| 摘要 |
1,162,046. Amplifying circuits; radio transmitting systems. C.I.T.-COMPAGNIE INDUSTRIELLE DES TELECOMMUNICATIONS. 26 April, 1967 [11 May, 1966], No. 19241/67. Headings H3W and H4L. A device for the automatic control of the energy dissipated in an amplifier from that received from a D.C. power supply maintains the energy dissipation below a maximum value, and comprises means 18 for combining the two outputs of a reflectometer 14 located between the amplifier 13 and its load impedance 15, with the output of a wattmeter circuit 17 measuring the energy supplied by the D.C. power supply 16. The combined output of the adding device 18 is compared with a reference voltage W in threshold means 19, whereby when the combined output exceeds the reference voltage a control is applied to the energy dissipated in the amplifier. As shown, the control means comprises a variable attenuator 12 connected in the drive from driver stage 11. In a second embodiment (Fig. 2, not shown), the two outputs of the reflectometer are combined in a differential amplifier, the output of which is combined in a second differential amplifier with the output of the wattmeter circuit; this comprises a resistor in the negative lead of the power supply, which is of the stabilized type. The threshold means comprises a diode with the combined output fed to its cathode and a negative delay bias applied to the anode via a series resistor; when the output voltage exceeds the delay, a negative-going control voltage is applied as bias to reduce the gain of a variable-gain amplifier connected between the driver stage and the power amplifier. The adding device may comprise a digital computer, more especially where several amplifiers are centrally controlled. |
