| 摘要 |
1,058,830. Automatic gain control. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. Nov. 8, 1963, No. 44149/63. Heading H4R. In an automatic gain control arrangement for a multi-channel carrier frequency transmission system which utilizes a large number of intermediate repeaters which are fed with power over the inner conductor of a coaxial cable and in which cable attentuation changes due to temperature variations are compensated by maintaining the supply voltage constant and utilizing the current change due to the variation of cable resistance with temperature to control the gain of the intermediate amplifiers via, for example, indirectly heated thermistor circuits, a pilot operated gain control device is located at the supply station and controls a variable gain amplifier at the supply station and in addition varies the supply voltage to the intermediate repeaters so that e.g. half the change in gain is obtained at the supply station amplifier and half at the intermediate repeaters. The preferred embodiment comprises a carrier system having main stations SA1 and SA2 joined by coaxial lines having intermediate repeaters V which are powered over the line by supply units G1 and G2 at the main stations, each station supplying half the repeaters between the adjacent stations, the supply loop being completed by inductors L and the line being sectioned to the D.C. supply by capacitors C. At each main station a gain regulated amplifier Va1 or Va2 is controlled in accordance with the level of a pilot signal by the gain regulating device R 1 or R 2 . The gain regulating device also controls the voltage of the power supply unit G1 or G2, thus varying the power supply current through the line and controlling, e.g. by cascaded indirectly heated thermistors, the gain of the repeaters V. In addition the resistance of the cables changes with changes in ambient temperature and the resulting supply current change varies the gain of the amplifiers V to compensate for the change in attenuation of the line. The control device R1 and R2 may be of the type in Specification 992,663 and the regulating thermistor response may be accelerated by the method described in Specification 996,954. |
