Automatic gain control of radio receiver for receiving digital high-definition television signals

A method for applying automatic gain control to a radio receiver for vestigial sideband (VSB) signals, which VSB signals include a pilot carrier and sidebands generated in response to multiple-level symbol codes, said method comprising the steps of:

• converting a selected one of said VSB signals to a intermediate-frequency signal in which said pilot carrier is at a prescribed frequency;
• bandpass filtering said intermediate-frequency signal, to separate said pilot carrier contained within said intermediate-frequency signal from said sidebands;
• synchronously detecting said pilot carrier separated from said intermediate-frequency signal, to obtain a first synchronous detection result that contains a substantially zero-frequency component;
• generating an automatic gain control signal responsive to the amount that said substantially zero-frequency component of said first synchronous detection result exceeds a prescribed threshold value;
• and
• reducing the gain of said intermediate-frequency signal in response to said automatic gain control signal.

A radio receiver for vestigial sideband (VSB) signals, which VSB signals include a pilot carrier and sidebands generated in response to symbol codes descriptive of digital signals, said radio receiver utilizing a number at least one of intermediate-frequency bands after utilizing a reception-frequency band for originally receiving said VSB signals, said radio receiver comprising:

• respective circuitry for converting a selected one of said VSB signals in each of said reception-frequency and intermediate-frequency bands utilized within said radio receiver, except the final intermediate-frequency band last utilized within said radio receiver, to the intermediate-frequency band next utilized;
• a respective intermediate-frequency amplifier for each said intermediate-frequency band, including at least a final intermediate-frequency amplifier which supplies a final intermediate-frequency signal in said final intermediate-frequency band in ultimate response to the selected one of said VSB signals, said final intermediate-frequency signal including a translated-in-frequency response to said pilot carrier, at least one said intermediate-frequency amplifier having gain thereof controlled by a respective gain-control signal;
• a synchronous detector for generating a synchronous detector response including a substantially zero-frequency response to said translated-in-frequency response to said pilot carrier;
• a filter for selecting, from said synchronous detector response, the substantially zero-frequency response to said translated-in-frequency response to said pilot carrier;
• a threshold detector for developing an automatic gain control signal responsive to said substantially zero-frequency response to said translated-in-frequency response to said pilot carrier exceeding an AGC threshold value;
• and
• an AGC delay network responsive to said automatic gain control signal for generating said respective gain-control signal for each said intermediate-frequency amplifier having the gain thereof controlled by its said respective gain-control signal.

A radio receiver for vestigial sideband (VSB) signals, which VSB signals include a pilot carrier and sidebands generated in response to symbol codes descriptive of digital signals, said radio receiver comprising:

• a first mixer for converting radio-frequency VSB signals to first intermediate-frequency VSB signals;
• a cascade connection of intermediate-frequency amplifier stages for supplying final intermediate-frequency VSB signals in response to receiving said first intermediate-frequency VSB signals, at least two of which intermediate-frequency amplifier stages provide gain each in an amount controlled by a respective gain control signal;
• a delayed AGC network responsive to an AGC signal for supplying said respective gain control signals to said intermediate-frequency amplifier stages that provide gain each in an amount controlled by its said respective gain control signal, said AGC signal at least at selected times corresponding to a VSB AGC signal;
• synchronous detection circuitry responsive to said final intermediate-frequency VSB signals for synchronously detecting said pilot carrier therein to generate a substantially zero-frequency component of synchronous detection response and for synchronously detecting said sidebands therein to generate a signal component of synchronous detection response the amplitude variations of which changes in accordance with said symbol codes descriptive of digital signals;
• an AGC threshold detector for generating said VSB AGC signal responsive to said substantially zero-frequency component of synchronous detection response exceeding an AGC threshold value;
• and
• a quantizer for reproducing said symbol codes responsive to said signal component of synchronous detection response, said quantizer having amplitude bin boundaries in prescribed ratios to said AGC threshold value.

A method for applying automatic gain control to a radio receiver for amplitude-modulated signals comprising at least one sideband of a suppressed carrier and a pilot carrier, which pilot carrier has a frequency that is the same as said suppressed carrier and has an amplitude independent of the amount of amplitude modulation provided by said at least one sideband of said suppressed carrier, said method comprising steps of:

• converting a selected one of said amplitude-modulated signals to a intermediate-frequency signal in which said pilot carrier is at a prescribed frequency;
• synchronously detecting said intermediate-frequency signal in the phasing of said pilot carrier to obtain a synchronous detection result that includes a substantially zero-frequency component;
• lowpass filtering said synchronous detection result to recover said substantially zero-frequency component;
• generating an automatic gain control signal responsive to the amount that said substantially zero-frequency component exceeds a prescribed threshold value;
• and
• reducing the gain of said intermediate-frequency signal in response to said automatic gain control signal.

A method for applying automatic gain control to a radio receiver for amplitude-modulated signals comprising at least one sideband of a suppressed carrier and a pilot carrier, which pilot carrier has a frequency that is the same as said suppressed carrier and has an amplitude independent of the amount of amplitude modulation provided by said at least one sideband of said suppressed carrier, said method comprising steps of:

• converting a selected one of said amplitude-modulated signals to a intermediate-frequency signal in which said pilot carrier is at a prescribed frequency;
• bandpass filtering said intermediate-frequency signal, to separate said pilot carrier contained within said intermediate-frequency signal from each said at least one sideband of said suppressed carrier;
• synchronously detecting said pilot carrier separated from said intermediate-frequency signal, to obtain a first synchronous detection result that contains a substantially zero-frequency component;
• generating an automatic gain control signal responsive to the amount that said substantially zero-frequency component of said first synchronous detection result exceeds a prescribed threshold value;
• and
• reducing the gain of said intermediate-frequency signal in response to said automatic gain control signal.

A radio receiver for amplitude-modulated signals comprising at least one sideband of a suppressed carrier and a pilot carrier, which pilot carrier has a frequency that is the same as said suppressed carrier and has an amplitude independent of the amount of amplitude modulation provided by said at least one sideband of said suppressed carrier,.sub.-- said radio receiver utilizing a number at least one of intermediate-frequency bands after utilizing a reception-frequency band for originally receiving said amplitude-modulated signals, said radio receiver comprising:

• respective circuitry for converting a selected one of said amplitude-modulated signals in each of said reception-frequency and intermediate-frequency bands utilized within said radio receiver, except the final intermediate-frequency band last utilized within said radio receiver, to the subsequently utilized intermediate-frequency band;
• a respective intermediate-frequency amplifier for each said intermediate-frequency band, including at least a final intermediate-frequency amplifier which supplies a final intermediate-frequency signal in said final intermediate-frequency band in ultimate response to the selected one of said amplitude-modulated signals, said final intermediate-frequency signal including a translated-in-frequency response to said pilot carrier, at least one said intermediate-frequency amplifier having gain thereof controlled by a respective gain-control signal;
• a synchronous detector for generating a synchronous detector response including a substantially zero-frequency response to said translated-in-frequency response to said pilot carrier;
• a filter for selecting, from said synchronous detector response, the substantially zero-frequency response to said translated-in-frequency response to said pilot carrier;
• a threshold detector for developing an automatic gain control signal responsive to said substantially zero-frequency response to said translated-in-frequency response to said pilot carrier exceeding an AGC threshold value;
• and
• an AGC delay network responsive to said automatic gain control signal for generating said respective gain-control signal for each said intermediate-frequency amplifier having the gain thereof controlled by its said respective gain-control signal.