Open Access
Application of coherently radiating periodic structures for feeding subarrays in limited-scan arrays
(IEEE, 2023) Juárez, Elizvan; Panduro, Marco A.; Covarrubias, David H.; Reyna, Alberto; Río Bocio, Carlos del; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza
This paper presents a new design technique to improve the reduction of phase shifters using sub-arrays and CORPS (coherently radiating periodic structures) technology. The CORPS network generates the values of cophasal excitation with reduced input ports. These values feed an optimal sub-arrays structure. Furthermore, fixed and variable amplifiers allow a low SLL (side lobe level) by using a raised cosine amplitude distribution along sub-arrays inputs. The theoretical model of CORPS-Subarrays, numerical and experimental results of several design cases are presented. The proposed design achieves a ±14° scanning range with a higher reduction of phase shifters than other techniques presented previously in the state of art. This paper illustrates, as a contribution, the complete antenna system based on the fabrication of a prototype and experimental results to analyze the reduction capacity of phase shifters and scanning possibilities of the proposed methodology in antenna arrays. The experimental results of the BFN (beam-forming networks) prototype at 6 GHz for 11 antenna elements and 3 phase shifters are provided. The proposed design achieves a reduction of 72% of phased shifters with ±14° beam scanning and −15 dB of SLL.
Open Access
Multi-channel feedarray reflector antenna based radar concept for HRWS SAR imaging
(IEEE, 2021) Castillo, Javier del; Orgaz, Lara; García, Quiterio; Memeletzoglou, Nafsika; Toso, Giovanni; Imbembo, Ernesto; Biurrun Quel, Carlos; Río Bocio, Carlos del; Institute of Smart Cities - ISC
Large deployable reflector based multi-channel antenna systems are a key component of next generation SAR missions as they allow implementing multi-beam imaging capabilities and provide an efficient way to overcome the classical SAR resolution-coverage trade-off, covering wide swaths with high azimuth resolution. The presented work shows the design of a multichannel L-band SAR system and antenna architecture based on different feeders concepts and capable to map 400 km ground swath with 5 meter spatial resolution in dual polarization. The paper describes a preliminary design and architecture of the SAR system and the antenna where different design aspects including beamforming concepts and feedarray implementation techniques have been identified and assessed in view of achieving the required SAR performances while reducing the overall complexity of the solution.
Open Access
Photonic-assisted 2-D terahertz beam steering enabled by a LWA array monolithically integrated with a BFN
(Optica, 2022) Haddad, Thomas; Biurrun Quel, Carlos; Lu, Peng; Tebart, Jonas; Sievert, Benedikt; Makhlouf, Sumer; Grzeslo, Marcel; Teniente Vallinas, Jorge; Río Bocio, Carlos del; Stöhr, Andreas; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
A novel photonic-assisted 2-D Terahertz beam steering chip using only two tuning elements is presented. The chip is based on an array of three leaky wave antennas (LWAs) with a monolithically integrated beamforming network (BFN) on a 50 µm-thick indium phosphide substrate. The THz beam angle in elevation (E-plane) is controlled via optical frequency tuning using a tunable dual-wavelength laser. An optical delay line is used for azimuth (H-plane) beam control. The simulated beam scanning range is 92° in elevation for a frequency sweep from 0.23 THz to 0.33 THz and 69.18° in azimuth for a time delay of 3.6 ps. For the frequency range from 0.26 THz to 0.32 THz, it is confirmed experimentally that the THz beam scans from −12° to +33°, which is in good agreement with the numerical simulations. The beam direction in azimuth scans with a total angle of 39° when applying a delay difference of 1.68 ps. A good agreement is found between theoretically predicted and experimentally determined THz beam angles with a maximum angle deviation below 5°. The experimental scanning angles are limited due to the mechanical constraints of the on-wafer probes, the on-chip integrated transition and the bandwidth of the THz receiver LNA. The mechanical limitation will be overcome when using a packaged chip.
Open Access
An innovative way of using coherently radiating periodic structures for phased arrays with reduced number of phase shifters
(IEEE, 2021) Juárez, Elizvan; Panduro, Marco A.; Covarrubias, David H.; Reyna, Alberto; Sánchez, Brian; Río Bocio, Carlos del; Institute of Smart Cities - ISC
This article presents an innovative design technique for feeding phase antenna arrays using coherently radiating periodic structure (CORPS) technology for reducing the number of phase shifters (PSs) in limited-scan applications with low sidelobe level (SLL). The proposed configuration is implemented taking advantage of the phase interpolation property of a CORPS network of one layer. This configuration is built by interconnecting 2×3 CORPS networks in a strategic way in order to provide a reduction in the number of PSs while maintaining the scanning capability. Experimental results and full-wave simulations based on CST Microwave Studio reveal that the proposed design technique reduces the recombination losses and generates a better phase slope with respect to the basic CORPS network providing a reduction in the number of PSs. As a novel contribution, this article provides the full antenna system design in order to analyze and study the PSs reduction performance and scanning capabilities of the proposed technique to feed linear antenna arrays. The proposed design technique provides a reduction in the number of PSs for a scanning range of ±25° in linear arrays. The array design model includes the application of the raised cosine amplitude distribution to generate a radiation pattern with minimum SLL. The linear array system was validated by experimental measurements of the full system prototype and full-wave simulations results are provided to verify the accuracy of the array model and to take mutual coupling into account. The proposed case provides a good design compromise with respect to other cases in the state of the art.
Open Access
New hexagonal CORPS-BFN for multibeam antenna applications
(IEEE, 2020) Biurrun Quel, Carlos; Montesano, Antonio; Ederra Urzainqui, Íñigo; Iriarte Galarregui, Juan Carlos; Río Bocio, Carlos del; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
This work presents a new topology of a Coherently Radiating Periodic Structure - Beam Forming Network (CORPS-BFN) and its application for multibeam systems. A unit cell, consisting of a transition from a coaxial input to an intersection of three strip-lines with an angular span of 120 degrees, is proposed and analysed. A periodical replication of the cell gives rise to a uniform layer, allowing a proper matching of the ports of the network. Stacked layers allow in-phase propagation and distribution of the energy through the structure, increasing the number of output ports with each layer.
Open Access
Noise in coherently radiating periodic structures beam forming networks
(IEEE, 2022) Biurrun Quel, Carlos; Río Bocio, Carlos del; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
Following the noise wave theory, beam forming networks based on Coherently Radiating Periodic Structures (CORPS-BFN) are analysed and proven to be capable of enhancing the Signal to Noise Ratio of the system by analogically multiplexing the signal and noise contributions present at every input port. The geometry of the network determines the maximum enhancement achievable, which is demonstrated to be independent from insertion losses. These findings are supported by a mathematical approach, as well as with experimental data.
Open Access
Freehand system for antenna diagnosis based on amplitude-only data
(IEEE, 2021) Álvarez Narciandi, Guillermo; Laviada, Jaime; Álvarez López, Yuri; Ducournau, Guillaume; Luxe, Cyril; Belem Goncalves, Cybelle; Gianesello, Frederic; Nachabe, Nour; Río Bocio, Carlos del; Las-Heras, Fernando; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
This article presents a portable system for freehand antenna diagnosis and characterization based on amplitude-only data. The amplitude-only samples are acquired by moving a handheld probe, which is tracked by a motion capture system, in front of the antenna under test (AUT) aperture. The acquired measurements are processed using the phaseless sources reconstruction method to compute an equivalent current distribution on the AUT aperture. Finally, the radiation pattern of the AUT can be obtained by evaluating the corresponding radiation integrals. Unlike previous work, the use of amplitude-only data avoids the need of a phase reference, paving the way to the diagnosis and characterization of antennas under operational conditions. This fact, together with the handheld capabilities, makes the system very convenient for measurements of already deployed and onboard antennas. Moreover, these amplitude-only acquisitions also simplify the required hardware. The system has been validated through measurements in a wide frequency range from Ka-band up to 300 GHz. Despite that one cannot expect the same degree of accuracy that can be achieved under laboratory conditions (including an anechoic environment and highly accurate positioners), the system shows excellent capabilities to detect malfunctions, such as wrong amplitude/phase distributions, as well as a fair estimation of the far field.
