SOURCEFORGE » RALF » 2015 Evaluation and test of an optical / L-band tranceiver

h1. Intermodulation (IMD)

Intermodulation measures the non-linear distortions on the signal.

h2. Creation of two tones for Intermodulation test

To measure the intermodulation in our system is necessary to generate two sinus at the input of the optical system and to evaluate them at the output. As the signal generator couldn't provide two sinus at the same time it has been decided to use the USRP with a Labview program to do so.  

An already programmed Labview example in which one tone was generated was modified in order to do so:

p=. !{width:700px}Main_Front_Panel.png!

Figure 1. Front Panel used to generate two sinus

Then, the part of the Labview block in which the tone was generated was duplicated, adding a new output and having the result observed below: 

p=. !{width:400px}Generate_Waveform.png!

Figure 2. Block modified to generate two sinus

After the Labview modifications it could be observed at the output of the USRP the two tones:

p=. !{width:500px}two_sinus.jpg!

Figure 3. Two sinus output from the USRP

h3. 3.2.2 Intermodulation test

Once the two tones generation was correctly done, ..........

h2. Measurement results

p=. !{width:700px}intermodulation_700MHz.png!

p=. !{width:700px}intermodulation_1000MHz.png!

p=. !{width:700px}intermodulation_2000MHz.png!