Feed forward amplifier

A feed forward amplifier comprising:

• RF amplification means, supplied with an input RF signal at an input terminal, for amplifying the same and thereby producing an output RF signal;
• a distortion extraction loop, supplied with said input RF signal from said input terminal and further with said output RF signal from said RF amplification means, for extracting, from said output RF signal, non-linear distortion components formed in said output RF signal as a result of amplification in said RF amplification means;
• distortion elimination means, supplied with a distortion output signal from said distortion extraction loop and further with said output RF signal from said amplification means, for canceling out said non-linear distortion components contained in said output RF signal by said non-linear distortion components contained in said distortion output signal and producing a distortion-eliminated output signal;
• pilot signal generation means for producing a pilot signal;
• pilot signal injection means for injecting said pilot signal into said output RF signal produced by said RF amplification means;
• pilot signal detection means, supplied with said pilot signal from said pilot signal generation means, for detecting a pilot signal component contained in the distortion-eliminated output signal produced by said distortion elimination means and for conducting d.c. detection by mixing said pilot signal into said distortion-eliminated output signal and producing a d.c. detection signal as an output;
• and
• control means supplied with the d.c. detection signal produced by said pilot signal detection means, said d.c. detection signal being produced by said pilot signal detection means as a result of said d.c. detection, said control means controlling said distortion elimination means so as to minimize the level of said d.c. detection signal;
• said pilot signal detection means further comprising phase control means for coinciding the respective phases of said pilot signal component contained in said distortion-eliminated output signal and said pilot signal injected for said d.c. detection.

A feed forward amplifier comprising:

• RF amplification means, supplied with an input RF signal, for amplifying the same and thereby producing an output RF signal;
• a distortion extraction loop, supplied with said input RF signal and further with said output RF signal from said RF amplification means, for extracting, from said output RF signal, non-linear distortion components formed in said output RF signal as a result of amplification in said RF amplification means, said distortion extraction loop thereby producing a distortion output signal containing therein non-linear distortion components;
• a distortion elimination loop, supplied with said distortion output signal from said distortion extraction loop and further with said output RF signal from said amplification means, for canceling out said non-linear distortion components contained in said output RF signal by non-linear distortion components contained in said distortion output signal, said distortion elimination loop further comprising:
• variable attenuation means, supplied with said distortion output signal produced by said distortion extraction loop, for modifying an amplitude of said distortion output signal,
• variable phase shifter means, supplied with said distortion output signal produced by said distortion extraction loop, for varying a phase of said distortion output signal, and
• distortion elimination means, supplied with said distortion output signal after processing thereof in said variable attenuation means and said variable phase shifter means and with said output RF signal from said amplification means, for synthesizing said distortion output signal and said output RF signal and thereby canceling out the non-linear distortion components contained in said output RF signal by the non-linear distortion components contained in said distortion output signal;
• and
• control means, supplied with said distortion output signal and said output RF signal, for controlling said variable attenuation means and said variable phase shifter means such that said non-linear distortion components in said output RF signal have an amplitude and a phase that are identical, respectively, to an amplitude and a phase of said non-linear distortion components contained in said distortion output signal.

A feed forward amplifier comprising:

• RF amplification means supplied with an input RF signal for amplifying the same and thereby to produce an output RF signal;
• a distortion extraction loop, supplied with said input RF signal and further with said output RF signal of said RF amplification means, for extracting non-linear distortion components formed in said output RF signal as a result of amplification by said RF amplification means, said distortion extraction loop thereby producing a distortion output signal containing said non-linear distortion components;
• and
• a distortion elimination loop, supplied with said distortion output signal from said distortion extraction loop and further with said output RF signal from said RF amplification means, for canceling out said non-linear distortion components contained in said output RF signal by said non-linear distortion components contained in said distortion output signal, 1 said distortion extraction loop further comprising:
• variable phase shifter means, supplied with said input RF signal, for changing a phase thereof;
• phase shifter means, supplied with said output RF signal from said RF amplification means, for causing a 90.degree. degree phase shift therein,
• synchronous detection means, supplied with said input RF signal after processing in said variable phase shifter means and further with said output RF signal as processed by said phase shifter means, for synchronously detecting same and thereby detecting main signal components contained in said output RF signal;
• control means, supplied with said main signal components detected by said synchronous detection means, for controlling said variable phase shifter means such that said main signal components are minimized;
• and
• distortion extraction means, supplied with said input RF signal after processing by said variable phase shifter means and further with said output RF signal as produced by said RF amplification means, for canceling said main signal contained in said input RF signal and main signal components contained in said output RF signal, said distortion extraction means producing an output signal essentially consisting of said non-linear distortion components.

A feed forward amplifier comprising:

• RF amplification means, supplied with an input RF signal from an input terminal, for amplifying the same and thereby producing an output RF signal;
• a plurality of distortion extraction loops, each supplied with said input RF signal from said input terminal and further with said output RF signal of said RF amplification means, for extracting, from said output RF signal, non-linear distortion components formed in said output RF signal as a result of amplification means, each of said distortion extraction loops producing a corresponding distortion output signal containing therein said non-linear distortion components;
• a plurality of distortion elimination loops, provided in correspondence to said plurality of distortion extraction loops, said distortion elimination loops being cascaded with each other and supplied with said output RF signal from said RF amplification means, each of said distortion elimination loops being further supplied with a corresponding distortion output signal from a corresponding distortion extraction loop for removing said non-linear distortion components from said output RF signal supplied thereto;
• and
• a plurality of distortion elimination loop control means, respectively provided in said plurality of distortion elimination loops and each thereof supplied with said output RF signal from which said non-linear distortion components are eliminated, for controlling said respective distortion elimination loop such that a level of said non-linear distortion components remaining in said output RF signal is minimized.