Low-Earth-orbit (LEO) satellite constellations are becoming increasingly important for non-terrestrial communication networks, including emerging direct-to-cell services. These systems create new opportunities for extending connectivity, but they also introduce challenges for reliable satellite downlink observation, including weak received signal strength, Doppler shift and limited capture windows caused by rapid satellite motion.
This project has established a low-cost, SDR-based satellite downlink testbed for receiving, tracking, and analyzing Ku-band signals from LEO constellations. The system consists of an LNB-based RF capture front end (Fig. 2) and acquisition/processing software for structured measurement of LEO satellite downlink activity. Satellite identification is performed by matching time-frequency representations of the measured signals against TLE-predicted Doppler S-curves. Building on this foundation, ongoing work focuses on automating the measurement pipeline, validating satellite-identification algorithms across additional datasets, and extending the system toward real-time monitoring.
In the longer term, the project will support real-time satellite identification and multi-antenna beamforming for direct-to-cell communication scenarios, enabling improved received signal strength and more robust satellite-to-device links.
Figure 1. System Block Diagram
Figure 2. Monitoring System Hardware Setup Figure 3. TLE-Based Doppler S-Curve Predictor
Figure 4. Measured Waterfall Spectrogram Figure 5. Satellite Identification via Doppler S-Curve Matching
