Automatic gain control systems

Claim 2

In a superheterodyne receiver including a tuner for selEctive, controllable-gain amplification of received RF signals and conversion thereof to intermediate frequencies and an AGC source providing a DC potential varying in response to received signal level variations, the combination comprising: an IF amplifier having an input circuit; means including a dynamic attenuator network for applying the intermediate frequency output of said tuner and said varying DC potential from said AGC source to said IF amplifier input circuit; an attenuator transistor included in said dynamic attenuator, the degree of conduction of said attenuator transistor controlling the degree of attenuation introduced by said attenuator network; means including an RF AGC drive transistor for developing an RF AGC output for gain control of the RF signal amplification in said tuner; and common amplitude delay means controlled by said varying DC potential for precluding conduction of both of said attenuator and RF AGC drive transistors when the received signal level falls in a first, weak-signal range, for precluding conduction of said attenuator transistor and permitting conduction of said RF AGC drive transistor when the received signal level falls in a second, medium-signal range, and for permitting conduction of both of said attenuator and RF AGC drive transistors when the received signal level falls in a third, strong-signal range.

Claim 3

Apparatus in accordance with claim 1 wherein said delay means includes a delay transistor biased into saturation in the absence of received signals.

Claim 4

Apparatus in accordance with claim 2 wherein conduction by said attenuator transistor when the received signal level falls in said strong-signal range closes a DC negative feedback loop opposing variations in the DC potential at said IF amplifier input circuit.

Claim 5

Apparatus in accordance with claim 1 wherein said amplitude delay means comprises means for driving said RF AGC drive transistor into saturation when the received signal level falls in said strong-signal range.

Claim 6

In a superheterodyne receiver including a tuner for selective, controllable-gain amplification of received RF signals and conversion thereof to intermediate frequencies and an AGC source providing a DC potential varying in response to received signal level variations, the combination comprising: an IF amplifier having a input circuit; signal translating means coupled between said tuner and said IF amplifier and responsive to said varying DC potential for applying the intermediate frequency signal output of said tuner to said IF amplifier input circuit without significant attenuation in a first operating mode prevailing when the level of said received signals falls in a given range of signal levels, and for applying the intermediate frequency output of said tuner to said IF amplifier input circuit with attenuation varying in accordance with said varying DC potential in a second operating mode prevailing when the level of said received signals exceeds said given range of signal levels; and means for developing an RF AGC output for gain control of the RF signal amplification in said tuner; said RF AGC output-developing means including an RF AGC drive transistor, and means for rendering said RF AGC drive transistor responsive to said varying DC potential in such manner as to preclude conduction of said RF AGC drive transistor when the received signal level falls in a first portion of said given range, to permit conduction of said RF AGC drive transistor to a degree varying in accordance with said DC potential variations when the received signal level falls in a second portion of said given range of higher level than said first portion, and to establish a substantially constant degree of conduction of said RF AGC drive transistor when the level of received signals exceeds said given range of signal levels.

Claim 7

In a superheterodyne receiver including a tuner for selective, controllable-gain amplification of received RF signals and conversion thereof to intermediate frequencies and an AGC source providing a DC potential varying in response to received signal level variations, the combination comprising: an IF amplifier having a input circuit; signal translating means coupled between said tuner and said IF amplifier and responsive to said varying DC potential for applying the intermediate frequency signal output of said tuner to said IF amplifier input circuit without significant attenuation in a first operating mode prevailing when the level of said received signals falls in a given range of signal levels, and for applying the intermediate frequency output of said tuner to said IF amplifier input circuit with attenuation varying in accordance with said varying DC potential in a second operating mode prevailing when the level of said received signals exceeds said given range of signal levels; and means for developing an RF AGC output for gain control of the RF signal amplification in said tuner; said RF AGC output-developing means including an RF AGC drive transistor, and means for rendering said RF AGC drive transistor responsive to said varying DC potential in such manner as to preclude conduction of said RF AGC drive transistor when the received signal level falls in a first portion of said given range, to permit conduction of said RF AGC drive transistor to a degree varying in accordance with said DC potential variations when the received signal level falls in a second portion of said given range of higher level than said first portion, and to establish a substantially constant degree of conduction of said RF AGC drive transistor when the level of received signals exceeds said given range of signal levels.

Claim 8

A combination in accordance with claim 5 also incorporating means for conTrolling the gain of said IF amplifier in accordance with said varying DC potential when the received signal level falls in said first portion of said given range.

Claim 9

A combination in accordance with claim 5 also incorporating means for controlling the gain of said IF amplifier in accordance with said varying DC potential whenever said first operating mode of said signal translating means prevails.

