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Calculate or plot ideal signal constellation
symbols = constellation(obj)
constellation(obj)
symbols = constellation(obj) returns the numerical values of the constellation.
symbols
obj
example
constellation(obj) generates a constellation plot for the object.
Note
For OQPSK, the constellation that displays does not depict the IQ delay introduced by the OQPSK modulator.
collapse all
Create a QPSK modulator.
mod = comm.QPSKModulator;
Determine the reference constellation points.
refC = constellation(mod)
refC = 4×1 complex 0.7071 + 0.7071i -0.7071 + 0.7071i -0.7071 - 0.7071i 0.7071 - 0.7071i
Plot the constellation.
constellation(mod)
Reconfigure the object for bit input and plot the constellation to show the binary values of the Gray-encoded mapping.
release(mod) mod.BitInput = true; constellation(mod)
Create a QPSK demodulator having phase offset set to 0.
0
demod = comm.QPSKDemodulator(0);
Plot the reference constellation. The constellation method works for both modulator and demodulator objects.
constellation
constellation(demod)
Create a PSK modulator.
mod = comm.PSKModulator;
refC = 8×1 complex 0.9239 + 0.3827i 0.3827 + 0.9239i -0.3827 + 0.9239i -0.9239 + 0.3827i -0.9239 - 0.3827i -0.3827 - 0.9239i 0.3827 - 0.9239i 0.9239 - 0.3827i
Create a PSK demodulator having modulation order 16.
demod = comm.PSKDemodulator(16);
Plot its reference constellation. The constellation method works for both modulator and demodulator objects.
Create a BPSK modulator.
mod = comm.BPSKModulator;
refC = 2×1 complex 1.0000 + 0.0000i -1.0000 + 0.0000i
Create a BPSK demodulator having phase offset set to π2.
demod = comm.BPSKDemodulator(pi/2);
refC = constellation(demod)
refC = 2×1 complex 0.0000 + 1.0000i -0.0000 - 1.0000i
Create a OQPSK modulator.
mod = comm.OQPSKModulator;
Determine the reference constellation points. The constellation that displays does not depict the IQ delay introduced by the OQPSK modulator.
Change the phase offset for the modulated symbols. Plot the constellation to show the rotated constellation points.
release(mod) mod.PhaseOffset = 45*pi/180; constellation(mod)
Create comm.PAMModulator and comm.PAMDemodulator System objects, and then calculate their ideal signal constellations.
comm.PAMModulator
comm.PAMDemodulator
Create modulator and demodulator objects.
mod = comm.PAMModulator; demod = comm.PAMModulator;
Calculate the constellation points.
refMod = constellation(mod)
refMod = 4×1 -3 -1 1 3
refDemod = constellation(demod)
refDemod = 4×1 -3 -1 1 3
Verify that both objects produce the same points.
isequal(refMod,refDemod)
ans = logical 1
Display the ideal signal constellation.
System object to return constellation for, specified as a modulator System object.
Data Types: object
object
Constellation points, returned as a complex vector.
Data Types: double | single Complex Number Support: Yes
double
single
Introduced in R2012a
comm.BPSKModulator
comm.BPSKDemodulator
comm.PSKModulator
comm.PSKDemodulator
comm.QPSKModulator
comm.QPSKDemodulator
comm.OQPSKModulator
comm.OQPSKDemodulator
comm.gpu.PSKModulator
comm.gpu.PSKDemodulator
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