Modulation error ratio

The modulation error ratio or MER is a measure used to quantify the performance of a digital radio (or digital TV) transmitter or receiver in a communications system using digital modulation (such as QAM). A signal sent by an ideal transmitter or received by a receiver would have all constellation points precisely at the ideal locations, however various imperfections in the implementation (such as noise, low image rejection ratio, phase noise, carrier suppression, distortion, etc.) or signal path cause the actual constellation points to deviate from the ideal locations. Transmitter MER can be measured by specialized equipment, which demodulates the received signal in a similar way to how a real radio demodulator does it. Demodulated and detected signal can be used as a reasonably reliable estimate for the ideal transmitted signal in MER calculation.

## Definition

An error vector is a vector in the I-Q plane between the ideal constellation point and the point received by the receiver. The Euclidean distance between the two points is its magnitude.

The modulation error ratio is equal to the ratio of the root mean square (RMS) power (in Watts) of the reference vector to the power (in Watts) of the error. It is defined in dB as:

MER(dB)=10log10(PsignalPerror)

where Perror is the RMS power of the error vector, and Psignal is the RMS power of ideal transmitted signal.

MER is defined as a percentage in a compatible (but reciprocal) way:

MER(%)=PerrorPsignal×100%

with the same definitions.

MER is closely related to error vector magnitude (EVM), but MER is calculated from the average power of the signal. MER is also closely related to signal-to-noise ratio. MER includes all imperfections including deterministic amplitude imbalance, quadrature error and distortion, while noise is random by nature.

## See also

* Error vector magnitude
* Carrier to Noise Ratio
* Signal-to-noise ratio

## References

* ETSI technical report ETR 290: "Measurement guidelines for DVB systems", Errata 1, May 1997

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Noise (physics and telecommunications)

General|

* Acoustic quieting
* Distortion
* Noise cancellation
* Noise control
* Noise measurement
* Noise power
* Noise reduction
* Noise temperature
* Phase distortion

Noise in...|

* Audio
* Buildings
* Electronics
* Environment
* Government regulation
* Human health
* Images
* Radio
* Rooms
* Ships
* Sound masking
* Transportation
* Video

Class of noise|

* Additive white Gaussian noise (AWGN)
* Atmospheric noise
* Background noise
* Brownian noise
* Burst noise
* Cosmic noise
* Flicker noise
* Gaussian noise
* Grey noise
* Jitter
* Johnson–Nyquist noise (thermal noise)
* Pink noise
* Quantization error (or q. noise)
* Shot noise
* White noise
* Coherent noise
* Value noise
* Gradient noise
* Worley noise

Engineering
terms|

* Channel noise level
* Circuit noise level
* Effective input noise temperature
* Equivalent noise resistance
* Equivalent pulse code modulation noise
* Impulse noise (audio)
* Noise figure
* Noise floor
* Noise shaping
* Noise spectral density
* Noise, vibration, and harshness (NVH)
* Phase noise
* Pseudorandom noise
* Statistical noise

Ratios|

* Carrier-to-noise ratio (C/N)
* Carrier-to-receiver noise density (C/kT)
* dBrnC
* Eb/N0 (energy per bit to noise density)
* Es/N0 (energy per symbol to noise density)
* Modulation error ratio (MER)
* Signal, noise and distortion (SINAD)
* Signal-to-interference ratio (S/I)
* Signal-to-noise ratio (S/N, SNR)
* Signal-to-noise ratio (imaging)
* Signal to noise plus interference (SNIR)
* Signal-to-quantization-noise ratio (SQNR)
* Contrast-to-noise ratio (CNR)

Related topics|

* List of noise topics
* Acoustics
* Colors of noise
* Interference (communication)
* Noise generator
* Radio noise source
* Spectrum analyzer
* Thermal radiation

Denoise
methods|

| General|

* Low-pass filter
* Median filter
* Total variation denoising
* Wavelet denoising

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2D (Image)|

* Gaussian blur
* Anisotropic diffusion
* Bilateral filter
* Non-local means
* Block-matching and 3D filtering (BM3D)
* Shrinkage Fields
* Denoising autoencoder (DAE)
* Deep Image Prior

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