Delay mismatched feed forward amplifier system using penalties and floors for control

A method for controlling an amplifier system having a control loop comprising a control loop input, a first signal path, a second signal path, and a control loop output, at least one of said first and second signal path including an amplifier, said method comprising:

• detecting a pilot signal at the control loop output;
• comparing the detected pilot signal to a floor value;
• if the pilot signal is greater than said floor value setting a loop control cost function equal to the pilot signal;
• if the pilot signal is less than said floor value, setting the loop control cost function equal to the floor value;
• determining the adjustment direction of the loop control;
• if the loop control is adjusting in an undesired direction adding a penalty to the floor value to derive a new cost function;
• and
• adjusting the phase of the second signal path so as to minimize the value of the cost function.

A method of controlling a control loop of an amplifier system, said control loop having a first signal path and a second signal path, an input and an output, said first and second signal paths having a substantial delay mismatch, said method comprising:

• detecting a pilot signal having a single pilot frequency at said output;
• adjusting the phase of at least one of said first and second delay mismatched signal paths;
• and
• controlling said adjusting so that said detected pilot signal is at a stable steady state level offset from a minimum value.

A method of controlling distortion cancellation of an RF signal in a control loop of an amplifier system, said control loop having a first signal path and a second signal path, an input and an output, said first and second signal paths having a delay mismatch, said method comprising:

• injecting a pilot tone into said RF signal, said pilot tone having a single pilot frequency offset from the center frequency of the RF signal bandwidth;
• detecting the pilot signal at said output;
• and
• controlling the phase of at least one of said first and second signal paths of the control loop to stabilize control loop distortion cancellation at a frequency offset from the pilot signal frequency and generally symmetrical about the center of the RF signal bandwidth.