Patent ID: 6091942
Filing Date: 2000-07-18
Classification: H03G

Abstract:
A constant gain amplifier circuit comprising:an input coupler for providing a first RF signal proportional to an RF input signal;a variable gain amplifier for amplifying said RF input signal and providing an RF output signal;an output coupler for providing a second RF signal proportional said RF output signal;a differential gain control circuit for providing a gain control signal to said variable gain amplifier proportional to a difference between levels of said first and second RF signals, wherein said gain control signal causes said constant gain amplifier circuit to maintain substantially constant gain over a range of RF frequencies; anda fixed gain amplifier coupled to an output of said variable gain amplifier for amplifying said RF output signal, said fixed gain amplifier providing a third RF signal to an input of the output coupler, the output coupler providing the second signal directly proportion to signal level of the third signal, said differential gain control providing said gain control signal causing the variable gain amplifier to compensate for variations in gain of said fixed gain amplifier.