Broadband linear-to-circular polarizing reflector for space applications in Ka-band

This communication presents a novel low-profile broadband polarizing reflector to convert dual linear polarization (LP) into dual circular polarization (CP). The polarizing cell is based on printed dipole technology and presents a wideband performance in Ka-band. The dimensions of the printed dipoles are adjusted cell by cell to improve the reflection phase performance against variations in the incidence angles or in the cell dimensions. A 25-cm flat polarizing reflector demonstrator has been designed, fabricated and tested. The design has been optimized for transmit (19.2-20.2 GHz) and receive (29-30 GHz) frequencies in Kaband, but the broadband behavior of the cell provides satisfactory results also at the intermediate frequencies. The measured patterns show a good agreement with the simulations, with an axial ratio lower than 1.8 dB within the 19.2-30 GHz band. The proposed polarizing reflector can be used for novel multibeam antenna configurations to produce multi-spot coverage in Ka-band with a smaller number of apertures.Agencia Estatal de Investigación | Ref. TEC2016-75103-C2-1-RMinisterio de Economía y Competitividad | Ref. TEC2015-65353-REuropean Space Agency ESTEC | Ref. 4000117113/16/NL/A

GPR system onboard a UAV for non-invasive detection of buried objects

Copia del artículo enviado al congreso (ya está aceptado para su presentación en el mismo)In this contribution, a novel subsurface imaging system to detect buried targets is presented. It is mainly composed by a Ground Penetrating Radar (GPR) mounted onboard an Unmanned Aerial Vehicle (UAV). Thus, the system can be used to inspect areas without being in contact with the soil, which makes it useful for detecting dangerous objects, such as landmines. The system architecture and some of the first prototype measurements, which are post-processed using a Synthetic Aperture Radar (SAR) algorithm, are presented in this contribution.This work has been supported by Government of Spain (under projects TEC2014-55290-JIN, TEC2015-73908-JIN and grant FPU15/06341), Government of Asturias (IDI/2017/000095) and Galician Government (under project GRC2015/018) and under agreement for funding AtlantTIC.IEEE Antennas and Propagation Society International Symposiu

On the use of compressed sensing techniques for improving multistatic millimeter-wave portal-based personnel screening

This work develops compressed sensing techniques to improve the performance of an active three dimensional (3D) millimeter wave imaging system for personnel security screening. The system is able to produce a high-resolution 3D reconstruction of the whole human body surface and reveal concealed objects under clothing. Innovative multistatic millimeter wave radar designs and algorithms, which have been previously validated, are combined to improve the reconstruction results over previous approaches. Compressed Sensing techniques are used to drastically reduce the number of sensors, thus simplifying the system design and fabrication. Representative simulation results showing good performance of the proposed system are provided and supported by several sample measurement

Synthetic aperture radar imaging system for landmine detection using a ground penetrating radar on board a unmanned aerial vehicle

This paper presents a novel system to obtain images from the underground based on ground penetrating radar (GPR). The proposed system is composed by a radar module mounted on board an unmanned aerial vehicle (UAV), which allows the safe inspection of difficult-to-access areas without being in direct contact with the soil. Therefore, it can be used to detect dangerous buried objects, such as landmines. The radar measurements are coherently combined using a synthetic aperture radar (SAR) algorithm, which requires cm-level accuracy positioning system. In addition, a clutter removal technique is applied to mitigate the reflection at the air-soil interface (which is caused by impedance mismatching). Besides the aforementioned advantages, the system can detect both metallic and dielectric targets (due to the use of a radar instead of a metal detector) and it allows to obtain high-resolution underground images (due to the SAR processing). The algorithms and the UAV payload are validated with measurements in both controlled and real scenarios, showing the feasibility of the proposed system.Ministerio de Economía y Competitividad | Ref. TEC2014-54005-PMinisterio de Economía y Competitividad | Ref. TEC2014-55290-JINMinisterio de Economía y Competitividad | Ref. TEC2015-73908-JINMinisterio de Economía y Competitividad | Ref. TEC2015-65353-RAgencia Estatal de Investigación | Ref. RYC-2016-20280Ministerio de Educación | Ref. FPU15/06341Gobierno del Principado de Asturias | Ref. PCTI 2013-2017Gobierno del Principado de Asturias | Ref. FC-15-GRUPIN14-114Gobierno del Principado de Asturias | Ref. IDI/2017/000095Xunta de Galicia | Ref. GRC2015/01

Transmit–receive parabolic reflectarray to generate two beams per feed for multispot satellite antennas in Ka-band

This contribution describes the design of a multibeam parabolic reflectarray to produce two adjacent beams per feed in orthogonal circular Polarization (CP) simultaneously at transmit (Tx) and receive (Rx) frequencies in Ka-band. The Variable Rotation Technique (VRT) has been applied to reflectarray cells based on two types of resonant elements, which makes it possible to provide orthogonal beams at Tx and Rx, as well as to implement an in-band optimization procedure to reduce the cross-polarization. A 90-cm parabolic reflectarray has been designed, manufactured and tested to produce multiple adjacent beams in RHCP and LHCP at both 20 and 30 GHz. The results are satisfactory and validate the concept of generating two spaced beams in orthogonal CP by a single feed, changing the polarization of the beam between Tx and Rx. This concept can be suitable for multispot satellites in Ka-band, enabling to halve the number of onboard antennas and feedsAgencia Estatal de Investigación | Ref. TEC2016-75103-C2-1-RAgencia Estatal de Investigación | Ref. FJCI-2016-29943European Space Agency | Ref. 4000117113/16/NL/A

