This work reports the concept and development of two mechanically frequency-tunable horn filtennas for microwave and millimeter-waves. Our design approach relies on the integration of a horn antenna with a mechanically tunable filter based on dual-post resonators. The proposed filtennas have been manufactured and experimentally characterized, by means of reflection coefficient, radiation pattern, and gain. Measurements demonstrate that both filtennas have a tuning ratio of approximately 1.37 with continuous adjustment. The first prototype operates from 2.56 to 3.50 GHz, whereas in the second one the bandwidth is from 17.4 to 24.0 GHz. In addition, the higher-frequency filtenna has been implemented in a 5.0-meter-reach indoor environment, using a 16-QAM signal at 24 GHz. The best configuration in terms of performance resulted in a root mean square error vector magnitude (EVMRMS) and antenna radiation efficiency of 3.69% and 97.0%, respectively.

This work reports the development of a dual‐band switched‐beam antenna array for multiple‐input multiple‐output (MIMO) fifth‐generation systems, operating in millimetre waves. The proposed antenna array consists of applying four slotted‐waveguide antenna arrays (SWAAs), rotated by 30°, as the final array element. The SWAA elements were designed to simultaneously operate in the 28 and 38 GHz bands, by using two groups of slots with different electrical lengths on the opposite faces of the waveguide. The measured array fractional bandwidth was ∼25.6 and 10% at 28 and 38 GHz, respectively. Its applicability for MIMO systems was evaluated as a function of mutual coupling, active reflection coefficient, total active reflection coefficient and envelope correlation coefficient. Experimental results demonstrate low mutual coupling as low as −36 dB within the 28 and 38 GHz frequency bands.

Multicarrier modulation allows for deploying wideband systems resilient to multipath fading channels, impulsive noise, and intersymbol interference compared to single-carrier systems. Despite this, multicarrier signals suffer from different types of distortion, including channel noise sources and long- and short-term fading. Consequently, the receiver must estimate the channel features and compensate it for data recovery based on channel estimation techniques, such as non-blind, blind, and semi-blind approaches. These techniques are model-based and designed with accurate mathematical channel models encompassing their features. Nevertheless, complex environments challenge accurate mathematical channel estimation modeling, which might neither be accurate nor correspond to reality. This impairment decreases the system performance due to the channel estimation accuracy loss. Fortunately, (AI) algorithms can learn the relationship among different system variables using a model-driven or model-free approach. Thereby, AI algorithms are used for channel estimation by exploiting its complexity without unrealistic assumptions, following a better performance than conventional techniques under the same channel. Hence, this paper comprehensively surveys AI-based channel estimation for multicarrier systems. First, we provide essential background on conventional channel estimation techniques in the context of multicarrier systems. Second, the AI-aided channel estimation strategies are investigated using the following approaches: classical learning, neural networks, and reinforcement learning. Lastly, we discuss current challenges and point out future research directions based on recent findings.

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This paper presents a comparison of two gain-enhancement techniques and the development of an extremely high-gain slotted waveguide antenna array (SWAA) aiming at applications in the millimeterwaves (mm-waves). The first technique utilizes pairs of grooved structures surrounding a given primary power source to improve its transmission properties, acting as secondary sources to re-radiate the surface wave energy, whereas the second is based on symmetrical wing-based reflectors. Those techniques and their combination have been applied to an SWAA based on an air-filled metallic rectangular waveguide. The proposed antenna array was designed for operation in the frequency range from 25.5 to 26.5 GHz and excited by a unique coaxial-to-waveguide transition with the TE 10 fundamental mode. These techniques enable us to enhance the gain of the array by up to 10 dB, making it comparable to those of parabolic antennas with similar size apertures. Numerical analyses of the performance-enhanced antenna arrays are presented to validate the design strategies. Experimental results of 27-and 41-slots SWAA prototypes demonstrate the potential of the wing-based reflector technique to improve its aperture efficiency over that of the grooved structures. The 41-slots SWAA prototype provides as high as 31 dBi-gain in the 26 GHz band, ranging from 30.52 to 31.13 dBi within the array impedance bandwidth. Furthermore, since the reflector structures are easily attached to and detached from the SWAA structure, the prototype has the potential to provide both sectoral and directive radiation patterns in the E-plane.INDEX TERMS 5G, antenna, grooved-structures, reflectors and slotted waveguide antenna array.

Resumo-Esse trabalho apresenta um algoritmo simples e rápido para cálculo de centroide de imagem com sensores digitais de Sol do tipo CMOS (complementary metal-oxide semiconductor). Interpreta-se a imagem como uma matriz de pixel e soma-se as intensidades de linhas e colunas, armazenando-as em vetores. Obtém-se as coordenadas do centroide (xc, yc) verificando o índice correspondente ao valor de maior intensidade do vetor linha e coluna, respectivamente. Comparou-se essa abordagem ao algoritmo básico para cálculo de centroide com thresholding em termos de tempo de processamento com redução da ordem de 58% e precisão similar.Palavras-Chave-Algoritmo, centroide de imagem, CMOS, sensor digital de Sol.

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This paper describes the ultra-wideband horn antenna design operating in quasi TEM mode. The antenna consists of a triangular plate with an inclination angle above a ground plane and directly fed by a coaxial cable. Broadband characteristics, radiation pattern, high gain, and a small reflection coefficient were achieved. Its performance analysis and main parameters effects were obtained by using ANSYS HFSS R software. In the numerical analysis, an optimized model was obtained in 1.57 to 12.85 GHz bandwidth an 11 to 14 dBi gain. The proposed antenna was manufactured and the measured reflection coefficient results show an operation frequency range between 1.48 and 10.12 GHz, agreeing very well with simulations.