EVM Measurement
Measures the magnitude of the error vector (EVM).
blockType: EVM
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Path in the library: |
Description
Block EVM Measurement measures the RMS EVM value, the maximum EVM value, and the EVM percentile of the received signal. The EVM is an indicator of the performance of a modulator or demodulator.
Ports
Input
#
Ref
—
the reference signal
array
Details
A reference signal in the form of an array of up to three dimensions. If you specify this input, the object measures the EVM of the Rcv input using this input as a reference constellation.
The dimensions of this input must match the dimensions of the Rcv input. The object uses each element of this input as a reference character for the corresponding input element Rcv.
| Data types |
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| Complex numbers support |
No |
#
Rcv
—
the received signal
array
Details
The received signal is in the form of an array of up to three dimensions.
| Data types |
|
| Complex numbers support |
No |
Output
#
RMS
—
The RMS EVM value as a percentage
scalar
Details
The RMS EVM value as a percentage of the configured measurement interval, returned as a scalar.
| Data types |
|
| Complex numbers support |
No |
Algorithms
The implementation supports three normalization methods. You can normalize the measurements according to the average power of the reference signal, the average power of the aggregate, or the peak power of the aggregate. Various industry standards follow one of these normalization methods.
The algorithm calculates the RMS EVM value differently for each normalization method.
| EVM normalization method | Algorithm |
|---|---|
The reference signal |
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Average power |
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Peak power |
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In these equations:
-
;
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— common-mode measurement -th character in the package;
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— measurement of the quadrature phase -th character in the package;
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— length of the input vector;
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— the average power of the constellation;
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— constellation’s peak power;
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and — ideal (reference) values;
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and — measured (received) symbols.
The maximum EVM is the maximum EVM value in a frame, or ,where — This is -th character in the length packet .
Definition it depends on which normalization method you choose to calculate the measurements. The implementation supports these algorithms.
| EVM normalization method | Algorithm |
|---|---|
The reference signal |
|
Average power |
|
Peak power |
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The implementation calculates -percentile EVM, creating a histogram of incoming values . This output provides the EVM value, below which the EVM values.