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This work was supported in part by the Spanish Government under Project PID2020-112545RB-C54 and, Project RTI2018-102002-A-I00, in part by “Junta de Andalucía” under Project B-TIC-402-UGR18, Project A-TIC- 608-UGR20, Project PYC20-RE-012-UGR and Project P18.RT.4830, and in part by the Predoctoral Grant FPU18/01965. (Corresponding author: Ángel Palomares-Caballero.), This paper presents a metal-only reflectarray that enables the control of incident orthogonal polarizations in a large bandwidth. The proposed reflectarray is based on a unit cell whose tuning elements allow the independent control of the reflection phase value for the vertical and horizontal impinging polarizations. Due to the symmetry of the unit cell, the same performance is produced by each polarization when its reflection phase response is modified. The proposed unit cell provides a fairly linear phase response along the frequency with a phase variation in the orthogonal polarization of ±1o. The performance under oblique incidence and the frequency limitation of the unit cell are also investigated. From this unit cell, a metal-only reflectarray that produces circular polarization from a linear polarization is designed. The reflectarray presents a simulated directivity greater than 27 dBi with an axial ratio below 1.5 dB from 32 GHz to 50 GHz (43.9% of bandwidth). A prototype is fabricated and the measured results agree well with the simulated ones. The obtained aperture efficiency is between 56% and 41% in the considered frequency band. The measured realized gain ranges from 27 dBi to 30.3 dBi where the achieved radiation efficiency is greater than 97%., Spanish Government PDC2022-133900-I00, PID2020-112545RB-C54, TED2021-129938B-I00, TED2021-131699B-I00, Junta de Andalucia B-TIC-402-UGR18, A-TIC-608-UGR20, PYC20-RE-012-UGR, P18.RT.4830, FPU18/01965

When the covariance matrix formulation is used for multi-look polarimetric synthetic aperture radar (SAR) data, Wilks’ Lambda can be used for change detection between acquisitions at two time points. We briefly describe the theory for dual polarization, diagonal only data. A case study illustrates thetechnique on Sentinel-1 C-band data covering the international Frankfurt Airport. We successfully detect change including direction of change in the sense that Wilks’ Lambda shows whether radar signal increases or decreases over time.

International audience; A low-cost dual linearly-polarized transmitarray antenna (TA) is presented for 5G and beyond networks at D-band. This TA is made of 40 40 unit-cells (UCs) and is illuminated by a stepped feed horn with a F/D ratio equal to 0.75. The flat lens panel is based on UCs with six different phase states at the center frequency of 150 GHz (thus leading in average to a 2-bit phase quantization and 0.7-dB insertion loss from 130 to 175 GHz). Each UC is made of only three metal layers and does not include any via connection to guaranty performance robustness with respect to fabrication dispersions. The measured1-dB and 3-dB TA gain bandwidths equal 16.8% and 19.8%, respectively, with a peak gain of 32 dBi, corresponding to an aperture efficiency of 32% at 150 GHz. The measured sidelobe and cross-polarization levels in E and H planes remain below -21 and -37 dB, respectively. An excellent agreement between measured and simulated radiation patterns was observed.

Based on a newly proposed planar Yagi antenna with magnetic and electric dipoles, a compact $1\times 4$ broadband dual-polarized (DP) array with endfire radiation is designed in this paper. The magnetic Yagi antenna operates on the vertical polarization while the electric one operates on the horizontal one. The compact configuration of $0.5\,\,\lambda _{0}\times 0.63\,\,\lambda _{0}\times 0.09\,\,\lambda _{0}$ benefits from the novel half-mode magnetic Yagi antenna and the arrangement with the electric Yagi antenna. The broadband characteristic comes from the directors of the magnetic and electric Yagi antennas and the reflector of magnetic Yagi antenna. The simulation and the measurement verify this design. The measured common bandwidth of $\vert S_{11}\vert < -10$ dB for both polarization ports is 23.8–30.1 GHz (23.7%), and the gains vary between 3 dBi and 4 dBi within 24.2–30 GHz band range. The $1\times 4$ DP array with $0.5~\lambda _{0}$ element space has the beam scanning range of ±43 ° at the endfire direction and the gain of higher than 7.1 dBi. The scanning performances are experimentally validated by two phase-shift feed networks for 0 ° and 30 ° main beam directions. The proposed endfire DP array has the good features of compact structure, a low profile and no clearance requirement, which is easy to integrate in 5G terminals.

