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Detecting objects in synthetic aperture radar (SAR) imagery has received much attention in recent years since SAR can operate in all-weather and day-and-night conditions. Due to the prosperity and development of convolutional neural networks (CNNs), many previous methodologies have been proposed for SAR object detection. In spite of the advance, existing detection networks still have limitations in boosting detection performance because of inherently noisy characteristics in SAR imagery; hence, separate preprocessing step such as denoising (despeckling) is required before utilizing the SAR images for deep learning. However, inappropriate denoising techniques might cause detailed information loss and even proper denoising methods does not always guarantee performance improvement. In this paper, we therefore propose a novel object detection framework that combines unsupervised denoising network into traditional two-stage detection network and leverages a strategy for fusing region proposals extracted from both raw SAR image and synthetically denoised SAR image. Extensive experiments validate the effectiveness of our framework on our own object detection datasets constructed with remote sensing images from TerraSAR-X and COSMO-SkyMed satellites. Extensive experiments validate the effectiveness of our framework on our own object detection datasets constructed with remote sensing images from TerraSAR-X and COSMO-SkyMed satellites. The proposed framework shows better performances when we compared the model with using only noisy SAR images and only denoised SAR images after despeckling under multiple backbone networks.

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This paper presents the fabrication results of a scalable X-band transmit/receive block used in an active electronically scanned array (AESA) antenna. Due to the disadvantages of the miniaturization of the existing brick-type planar structure and the complexity of the tile-type stacked structure, a quasi-tile structure-based transmit/receive block was developed. The developed antenna had a radio-frequency circuit that was easy to implement in a flat type, and the control part had the advantage of miniaturization in a stacked type. It is easy to develop an AESA antenna of a desirable size by connecting the transmit/receive blocks. An ethylene glycol water-cooling structure was not added inside the transmit/receive block, as it was designed to cool one side of the block. The temperature difference between the high power amplifier(HPA) and the contact surface of the cooling plate improved by approximately 15 %. Gallium nitride devices were used in the transmit/receive module and had a higher breakdown field than conventional gallium arsenide devices. Hence, the module exhibited high efficiency when used in power-switching circuits and showed good heat dissipation efficiency and thermal conductivity. The transmit power of each transmit/receive block channel was 10 W, the receive gain was 28.4 dB, and the noise figure value was 3.4 dB.