| 摘要 |
A POWER AMPLIFIER (90) USES A MODULATION TECHNIQUE THAT VARIES AMPLITUDE OF A DRIVE SIGNAL AND, OPTIONALLY, PHASE ANGLE OF THE DRIVE SIGNAL. THE POWER AMPLIFIER COMPRISES TWO COUPLED AMPLIFIERS (120, 150), A FIRST ONE OF WHICH IS OPERATED SATURATED TO PRODUCE A CONSTANT VOLTAGE OUTPUT. THE FIRST AMPLIFIER (120) IS COUPLED TO A SECOND ONE OF THE AMPLIFIERS VIA A QUARTER WAVE TRANSMISSION LINE (160). THE SECOND AMPLIFIER (150) IS OPERATED IN A LINEAR MODE TO DELIVER AN OUTPUT SIGNAL CONTROLLED BY AN AMPLITUDE-MODULATING SIGNAL. THE AMPLITUDE-MODULATING SIGNAL MAY BE A BIPOLAR MODULATION SIGNAL THAT PRODUCES BOTH POSITIVE AND NEGATIVE OUTPUTS FROM THE SECOND AMPLIFIER THAT ADD TO OR SUBTRACT FROM THE OUTPUT FROM THE FIRST AMPLIFIER (120) TO DEVELOP AT A LOAD IMPEDANCE NET OUTPUT SIGNAL AMPLITUDES VARYING BETWEEN A MINIMUM OR "TROUGH" AMPLITUDE AND A MAXIMUM OR "CREST" AMPLITUDE. THE COUPLING OF THE FIRST AND SECOND AMPLIFIERS (120, 150) THROUGH A QUARTER-WAVE LINE (160) ALLOWS THE SIGNAL CURRENT OF THE SECOND AMPLIFIER TO MODULATE THE EFFECTIVE LOAD IMPEDANCE SEEN BY THE FIRST AMPLIFIER TO PROVIDE EFFICIENT AMPLIFIER COUPLING.
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