Patent ID: 7756493
Filing Date: 2010-07-13
Classification: H03F

Abstract:
1. A method for controlling alignment of a feed forward amplifier system comprising an input for receiving an input signal, a first carrier cancellation control loop coupled to the input and having a main amplifier and a delay, a second error cancellation control loop coupled to the first control loop and having an error amplifier and a gain adjuster and a phase adjuster, and an output coupled to the second control loop and providing an output signal, the method comprising: sampling the output signal; within the first carrier cancellation loop, splitting the input signal between two paths, one path containing the main amplifier, the other path containing the delay; generating a variable frequency pilot signal from the sampled output signal and injecting it into the first control loop into the path containing the main amplifier; measuring the frequency of the generated pilot signal; adjusting the settings of the gain and phase adjusters in said second control loop from a first adjustment setting to a second adjustment setting using an alignment direction; measuring the frequency of the generated pilot signal after said adjusting; measuring the difference in the frequency of the generated pilot signal between said first and second adjustment settings; altering the alignment direction using the frequency difference between said first and second adjustment settings; and adjusting the settings of the gain and phase adjusters in said second control loop from the second setting to a third setting using the altered alignment direction.