Patent ID: 6046637
Filing Date: 2000-04-04
Classification: H03F

Abstract:
A feedforward amplifier using two kinds of signal cancel loops, comprising:an error signal extraction loop including a first power divider for distributing an input signal to a first path and a second path, a main amplifier for amplifying the input signal distributed to said first path, a second power divider for distributing an output signal from said main amplifier to a third path and a fourth path, a first vector adjustor for adjusting attenuation and phase shift levels for the input signal distributed to said second path, a first power combiner for adding the output signal distributed to said third path and an output signal from said first vector adjustor, an error amplifier for amplifying an output signal from said first power combiner, first level observation means for detecting a level of an output signal from said error amplifier, first control means for controlling attenuation and phase shift levels of said first vector adjustor so that a detection level of said first level observation means is minimized, a pilot signal oscillator for generating a pilot signal having a particular frequency, and a third power combiner for supplying the pilot signal generated by said pilot signal oscillator to an arbitrary point on a signal route extending from said first power divider to said second power divider; andan error signal elimination loop including a second vector adjustor for adjusting attenuation and phase shift levels for the output signal from said error amplifier, a second power combiner for adding the output signal distributed to said fourth path and an output signal from said second vector adjustor, second level observation means for detecting a level of the pilot signal contained in an output signal from said second power combiner, and second control means for controlling attenuation and phase levels of said second vector adjustor so that a detection level of said second level observation means is minimized;wherein a switch is disposed between said pilot signal oscillator and said third power combiner, and third control means for controlling the opening/closing of said switch is provided so that the pilot signal is stopped when said first control means performs control operation of attenuation and phase shift levels of said first vector adjustor and that the pilot signal is supplied when said second control means performs control operation of attenuation and phase shift levels of said second vector adjustor.