aaron_do wrote on May 6th, 2008, 1:20am:The amplifiers are operated in an open loop so linearity is poor. Anyway their job is basically to compress the signal so their intermodulation is bound to be high especially when the signal is large. My question is basically "will this matter"?
As far as limiter is well designed, limiter produces only odd order harmonics of carrier.
If an input envelope to limiter is already constant, a main lobe of spectrum around carrier will not spread even after limiter.
Although actually limiter produces even order harmonics, you can suppress this with careful design.
If an input envelope to limiter is not constant, a spectrum around carrier after limiter will spread.
But after band limiting by channel selection filter, it comes to have envelope fluctuation again.
Anyway if limiter is well designed, it never causes unrecoverable distortion as far as there is no large interference input to limiter.
aaron_do wrote on May 6th, 2008, 1:20am:I understand the channel filter will ease the requirements of the limiter linearity, but with 80 dB gain, you would need an enormous out-of-band rejection in the channel filter....
Large rejections are required at higher order harmonics frequency.
In attached figure, an input envelope to limiter is already constant, a main lobe of spectrum around carrier will not spread even after limiter.