FM/TV Automatic gain control system

Claim 2

In a frequency modulated television (FM/TV) system, a transmitter for transmitting an FM/TV signal over a transmission path having a certain frequency bandwidth and comprising means at the transmitter for generating an FM/TV signal, a variable gain amplifier responsive to said FM/TV signal to produce an amplifier video signal, and means for up-converting said amplified FM/TV signal for transmission thereof, an improved automatic gain control system comprising: means responsive to said FM/TV signal for producing a first control signal whose amplitude reflects the particular energy content of that portion of said up-converted FM/TV signal lying outside a given percentage of said certain frequency bandwidth; and said variable gain amplifier responsive to said first control signal to vary its gain substantially inversely as said particular energy content varies.

Claim 3

A system as in claim 1 and further comprising: a receiver; detecting means at said receiver for detecting the variation in gain applied to said FM/TV signal at said transmitter to produce a second control signal which reflects said variation in gain at said transmitter; and a second variable gain amplifier at said receiver responsive to said second control signal to provide gain to said received FM/TV signal which is complementary to said gain applied to said FM/TV signal at said transmitter.

Claim 4

A system as in claim 2 and further comprising: means at said transmitter for generating a constant amplitude signal, in the absence of gain at said transmitter, as a component of said FM/TV signal; and in which said detecting means is responsive to those amplitude variations in said originally generated constant amplitude signal which were produced by said variable gain amplifier at said transmitter to produce said second control signal.

Claim 5

A system as in claim 2 and further comprising: generating means at said transmitter for modulating said FM/TV signal with a frequency spreading triangularly-shaped waveform of a known low frequency and known slope; and in which said detecting means comprises slope detecting means containing a reference slope for detecting and comparing the slope of the received triangularly-shaped waveform with said reference slope to produce said second control signal.

Claim 6

A system as in claim 2 in which said detecting means comprises: band eliminating means responsive to said received FM/TV signal to determine that portion thereof lying outside said transmission bandwidth; and means responsive to said portion lying outside said transmission bandwidth to produce said second control signal.

Claim 7

In a frequency modulated television (FM/TV) transmitting system, a transmitter for transmitting an FM/TV signal over a transmission path having a certain frequency bandwidth and means at the transmitter for generating a pre-emphasized, FM/TV signal, a variable gain amplifier responsive to said pre-emphasized FM/TV signal to produce an amplified FM/TV signal, and a frequency modulator (FM) circuit for modulating a carrier signal with the amplified FM/TV signal output of said variable gain amplifier, an improved automatic gain control system comprising: means responsive to said pre-emphasized FM/TV signal for producing a first control signal whose amplitude reflects the energy content of a predetermined percentage of that portion of said pre-emphasized FM/TV signal lying outside said transmission bandwidth; said variable gain amplifier responsive to said first control signal to vary its gain substantially inversely as said energy content varies; a receiver; detecting means at said receiver for detecting the variation in gain applied to said FM/TV signal at said transmitter to produce a second control signal which reflects said variation in gain at said transmitter; and a second variable gain amplifier at said receiver responsive to said second control signal to provide gain to said received FM/TV signal which is complementary to said gain applied to said FM/TV signal at said transmitter.

Claim 8

In a frequency modulated television (FM/TV) transmitting system, a transmitter for transmitting an FM/TV signal over a transmission path having a certain frequency bandwidth and means at the transmitter for generating a pre-emphasized, FM/TV signal, a variable gain amplifier responsive to said pre-emphasized FM/TV signal to produce an amplified FM/TV signal, and a frequency modulator (FM) circuit for modulating a carrier signal with the amplified FM/TV signal output of said variable gain amplifier, an improved automatic gain control system comprising: means responsive to said pre-emphasized FM/TV signal for producing a first control signal whose amplitude reflects the energy content of a predetermined percentage of that portion of said pre-emphasized FM/TV signal lying outside said transmission bandwidth; said variable gain amplifier responsive to said first control signal to vary its gain substantially inversely as said energy content varies; a receiver; detecting means at said receiver for detecting the variation in gain applied to said FM/TV signal at said transmitter to produce a second control signal which reflects said variation in gain at said transmitter; and a second variable gain amplifier at said receiver responsive to said second control signal to provide gain to said received FM/TV signal which is complementary to said gain applied to said FM/TV signal at said transmitter.

Claim 9

A system as in claim 6 and further comprising: means at said transmitter for generating a constant amplitude signal as a component of said FM/TV signal; and in which said detecting means is responsive to those amplitude variations in said originally generated constant amplitude signal which were produced by said variable gain amplifier at said transmitter to produce said second control signal.

