2.65Gbps Downlink Communications with Polarization Multiplexing in X-Band for Small Earth Observation Satellite

• KANEKO Tomoki

  Department of Electrical Engineering and Information Systems, The University of Tokyo

• KAWANO Noriyuki

  Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency

• NAGAO Yuhei

  Radrix Co. Ltd.

• MURAKAMI Keishi

  Synspective Inc.

• WATANABE Hiromi

  Keio University

• MITA Makoto

  Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency

• TOMODA Takahisa

  Synspective Inc.

• HIRAKO Keiichi

  Keio University

• SHIRASAKA Seiko

  Keio University

• NAKASUKA Shinichi

  Department of Aeronautics and Astronautics, The University of Tokyo

• SAITO Hirobumi

  Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency

• HIROSE Akira

  Department of Electrical Engineering and Information Systems, The University of Tokyo

Abstract

This paper reports our new communication components and downlink tests for realizing 2.65Gbps by utilizing two circular polarizations. We have developed an on-board X-band transmitter, an on-board dual circularly polarized-wave antenna, and a ground station. In the on-board transmitter, we optimized the bias conditions of GaN High Power Amplifier (HPA) to linearize AM-AM performance. We have also designed and fabricated a dual circularly polarized-wave antenna for low-crosstalk polarization multiplexing. The antenna is composed of a corrugated horn antenna and a septum-type polarizer. The antenna achieves Cross Polarization Discrimination (XPD) of 37-43dB in the target X-band. We also modify an existing 10m ground station antenna by replacing its primary radiator and adding a polarizer. We put the polarizer and Low Noise Amplifiers (LNAs) in a cryogenic chamber to reduce thermal noise. Total system noise temperature of the antenna is 58K (maximum) for 18K physical temperature when the angle of elevation is 90^° on a fine winter day. The dual circularly polarized-wave ground station antenna has 39.0dB/K of Gain - system-noise Temperature ratio (G/T) and an XPD higher than 37dB. The downlinked signals are stored in a data recorder at the antenna site. Afterwards, we decoded the signals by using our non-real-time software demodulator. Our system has high frequency efficiency with a roll-off factor α=0.05 and polarization multiplexing of 64APSK. The communication bits per hertz corresponds to 8.41bit/Hz (2.65Gbit/315MHz). The system is demonstrated in orbit on board the RAPid Innovative payload demonstration Satellite (RAPIS-1). RAPIS-1 was launched from Uchinoura Space Center on January 19th, 2019. We decoded 10¹⁰ bits of downlinked R- and L-channel signals and found that the downlinked binary data was error free. Consequently, we have achieved 2.65Gbps communication speed in the X-band for earth observation satellites at 300 Mega symbols per second (Msps) and polarization multiplexing of 64APSK (coding rate: 4/5) for right- and left-hand circular polarizations.

Journal

• IEICE Transactions on Communications

  IEICE Transactions on Communications E104.B (1), 1-12, 2021-01-01

  The Institute of Electronics, Information and Communication Engineers

Keywords

• satellite communications
• small satellite
• DVB-S2X
• Cross Polarization Discrimination (XPD)
• polarization multiplexing

Details

• CRID: 1390286981364944384
• NII Article ID: 130007964960
• DOI: 10.1587/transcom.2019ebn0009
• ISSN: 17451345
• ISSN: 09168516
• Web Site: https://www.jstage.jst.go.jp/article/transcom/E104.B/1/E104.B_2019EBN0009/_pdf
• Text Lang: en
• Data Source:
  • JaLC
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed