Error vector magnitude (EVM) and linearity in next-gen earth observation ground stations

As Earth-observation missions push to higher data-rates and wider bandwidths, ground-station receive chains are being driven closer to their linearity limits. Our updated measurements of LNB Error Vector Magnitude (EVM) show a clear trend: modern high-throughput downlinks demand significantly better linearity than many commercial LNBs were designed to deliver.

How linearity specs impact error vector magnitude (P1dB & OIP3)

Real downlinks rarely sit in the low-power, “easy” part of the curve. As the carrier level increases – whether due to larger antennas, higher-gain RF front ends, or stronger satellite EIRP – the LNB begins to compress.

• P1dB defines where the device’s gain starts to fall off.
• OIP3 predicts how quickly intermodulation distortion rises with input power.

Our new EVM data shows that if you are operating near the upper end of these curves, you need an LNB with a correspondingly higher OIP3 to preserve demodulation margin and avoid BER degradation.

How commercial LNBs compare

Typical off-the-shelf LNBs often provide OIP3 performance sufficient for broadcast or general satcom use, but Earth-observation downlinks push these limits much harder, especially with wideband QPSK/8PSK/16APSK signals.

What this means for ground stations

If you are using a large reflector (e.g., 7–13 m) or receiving high-power Earth-observation missions, the input level at the LNB can be high enough that traditional LNBs introduce measurable distortion. The result is a direct, observable increase in BER.

Interested in the full technical results?

We have released Version 2.0 of our technical paper, now including updated LNB EVM measurements performed on our own X-band LNB.

CLICK HERE for a copy of the full EVM academic paper.

CONTACT US Our engineering team can help evaluate whether your existing LNB is limiting your system sensitivity and what linearity level is required for your mission profile.