Parabolic reflectarray antenna to generate multiple beams for geostationary high throughput satellites in Ka-band

This contribution describes the design and simulations of a multibeam 1.8 m parabolic reflectarray antenna for geostationary high throughput satellites (HTS) in Ka-band. The parabolic reflectarray generates two orthogonal circularly polarized beams per feed simultaneously at 19.7 and 29.5 GHz, by the variable rotation technique. The antenna is made of 62 654 reflectarray cells, which include two types of printed elements independently rotated and adjusted. The elements have been optimized one by one to ensure the required phase-shift at each frequency. A novel design approach has made it possible to promptly obtain an initial layout of every element with a very low computational cost. The simulated radiation patterns show that the parabolic reflectarray, illuminated by 27 dual-circularly polarized feeds, can generate 54 spot-beams in two orthogonal polarizations, with a beam spacing of 0.56° between adjacent beams. The design and simulation tools have been validated by a parabolic reflectarray scaled in a factor of 0.5, which has been manufactured and tested. The proposed reflectarray would allow to generate a complete multi-spot coverage from a geostationary HTS with only two parabolic reflectarrays, instead of four reflector antennas, also reducing the number of feeds by half, since every feed generates two beams.Agencia Estatal de Investigación | Ref. PID2020-113979RB-C22Agencia Estatal de Investigación | Ref. PID2020-114172RB-C21-2Agencia Estatal de Investigación | Ref. PDC2021-120959-C2

Advanced multibeam antenna configurations based on reflectarrays: providing multispot coverage with a smaller number of apertures for satellite communications in the K- and Ka-bands

This article presents some recent developments in multiplebeam antennas (MBAs) based on reflectarrays for communication satellites in the Kurz (K) and Kurz-above (Ka) bands. The existing high-throughput satellites commonly employ four reflector antennas to provide cellular coverage that is formed by multiple spot beams in a four-color scheme. Reflectarray antennas are proposed as an attractive solution for the design of novel MBA configurations to produce multispot coverage, with a smaller number of apertures than conventional MBA systems based on reflector technology. Single and dual reflectarray configurations have been considered for the purpose of exploiting their ability to produce independent beams in different polarizations and frequencies.Agencia Estatal de Investigación | Ref. TEC2016-75103-C2-1-RMinisterio de Economía y Competitividad | Ref. TEC2015-65353-RXunta de Galicia | Ref. GRC2015/018European Space Agency | Ref. 4000117113/16/NL/A

Array Optimization for an On-The-Move 3D Imaging System Demonstrator

IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting ( 2018. Boston)In this work, array optimization for an imaging system demonstrator is presented. It is able to create 3D images of people as they walk through the scanner and it makes use of a very low number of transceivers. The array positions have been optimized to minimize grating lobes and maximize resolution for a given number of array elements

A Physical optics simulator for multireflector THz imaging systems

This article presents a physical optics-based simulator for the analysis of terahertz (THz) imaging systems. The simulation starts by calculating the electromagnetic interactions inside the multireflector system and the incident field that the focusing system creates on the target under inspection. In a second step, the electric field that the modeled target scatters back to the system receiver, is also calculated. This allows to predict the imaging behavior of the system for different targets before manufacturing. The simulator results are validated by using measurements from an existing 300-GHz standoff imaging system. This contribution aims to help in the development of better imaging systems for security applications in the near future.Atlantic Research Center for Information and Communication TechnologiesMinisterio de Economía y Competitividad | Ref. TEC2015-65353-RMinisterio de Economía y Competitividad | Ref. TEC2015-73908-JINAgencia Estatal de Investigación | Ref. TEC2017-87061-C3-1-RXunta de Galicia | Ref. GRC2015/01

Unmanned aerial system for antenna measurement (UASAM)

European Conference on Antennas and Propagation (EuCAP 2018) (12th. 2018. London)The main goal of this contribution is to provide an overview of an Unmanned Aerial System for Antenna Measurement (UASAM), which will be presented at the AMTA Scientific Workshop on “UAV-based Antenna and Field Measurements”. UASAM is a compact low-cost system that can be used for in-situ antenna measurement and diagnostics. It makes use of a Real Time Kinematik (RTK) and a laser altimeter to georefer the measurements with cm-level accuracy. Field radiated by the Antenna Under Test (AUT) is measured with a low-cost power detector at several acquisition surfaces (even non-canonical surfaces) around the AUT (in the near field region). Next, an iterative phase retrieval technique is applied, being able to recover the AUT aperture fields. Furthermore, from these fields, Near-Field to Far-Field (NF-FF) transformation can be used to retrieve the radiation pattern. Several application examples for different kinds of AUTs will be shown in the workshop. In addition, the impact of positioning and geo-referring accuracy will be discussed as well. This system is of great interest for those industrial applications where antenna diagnostics and radiation pattern assessment capabilities are required (e.g. analysis of antenna arrays, tilt testing of base station antennas, etc.) avoiding the need of stopping operational conditions