Claim 10

In a frequency modulated television FM/TV transmission system comprising a transmitter for transmitting an FM/TV signal over a transmission path having a certain bandwidth, means at the transmitter for generating a pre-emphasized baseband TV signal, and a variable gain amplifier responsive to said pre-emphasized baseband TV signal to produce an amplified baseband TV signal, an improved automatic gain control system for FM/TV transmission comprising: a frequency modulator (FM) circuit responsive to said pre-emphasized baseband TV signal to generate a frequency spectrum a first part of which lies within the bandwidth of the transmission path and a second part of which lies outside said bandwidth; a band eliminating filter responsive to the output of said FM circuit to filter out the first portion of the output of said FM circuit; and means responsive to the output of said band eliminating filter to produce a control signal which is proportional to the energy content of said first portion of the output of said band eliminating filter; and said variable gain amplifier responsive to said control signal to increase its gain inversely, in a predetermined relationship, as said gain correcting signal varies.

Claim 11

In a frequency modulated television FM/TV transmission system comprising a transmitter for transmitting an FM/TV signal over a transmission path having a certain bandwidth, means at the transmitter for generating a pre-emphasized baseband TV signal, and a variable gain amplifier responsive to said pre-emphasized baseband TV signal to produce an amplified baseband TV signal, an improved automatic gain control system for FM/TV transmission comprising: a frequency modulator (FM) circuit responsive to said pre-emphasized baseband TV signal to generate a frequency spectrum a first part of which lies within the bandwidth of the transmission path and a second part of which lies outside said bandwidth; a band eliminating filter responsive to the output of said FM circuit to filter out the first portion of the output of said FM circuit; and means responsive to the output of said band eliminating filter to produce a control signal which is proportional to the energy content of said first portion of the output of said band eliminating filter; and said variable gain amplifier responsive to said control signal to increase its gain inversely, in a predetermined relationship, as said gain correcting signal varies.

Claim 12

In a television (TV) transmission system comprising a transmitter for transmitting a TV signal to a receiver over a transmission path having a certain bandwidth and in which said transmitter comprises means for generating a baseband TV signal, a pre-emphasis circuit responsive to said baseband TV signal to produce a pre-emphasized output signal, and means including a variable gain amplifier responsive to said pre-emphasized output signal to produce an amplified baseband video signal, a method of automatically controlling the gain of said system comprising the steps of: determining the energy content of that portion of said pre-emphasized output signal which lies outside a given percentage of the transmission path bandwidth; varying the gain of said variable gain amplifier in a predetermined inverse relationship to said energy content; and amplifying the received TV signal at said receiver in a predetermined inverse relationship to the variation of the gain of said variable gain amplifier.

Claim 13

In a television (TV) transmission system comprising a transmitter for transmitting a TV signal to a receiver over a transmission path having a certain bandwidth and in which said transmitter comprises means for generating a baseband TV signal, a pre-emphasis circuit responsive to said baseband TV signal to produce a pre-emphasized output signal, and means including a variable gain amplifier responsive to said pre-emphasized output signal to produce an amplified baseband video signal, a method of automatically controlling the gain of said system comprising the steps of: determining the energy content of that portion of said pre-emphasized output signal which lies outside a given percentage of the transmission path bandwidth; varying the gain of said variable gain amplifier in a predetermined inverse relationship to said energy content; and amplifying the received TV signal at said receiver in a predetermined inverse relationship to the variation of the gain of said variable gain amplifier.

Claim 14

In a frequency modulated television (FM/TV) transmission system comprising a transmitter for transmitting an FM/TV signal to a receiver over a transmission path having a certain bandwidth and with said transmitter comprising means for generating a TV signal, means including a variable gain amplifier responsive to said TV signal for producing an amplified FM/TV signal and means for up-converting said amplified FM/TV signal for transmission thereof, a method of automatically controlling the gain of said system comprising the steps of: determining the energy content of that portion of said FM/TV signal which lies outside a given percentage of the transmission path bandwidth; varying the gain of said variable gain amplifier in a predetermined inverse relationship to said energy content; and amplifying the received FM/TV signal at said receiver in a predetermined inverse relationship to the variation of the gain of said variable gain amplifier at said transmitter.

Claim 15

In a frequency modulated television (FM/TV) transmission system comprising a transmitter for transmitting an FM/TV signal to a receiver over a transmission path having a certain bandwidth and with said transmitter comprising means for generating a TV signal, means including a variable gain amplifier responsive to said TV signal for producing an amplified FM/TV signal and means for up-converting said amplified FM/TV signal for transmission thereof, a method of automatically controlling the gain of said system comprising the steps of: determining the energy content of that portion of said FM/TV signal which lies outside a given percentage of the transmission path bandwidth; varying the gain of said variable gain amplifier in a predetermined inverse relationship to said energy content; and amplifying the received FM/TV signal at said receiver in a predetermined inverse relationship to the variation of the gain of said variable gain amplifier at said transmitter.