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13. Antenna isolation method using sub-array structure with soft-surface for Tx/Rx separated FDD hybrid beamforming system.

Author

Kim, Young-Dam, Joo, Taehwan, Hwang, Chan-Ho, Kim, Kichul, and Jung, Jae-Soo

Subjects
*HYBRID systems, *ANTENNAS (Electronics), *CURRENT transformers (Instrument transformer)
Abstract

The FDD method is normally used for the stability of the Tx and the Rx links in a fast-varying channel. It is required to physically separate the Tx and Rx arrays for independent Tx and Rx beam control. In this system, it is important to reduce the Tx self-interference (SI) that causes the problem of active element saturation and ADC dynamic range in the Rx beamformer. To suppress Tx SI, we proposed two simple techniques. The first is the general soft-surface which attenuates the surface current flow from the Tx tile array to the Rx array. The second is the sub-array structure of the Rx hybrid beamforming system. Based on the Cauchy–Schwartz inequality, the electrical sum by the sub-array acts as a destructive interference of the complex SI signals, and it can be shown as an additional isolation effect. The proposed idea was validated through measurement. [ABSTRACT FROM AUTHOR]

Published
2021
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18. Fast Fourier-Domain Optimization Using Hybrid L1−/L ${}_{p}$ -Norm for Autofocus in Airborne SAR Imaging.

Author

Kim, Jin-Woo, Kim, Young-Dam, Yeo, Tae-Dong, Khang, Seung-Tae, and Yu, Jong-Won

Subjects
*SYNTHETIC aperture radar, *FAST Fourier transforms, *SCALABILITY, *DATA compression
Abstract

In maneuverable airborne synthetic aperture radar (SAR), high-frequency phase errors (HPEs), which are hard to be compensated by the phase gradient autofocus, often occur causing spurious targets and contrast degradation in SAR imagery. The metric-optimization approaches improve the phase error estimation scalability, including HPEs, but show much lower speed because of the computational burden by the inverse fast Fourier transform (IFFT). Proposed autofocus based on the metric optimization enables the rapid estimation with the scalability including the HPE by eliminating the IFFT. In addition, the metric is adapted to the range compressed data corresponding to the input of the autofocus taking advantage of the convergence speed and the stability in its optimization using a hybrid form of L1− and Lp-norm. In the simulation, we focused on the suggestion of the proof of performance generality. [ABSTRACT FROM AUTHOR]

Published
2019
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