How anti-spoofing keeps a false constellation out of your fix
Spatial signatures give a counterfeit constellation away: real satellites arrive from everywhere, a spoofer arrives from one direction. That is the opening a DPA terminal uses.
What a spoofer actually does
A spoofer generates signals with the structure of real GNSS transmissions — correct codes, plausible ephemeris, consistent timing — but describing a position of its choosing. Because the counterfeit arrives far stronger than a genuine satellite signal from 20 000 km away, a conventional receiver prefers it.
The transition is usually smooth. The receiver does not report an error, because by its own logic nothing has gone wrong: it is tracking strong, well-formed signals and computing a valid solution from them.
The spatial signature gives it away
Every counterfeit satellite in a spoofed constellation comes from the same transmitter, so it arrives from the same direction with the same wavefront. A genuine constellation cannot do that — real satellites are spread across the sky, and their signals arrive from many directions at once.
This is the discriminator an array can use and a single-element antenna cannot. One patch antenna sees only a sum of everything arriving; it has no way to ask where any of it came from.
How the DPA models use it
Our dual-protection terminals — TX2501-AJS-4CH-DPA at four elements and TX2512-AJS-16CH-DPA at sixteen — run spoofing rejection alongside jamming suppression on the same aperture. Signals sharing a single spatial origin are attenuated as a group, in the same way a jammer's direction is nulled.
The specified result is residual spoofing signal C/N₀ held to ≤20 dB at the output: what reaches the receiver is too weak to outcompete genuine satellites for correlation. The navigation solution is computed from the real constellation because the false one never arrives with enough power to matter.
Where the limits are
Spatial rejection works because the spoofer occupies one direction. A sophisticated attack using several distributed transmitters presents more than one origin, and consumes degrees of freedom the same way multiple jammers do — which is a further argument for sixteen elements where the threat is serious.
It is also worth being clear about what this is not: it is suppression at the antenna, not authentication of the signal. It keeps a false constellation from reaching your navigation solution. It does not cryptographically prove that what did reach it is genuine.