Patent ID: 6791409
Filing Date: 2004-09-14
Classification: H03F

Abstract:
A feedforward amplifier comprising:a first coupler of dividing an input signal into two outputs; a first vector adjuster connected to one of the outputs of said first coupler, of adjusting an amplitude and a phase of a passing signal; a main amplifier connected to the output of said first vector adjuster; a first delay element connected to the other output of said first coupler; a second coupler connected to the output of said main amplifier and the output of said first delay element, of outputting the output of said main amplifier as it is as a first output and outputting as a second output a component in which the output of said main amplifier and the output of said first delay element are combined in an opposite phase; a second delay element connected to the first output of said second coupler; a second vector adjuster connected to the second output of said second coupler, of adjusting the amplitude and the phase of the passing signal; an error amplifier connected to the output of said second vector adjuster; a third coupler connected to the output of said second delay element and the output of said error amplifier, of outputting a component in which the output of said second delay element and the output of said error amplifier are combined in the opposite phase; a fourth coupler inserted into at least one location between the output of said first vector adjuster and the output of said main amplifier; a fifth coupler inserted between the output of said main amplifier and said second coupler; a sixth coupler inserted between the second output of said second coupler and the input of said second vector adjuster; a seventh coupler connected to the output of said third coupler; a distortion cancellation loop control circuit of dividing in two the output of at least one predetermined local oscillator, connecting one of the outputs to a combined input of said fourth coupler, inputting the other output and a combined output of said seventh coupler, and comparing an output signal of said at least one local oscillator to a combined output signal of said seventh coupler to acquire an error in the amplitude and an error in the phase so as to provide a control voltage to two control terminals of said second vector adjuster; an in-phase power dividing circuit connected to the combined output of said fifth coupler; a 90-degree power dividing circuit connected to the combined output of said sixth coupler; a first log amplifier connected to one of the outputs of said in-phase power dividing circuit; a second log amplifier connected to one of the outputs of said 90-degree power dividing circuit; a first mixer connected to the output of said first log amplifier and the output of said second log amplifier; a subtraction circuit connected to the output of said first log amplifier and the output of said second log amplifier; an inversion circuit connected to the output of said subtraction circuit; a switching circuit of having the output of said subtraction circuit and the output of said inversion circuit inputted therein and outputting one of them; a second mixer connected to the other output of said in-phase power dividing circuit and the other output of said 90-degree power dividing circuit; and a comparator connected to the output of said second mixer, and wherein: the two outputs of said distortion cancellation loop control circuit are connected to the two control terminals of said second vector adjuster; the output of said comparator is connected to a switching control terminal of said switching circuit; the output of said first mixer and the output of said switching circuit are connected to the two control terminals of said first vector adjuster directly or via at least one predetermined level changing means; and (1) as for the output of said second mixer, inversion and non-inversion of the output of said subtraction circuit are switched by using said switching circuit to be rendered as the error in said amplitude according to a phase comparison output between a combined output signal of said fifth coupler and a combined output signal of said sixth coupler and an output result of said comparator; and (2) the output of said first mixer is rendered as the error in said phase, and the control voltage is provided to the two control terminals of said first vector adjuster based on the error in the amplitude and the error in the phase.