SOURCEFORGE » RALF » 2015 Quantitative analysis of RF signals

1. Definition of inputs and ways to compute the outputs - Theory¶

1. Display of the power spectrum

Figure 9: Computation of the Power Spectrum

The incoming signal passes through the "power spectrum block" of LabView. The power spectrum of the given signal is then displayed.

2. Computation of the power of the useful signal

Figure 10: Computation of the Power of the useful signal

The value of the autocorrelation of the signal taken at 0 gives the total power of the signal. If the signal is noisy, the result will be the power of the useful signal added to the one of the noise. Generally, the power of the useful signal is much higher than the power of the noise. Therefore, this model is valid when the power of the noise is much lower than the one of the useful signal. This model is only valid for the simulation, it will be modified in subsection 3. Moving from simulation to acquisition of real signals.

3. Computation of the power of the noise

The noise will be known for the simulation, therefore, its power will be known and the signal-to-noise ratio will be approximated by dividing the measured power of the useful signal by the power of the noise.

4. Display of the constellation

Figure 11: Display of the constellation

The signal is demodulated with the appropriate demodulation parameters.

5. Computation of the error measurements

Now, let’s have a look to digital results. We want to observe the constellation of the signal and some results like mean error vector magnitude or mean phase error. Our signal analyser does not determine automatically what is the constellation used to transmit the signal, we have to know it before and to enter it in the program as a parameter. Then we can observe the received constellation, the mean error vector magnitude, the mean phase error, and the mean magnitude error.