Field Guide · technology

Also known as: Starlink

Starlink is SpaceX’s satellite-internet system: a mega-constellation of thousands of low-earth-orbit satellites at around 550 km, paired with a flat user terminal that connects homes and vehicles to broadband. Its defining piece of RF engineering is that terminal — an electronically steered phased-array antenna that tracks fast-moving satellites across the sky with no moving parts, forming and re-pointing its beam purely by adjusting the phase of hundreds of antenna elements.1

flat phased-array terminal (no moving parts) LEO satellites crossing overhead (~550 km)
The Starlink terminal is a phased array: it steers and hands off its beam electronically as satellites sweep across the sky in minutes.

How it works

A satellite at 550 km is only in view for a few minutes and moves fast across the sky, so a fixed dish would need constant mechanical aiming. Starlink instead uses a phased array: many small radiating elements whose signals are combined with controlled phase offsets. By stepping those phases, the array synthesises a beam pointed in any direction and slews it electronically — the essence of beamforming — then hands off from one satellite to the next without ever moving.2 The links run in the microwave Ku and Ka bands (roughly 10.7–12.7 GHz user downlink, ~14 GHz and higher for uplink), using wide channels and a high-order OFDM-style waveform to pack in gigabit-class capacity. Later satellites add laser inter-satellite links so traffic can hop between spacecraft without a ground station under every satellite.

The user terminal also has to cope with a large, continuously changing Doppler shift as the satellite races overhead, and with the free-space path loss of a microwave link over hundreds of kilometres — hence the array’s high gain and an integrated low-noise amplifier front end.

Relevance to SDR

Starlink is not a hobbyist decode target: the user data is encrypted and the waveform is proprietary, so there is no open payload to demodulate the way there is for Orbcomm or the NOAA APT weather birds. What Starlink is useful for is as the highest-profile real-world example of an electronically steered phased array in consumer hands — the same beamforming principle behind military radar, 5G base stations, and direction-finding receivers. Researchers have also exploited Starlink’s synchronisation and beacon sequences as an opportunistic positioning signal, demonstrating GPS-independent navigation from the constellation’s downlink structure.

GopherTrunk is a terrestrial land-mobile trunking receiver and does nothing with Starlink; the entry sits in this guide to connect the phased-array and beamforming articles to a system readers will recognise. GopherTrunk is a pure receiver with no phased-array hardware, so it does not beamform — it relates to these concepts only as background RF theory.

Sources

  1. Starlink — Wikipedia, for the constellation, orbit, Ku/Ka-band links, and the phased-array user terminal. ↩

  2. Phased array — Wikipedia, for how phase control across elements steers a beam electronically. ↩

See also