A fully planar dual polarized radiating element with internal embedded coupled dipoles is presented in this paper. The inclusion of these elements allows achieving three different goals: firstly, an extension of the bandwidth towards lower frequencies (from 1.69 GHz to 1.427 GHz) as required in new 5G standards; secondly, a reduction of the antenna size in comparison with other topologies for bandwidth extension and, finally, a reduction of the secondary lobes. The proposed dual polarized broadband antenna is based on two sets of dual polarized dipoles, with a fully planar structure. The objective of this paper is the design of an antenna working in the extended 5G band in order to fulfil the future 5G requirement in the microwave region, in which the new frequency bandwidth goes from 1.427 up to 2.69 GHz with the return losses lower than -14 dB and the crosspolar isolation larger than 28 dB. This work was supported in part by the Spanish Ministry of Education, Culture and Sport under a grant for predoctoral contracts for University Teacher Training under Grant FPU16/00459, and in part by the Spanish Ministry of Science, Innovation and Universities, (program ``Programa Estatal de I+D+i orientada a los Retos de la Sociedad'') under Grant RTC-2017-6394-7.

This letter presents a simple and compact dual-polarized linear antenna array characterizing high interport isolation for in-band full-duplex communications. By using the symmetrically shared-interface configuration integrated with a 180° hybrid, the self-interference resulting from the impedance mismatching between the antenna and feeding network and the coupling among the antenna elements can be well suppressed theoretically. Furthermore, to achieve the high isolation in practice among a wide frequency band, a slotline-based 180° hybrid is proposed and studied, which features a high isolation between the sum and differential ports. For further verification, a demonstrator of a 1 × 4 array centered at 5.0 GHz is developed and fabricated. The measurements denote that the shared -10 dB impedance bandwidth of the two ports is from 4.75 to 5.18 GHz, and the interport 50 dB isolation bandwidth is from 4.55 to 5.66 GHz (over 21.7%).

This paper presents the design of a modulated metasurface (MTS) antenna capable to provide both righthand (RH) and left-hand (LH) circularly polarized (CP) boresight radiation at Ku-band (13.5 GHz). This antenna is based on the interaction of two cylindrical-wavefront surface wave (SW) modes of transverse electric (TE) and transverse magnetic (TM) types with a rotationally symmetric, anisotropic-modulated MTS placed on top of a grounded slab. A properly designed centered circular waveguide feed excites the two orthogonal (decoupled) SW modes and guarantees the balance of the power associated with each of them. By a proper selection of the anisotropy and modulation of the MTS pattern, the phase velocities of the two modes are synchronized, and leakage is generated in broadside direction with two orthogonal linear polarizations. When the circular waveguide is excited with two mutually orthogonal TE11 modes in phase–quadrature, an LHCP or RHCP antenna is obtained. This paper explains the feeding system and the MTS requirements that guarantee the balanced conditions of the TM/TE SWs and consequent generation of dual CP boresight radiation. This work was supported by COST ACTION IC1102, NEWFOCUS Research Networking Program and Spanish Ministry of Science and Innovation (project TEC2013-47753-C3-1-R).

We present the likelihood ratio test statistic for the homogeneity of several complex variance–covariance matrices that may be used in order to assess whether at least one change has taken place in a time series of SAR data. Furthermore, we give a factorization of this test statistic into a product of test statistics that each tests simpler hypotheses of homogeneity up to a certain point and that are independent if the hypothesis of total homogeneity is true. This factorization is used in determining the (pixelwise) time points of change in a series of six L-band EMISAR polarimetric SAR data. The pixelwise analyses are applied on homogeneous subareas covered with different vegetation types using the distribution of the observed p-values.

