Session

Technical Session XII: Communications

Location

Utah State University, Logan, UT

Abstract

This paper reports our new communication system and downlink demonstrations with a small satellite of 2.65 Gbps data rate with 64 APSK modulation and 3.3Gbps data rate with 256 APSK modulation by utilizing two circular polarization channels of X band. We have developed an on-board X-band transmitter, an on-board dual circularly polarized-wave antenna with 17dBi gain and >37dB Cross Polarization Discrimination (XPD) and a 10m ground station with 39dB/K of G/T and >37dB XPD for low-crosstalk polarization multiplexing. Since there are not real- time demodulator systems in such high communication speed, the downlinked signals are stored in a data recorder at an antenna site. Afterwards, we decode downlinked signals by using our non-real-time software demodulator. The system was demonstrated in orbit the RAPid Innovative payload demonstration Satellite (RAPIS-1) of JAXA in 2019. We have achieved 2.65 Gbps and 3.3Gbps communication speed in the X-band for LEO satellite at 300 M symbols per second (Msps) and polarization multiplexing of 64APSK (coding rate 4/5) and 256APSK (coding rate 3/4) following DVB-S2X protocol with roll-off factor α=0.05. The communication speeds correspond to of frequency efficiency 8.4 bit/s/Hz and 10.8 bit/s/Hz of frequency utilization efficiency. As far as authors know, these direct downlink communication speeds and frequency utilization efficiencies are the highest ones at present in LEO satellites, excluding bent-pipe communication systems.

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Aug 1st, 12:00 AM

Demonstration of 2.65 / 3.3 Gbit per sec X Band Radiowave Down Link Communications from LEO Small Satellite

Utah State University, Logan, UT

This paper reports our new communication system and downlink demonstrations with a small satellite of 2.65 Gbps data rate with 64 APSK modulation and 3.3Gbps data rate with 256 APSK modulation by utilizing two circular polarization channels of X band. We have developed an on-board X-band transmitter, an on-board dual circularly polarized-wave antenna with 17dBi gain and >37dB Cross Polarization Discrimination (XPD) and a 10m ground station with 39dB/K of G/T and >37dB XPD for low-crosstalk polarization multiplexing. Since there are not real- time demodulator systems in such high communication speed, the downlinked signals are stored in a data recorder at an antenna site. Afterwards, we decode downlinked signals by using our non-real-time software demodulator. The system was demonstrated in orbit the RAPid Innovative payload demonstration Satellite (RAPIS-1) of JAXA in 2019. We have achieved 2.65 Gbps and 3.3Gbps communication speed in the X-band for LEO satellite at 300 M symbols per second (Msps) and polarization multiplexing of 64APSK (coding rate 4/5) and 256APSK (coding rate 3/4) following DVB-S2X protocol with roll-off factor α=0.05. The communication speeds correspond to of frequency efficiency 8.4 bit/s/Hz and 10.8 bit/s/Hz of frequency utilization efficiency. As far as authors know, these direct downlink communication speeds and frequency utilization efficiencies are the highest ones at present in LEO satellites, excluding bent-pipe communication systems.