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.
Open Access
Hybrid analog-digital SAR instrument with reflector antenna and overlapped subarray feed for earth observation
(IEEE, 2021) García, Quiterio; Orgaz, Lara; Castillo, Javier del; Toso, Giovanni; Imbembo, Ernesto; Biurrun Quel, Carlos; Río Bocio, Carlos del; Memeletzoglou, Nafsika; Institute of Smart Cities - ISC
As part of the European Space Agency (ESA) studies of new instrument for Earth observation, the design of a synthetic aperture radar (SAR) architecture based on overlapped array antennas was launched last year. The objective of the activity is to develop a test unit of a reflector based SAR antenna fed by an array organized in overlapped subarrays, supporting novel multichannel wide-swath SAR architectures, and exploiting multiple beams in both azimuth and range/elevation directions. In the letter, a hybrid analog/digital beamforming on reception with analog beamforming approach on transmission is analyzed. The antenna system consists of a large oversize reflector with a feedarray capable of generating multiple beams on receive for digital processing. In the letter, a description of the hybrid SAR Instrument is presented, describing the characteristics of the system, the antenna, the considered feedarray options and the main characteristics and system performances.
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
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
Evaluating noise in passive beam forming networks for multibeam applications
(Elsevier, 2023) Biurrun Quel, Carlos; Río Bocio, Carlos del; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
In this work, we identify that the analysis in terms of noise of multibeam passive beam forming networks requires a proper formulation, in order not to overestimate the noise generated by the network. We show that the inherent spatial diversity offered by this type of networks results in an improvement of the SNR, similar to the one obtained by digital architectures, with a penalty due to the insertion loss. To illustrate this phenomena, two generalized equivalent circuits are proposed are a numerical example is presented.
Open Access
Hexagonal CORPS-BFN to feed OLAF SAR instrument
(IEEE, 2021) Biurrun Quel, Carlos; Iriarte Galarregui, Juan Carlos; Ederra Urzainqui, Íñigo; Río Bocio, Carlos del; Institute of Smart Cities - ISC
The concept of Coherently Radiating Periodic Structures-based Beam Forming Networks is applied to feed OLAF (OverLapped SubArray Fed) antenna for SAR Instrument at L-Band. The proper feeding of this system requires the multiple beams to be highly overlapped, and that is generated by a CORPS-BFN using a new 4-port Gysel power combiner/divider implemented in a suspended stripline technology. The network provides high isolation between inputs/outputs, low insertion loss, great return loss and the desired ovelapping of the different beams.
Open Access
A design proposal using coherently radiating periodic structures (CORPSs) for 2-D phased arrays of limited scanning
(MDPI, 2024-09-18) Calvillo, Gilberto; Panduro, Marco A.; Juárez, Elizvan; Reyna, Alberto; Río Bocio, Carlos del; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza
New configurations of 2-D phased arrays are proposed in this paper for reducing the number of phase shifters. This design methodology is based on the use of a novel coherently radiating periodic structures (CORPSs) block for 2-D phased arrays. Two new antenna systems for 2-D phased arrays are studied and analyzed utilizing the CORPSs blocks of four inputs and nine outputs. These CORPSs feeding blocks are applied in a smart way to feed the planar antenna arrays by generating the required phase plane and reducing the number of control ports. Interesting results are provided based on the experimental measurements and full-wave simulations. These results illustrate a great reduction of the active devices (phase shifters), providing a good design compromise in terms of the scanning range and side lobe level performance. Furthermore, the provided results illustrate a maximum reduction capability in the number of phase shifters of 81%, considering a scanning range of ±30° in azimuth and ±30° in elevation. A raised cosine distribution is applied to reach side lobe levels of −19 dB for ±18° and −17 dB for ±30° in elevation. These benefits could be of interest to designers of phased antenna systems.
Open Access
Studying the noise performance of CORPS beam forming networks
(IEEE, 2022-05-11) Biurrun Quel, Carlos; Río Bocio, Carlos del; Institute of Smart Cities - ISC
The classical noise wave theory is employed in the field of Coherently Radiating Periodic Structures (CORPS). The coherent properties of these type of networks allow the distribution of a signal across the network and the in-phase recombination of each distributed component at an output port. Whereas these distribution and recombination processes are coherent for the signal and hence do not incur in power loss, the intrinsically incoherent noise contributions incident at the port terminations are not sum coherently. This is especially significant in presence of incident noise powers much larger than the intrinsically generated thermal noise. As a result, an enhancement in terms of Signal-to-Noise Ratio (SNR) is demonstrated analytically by means of noise wave theory. The maximum achievable SNR enhancement depends on the internal structure of the CORPS network. Validation of the proposed theory is provided by means of a commercial circuital software.
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
Reduction of phase shifters in planar phased arrays using novel random subarray techniques
(MDPI, 2024-07-06) Valle, Juan L.; Panduro, Marco A.; Río Bocio, Carlos del; Brizuela, Carlos A.; Covarrubias, David H.; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza
Reducing the number of phase shifters by grouping antenna elements into subarrays has been extensively studied for decades. The number of phase shifters directly affects the cost, complexity, and power consumption of the system. A novel method for the design of phased planar antenna arrays is presented in this work in order to perform a reduction of up to 70%70% in the number of phase shifters used by the array, while maintaining the desired radiation characteristics. This method consists of creating fusions of subarrays to generate random sequences that form the best feeding network configuration for planar phased arrays. The obtained solution allows scanning the mainlobe at 𝜃=−40∘θ=−40∘ elevation with a range of scanning of [−75∘<𝜙<75∘][−75∘<ϕ<75∘] in the azimuth plane, while maintaining a side lobe level below −10−10 dB and achieving a reduction of 62%62% in the number of phase shifters. It is shown that each solution is created based on search criteria, which influence the morphology of the array in terms of subarray size and orientation. The proposed methodology shows great flexibility for creating new phased antenna array designs that meet the requirements of specific applications in a short period of time.