed, and a demonstrator has been manufactured and measured. The results prove the correctness of the design procedure and the feasibility of this type of antenna, pointing out the differences, also in terms of radiation performances, with respect to a planar reflectarra

Frequency Selective Surface for Ultra-Wide Band Filtering and Shielding

A frequency selective surface for spatial filtering in the standardized Ultra-Wide Band (UWB) frequency range is proposed. A very large stop-band of 1.75–15.44 GHz has been obtained, with good polarization insensitivity and an angular stability of more than 60∘ and more than 50∘ in TE and TM incidence, respectively. Circuit models have been devised. The structure has been assessed by electromagnetic simulation and implemented on an FR4 substrate of 1.6 mm thickness, with an edge of the square-shaped unit cell of 15 mm. Tests in an anechoic chamber demonstrated good matching between simulation and experimental results and proper operation of the device

Design and Verification of a Q-Band Test Source for UAV-Based Radiation Pattern Measurements

In the last years, the unmanned aerial vehicles (UAVs) generated significant innovations in in situ antenna measurements. UAV-mounted test sources have been exploited to characterize the radiation pattern of receiving antennas and arrays for HF radars, radio telescopes in very high-frequency (VHF) band, and up to the X-band for radar characterization. A UAV test source operating in the Q-band has been recently developed within the large-scale polarization explorer (LSPE) project. It will be used for the in situ validation of a ground-based cluster of coherent polarimeters for cosmology observation. This article presents the payload solution that is actually applicable to general UAV-based radiation pattern measurements in the Q-band. It is based on a phase-locked loop synthesizer and an active multiplier coupled with a power detector to compensate for signal power drifts in postprocessing. Relevant system tests have been performed in both laboratory environment and operative conditions. The measured outdoor radiation patterns are in good agreement with both the anechoic chamber measurements and simulated data

3D-Printable Dielectric Transmitarray With Enhanced Bandwidth at Millimeter-Waves

In this paper, a three-layer dielectric structure is presented as innovative unit-cell element for transmitarray (TA) antennas with enhanced bandwidth. It consists of a central layer, with a varying size square hole, used to compensate the phase of the incident field and located between two other identical layers with linearly tapered square holes, acting as matching circuits. The effectiveness of this unit-cell is demonstrated by the numerical and the experimental results here presented. As a first step, three different TAs with increasing size are designed and simulated: their 1-dB gain bandwidth, centered at 30 GHz, varies from the 30.9% of the smallest configuration, having size of $10\lambda _{0}\times 10\lambda _{0}$ , to the 17.5% of the $20\lambda _{0}\times 20\lambda _{0}$ TA. A slightly modified unit-cell is then designed, with the aim of realizing a prototype with an additive manufacturing (AM) technique. A 3D-printed dielectric TA with a size of $15.6\lambda _{0}\times 15.6\lambda _{0}$ has been manufactured and experimentally characterized. The measured prototype shows excellent performances, achieving a 1-dB gain bandwidth of 21.5%: these results prove the enhanced features of the introduced unit-cell and demonstrate the TA feasibility with AM techniques

Electrically-small wearable antennas for emergency services applications

This paper presents the results of a study on electrically small wearable antennas, for use in emergency and security applications in the low UHF band, around 860 MHz. Realization of prototypes in textile materials has also been considered and implemented