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Modulate using BPSK method


The comm.BPSKModulator object modulates using the binary phase shift keying method. The output is a baseband representation of the modulated signal. The input signal must be a discrete-time binary-valued signal. If the input bit is 0 or 1, then the modulated symbol is exp(jθ) or -exp(jθ), respectively. The PhaseOffset property specifies the value of θ in radians.

To modulate a signal using BPSK method:

  1. Create the comm.BPSKModulator object and set its properties.






bpskmodulator = comm.BPSKModulator creates a modulator System object™ to modulate input signals using the binary phase shift keying (BPSK) method.

bpskmodulator = comm.BPSKModulator(Name,Value) creates a BPSK modulator object with each specified property set to the specified value. You can specify additional name-value pair arguments in any order as (Name1,Value1,...,NameN,ValueN).

bpskmodulator = comm.BPSKModulator(phase,Name,Value) creates a BPSK modulator object with the PhaseOffset property set to phase, and the other specified properties set to the specified values.


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Phase of zeroth point of the constellation in radians, specified as a scalar.

Data Types: double

Output datatype, specified as 'double', 'single' or 'Custom'.

Data Types: char

Fixed-Point Properties

Fixed-point data type of the output, specified as a numerictype (Fixed-Point Designer) object with a signedness of Auto.


This property applies when you set the OutputDataType property to 'Custom'.




waveform = bpskmodulator(data) applies BPSK modulation to the input data and returns the modulated BPSK baseband signal.

Input Arguments

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Input signal data, specified as a column vector or matrix.

Data Types: double

Output Arguments

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BPSK modulated baseband signal, returned as a column vector or matrix of the same size as the input signal. For more information about the output datatype, see the OutputDataType property.

Data Types: double | single | fi
Complex Number Support: Yes

Object Functions



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constellationCalculate or plot ideal signal constellation
stepRun System object algorithm
resetReset internal states of System object


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This example creates binary data, modulates it, and then displays the data using a scatter plot.

Create binary data symbols.

data = randi([0 1],100,1);

Create a BPSK modulator System object.

bpskModulator = comm.BPSKModulator;

Change the phase offset to pi/16.

bpskModulator.PhaseOffset = pi/16;

Modulate and plot the data.

modData = bpskModulator(data);

Figure Scatter Plot contains an axes object. The axes object with title Scatter plot contains an object of type line. This object represents Channel 1.


Phase modulation is a linear baseband modulation technique in which the message modulates the phase of a constant amplitude signal. Binary Phase Shift Keying (BPSK) is a two phase modulation scheme, where the 0’s and 1’s in a binary message are represented by two different phase states in the carrier signal


for (n1)TbtnTb, n=1,2, 3,where:

  • ϕn = πm, m∈{0,1}.

  • Eb is the energy per bit.

  • Tb is the bit duration.

  • fc is the carrier frequency.

In MATLAB®, the baseband representation of a BPSK signal is


The BPSK signal has two phases: 0 and π. The probability of a bit error in an AWGN channel is


where N0 is the noise power spectral density.

Extended Capabilities

Version History

Introduced in R2012a