Doppler Analysis for the S-AIS Receiver for the Indonesian LEO Constellation

The S-AIS (Space-based Automatic Identification System) receiver is one of the payloads to be carried by the NEI (Nusantara Equatorial Internet of Things) project for the maritime monitoring mission. The project will ensure sustainable maritime monitoring in Indonesia. The performance of the developed S-AIS receiver needs to be well characterized, in particular Doppler shift that occurs due to satellite motion in orbit. Calculation of Doppler shift is carried out to obtain minimum requirements that the developed S-AIS receiver must achieve. This value needs to be verified by testing the device through different scenarios. The test was carried out in the laboratory. The device was connected with a cable to an AIS transmitter. This test configuration is conducted to reduce interference so that it is obtained accurate results. Based on the calculations, the required Doppler shift value is around 3.7 kHz, while the performance of the S-AIS Receiver can receive AIS data with a Doppler shift value of up to ±5 kHz. The developed S-AIS RX can still detect AIS signals down to ±10 kHz of the fundamental frequency.