How does a 5G antenna steer a beam without physically turning?

5G NR
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By controlling the phase of the signals across its antenna elements.
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This animation visualizes the principle using an eight-element array. Watch the beam direction, feed signals, phase weights, and radiation pattern change together.
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◆ What to watch in the video
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● Equal phase → broadside beam
When all elements transmit with equal phase, their signals reinforce one another straight ahead, perpendicular to the array.
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● Progressive phase → electronic steering
A phase step between neighboring elements shifts the direction in which the signals combine constructively.
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● Updated weights → a moving beam
As the user changes direction, updating the phase weights steers the beam toward the new angle.
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● Sidelobes remain
The radiation pattern shows a dominant main lobe and smaller sidelobes. Beamforming does not eliminate radiation in every other direction.
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◆ A useful numerical example
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With half-wavelength element spacing, steering to 30° requires a 90° phase-step magnitude between adjacent elements.
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The animation uses an ideal, uniformly excited array with perfect tracking. It illustrates the underlying principle; it is not a measurement of commercial 5G equipment.
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The key idea: coordinated phase controls where the signals reinforce each other.

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One useful addition for the field-testing side: the SSB beam and the PDSCH traffic beam don’t have to be the same. So an SS-RSRP change alone won’t tell us whether the data beam improved. I’d keep the measurement reference explicit, then compare it with PDSCH performance during active traffic. Otherwise, we can end up judging user-specific beamforming from a broadcast-signal measurement. Showing those two beam patterns side by side would make a useful follow-up to this example.