This mode is identical to the “sensitivity” mode since the only difference is that the Blocking value (relative to the noise floor) is provided in dB. The software processes the information using exactly the same method to obtain the value of the receiver attenuation (see Figure 12).
The function blockProtection Ratio(Df) that you entered represents the protection ratio, i.e. the ratio of maximum acceptable level of interfering signal to the wanted signal level, at a given frequency separation.
In this case SEAMCAT calculates the receiver attenuation aVLR(Df) to be applied to the interfering signal by using the following expression (see Figure 109):
Attenuation (Df) = blockProtection Ratio(Df) (dB) + C/(N+I) (dB) + (N+I)/N (dB) – I/N (dB) (Eq. 24)
Attenuation (Df ) = 40 + 16 + 3 - 0 = 59 dB
iRSSblocking = Interfering Signal Level (f it ) = -54.5 - 59 = -113.5 dBm
Figure 109: Mean iRSSblocking in case of Protection-ratio mode