Modulation Error Ratio

MER is a parameter that measures the phase shift error of the RF signal in the modulation and demodulation of the digital content.

Figure 3: Basic MER Vector Diagram

It is the sum of the squares of the magnitudes of the ideal symbols vectors and divided by the sum of the squares of the symbol error vectors. The result is expressed as a power ratio in dB.

When measuring digital signals the MER should be one of the main parameters to be measured. Terrestrial MER >32dB The reason for this measurement rather than measuring BER, is that BER can be influenced by the forward error correction method incorporated in the digital demodulator. While MER has the advantage that this measurement is before forward error correction, so it gives us a better idea of how the signal and hence how the installation is performing.

Poor MER affects the picture quality right from the beginning to complete failure.

  Return to Technical Information Table of Contents
  Previous: Signal Level
  Next: Bit Error Ratio (BER)