IEEE Open Journal of Antennas and Propagation - OJAP

[Design Guidelines and Performance Analysis of a Wideband Coaxial Horn Antenna Fabricated via Additive Manufacturing] Elígia Simionato, Ivan Aritz Aldaya, José A. de Oliveira, André Jardini , Julian Avila, Guilherme S. da Rosa and Rafael A. Penchel introduce a Ka-band coaxial horn antenna that incorporates a specialized dielectric supporting structure and a transition to a 2.4 mm connector. The inner and outer radii of the coaxial aperture were sized using an approximated model for an open-ended coaxial waveguide. The theory of small reflections was then used to account for the reflection coefficient resulting from an additional cascading cylindrical-conical section. A refined numerical model, representing more accurately a prototype, featured a transition region to standardized connectors and a dielectric structure that offers mechanical support for the inner conductor and impedance matching. Read their article here: https://lnkd.in/gs22Smws #HornAntennas #Dielectrics #Gain #Connectors #Conductors #AntennaRadiationPatterns #ReflectorAntennas #APS #IEEE #OJAP

[An Improved Uniaxial Perfectly Matched Layer Based on Finite Element Method for Hyperbolic Media] Na Liu, Yansheng Gong, Rui Xu, Huanyang Chen and Guoxiong Cai analyze the reason for the failure of uniaxial perfectly matched layer (UPML) in absorbing electromagnetic waves with hyperbolic media (HM). They also propose an improved UPML based on the frequency domain finite element method (FEM) to truncate the unbound hyperbolic computational domain. Finally, the excellent absorption effect of the improved UPML is verified by representative examples such as an infinite HM, a linear-crossing metamaterial, and a Bessel beam. Read their article here: https://lnkd.in/gdfSBV9j #FiniteElementAnalysis #Permeability #Tensors #Permittivity #PerfectlyMatchedLayers #Media #MathematicalModels #APS #IEEE #OJAP

[Design of a Dual-Band Planar Sleeve Monopole Antenna With the Substrate-Integrated Coaxial Line Technology] Ying C. Zheng, L. Zhu, C. Ni, J. Ding, K. Cao and B. Liu propose a dual-band sleeve monopole antenna with the substrate-integrated coaxial line (SICL) technology. Both the radiation structure and the feeding network are modified from the SICL structure. The antenna provides dual-band operation for LoRa (Long Range Radio) applications covering 433 MHz and 868 MHz bands. This antenna operates as a quarter-wavelength monopole with practical omnidirectional radiation performance for each band. The antenna exhibits a gain of 2.0 dBi at 433 MHz with more than 90% radiation efficiency, and a gain of 1.7 dBi at 868 MHz with more than 90% radiation efficiency. Read their article here: https://lnkd.in/gX3enqTx #Antennas #DualBand #Substrates #AntennaMeasurements #ReflectionCoefficient #Impedance #Gain #APS #IEEE #OJAP

[Multibeam Compact Reflectarray Antenna With Low Scan Loss and Wide-Angle Performance Using a Multi-Feed Configuration] Andrés Gómez Álvarez, Álvaro F. Vaquero, Ph.D., Manuel Arrebola Baena and Marcos Rodriguez Pino present two multibeam reflectarray antennas for Ka-band in a multi-feed configuration. Both feature a wide-angle scanning range with very low scan losses. They are designed using an iterative optimization process based on a phase-only optimization (POO) which allows fine control over the gain for each beam. The phase responses of the lattice cells are selected taking into account the illumination levels and radiation requirements of all feeds in the system. Minimization of scanning losses and overall antenna compactness are prioritized in the design. The feeding elements are placed along a tilted arc with a low F/D of 0.58. Compared to other beam scanning reflectarray designs in the literature, inter-feed blockage is avoided and thus simultaneous multibeam operation is supported. Read their article here: https://lnkd.in/gVzzXKFK #ReflectorAntennas #AntennaFeeds #Optimization #Geometry #Gain #Costs #ReflectionCoefficient #APS #IEEE #OJAP

[A State-of-the-Art Survey on Advanced Electromagnetic Design: A Machine-Learning Perspective] Masoud Salmani Arani, Reza Shahidi and Lihong Zhang present an overview of recent developments in optimization and design automation techniques for EM-component design and modeling. Limitations of conventional optimization methods are discussed, while the need for novel machine learning techniques capable of handling multiple objectives and large design spaces is highlighted. In this study, existing methods in the literature are reviewed from four viewpoints: structural view, algorithm view, component view, and application view. Different schemes in distinct design stages or applications are examined with advantages and drawbacks laid out for easier comprehension. Read their article here: https://lnkd.in/gEndwP2h #Optimization #ComputationalModeling #SolidModeling #DataModels #AdaptationModels #FeatureExtraction #DesignAutomation #APS #IEEE #OJAP

