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With the development of computer vision and remote sensor devices, object detection in aerial images has drawn considerable attention because of its ability to provide a wide field of view and a large amount of information. Despite this, object detection in aerial images is a challenging task owing to densely packed objects, oriented diversity, and complex background. In this study, we optimized three aspects of the YOLOv5 algorithm to detect arbitrary oriented objects in remote sensing images, including head structure, features from the backbone, and angle prediction. To improve the head structure, we decoupled it into four submodules, which are used for object localization, foreground, category, and oriented angle classification. To increase the accuracy of the features from the backbone, we designed a block dimensional attention module, which is developed by splitting the image into smaller patches based on a dimensional attention module. Compared with the original YOLOv5 algorithm, our approach has a better performance for oriented object detection-the mAP on DOTA-v1.5 is increased by 1.25%. It was tested to be effective on DOTA-vl.0, HRSC2016, and DIOR-R datasets as well. [ABSTRACT FROM AUTHOR]

This paper presents the first coupled-line coupler that provides independent power division ratios at dual bands. In contrast with previous dual-band coupled-line couplers, the power division ratios k²(f1) and k²(f2) at each band (f1 and f2) can be independently controlled in order to satisfy the requirements of various communication protocols at different bands. Moreover, it has a compact size due to the usage of coupled lines rather than transmission lines. Explicit design equations and design guide of the coupler are provided. In this letter, one prototype of the proposed coupler is simulated, fabricated, and measured. It provides power division ratios k²(f1) = 4dB at f1 = 1GHz and k²(f2) = 8dB at f2 = 2.4GHz. The measured result agrees well with the simulation. [ABSTRACT FROM AUTHOR]

This study presents a novel planar coupled-line directional coupler with tunable both power division ratio and operating frequency, which is achieved using microstrip technology for the first time. Its tunability of the operating frequency and the power division ratio, or coupling ratio, can be independently controlled by the bias voltages. Moreover, it can simultaneously maintain perfect port match and isolation. On the basis of the even-odd mode analysis method, both the closed-form analytical equations and parameter discussions are provided to facilitate the practical design. An experimental prototype of the tunable coupler is simulated, fabricated, and measured to demonstrate how it works. The measured results indicate that power division ratio can vary from 0.35 (9 dB) to 0.71 (3 dB) when operating frequency ranges from 0.55 to 1.48 GHz (91.63%) while power division ratio varies from 0.35 (9 dB) to 1 (0 dB) when operating frequency is fixed at 1 GHz, which validated the reliability of the proposed model. [ABSTRACT FROM AUTHOR]

In this paper, a compact and miniaturized broadband phase shifter using coupled-lines (CL) is proposed. This broadband phase shifter merely consists of two sections, one pair of CL as the reference and another two parallel CLs as the main body. An analysis of even-odd mode on the theoretical circuit is shown to explain the basic principle of the proposed phase shifter. For demonstration of this novel configuration, a broadband 90° phase shifter was designed and fabricated. The measured results present that the proposed phase shifter can provide a stable wide bandwidth (over 80%) of 90° phase difference with deviation less than 6.7°, good return losses more than 10 dB and low insertion losses less than 0.53 dB. [ABSTRACT FROM AUTHOR]

A novel dual-band bandpass filter with a compact structure and a wide stopband is proposed. The total structure includes coupled-line stubs and coupled-line connected sections, leading to a compact circuit. This proposed filter can be implemented easily by using single-layer microstrip technology. The measured results of a prototype filter show that it can operate at both 1.32 and 2.67 GHz and up to the 8 GHz 15 dB stopband. [ABSTRACT FROM AUTHOR]