SatGen can reduce the signal-to-noise ratio in a simulation by adding artificial noise to the data.
The carrier-to-noise-density ratio (C/No) is expressed as attenuation from the pure signal level. SatGen 4 can reduce the C/No by up to 15 dBHz in 1 dBHz steps. If the attenuation is zero, it will generate a pure signal. If you have applied attenuation the set level of artificial noise is added to all the simulated signals.
NOTE
The attenuation is not calibrated. Therefore, you should not assume that a 6 dB change in attenuation will adjust the effective C/No by exactly 6 dBHz.
We recommend generating pure signals (with the software attenuation disabled). However, some GNSS receivers may require a lower signal level to acquire the signal and get a lock.
When you are using LabSat 3 or LabSat 3 Wideband units, you can reduce the output signal level with the up and down buttons on the unit. If you are using LabSat or LabSat 2 units, we recommend hardware signal attenuators connected to the RF output.
Different receivers can accept different signal levels, and some of them may require attenuation of as much as -30 dB or even -40 dB. You may need to experiment to find the right level. You should only use software attenuation in SatGen if hardware attenuation is unavailable.
NOTE
Noise functionality will be disabled on LabSat 3 Wideband scenarios if you use more than 3 frequency bands and it will create pure signals instead.