Claim 10

In a superheterodyne receiver including a tuner for selective, controllable-gain amplification of received RF signals and conversion thereof to intermediate frequencies and an AGC source providing a DC potential varying in response to received signal level variations, the combination comprising: an IF amplifier having an input circuit, and subject to gain variations in accordance with said varying DC potential for a limited gamut of received signal levels; signal-translating means coupled between said tuner and said IF amplifier and responsive to said varying DC potential for applying the intermediate frequency signal output of said tuner to said IF amplifier input circuit without significant attenuation in a first operating mode prevailing when the level of said received signals falls in a given range encompassing said limited gamut of signal levels, and for applying the intermediate frequency output of said tuner to said IF amplifier input circuit with attenuation varying in accordance with said varying DC potential in a second operating mode prevailing when the level of said received signals exceeds said given range of signal levels; and means coupled to said signal-translating means and responsive to said varying DC potential for developing an RF AGC output for gain control of the RF signal amplification in said tuner; said RF AGC output developing means including an RF AGC driver transistor, and means for rendering said RF AGC drive transistor responsive to said varying DC potential in such manner as to preclude conduction of said RF AGC drive transistor when the received signal level falls in a first, low level portion of said given range, to permit conduction of said RF AGC drive transistor to a degree varying in accordance with said DC potential variations when the received signal level falls in a second portion of said given range of higher level than said first portion, and to establish a substantially constant degree of conduction of said RF AGC drive transistor when the level of received signals exceeds said given range of signal levels.

Claim 11

In a superheterodyne receiver including a tuner for selective, controllable-gain amplification of received RF signals and conversion thereof to intermediate frequencies and an AGC source providing a DC potential varying in response to received signal level variations, the combination comprising: an IF amplifier having an input circuit, and subject to gain variations in accordance with said varying DC potential for a limited gamut of received signal levels; signal-translating means coupled between said tuner and said IF amplifier and responsive to said varying DC potential for applying the intermediate frequency signal output of said tuner to said IF amplifier input circuit without significant attenuation in a first operating mode prevailing when the level of said received signals falls in a given range encompassing said limited gamut of signal levels, and for applying the intermediate frequency output of said tuner to said IF amplifier input circuit with attenuation varying in accordance with said varying DC potential in a second operating mode prevailing when the level of said received signals exceeds said given range of signal levels; and means coupled to said signal-translating means and responsive to said varying DC potential for developing an RF AGC output for gain control of the RF signal amplification in said tuner; said RF AGC output developing means including an RF AGC driver transistor, and means for rendering said RF AGC drive transistor responsive to said varying DC potential in such manner as to preclude conduction of said RF AGC drive transistor when the received signal level falls in a first, low level portion of said given range, to permit conduction of said RF AGC drive transistor to a degree varying in accordance with said DC potential variations when the received signal level falls in a second portion of said given range of higher level than said first portion, and to establish a substantially constant degree of conduction of said RF AGC drive transistor when the level of received signals exceeds said given range of signal levels.

Claim 12

In a superheterodyne receiver including a tuner having an RF amplifier for selective, controllable-gain amplification of received RF signals and means for converting the output thereof to intermediate frequencies, said receiver also including a controllable-gain IF amplifier having an input circuit, and a signal-translating network for applying the intermediate frequency signal output of said tuner to said IF amplifier input circuit; an automatic gain control system comprising the combination of: means responsive to the output of said IF amplifier for providing a DC potential varying in response to received signal level variations; first means responsive to said DC potential for causing said signal translating network to attenuate the intermediate frequency signal applied to said IF amplifier input circuit to a degree varying in accordance with the variations of said DC potential when the level of said received signals exceeds a predetermined range of intermediate signal levels to the exclusion of when the level of said received signals falls within or below said predetermined range of levels; additional means responsive to said DC potential for controlling he gain of said RF amplifier in accordance with variations of said DC potential when the level of said received signals falls within said predetermined range of levels to the exclusion of when the level of said received signals falls below or above said predeteRmined range; and further means responsive to said DC potential for controlling the gain of said IF amplifier in accordance with the variations of said DC potential when the level of said received signals falls below said predetermined range of levels.

Claim 13

In a superheterodyne receiver including a tuner having an RF amplifier for selective, controllable-gain amplification of received RF signals and means for converting the output thereof to intermediate frequencies, said receiver also including a controllable-gain IF amplifier having an input circuit, and a signal-translating network for applying the intermediate frequency signal output of said tuner to said IF amplifier input circuit; an automatic gain control system comprising the combination of: means responsive to the output of said IF amplifier for providing a DC potential varying in response to received signal level variations; first means responsive to said DC potential for causing said signal translating network to attenuate the intermediate frequency signal applied to said IF amplifier input circuit to a degree varying in accordance with the variations of said DC potential when the level of said received signals exceeds a predetermined range of intermediate signal levels to the exclusion of when the level of said received signals falls within or below said predetermined range of levels; additional means responsive to said DC potential for controlling he gain of said RF amplifier in accordance with variations of said DC potential when the level of said received signals falls within said predetermined range of levels to the exclusion of when the level of said received signals falls below or above said predeteRmined range; and further means responsive to said DC potential for controlling the gain of said IF amplifier in accordance with the variations of said DC potential when the level of said received signals falls below said predetermined range of levels.

Claim 14

Apparatus in accordance with claim 9 wherein said IF amplifier, said signal translating network, said attenuation causing means, said RF amplifier gain controlling means, and said IF amplifier gain controlling means are all realized in integrated form on a single, monolithic integrated circuit chip.