Patent ID: 7218172

Claim:
A feed-forward amplifier having a signal cancellation loop including a cancellation node, comprising: a gain controller and a phase controller, each controller for providing a discrete tap steering signal and modulating the corresponding tap steering signal with a discrete tracer signal that takes on a preselected sequence of values, the sequence chosen so that the tracer signal is mutually orthogonal to each other tracer signal over a preselected period; a gain and phase adjuster connected to the outputs of the controllers for providing a controlled gain change and phase shift in the signal cancellation loop, the magnitude of the gain change and phase shift controlled by the corresponding tap steering signals presented to the gain and phase adjuster by the controllers; and a detector, the input of which is connected to the cancellation node and the output of which is connected to the controllers, the detector outputting a measure of the envelope of the signal at the cancellation node, wherein after the preselected period new values for the tap steering signals presented to the gain and phase adjuster by the controllers are obtained by multiplying detector output by the respective tracer signal, each over the respective preselected period, summing each resulting series of values, and changing the tap steering signals to be modulated and presented to the gain and phase adjuster in accordance with the values of the respective sums.