Moving object detection is a vital research area that plays an essential role in intelligent transportation systems (ITSs) and various applications in computer vision. Recently, researchers have utilized convolutional neural networks (CNNs) to develop new techniques in object detection and recognition. However, with the increasing number of machine learning strategies used for object detection, there has been a growing need for large datasets with accurate ground truth used for the training, usually demanding their manual labeling. Moreover, most of these deep strategies are supervised and only applicable for specific scenes with large computational resources needed. Alternatively, other object detection techniques such as classical background subtraction need low computational resources and can be used with general scenes. In this paper, we propose a new a reliable semi-automatic method that combines a modified version of the detection-based CNN You Only Look Once V4 (YOLOv4) technique and background subtraction technique to perform an unsupervised object detection for surveillance videos. In this proposed strategy, background subtraction-based low-rank decomposition is applied firstly to extract the moving objects. Then, a clustering method is adopted to refine the background subtraction (BS) result. Finally, the refined results are used to fine-tune the modified YOLO v4 before using it in the detection and classification of objects. The main contribution of this work is a new detection framework that overcomes manual labeling and creates an automatic labeler that can replace manual labeling using motion information to supply labeled training data (background and foreground) directly from the detection video. Extensive experiments using real-world object monitoring benchmarks indicate that the suggested framework obtains a considerable increase in mAP compared to state-of-the-art results on both the CDnet 2014 and UA-DETRAC datasets.

In this letter, we propose a three-port multiple-input-multiple-output (MIMO) dielectric resonator antenna using three mutually decoupled and near-degenerate modes for X-band applications. To achieve decoupling, two of the three excited modes are chosen such that there is low mutual spatial overlapping between their field magnitudes; then, a third mode is imposed such that its field components are perpendicular to the other two modes. The impedance bandwidths of the three ports are 880 MHz, 870 MHz, and 2.61 GHZ, respectively, where contiguous bandwidth for the third port is achieved by utilizing the overlap of two resonances of TE _2δ1 ^y mode. The proposed antenna could be used either as a three-port MIMO antenna with operating bandwidth of 720 MHz, or as a two-port MIMO antenna with operating bandwidth of 880 MHz, at center frequency of 9.48 GHz. The gains of the three patterns at center frequency are 8.1 dB, 7.5 dB, and 7.4 dB, respectively.

A hexa-band, quad circular polarization (CP) slotted patch antenna for 5G (3.5 GHz), GPS L5 (1.17 GHz), GPS L1 (1.57 GHz), WLAN IEEE 802.11b/g/n (2.4 GHz), LTE (0.7 GHz), and radio navigation (1.3 GHz) applications, is proposed in this paper. Primarily, the patch antenna is optimized to excite the modes TM₁₀₀, TM₁₁₀, TM₂₁₀, and TM₂₂₀ at 0.7GHz, 1.17GHz, 1.57GHz, and 2.4GHz, respectively, while being fed by a single microstrip line. Then, the dimensions of the feeding microstrip line are fine-tuned such that three additional hybrid modes EH₁, EH₃, and EH₄ are excited to resonate at 1.3GHz and a contiguous band 2.7-3.6GHz. Meanwhile, a rotated and inverted s-shaped slot is etched on the patch metal to split surface currents of each of the modes TM₁₁₀, TM₂₁₀, EH₃, and EH₄ into two orthogonal and 90 phase-shifted versions, enabling the antenna to radiate CP waves at 1.17GHz, 1.57GHz, 3.18GHz and 3.5GHz. While supporting quad-band CP operation, the proposed antenna is simply proximity-fed by a single microstrip line, which omits the need for external feeding networks and reduces the cost and complexity. The proposed antenna gain ranges from 3 to 9 dBi/dBic over operating bands.

