Feedforward amplifier

A feedforward amplifier, comprising:

• a main amplifier,
• a distortion detecting loop for detecting a nonlinear distorted signal component appearing due to amplification of a multifrequency input signal by a main amplifier and
• a distortion removing loop for removing a distorted signal component from the multifrequency input signal amplified by said main amplifier, according to the distorted signal component detected by said distortion detecting loop;
• a pilot signal oscillating means for alternately outputting a pilot signal for a detecting operation of a distorted signal component of said distortion detecting loop and a removing operation of a distorted signal component of said distortion removing loop;
• and
• a detecting means for alternately receiving mixed signals from said distortion detecting loop and said distortion removing loop and detecting a pilot signal component in the mixed signals received from said loops, wherein:
• said pilot signal oscillating means includes output change-over means for outputting the pilot signal to either one of said distortion detecting loop and said distortion removing loop, said output change-over means including a multistage change-over switch;
• said detecting means includes input change-over means for receiving the mixed signal from either one of said distortion detecting loop and said distortion removing loop, said input change-over means including a multistage change-over switch and;
• said output change-over means comprises:
• a first change-over switch for connecting the pilot signal to either one of two output terminals;
• at least one stage of a second change-over switch disposed for each pair of two output terminals of said first change-over switch for connecting the pilot signal delivered from said first change-over switch to an input of a change-over switch in a succeeding stage or to ground;
• and
• a third change-over switch disposed for each pair of two output terminals of said second change-over switch for connecting the pilot signal fed from said second change-over switch to an output terminal of said pilot signal oscillating means or to ground.

A feedforward amplifier, comprising

• a main amplifier,
• a distortion detecting loop for detecting a nonlinear distorted signal component appearing due to amplification of a multifrequency input signal by a main amplifier and
• a distortion removing loop for removing a distorted signal component from the multifrequency input signal amplified by said main amplifier, according to the distorted signal component detected by said distortion detecting loop;
• a pilot signal oscillating means for alternately outputting a pilot signal for a detecting operation of a distorted signal component of said distortion detecting loop and a removing operation of a distorted signal component of said distortion removing loop;
• and
• a detecting means for alternately receiving mixed signals from said distortion detecting loop and said distortion removing loop and detecting a pilot signal component in the mixed signals received from said loops, wherein:
• said pilot signal oscillating means includes output change-over means for outputting the pilot signal to either one of said distortion detecting loop and said distortion removing loop, said output change-over means including a multistage change-over switch;
• said detecting means includes input change-over means for receiving the mixed signal from either one of said distortion detecting loop and said distortion removing loop, said input change-over means including a multistage change-over switch;
• and
• said output change-over means comprises:
• a change-over switch in a preceding stage for connecting an output of the pilot signal to either one of two output terminals;
• and
• a change-over switch in a succeeding stage disposed for each pair of the two output terminals of said second change-over switch in the preceding stage for connecting the pilot signal outputted from the change-over switch in the preceding stage to an output terminal of said pilot signal oscillating means or to ground.

A feedforward amplifier, comprising:

• a main amplifier;
• a distortion detecting loop for detecting a nonlinear distorted signal component appearing through amplification of a multifrequency input signal by said main amplifier;
• a distortion removing loop for removing a distorted signal component from the multifrequency input signal amplified by said main amplifier, according to the distorted signal component detected by said distortion detecting loop;
• pilot signal oscillating means for alternately outputting a pilot signal for a detecting operation of a distorted signal component of said distortion detecting loop and a removing operation of a distorted signal component of said distortion removing loop;
• and
• detecting means for alternately receiving a mixed signal from said distortion detecting loop and said distortion removing loop and detecting a pilot signal component in the mixed signal received from said loops, wherein:
• said pilot signal oscillating means includes output change-over means for outputting the pilot signal to either one of said distortion detecting loop and said distortion removing loop;
• said output change-over means is disposed for each pair of two output terminals of said pilot signal oscillating means and includes an isolator to guarantee isolation between the two output terminals and a change-over switch disposed in a stage preceding said isolator to connect an output of a pilot signal to either one of said isolators;
• said detecting means includes input change-over means for receiving the mixed signal from either one of said distortion detecting loop and said distortion removing loop;
• and
• said input change-over means is disposed for each pair of two input terminals of said detecting means and includes an isolator to guarantee isolation between the two input terminals and a change-over switch disposed in a stage succeeding said isolator to connect an output from either one of said isolators to an input terminal of said detecting means.

A feedforward amplifier:

• a directional coupler for mixing an input multifrequency multiplexed signal inputted thereto with a pilot signal received via a first output terminal of a output change-over means from a pilot signal oscillating means;
• a two-output distributor for dividing the mixed signal into tow output signals;
• a first vector adjuster for receiving the first output signal from said two-output distributor and for adjusting quantity of phase and quantity of attenuation of the first output signal;
• a main amplifier for amplifying an output signal from said first vector adjuster;
• a first coupler for separating a part of an amplified signal from said main amplifier and for outputting therefrom the signal separated from the amplified signal;
• a first delay line for delaying propagation of a second output signal from said two-output distributor for a propagation time of a signal in said main amplifier and said first vector adjuster;
• a second coupler for mixing a signal delayed by the first delay line with a signal received from said first coupler, the delayed signal having a phase opposite to that of the signal received from said first coupler;
• a third coupler for separating a part of a mixed signal from said second coupler and for outputting therefrom the signal separated from the mixed signal;
• a control circuit for receiving an output signal from said third coupler via a first input terminal of said input change-over means and for controlling quantity of phase and quantity of attenuation in said first vector adjuster, thereby minimizing a level of a pilot signal component detected in said output signal from said third coupler by a detecting means;
• a fourth coupler for mixing, after the control operation is conducted for said first vector adjuster by said control circuit, a pilot signal received via a second output terminal of said output change-over means from said pilot signal oscillating means with an output signal from said first vector adjuster;
• a second vector adjuster for receiving a signal obtained by mixing by said second coupler a part of a signal attained by amplifying by said main amplifier a mixed signal from said four coupler with a signal delayed by said delay line and received by said second coupler and for adjusting quantity of attenuation and quantity of phase of the signal from said second coupler;
• a subordinate amplifier for amplifying an output signal from said second vector adjuster;
• a second delay line for delaying propagation of a signal for which a pilot signal have been mixed by said four coupler and which has been outputted from said main amplifier for a propagation time of a signal in said second vector adjuster said subordinate amplifier;
• a fifth coupler for mixing a signal delayed by said second delay line and received therefrom with a signal received from said subordinate amplifier, the delayed signal having a phase opposite to that of the signal from said subordinate amplifier, and for outputting a mixed signal resultant from the mixing to an output terminal;
• and
• a sixth coupler for separating a part of the signal fed to the output terminal and for outputting the separated signal therefrom, wherein:
• said input change-over means receives the output signal from said sixth coupler via a second input terminal;
• and
• said control circuit adjusts quantity of attenuation and quantity of phase of said second vector adjuster to minimize a level of a pilot signal component detected by the detecting means in a signal received via a second input terminal.