Evaluation of the MODCOD and (GT) required¶

Supposing that the specifications and frequency band are known (Rb, R, f, B and EIRP are known), we directly get all the parameters for the system design by following the method described previously.

f= 869,5 MHz B= 250 kHz PAR= 0.5 W Rb=500 bits/s R=50 km:

f= 5 GHz B= 500 kHz EIRP= 1 W Rb=500 bits/s R=50 km:

We can see from these two simulations that:

• The higher the Bandwidth, the lower the Modcod
• The higher the frequency, the higher the free space loss, and then the higher the (G/T) and EIRP requested to compensate these losses.

Moreover, we can evaluate the requested gain of the antennas from the (G/T) values. In fact, we have been told by Mr Perrin that the receivers temperature was between 400K and 600K, depending on the quality receiver and the directivity of the antenna (looking toward the ground or not?).

Then, a (G/T) of -27.3 dB corresponds more or less to an isotropic antenna, and a (G/T) of -16.9 dB corresponds to a 9 dB gain antenna, which is easily feasible at the 5 GHz frequency.