commmeasure.EVM - Create EVM measurement object

Syntax

h = commmeasure.EVM h = commmeasure.EVM('PropertyName',PropertyValue,...)

Description

h = commmeasure.EVM constructs a default error vector magnitude (EVM) object, h.

h = commmeasure.EVM('PropertyName',PropertyValue,...) constructs an EVM object, h, with property values set to PropertyValues. See Properties for valid a list of valid PropertyNames.

The EVM object measures RMS EVM, maximum EVM, and percentile EVM. The unit for each measurement is a percentage.

Properties

An EVM measurement object has the properties shown in the following table. You can write to all properties except for the ones explicitly noted otherwise.

Property	Description
Type	'EVM Measurements'. This property is read only.
NormalizationOption	Specify EVM normalization method. Possible values are: 'AveragePower', 'PeakPower', and 'RMSEVM'.
AveragePower	Average constellation power. Relevant when NormalizationOption is 'Average constellation power'.
PeakPower	Peak constellation power. Relevant when NormalizationOption is 'Peak constellation power'.
RMSEVM	RMS EVM measurement result. Relevant when NormalizationOption is 'RMSEVM'. This property is read only.
MaximumEVM	Maximum EVM measurement result. This property is read only.
Percentile	Percentile value to calculate PercentileEVM.
PercentileEVM	Percentile EVM measurement result. This property is read only.
NumberOfSymbols	Number of processed symbols.

Methods

An EVM measurement object has the following three methods.

update

This method updates the EVM measurements with new data.

update(h, rcv, xmt) updates the EVM object h with new data. rcv represents the symbols under test, and mxt represents the ideal symbols.

reset

This method resets the EVM object.

reset(h) resets the EVM object h. This operation removes all the previously collected data from the object memory.

reset(h, meas1, ...) resets the meas1 measurement of the EVM object h. meas1 can be 'RMSEVM', 'MaximumEVM', or 'PercentileEVM'. The NumberOfSymbols property is not reset. You can use this method for implementing frame-based measurements.

copy

This method copies the EVM object.

hcopy = copy(h) copies the EVM object handle returns it in hcopy. h and hcopy are independent but identical objects; modifying the object does not affect hcopy object.

Algorithm for EVM Calculations

The Communications Toolbox™ software provides three different normalization methods. You can normalize measurements according to the average power of the reference signal, average constellation power, or peak constellation power. Different industry standards follow one of these normalization methods.

The following table lists how the Communications Toolbox software calculates the RMS EVM value for different normalization methods.

EVM Normalization Method	Algorithm
Reference Signal
Average Power
Peak Power

where,

e_k =

I_k = In-phase ideal reference value of the kth symbol in the burst

Q_k = Quadrature phase ideal reference value of the kth symbol in the burst

N = Input vector length

P_avg = The value for Average constellation power

I_k and Q_k represent ideal (reference) values. and represent measured (received) symbols.

EVM _max is the maximum EVM value, of individual symbols, EVM_k, in a frame or

where k is the kth symbol in a burst of length N.

The definition for EVM_k varies depending upon which normalization method you select for computing measurements. The Communications Toolbox software supports the algorithms in the following table.

EVM Normalization	Algorithm
Reference Signal
Average Power
Peak Power

The toolbox calculation for % EVM uses a histogram of all the incoming EVMk values. The output provides the EVM value below which X% of the EVM values lay.