Method and apparatus for controlling adaptive circuits
View Patent ↗A feed-forward amplifier having a signal cancellation loop including a cancellation node that includes a gain controller and a phase controller. Each controller provides a discrete tap steering signal and modulates 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 provides 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. A detector, the input of which is connected to the cancellation node and the output of which is connected to the controllers, outputs a measure of the envelope of the signal at the cancellation node. 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.
1. A circuit having a node at which a signal is adaptively minimized by the circuit, comprising:
a controller providing an output voltage level, the output voltage level modulated by a low level signal that takes on a preselected sequence of values over a preselected period;
an adjuster connected to the output of the controller for providing a controlled change in a characteristic of the adaptive circuit that results in a change in the envelope of the signal at the node, the magnitude of the change in the characteristic controlled by the voltage level presented to the adjuster by the controller; and
a detector, the input of which is connected to the node and the output of which is connected to the controller, the detector outputting a measure of the envelope of the signal at the node,
wherein after the preselected period a new setting for the voltage level presented to the adjuster by the controller is obtained by multiplying the detector output by the low level signal, summing the resulting series of values, and changing the voltage level presented to the adjuster in accordance with the value of the sum.
2. The circuit of claim 1 , wherein the output voltage level is increased or decreased depending upon the polarity of the sum.
3. The circuit of claim 1 , wherein the output voltage level is left unchanged if the sum is zero or within a preselected range about zero but, if the sum is outside the preselected range about zero, increasing or decreasing the output voltage level depending upon the polarity of the sum.
4. The circuit of claim 3 , wherein the output voltage level is increased if the sum is positive and decreased if the sum is negative.
5. The circuit of claim 3 , wherein the low level signal voltage level is changed in proportion to a magnitude of the sum.
6. The circuit of claim 5 , wherein the low level signal is chosen to be a Walsh code.
7. The circuit of claim 5 , wherein the low level signal is chosen to be a pseudo noise sequence.