| 摘要 |
1525532 Television THOMSON-CSF 16 Jan 1976 [17 Jan 1975] 01828/76 Heading H4F A television power transmitter arrangement comprises a non-linearity precorrection device designed to precorrect distortions introduced by non-linear power stages of a transmitter whose gain slightly varies as the value of the variable mean component of a composite video signal' modulating the high frequency signal amplified by said power stages. The precorrection device comprises a variable gain amplifier consisting of a transistor 17 having its laser coupled for receiving a signal whose mean component is variable and an emitter for coupling at S to said non-linear amplifier, means for detecting the mean component of said signal and consisting of a low-pass network comprising resistor 9 and capacitor 11 and of a transistor 21, and means for controlling the gain of said variable gain amplifier and including diodes 23, 26 and resistors 22, 25, said diodes being blocked or unblocked according to the mean signal component applied to the base of transistor 17, said gain increasing as said mean component decreases. The device includes an inverter circuit 4 receiving the video frequency signal to be precorrected, the inverted signal appearing at the output of transistor 5 being clamped by clamping pulses at the line frequency applied to an input E 2 . More than two resistor and diode branches 22, 23 and 25, 26 may be provided to achieve a more continuous variation in the gain of transistor 17 as a function of the mean signal component applied thereto. The non-linear amplifier which is coupled to the device at S is followed by a conventional non-linearity correction device. |
