| 摘要 |
An improved automatic gain control system for a frequency modulated television (FM/TV) transmitter transmission system comprising a transmitter for generating and transmitting a television (TV) signal, a satellite repeater, and at least one receiver having a demodulator and which collectively form a transmission path having a certain frequency bandwidth with the transmitter comprising a pre-emphasis circuit for pre-emphasizing the TV signal and an FM circuit for frequency modulating the output of the pre-emphasis circuit. The invention provides a filter located at the transmitter for simulating the filter characteristics of the overall transmission path and responsive to the frequency modulated TV signal generated at the transmitter to produce a control signal in the event the spectrum of the frequency modulated TV signal exceeds the transmission path bandwidth. Also provided are variable gain amplifying means responsive to the control signal to amplify the frequency modulated TV signal when this event occurs and thereby preventing the signal presented to the demodulator at the receiver from falling below a recoverable threshold.
|
