DPSK Modulation-Demodulation Compatibility Considerations

Replace all instances of modem.dpskmod and modem.dpskdemod with comm.DPSKModulator and comm.DPSKDemodulator.

  • User-defined symbol mapping is not supported.

  • The comm.DPSKModulator System object™ does not support initial phase specification. However, this code sample shows you how to specify initial phase for DPSK-modulated signals: 

    %% Initial Phase
x = randi([0,7],10,1); 
phRot = pi/8;
initPh = pi/4;

%% Using modem.dpskmod modulate the signal
m = modem.dpskmod('M',8,'PhaseRotation',phRot,'InitialPhase',initPh);
ym = modulate(m, x);

%% Using comm.DPSKModulator modulate the signal
s = comm.DPSKModulator('PhaseRotation',phRot,'SymbolMapping','Binary');
ys = s(x);
ys1 = ys .* exp(1i * initPh);

%% Compare results
err = max(abs(ys1 - ym))

    err =

   2.6390e-15

  • This code sample shows you how to simulate multichannel input/output for DPSK-modulated signals: 

    %% Multichannel input/output
x = randi([0,7],10,3);
phRot = pi/8;

%% Using modem.dpskmod modulate the signal
m = modem.dpskmod('M',8,'PhaseRotation',phRot);
ym1 = m.modulate(x);
% Process one more frame to verify interframe state handling
ym2 = m.modulate(x);

%% Using comm.DPSKModulator modulate the signal
% Create as many System objects as number of channels
s1 = comm.DPSKModulator('PhaseRotation',phRot,'SymbolMapping','Binary');
s2 = comm.DPSKModulator('PhaseRotation',phRot,'SymbolMapping','Binary');
s3 = comm.DPSKModulator('PhaseRotation',phRot,'SymbolMapping','Binary');

ys1 = complex(zeros(size(x),'like',x));
ys2 = ys1;

% Process first frame
% Process each channel by its specific System object
ys1(:,1) = s1(x(:,1)); 
ys1(:,2) = s2(x(:,2)); 
ys1(:,3) = s3(x(:,3)); 

% Process second frame
ys2(:,1) = s1(x(:,1)); 
ys2(:,2) = s2(x(:,2)); 
ys2(:,3) = s3(x(:,3)); 

%% Compare results
err1 = (max(abs(ys1(:) - ym1(:))))
err2 = (max(abs(ys2(:) - ym2(:))))


    err1 =

   2.0411e-15

err2 =

   2.4431e-15