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BPSK Modulator Baseband

Modulate signal by using BPSK method

  • Library:
  • Communications Toolbox / Modulation / Digital Baseband Modulation / PM

    Communications Toolbox HDL Support / Modulation / PM

  • BPSK Modulator Baseband block


The BPSK Modulator Baseband block modulates a signal by using the binary phase shift keying (BPSK) 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, where θ represents the Phase offset (rad) parameter.



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Input signal, specified as a scalar or vector.

  • If you specify a scalar, it must be an integer from 0 to M – 1, where M is the modulation order.

  • If you specify a vector, the elements must be either integers from 0 to M-1 or binary values. If you specify a binary vector, the number of elements must be an integer multiple of the number of bits per symbol. The number of bits per symbol is equal to log2(M).

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean


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BPSK-modulated baseband signal, returned as a complex scalar or vector of complex values.

Data Types: single | double | fixed point
Complex Number Support: Yes


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Specify a finite real-valued scalar for the phase of the zeroth point of the constellation in radians.

Example: pi/4

Data type of output,. Set this parameter to one of the fixed point options or <data type expression> to enable parameters in which you specify additional details. Set this parameter to Inherit via back propagation, to match the output data type and scaling to the following block in the model.

Block Characteristics

Data Types

Boolean | double | fixed point[a][b] | integer | single

Multidimensional Signals


Variable-Size Signals


[a] ufix(ceil(log2(M))) only at the input for M-ary modulation.

[b] Fixed-point outputs must be signed.


The BPSK Modulator Baseband block provides the capability to visualize a signal constellation from the block mask. This constellation visualization feature allows you to visualize a signal constellation for the specified block parameters. For more information, see Constellation Visualization.


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

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Introduced before R2006a