How do user terminal antennas track high-speed moving satellites?

Okay, it's not as mysterious as it sounds; I'll give you a few analogies to make it clear.

You probably had one of those "big dishes" for watching TV at home, right? That dish had to be pointed at a fixed satellite in the sky; move it even a little, and the signal was gone. That kind of satellite is called a "geostationary satellite"; it moves in sync with the Earth's rotation, so it appears motionless in the sky.

But satellite internet systems like Starlink use "Low Earth Orbit (LEO) satellites." They are closer to Earth, resulting in lower signal latency, but at a cost: they move incredibly fast! They're like a swarm of bees buzzing over your head, not a fixed light bulb. Their speed is about 7.8 kilometers per second, meaning they can cross the sky from one horizon to the other in just over ten minutes.

If you tried to use that old-fashioned dish, even with a strong person shaking it hard, they couldn't keep up with that speed. So, the user terminal (that flat antenna that looks like a pizza box) uses a much smarter technology.

The Core Magic: Phased Array Antenna

The name sounds intimidating, but the principle is simple. Don't think of it as a "dish" or a "big eye"; imagine it as an array composed of hundreds or even thousands of "mini-antennas" or "small eyes."

Analogy: The Stadium Wave

• Traditional Antenna: It's like a single person in a stadium. If they want to watch the game in different directions, they have to keep turning their head. Turning takes time and effort.
• Phased Array Antenna: Now, imagine the entire stands are filled with people (hundreds or thousands of antenna elements). They don't need to turn their heads, or even stand up. Everyone just needs to "raise their hand" in a specific rhythm and sequence to create what looks like a moving "wave." The direction of this "wave" is the direction of the signal transmission or reception.

(A simple diagram of the phased array principle)

This "raising hands" action, in the antenna, means adjusting the "phase" (which can be understood as a tiny time delay) of the signal emitted by each small element. By precisely controlling these delays with a computer, the synthesized signal beam can be pointed to any position in the sky. This pointing process is entirely electronic, completed instantly, with no mechanical parts moving.

Three Steps to Satellite Tracking

With the "magic" explained above, the tracking process is easy to understand.

1. Get the "Satellite Schedule" When your terminal powers on, it first downloads "ephemeris data" from the satellite network, which is like a detailed train timetable. It clearly knows which satellite will be coming from which direction and going to which direction in the next few minutes.

2. Electronic Beam "Aiming" and "Tracking" As soon as the antenna "calculates" that a satellite is about to enter its service area, it instantly forms a highly focused signal beam using the "wave" method mentioned earlier, "zapping" it directly at that satellite. As the satellite moves rapidly across the sky, the computer in the antenna continuously adjusts the delays of those "mini-antennas," allowing this beam to steadily follow the satellite like a spotlight. All of this is electronically controlled, silent, and without any wear and tear.

3. Seamless "Handover" This is the most crucial step. As a satellite is about to fly out of range, the antenna doesn't wait for the signal to drop before searching for the next one. Based on that "schedule," it has already "seen" where the next relay satellite is. In the fraction of a second before disconnecting from the current satellite, it simultaneously establishes a connection with the next satellite. This process is called "make-before-break," just like a track and field relay race: the next team member has already started running and received the baton before the previous one lets go. This ensures your network experiences virtually no interruption.

In Summary

So, the user terminal tracks high-speed satellites not by "dumb" mechanical rotation, but by "smart" electronic scanning.

• One Core Technology: The phased array antenna, using thousands of small elements working in concert, replaces bulky mechanical rotation.
• One Smart Brain: The built-in computer, armed with the "satellite schedule," precisely calculates and controls the direction of the signal beam.
• One Seamless Process: It "straddles two boats" before a satellite flies away, ensuring the network connection doesn't drop.

The entire process is like using your eyes to watch planes in the sky, but your eyeballs don't need to move. Instead, through some magical means, your gaze instantly shifts focus from one plane to another, quickly and steadily.