| 摘要 |
<p>A radio frequency ( r.f.) amplifier power control system comprising an r.f. power amplifier for supplying r.f. transmission power to an antenna, a current sensing resistor via which operating current is fed to the power amplifier, a differential amplifier to a first input terminal of which a feed-back voltage derived from the sensing resistor indicative of r.f. transmission power is fed and to a second input terminal of which a reference voltage is fed thereby to produce in the presence of a voltage difference between the feed-back voltage and the reference voltage a control voltage in dependence upon which the output of the power amplifier is controlled in a sense such that the voltage difference tends to be nullified, whereby the transmission power is controllable in dependence upon the reference voltage, and a shunt which is fed with current from the sensing resistor the impedance of which shunt is arranged to vary responsively to the control voltage. <IMAGE></p> |
