EngeeComms.EVM
Measures the magnitude of the error vector (EVM) of the received signal.
| Library |
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| Block |
Description
To measure the EVM of the received signal, follow these steps:
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Create an object EngeeComms.EVM and set its properties.
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Call the object with arguments as if it were a function.
To learn more about how to work with system objects, see Engee System Objects.
Arguments
Input arguments
refSym — reference signal
+
scalar | vector | the matrix | three-dimensional array
Details
A reference signal specified as a scalar, vector, matrix, or three-dimensional array. If you specify this input, the system object will measure the EVM of this rxSym using this entrance as a signal constellation.
The dimensions of this entrance must match the dimensions of the entrance rxSym. The system object uses each element of this input as a reference symbol for the corresponding input element. rxSym.
This object accepts inputs of variable size. After locking the object, you can change the size of each input channel, but you cannot change the number of channels.
| Типы данных |
|
| Support for complex numbers |
Yes |
rxSym — received signal
+
scalar | vector | the matrix | three-dimensional array
Details
The received signal is specified as a scalar, vector, matrix, or three-dimensional array.
| Типы данных |
|
| Support for complex numbers |
Yes |
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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where
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;
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represents the in-phase measurement of the kth symbol in the packet;
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represents the measurement of the quadrature phase of the kth symbol in the packet;
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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 they represent ideal (reference) values. and represent the measured (received) symbols.
The maximum EVM is the maximum EVM value in a frame, or , where — this is the kth 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 |
|
The implementation calculates -percentile EVM, creating a histogram of incoming values . This output provides the EVM value, below which the EVM values.