[Wideband and High-Efficiency Circularly Polarized Unit-Cell for X and Ka-Band Transmitarrays] Alessandro de Oliveira Cabral Junior, Hamza KAOUACH and André Barka present a novel approach for linear to circular polarization (LP-CP) conversion in transmitarray antennas. The proposed conversion mechanism differs significantly from previous published realizations. The concept utilizes a transmission line modeling-based excitation technique, in which a centralized via excitation is split into two striplines carefully designed to balance excitations and guarantee a phase quadrature. The striplines are embedded at the center of the patch antenna allowing a compact footprint and a simple design structure. The applied true-time delay (TTD) technique assures the radiation of a wideband and low axial ratio circularly polarized (CP) field. Read their article here: https://lnkd.in/g9gYBhMN #Bandwidth #Polarization #MillimeterWaveCommunication #ApertureAntennas #Wideband #PatchAntennas #Gain #APS #IEEE #OJAP

[Beamforming of Transmit Antennas Using Grey Wolf Optimization and L2-Norm for Performance Enhancement of Beyond 5G Communications] samar Farghaly, Mostafa M. Fouda and Manal Emara proposes a new beamforming strategy based on a hybrid combination between grey wolf optimizer (GWO) with L2 -norm called proposed GWO. This approach is applied to synthesized uniform linear arrays (ULA), Chebyshav arrays, and shaped pattern arrays. Moreover, it is utilized for side lobe level (SLL) and size reduction of antenna elements. In this strategy, the GWO is utilized to optimize the element spacing to adjust the half-power beamwidth (HPBW) to save it the same as desired pattern. Furthermore, the excitations of the antenna elements are optimized via the L2 -norm minimization problem. The proposed GWO has low complexity (fewer iterations and computing time) compared to other algorithms. Read their article here: https://lnkd.in/gQgFh3hQ #AntennaArrays #Optimization #ArraySignalProcessing #MIMOCommunication #Antennas #Precoding #LinearAntennaArrays #APS #IEEE #OJAP

[A Mutual Coupling-Based Full Self-Online Calibration Method for Antenna Arrays in Uplink] Aral Ertug Zorkun, Miguel A. Salas Natera, Alvaro Araujo Pinto, Ramón Martínez Rodríguez-Osorio and Manuel Sierra Pérez propose a mutual coupling based self-calibration method for transmit mode large scale antenna arrays. In accord with the proposed active antenna array model, gain/phase uncertainties, antenna element position errors and mutual coupling effects are reduced to an error matrix. The expansion of equations of the proposed calibration method are presented. The proposed calibration procedure is capable of compensating the error matrix while the system is operating and is suitable for off-line, on-site and online calibration procedures. Read their article here: https://lnkd.in/gmvyDbpg #Calibration #AntennaMeasurements #PhasedArrays #MutualCoupling #Couplings #PhaseMeasurement #MeasurementUncertainty #APS #IEEE #OJAP

[Point Cloud-Based Prediction Models of Dynamic Human Body Shadowing at 58 GHz] Chechia Kang , Xin Du and Jun-Ichi Takada propose screen models and an elliptic cylinder model based on the instantaneous point clouds (PC) of human geometry for the human body shadowing (HBS) channel simulation using the uniform theory of diffraction (UTD). The proposals enable fair evaluation via a simultaneous measurement of the HBS channel and the PC. The HBS gains at the 58 GHz band in an indoor environment (6.5 m) between the measured and the simulated results based on the proposed models are compared. Read their article here: https://lnkd.in/g9TAT3TQ #BiologicalSystemModeling #ShadowMapping #PredictiveModels #Diffraction #Shape #FresnelReflection #Geometry #APS #IEEE #OJAP

[RF Circuit Analysis of UWB Planar Log Periodic Antenna for 5G Communications Using Theory of Characteristic Modes] P. Sumithra, Gulam Nabi Alsath Mohammed, JEGADISH KUMAR K J and Kannadassan D present the systematic RF analysis, fabrication, and equivalent circuit modeling for sub-6GHz 5G application using theory of characteristic modes (TCM). The fabricated pLPA is designed to cover the 5G bands with a high gain of >5 dBi and a fractional bandwidth of >1. Using simulation tool based on method of moments, radiating and non-radiating modes are tracked and studied with detailed physics. These modes are modeled using analytically derived equivalent circuit and assembled in an RF/microwave circuit simulator. Read their article here: https://lnkd.in/gPWMFG2S #AntennaRadiationPatterns #IntegratedCircuitModeling #FrequencyMeasurement #AnalyticalModels #5GMobileCommunication #RadioFrequency #GainMeasurement  #APS #IEEE #OJAP