Open Access
Design and characterization of terahertz CORPS beam forming networks
(Springer, 2023) Biurrun Quel, Carlos; Haddad, Thomas; Sievert, Benedikt; Kress, Robin; Weimann, Nils; Erni, Daniel; Rennings, Andreas; Stöhr, Andreas; Teniente Vallinas, Jorge; Río Bocio, Carlos del; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
This work reviews the design and applicability of beam-forming networks based on Coherently Radiating Periodic Structures (CORPS-BFN) at Terahertz (THz) frequency bands. These versatile networks offer two operation modes: a continuous beam steering – feeding an antenna array with a linearly progressive phase distribution – using a reduced number of phase controls; or a multi-beam operation, generating independent, overlapped beams. These networks are built upon the concatenation of power combiners/dividers (PCDs) with isolated outputs. The isolation is provided by monolithically integrated resistors, implemented with Ti/TiO thin films for the first time. In this work, a planar prototype of a (inputs/outputs) microstrip CORPS-BFN for operation in the WR3.4/WM-864 band (220–330 GHz) on a thin 50 m Indium Phosphide (InP) substrate is designed, fabricated, and characterized. The measured S-parameters show a reflection coefficient better than -15 dB and an insertion loss between 1.6 and 3.2 dB in the whole band. In addition, an isolation better than 20 dB between the input ports has been measured. An overall remarkable agreement is observed between the measurements and the simulations. Last, the applications, scalability and efficiency of this type of networks at the targeted band are discussed in detail.
Open Access
3-D-printed transmit-array antenna for broadband backhaul 5G links at V-band
(IEEE, 2020) Matos, Sérgio A.; Teixeira, Jorge P.; Costa, Jorge R.; Fernandes, Carlos A.; Río Bocio, Carlos del; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
The low cost and compactness of transmit-array antennas (TAs) make them attractive for 5G backhaul links. However, the TA advantage is less obvious when considering the broadband operation requirement. Two main factors influence the bandwidth performance, namely: 1) the bandwidth of the unit cells, and 2) the number of 360° phase wrapping zones in the aperture, which are designed for a specific frequency. Herein, we overcome these limitations by using all-dielectric unit cells (inherently broadband) and by developing a general method to quantify and manage the intricate relation between antenna gain, bandwidth, and antenna height. Based on this framework we optimize, as an example, a TA design (focal distance, \boldsymbol{F} = \text{63 mm} and aperture diameter \boldsymbol{D} = \text{80 mm}) to comply with typical gain specification for 5G backhaul links (>30 dBi) in the WiGiG band (from 57 to 66 GHz). The feed is a dedicated compact horn (\text{8 }\times \text{5} \times \text{22 mm}^3) that provides a proper illumination of the aperture. Additive manufacturing is used to simplify the manufacturing process of the antenna. A very good agreement between simulations and experimental results is obtained, achieving good aperture efficiency for this type of antenna (42%), which rivals with existing solutions based on more expensive manufacturing techniques.
Open Access
Feeder system design for OLAF SAR instrument
(IEEE, 2022-04-11) Biurrun Quel, Carlos; García-García, Quiterio; Río Bocio, Carlos del; Institute of Smart Cities - ISC
The design of the feeding system for the focal array in OLAF (Over-Lapped Sub-Array Fed) antenna for SAR Instrument at L-Band is presented. The proposed design consists of a circular patch with a balanced excitation all of it embedded in a ground plane which is connected to the lower ground plane by some shorting pins, reducing the mutual coupling with the neighbour radiating elements of the focal array. The balanced excitation has been implemented with a 180° hybrid using the differential input port. Dual polarization is achieved by using two 180° hybrids within the same layer. The stringent requirements for the system, namely low in cross-polarization, high isolation between the two polarizations (both below the-25dB reference level) and azimuthal symmetry of the radiation pattern are fulfilled within all the working bandwidth.