Design and implementation of automatic gain control algorithm for Ocean 4A scatterometer

doi:10.23919/JSEE.2024.000094

Journal of Systems Engineering and Electronics ›› 2025, Vol. 36 ›› Issue (2): 344-352.doi: 10.23919/JSEE.2024.000094

• ELECTRONICS TECHNOLOGY • Previous Articles

Design and implementation of automatic gain control algorithm for Ocean 4A scatterometer

Yongqing LIU¹^,²(), Peng LIU¹(), Limin ZHAI¹^,²(), Shuyi LIU¹^,²(), Yan JIA¹^,²(), Xiangkun ZHANG¹^,²^,*()

¹ National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China
² School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China

Received:2023-10-31 Accepted:2024-06-26 Online:2025-04-18 Published:2025-05-20
Contact: Xiangkun ZHANG E-mail:liuyongqing20@mails.ucas.ac.cn;liupeng@mirslab.cn;985422574@qq.com;919379957@qq.com;jiayan18@mails.ucas.ac.cn;zhangxiangkun@mirslab.cn
About author:
LIU Yongqing was born in 1998. He received his B.S. degree in electronic information engineering from Henan Polytechnic University, Jiaozuo, China, in 2020. He is pursuing his Ph.D. degree with the National Space Science Center (NSSC), Chinese Academy of Sciences (CAS), Beijing, China. His research interests include microwave remote sensing, radar system design, and signal processing. E-mail: liuyongqing20@mails.ucas.ac.cn

LIU Peng was born in 1983. He received his B.S. degree from Xidian University, Xi’an, China, in 2006, and M.S. and Ph.D. degrees from the National Space Science Center (NSSC), Chinese Academy of Sciences (CAS), Beijing, China, in 2009 and 2018, respectively. He is currently a senior engineer and a master’s student adviser with NSSC. His research interests include radar altimeters and microwave scatterometers, with expertise in digital signal processing. E-mail: liupeng@mirslab.cn

ZHAI Limin was born in 1999. She received her B.S. degree from China University of Mining and Technology, Beijing in 2021. She is currently a doctoral candidate with the National Space Science Center (NSSC), Chinese Academy of Sciences (CAS), Beijing, China. Her research interests are microwave remote sensing measurement technology, and microwave remote sensing radar image processing algorithms. E-mail: 985422574@qq.com

LIU Shuyi was born in 1997. She received her B.S. degree from Shandong Normal University in 2019. She is pursuing her Ph.D. degree with the National Space Science Center. Her research interests are ultra-resolution microwave imaging technology and broadband signal synthesis technology. E-mail: 919379957@qq.com

JIA Yan was born in 1994. He received his B.S. degree in remote sensing science and technology from Shandong Agricultural University, Taian, China, in 2017. He is currently pursuing his Ph.D. degree with University of Chinese Academy of Sciences. His research interests include microwave remote sensing, radar system design, and signal processing. E-mail: jiayan18@mails.ucas.ac.cn

ZHANG Xiangkun was born in 1972. He received his B.S. degree from Harbin Engineering University in 1994. He received his M.S. and Ph.D. degrees at the National Space Science Center (NSSC), Chinese Academy of Sciences (CAS) in 2002 and 2007 respectively. He is currently a research fellow and doctoral director at NSSC, Beijing, China. His research interests are microwave remote sensing imaging theory and technology, and microwave measurement technology. E-mail: zhangxiangkun@mirslab.cn

Abstract

Abstract:

The Ocean 4A scatterometer, expected to be launched in 2024, is poised to be the world’s first spaceborne microwave scatterometer utilizing a digital beamforming system. To ensure high-precision measurements and performance stability across diverse environments, stringent requirements are placed on the dynamic range of its receiving system. This paper provides a detailed exposition of a field-programmable gate array (FPGA)-based automatic gain control (AGC) design for the spaceborne scatterometer. Implemented on an FPGA, the algorithm harnesses its parallel processing capabilities and high-speed performance to monitor the received echo signals in real time. Employing an adaptive AGC algorithm, the system generates gain control codes applicable to the intermediate frequency variable attenuator, enabling rapid and stable adjustment of signal amplitudes from the intermediate frequency amplifier to an optimal range. By adopting a purely digital processing approach, experimental results demonstrate that the AGC algorithm exhibits several advantages, including fast convergence, strong flexibility, high precision, and outstanding stability. This innovative design lays a solid foundation for the high-precision measurements of the Ocean 4A scatterometer, with potential implications for the future of spaceborne microwave scatterometers.

Key words: spaceborne scatterometer, automatic gain control (AGC), field-programmable gate array (FPGA), signal acquisition

Yongqing LIU, Peng LIU, Limin ZHAI, Shuyi LIU, Yan JIA, Xiangkun ZHANG. Design and implementation of automatic gain control algorithm for Ocean 4A scatterometer[J]. Journal of Systems Engineering and Electronics, 2025, 36(2): 344-352.

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Beam	Angle/(°)	Beam	Angle/(°)
0	−29	11	3.8
1	−26.8	12	6.8
2	−24.6	13	9.9
3	−21.8	14	12.9
4	−18.9	15	15.9
5	−15.9	16	18.9
6	−12.9	17	21.8
7	−9.9	18	24.6
8	−6.8	19	26.8
9	−3.8	20	29
10	0	−	−

Resource	Utilization	Availability	Utilization/%
LUT	438	203 800	0.21
Register	402	407 600	0.09
Digital signal processing	8	840	0.10

Echo simulator transmit power/dBm	AGC value	True attenuation value/dB	Digital unit receiving echo power
−43	9	18	9306
−41	10	20	9241
−39	11	22	9330
−37	12	24	9236
−35	13	26	9293
−33	14	28	9225
−31	15	30	9229

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Design and implementation of automatic gain control algorithm for Ocean 4A scatterometer

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