This work proposes a novel millimeter-wave (mm-wave) wideband circularly polarized (CP) antenna array for Internet of Things (IoT) applications. The proposed design addresses the issues of having IoT sensors deployed in remote locations or over large geographical regions. Elliptically shaped dielectric resonator antennas (DRAs) are used as array elements to improve radiation characteristics and achieve circular polarization over a wide impedance bandwidth around 28 GHz. Two different sequential-phase corporate feed networks are studied and compared to obtain wider impedance, 3-dB gain, and axial ratio (AR) bandwidths. Furthermore, a ridge gap waveguide technique based on the low-cost PCB technology is adopted to reduce the transmission losses in the considered sequential-phase feed networks. The proposed mm-wave antenna exhibits an impedance bandwidth of 35% (28.1–40 GHz) and 3-dB gain bandwidth of 19.3% (27.6–33.5 GHz). The achieved 3-dB AR bandwidth is 22.6% (27.5–34.5 GHz). The proposed antenna was fabricated and measured, and good agreement between measured and simulated results was obtained. The reported results show that the suggested wideband CP mm-wave antenna has a lot of promise in preventing polarization mismatch losses between IoT devices and satellites caused by their varying orientations.

This paper introduces a tri-band stacked elliptical patch antenna featuring a right-handed circular polarized, designed to operate at the L2, L5, and L1 Global Navigation Satellite System bands. Initially, an elliptic patch is constructed and fed by a probe feed to generate TM₁₁₀ and TM₂₁₀ modes at resonance frequencies calculated using Mathieu functions. The probe position is precisely adjusted to excite the quasi-orthogonal mode of TM₁₁₀ to generate circularly polarized (CP) waves at the L2 and L5 bands. Subsequently, an eye-shaped aperture is engraved into the elliptical patch to enhance the axial ratio (AR) beamwidth in the L2 and L5 bands and stimulate the orthogonal mode of TM₂₁₀ to produce CP waves at the L1 band. Lastly, a stacked partially elliptical parasitic element is placed beneath the upper slotted elliptical patch to enhance the orthogonality of TM₂₁₀ surface current versions and thus improve the AR beamwidth at the L1 band. The proposed antenna shows low reflection coefficient values at 1.12–1.33 (L2/L5), and 1.5–1.66 GHz (L1). The AR beamwidths are 133/213^∘, 167/163^∘, and 36/103^∘ at two orthogonal cutplanes at L5, L2, and L1 bands, respectively. The antenna also has decent gains of 6–6.9 dBic across the three bands.

This paper proposes a quadruple band stacked oval patch antenna with sunlight-shaped slots supporting L1/L2/L5 GNSS bands and the 2.3 Ghz WiMAX band. The antenna produces right-hand circular polarization waves with wide axial-ratio beamwidth of 223/216 $$^{\circ }$$∘ and 231/203 $$^{\circ }$$∘ at two orthogonal cutplanes at L5 and L2 GNSS bands, respectively. Firstly, the resonant modes $$TM_{110}$$T M 110 and $$TM_{210}$$T M 210 are excited inside a single layer oval patch antenna, where resonance frequencies are calculated using Mathieu functions. Meanwhile, it is shown that another version of the mode $$TM_{110}$$T M 110 with similar distribution but orthogonal direction is excitable inside the same oval patch. Then, a second stacked oval patch layer is added, which splits the resonance frequency of each of the modes $$TM_{110}$$T M 110 and $$TM_{210}$$T M 210 into two different values. Depending on the probe feed position and the separation between the two layers, the phase shifts between modes versions in the upper and the lower layers change. Thus, by fine-tuning the probe feed position and the separation between layers, spatially-orthogonal with quadrature-phase-shift versions of the mode $$TM_{110}$$T M 110 are obtained, producing a circularly polarized waves at L2 and L5 bands. Furthermore, sunlight shaped slots are etched into the upper and lower layer patches to fine tune the phase shifts between different modes versions, which enhances the overall axial-ratio beamwidth. Despite the simplicity of the overall structure and the feeding mechanism utilized in the proposed design, wide axial-ratio beamwidths are obtained, as compared to previous works. The proposed antenna shows low reflection coefficient values at 1.14–1.29 GHz (L2/L5), 1.45–1.6 GHz (L1), and 2.26–2.4 GHz (WiMAX). The antenna gains are 5.9, 5.6, 6, and 6.5 dBi/dBic at L5, L2, L1, and WiMAX bands, respectively. The half-power beamwidths are 99/96 $$^{\circ }$$∘ , 102/96 $$^{\circ }$$∘ , 112/85 $$^{\circ }$$∘ , and 65/48 $$^{\circ }$$∘ at two orthogonal cutplanes at L5, L2, L1, and WiMAX bands, respectively.