Back off of RF receiver?
average ratio of OFDM modulation? i.e. the input power is lower several dB than
P1dB of RF receiver.
Uh, you are making a receiver that operates at the 1 dB compression point? Unless you are receiving FM, you need to go back to schkoool.
You will need to make sure that you have headroom at the A/D Converter to allow for the PAR of the OFDM signal, when your receiver input is at a Max.
Dave
How to decide the back off requirement of receiver? May I utilize the requirement
of TX to specify receiver? For example, if the BO requirement of 802.11g is 7dB,
then I can specify the requirement of receiver is 7dB?
Yes, the principle is the same for RX and TX. The TX is normally specified harder because the EVM noise budget in the link is distributed between TX and RX. For low S/N situations the NF of receiver dominates and the TX EVM contribute some part. If you have a high signal level in receive you have to ensure the receive EVM for the highest modulation. That is because the radio does not know the modulation in advance. The backoff from ideal clipping is about 12 to 14dB for very low contribution.
In case the model is Rapp's model rather than ideal clipping, how many backoff
should be take? Any simple rule of thumb?
The only rule of thumb is that the "softness" coefficient of the rapp have the effect on the EVM that the backoff is higher than the clippling. Clipping is the extreme cases for the rapp model.
If you target e.g. -40dB EVM it is interessting to know the approximate expression (math rule side of thumb) of required backoff versus rapp exponent.