Error vector magnitude

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 locations, however various imperfections in the implementation (such as carrier leakage, low image rejection ratio, phase noise etc.) cause the actual constellation points to deviate from the ideal locations. Informally, EVM is a measure of how far the points are from the ideal locations.

Transmitter EVM can be measured by specialised equipment, which demodulates the received signal in a similar way to how a real radio demodulator does it. One of the stages in a typical phase-shift keying demodulation process produces a stream of I-Q points which can be used as a reasonably reliable estimate for the ideal transmitted signal in EVM 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. Its average length (or magnitude), defined as the Euclidean distance between the two points, is the EVM.

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

:mathrm{EVM (dB)} = 10 log_{10} left ( {P_mathrm{error} over P_mathrm{reference ight )

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

EVM is defined as a percentage in a compatible way:

:mathrm{EVM (%)} = sqrt{ {P_mathrm{error} over P_mathrm{reference } * 100%

with the same definitions.

EVM has been used also for modulation formats that use more complex constellation diagrams. It is closely related to the modulation error ratio (MER), but for EVM the power of the constellation point with the highest power is used as the reference power.

ee also

*Modulation error ratio
*Carrier to Noise Ratio
*Signal-to-noise ratio


Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • 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… …   Wikipedia

  • Constellation diagram — A constellation diagram is a representation of a signal modulated by a digital modulation scheme such as quadrature amplitude modulation or phase shift keying. It displays the signal as a two dimensional scatter diagram in the complex plane at… …   Wikipedia

  • EVM — can be an abbreviation for:* Earned value management * Economic value management; see economic value added * Electronic voltmeter; see voltmeter, a device to measure voltage * Electronic voting machine; see electronic voting * Error vector… …   Wikipedia

  • EVM — ist die Abkürzung für: Earned Value Analysis, eine Technik aus dem Bereich des Projektmanagements Energieversorgung Mittelrhein in Koblenz Energieversorgung Margarethen am Moos im Bezirk Bruck an der Leitha Error Vector Magnitude, ein Messwert… …   Deutsch Wikipedia

  • EVM — (homonymie) Cette page d’homonymie répertorie les différents sujets et articles partageant un même nom. Le sigle EVM peut signifier : Dans le domaine militaire, l Étoile de la vaillance militaire, une décoration militaire canadienne. En… …   Wikipédia en Français

  • EVM (homonymie) — Cette page d’homonymie répertorie les différents sujets et articles partageant un même nom. Le sigle EVM peut signifier : Dans le domaine militaire, l Étoile de la vaillance militaire, une décoration militaire canadienne. En signalisation… …   Wikipédia en Français

  • Euler method — In mathematics and computational science, the Euler method, named after Leonhard Euler, is a first order numerical procedure for solving ordinary differential equations (ODEs) with a given initial value. It is the most basic kind of explicit… …   Wikipedia

  • physical science, principles of — Introduction       the procedures and concepts employed by those who study the inorganic world.        physical science, like all the natural sciences, is concerned with describing and relating to one another those experiences of the surrounding… …   Universalium

  • mechanics — /meuh kan iks/, n. 1. (used with a sing. v.) the branch of physics that deals with the action of forces on bodies and with motion, comprised of kinetics, statics, and kinematics. 2. (used with a sing. v.) the theoretical and practical application …   Universalium

  • Errors-in-variables models — In statistics and econometrics, errors in variables models or measurement errors models are regression models that account for measurement errors in the independent variables. In contrast, standard regression models assume that those regressors… …   Wikipedia

Share the article and excerpts

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