modnorm
Scaling factor for normalizing modulation output
Description
returns
a scale factor for normalizing a PAM or QAM modulator output using
the specified reference constellation, normalization type, and output
power.normfactor
= modnorm(refconst
,type
,power
)
Examples
Normalize Power of QAM Signal
Generate a 16-QAM reference constellation.
refconst = qammod(0:15,16);
Generate random symbols and apply 16-QAM modulation.
x = randi([0 15],1000,1); y = qammod(x,16);
Plot the constellation.
h = scatterplot(y);
Compute the normalization factor so that the output signal has a peak power of 1 W.
nf = modnorm(refconst,'peakpow',1);
z = nf*y;
Confirm that no element of the normalized signal has a power greater than 1 W.
max(z.*conj(z))
ans = 1.0000
Add the normalized constellation to the scatter plot.
hold on scatterplot(z,1,0,'ro',h) hold off
Input Arguments
refconst
— Reference constellation
vector
Reference constellation, specified as a vector of complex elements that comprise the reference constellation points.
Example: qammod(0:15,16)
Data Types: double
Complex Number Support: Yes
type
— Normalization type
'avpow'
| 'peakpow'
Normalization type, specified as either 'avpow'
or 'peakpow'
.
If
type
is'avpow'
, the normalization factor is calculated based on average power.If
type
is'peakpow'
, the normalization factor is calculated based on peak power.
Data Types: char
power
— Target power
scalar
Target power, specified as a real scalar. The target power is
the intended power of the modulated signal multiplied by normfactor
.
Data Types: double
Output Arguments
normfactor
— Normalization factor
scalar
Normalization factor, returned as a real scalar. When a modulated signal is multiplied by the normalization factor, its average or peak power matches the target power. The function assumes that the signal you want to normalize has a minimum distance of 2.
Version History
Introduced before R2006a
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