Modulation error ratio

Modulation error ratio

The modulation error ratio or MER is a measure used to quantify the performance of a digital radio 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 specialised 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 of the error vector to the power of the reference. It is defined in dB as:

\mathrm{MER (dB)} = 10 \log_{10} \left ( {P_\mathrm{signal} \over P_\mathrm{error}} \right )

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:

\mathrm{MER (%)} = \sqrt{ {P_\mathrm{error} \over P_\mathrm{signal}} } * 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

References

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

Wikimedia Foundation. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • Bit Error Ratio — Taux d erreur Le taux d erreur ou B.E.R., abréviation de l expression anglaise Bit Error Rate, désigne une valeur relative au taux d erreur mesuré à la réception d une transmission numérique, relative au niveau d atténuation et/ou de perturbation …   Wikipédia en Français

  • Bit error ratio — Taux d erreur Le taux d erreur ou B.E.R., abréviation de l expression anglaise Bit Error Rate, désigne une valeur relative au taux d erreur mesuré à la réception d une transmission numérique, relative au niveau d atténuation et/ou de perturbation …   Wikipédia en Français

  • Error vector magnitude — The error vector magnitude or EVM is a measure used to quantify the performance of a digital radio transmitter or receiver. A signal sent by an ideal transmitter or received by a receiver would have all constellation points precisely at the ideal …   Wikipedia

  • Signal-to-noise ratio — For signal to noise ratio in statistics, see Cohen s d. Signal to noise ratio (often abbreviated SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined… …   Wikipedia

  • Contrast-to-noise ratio — Haze over Kuala Lumpur. Contrast to noise ratio (CNR) is a measure used to determine image quality. CNR is similar to the metric, signal to noise ratio (SNR), but subtracts off a term before taking the ratio. This is important when there is a… …   Wikipedia

  • Delta-sigma modulation — Delta sigma (ΔΣ; or sigma delta, ΣΔ) modulation is a method for encoding high resolution or analog signals into lower resolution digital signals. The conversion is done using error feedback, where the difference between the two signals is… …   Wikipedia

  • Delta modulation — Principle of the delta PWM. The output signal (blue) is compared with the limits (green). These limits correspond to the reference signal (red), offset by a given value. Every time the output signal reaches one of the limits, the PWM signal… …   Wikipedia

  • Pulse-code modulation — PCM redirects here. For other uses, see PCM (disambiguation). Pulse code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form for digital audio in computers and various Blu ray, Compact Disc and …   Wikipedia

  • Pulse-width modulation — (PWM) of a signal or power source involves the modulation of its duty cycle, to either convey information over a communications channel or control the amount of power sent to a load. PrinciplePulse width modulation uses a square wave whose pulse… …   Wikipedia

  • Forward error correction — In telecommunication, information theory, and coding theory, forward error correction (FEC) or channel coding[1] is a technique used for controlling errors in data transmission over unreliable or noisy communication channels. The central idea is… …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”