Patent ID: 7038540

Claim:
A feed forward amplifier, comprising: an input for receiving an RF signal; a main amplifier receiving and amplifying said RF signal; a main amplifier output sampling coupler; a first delay coupled to the input and providing a delayed RF signal; a carrier cancellation combiner coupling the delayed RF signal from the first delay and to the output of the output sampling coupler; an error amplifier receiving and amplifying the output signal of the carrier cancellation combiner; a second delay coupled to the output of the main amplifier; an error coupler combining the output of the error amplifier and a delayed main amplifier output from the second delay so as to cancel distortion introduced by the main amplifier; an output sampling coupler coupled to the output of the error coupler and providing a sampled output signal; a carrier signal reduction circuit coupled to the output sampling coupler and providing a reduced carrier sampled output signal with a reduced carrier component; and a spurious signal detector coupled to the carrier signal reduction circuit, comprising a variable frequency down converter and a digital signal processor, for detecting out of band distortion in the reduced carrier sampled output signal; wherein the error amplifier has an inherent third delay associated with a signal path and wherein said second delay is substantially less than said third delay.