When the covariance matrix formulation is used for multilook polarimetric synthetic aperture radar (SAR) data, the complex Wishart distribution applies. Based on this distribution, a test statistic for equality of two complex variance–covariance matrices and an associated asymptotic probability of obtaining a smaller value of the test statistic are given. In a case study, airborne EMISAR C- and L-band SAR images from the spring of 1998 covering agricultural fields and wooded areas near Foulum, Denmark, are used in single- and bifrequency, bitemporal change detection with full and dual polarimetry data.

The use of dual polarization in mobile satellite systems is very promising for increasing the channel capacity. Polarized Modulation is proposed in this paper for use in practical systems, by providing simple equations for computing its capacity and featuring a link adaptation algorithm. This scheme shows remarkable gains in the spectral efficiency when compared with single polarization and other multi-antenna techniques such as V-BLAST. Polarized Modulation is a particular instance of more general Index Modulations, which are being considered for 5G networks. Thus, the proposed link adaptation algorithm could find synergies with current activities for future terrestrial networks.

This communication proposes a new patch antenna with dual circularly polarized capability at 2.575 GHz. The design exploits the even and odd modes in a coplanar waveguide transmission line and enables simultaneous right- and left-handed circular polarization, with two individual excitation ports. A patch antenna is fed by multimode transmission line and the advantages and disadvantages are discussed. A prototyped antenna realized up to 20 dB isolation between ports with S21

This letter relates to the development of satellite reflectarrays able to scan a single dual-polarized beam, based on monolayer resonating cells embedding digital microelectromechanical systems (MEMS). We study general topology constraints to be imposed on the elementary cell to ensure dual-polarized operation, minimal cross-polarization, and a reduced number of MEMS for a given phase resolution. It is shown that an element electrically invariant to a 90 degrees rotation is the most favorable one, and the theoretical considerations are verified by a design example under both normal and oblique incidence.

Three mesh antennas, all having an extremely small antenna height of approximately 0.06 wavelength above a ground plane, are presented. First, a mesh antenna excited with a balanced feed is analyzed. It is revealed that the mesh antenna radiates a linearly polarized wave with no cross-polarization component in the principal planes. The radiation mechanism is explained using the current distribution. Second, a mesh antenna excited with an unbalanced feed is analyzed. This antenna shows almost the same radiation characteristics as the mesh antenna with a balanced feed. The frequency bandwidth for a VSWR=2 criterion is evaluated to be approximately 3%. Third, a mesh antenna having two perturbation elements is analyzed. It is found that the antenna acts as a radiation element of circular polarization. The frequency bandwidth for a 3-dB axial ratio criterion is calculated to be approximately 1%. The mesh antennas in the first and second analyses can be used as dual linear polarization elements by appropriately switching the feed. Similarly, the mesh antenna in the third analysis can be used as a dual circular polarization element by switching the feed.

A waveguide polarizer exploiting two different phase shift phenomena is presented in this letter. Iris-type discontinuities are in fact introduced in a waveguide structure having different propagation constants for the two principal polarizations. In this way, the required 90 Deg differential phase shift is obtained combining the iris phase shift with the waveguide one. Several operative conditions arise from the combination of the two contributions. This approach has been used to design a broadband waveguide polarizer for the -band antenna feed system of the Sardinia Radio Telescope with 40 dB reflection coefficients and a 35 dB cross polarization level in a 30% bandwidth.

Novel profiled irises for the design of waveguide polarizers are presented. The two degrees of freedom of their piecewise- circular profile allow one to better control the frequency behavior of the differential phase shift. Thanks to this feature, an optimum iris set can be found by selecting the discontinuities for which the differential-phase-shift deviation from the average value is minimum in the operative bandwidth. This optimum iris set can be identified for several values of the ratio r/lambda0, where r is the waveguide radius and lambda0 is the free-space wavelength at the central frequency. Hence, even if both the waveguide size and central frequency are assigned in the specifications, polarizers with a very low deviation from 90 Deg of the total differential phase shift can be designed. In this way, the number of waveguide transitions in the antenna feed system can be reduced and the effect of spurious higher-order-mode coupling can be minimized. A Ka-band polarizer in circular waveguide with piecewise-circular-profile irises is described, showing a return loss better than 55 dB and a phase error of about 0.9 Deg in a 10% bandwidth.