comm.DBPSKModulator

R2026b

Modulate using DBPSK method

Description

The comm.DBPSKModulator System object™ modulates a signal using the differential binary phase shift keying (DBPSK) method. The output is a baseband representation of the modulated signal.

To modulate a signal using the DBPSK method:

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

2. Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects?

Creation

Syntax

dbpskmod = comm.DBPSKModulator

dbpskmod = comm.DBPSKModulator(phase)

dbpskmod = comm.DBPSKModulator(___,Name=Value)

Description

dbpskmod = comm.DBPSKModulator creates a modulator System object, dbpskmod. This object modulates the input signal using the DBPSK method.

dbpskmod = comm.DBPSKModulator(phase) additionally sets the PhaseRotation property to phase.

dbpskmod = comm.DBPSKModulator(___,Name=Value) creates a DBPSK modulator object using any of the previous syntaxes and sets properties using one or more name-value arguments. For example, OutputDataType="double" sets the data type of output to "double".

Properties

Unless otherwise indicated, properties are nontunable, which means you cannot change their values after calling the object. Objects lock when you call them, and the release function unlocks them.

If a property is tunable, you can change its value at any time.

For more information on changing property values, see System Design in MATLAB Using System Objects.

PhaseRotation — Additional phase shift

0 (default) | scalar

Additional phase shift in radians, specified as a scalar. This value corresponds to the phase difference between previous and current modulated bits when the input is zero.

Data Types: double

OutputDataType — Data type of output

"double" (default) | "single"

Data type of output, specified as "double" or "single".

Usage

Syntax

Y = dbpskmod(X)

Description

Y = dbpskmod(X) applies DBPSK modulation to the input data, X, and returns the DBPSK-modulated baseband signal, Y.

Input Arguments

X — Input data

scalar | column vector

Input data, specified as a scalar or column vector of bits.

Data Types: double | logical

Output Arguments

Y — Output data

scalar | column vector

Output data, returned as a scalar or column vector. The data type of the output data depends on the OutputDataType property.

Data Types: double | single

Object Functions

To use an object function, specify the System object as the first input argument. For example, to release system resources of a System object named obj, use this syntax:

release(obj)

Common to All System Objects

step	Run System object algorithm
release	Release resources and allow changes to System object property values and input characteristics
reset	Reset internal states of System object

Examples

DBPSK Signal in AWGN

Create a DBPSK modulator and demodulator pair.

dbpskmod = comm.DBPSKModulator(pi/4);
dbpskdemod = comm.DBPSKDemodulator(pi/4);

Create an error rate calculator. Set the ComputationDelay property to 1 to account for the one bit transient caused by the differential modulation.

errorRate = comm.ErrorRate('ComputationDelay',1);

Process the signal. The process includes these steps:

1. Generate 50-bit frames.

2. DBPSK-modulate the signal.

3. Pass the modulated signal through an AWGN channel.

4. DBPSK-demodulate the noisy signal.

5. Collect error statistics.

for counter = 1:100
    txData = randi([0 1],50,1);
    modSig = dbpskmod(txData);
    rxSig = awgn(modSig,7);
    rxData = dbpskdemod(rxSig);
    errorStats = errorRate(txData,rxData);
end

Display the error statistics.

ber = errorStats(1)

ber = 
0.0034

numErrors = errorStats(2)

numErrors = 
17

numBits = errorStats(3)

numBits = 
4999

Algorithms

For a phase rotation of ϕ radians, the DBPSK modulation method follows these rules:

• If the first input bit is 0 or 1, respectively, then the first modulated symbol is e^(jϕ) or –e^(jϕ), respectively.

• If a successive input bit is 0 or 1, respectively, then the modulated symbol is the previous modulated symbol multiplied by e^(jϕ) or –e^(jϕ), respectively.

ϕ is the PhaseRotation property value.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

See System Objects in MATLAB Code Generation (MATLAB Coder).

GPU Code Generation

Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Refer to the usage notes and limitations in the C/C++ Code Generation section. The same usage notes and limitations apply to GPU code generation.

Version History

Introduced in R2012a