Constellation

Constellation – Block used in order to perform the constellation associated with a signal.

Figure: Diagram block


The input pins are :

  • Ref : equivalent Bits transmitted after coding.
  • In : output complex envelope to analyse

It is convenient to draw a graph of bq (t) against bp (t) for a modulated signal. This equates to an Argand diagram (representation of the imaginary part with respect to the real part) of the complex baseband signal b (t). The diagram will consist of points indicating the possible states of amplitude and phase of the signal. This is the constellation of the modulated signal. The constellation of the modulated signal (which is a QPSK) is shown with that of BPSK in following figure, indicating the four possible phase states (with the transitions between them shown in gray).



Since this is a polar diagram, the amplitude of the modulated signal is given by the distance to the origin and the phase is the angle between the line and the positive (real) axis in phase. It is therefore noted that the QPSK signal has four possible states, all of the same amplitude (here V2) and phases pi/4, 3pi / 4, 5pi/4 and 7pi / 4.

Figure: Dialog box


  • Name : the name which appears in output results window.

    In order to perform the demodulation the schema and modulation type must be filled here.