Digital automatic gain control employing two-stage gain-determination process
First Claim
1. For use in an automatic gain control that receives a digital signal from a digital circuit having a given dynamic range and develops therefrom a gain signal to be applied to a variable gain amplifier, an analyzing circuit for determining a magnitude of said gain signal, comprising:
- a peak sampling subcircuit that samples peak values of said digital signal over variable length sampling periods; and
a gain signal adjustment subcircuit, coupled to said peak sampling subcircuit, that operates in a selected one of;
a search mode in which said gain signal adjustment subcircuit adjusts said variable length sampling periods to a first interval length and adjusts said gain signal at a first rate until a first one of said sampled peak values falls within said dynamic range of said digital circuit; and
a direct step mode in which said gain signal adjustment subcircuit adjusts said variable length sampling periods to a second interval length and adjusts said gain signal at a second rate as a function of a deviation of an average of a plurality of sampled peak values from a target average peak value, said analyzing circuit thereby applying a two-stage gain determination process to said digital signal to approach said target average peak value.
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Abstract
For use in an automatic gain control that receives a digital signal from a digital circuit having a given dynamic range and develops therefrom a gain signal to be applied to a variable gain amplifier, an analyzing circuit for, and method of, determining a magnitude of the gain signal. The analyzing circuit includes: (1) a peak sampling subcircuit that determines an average peak value of the digital signal over variable periods of time and (2) a gain signal adjustment subcircuit, coupled to the peak sampling subcircuit, that operates in a selected one of: (a) a search mode in which the gain signal adjustment subcircuit decreases the periods of time and adjusts the gain signal at a first rate until the average peak value falls within the dynamic range of the digital circuit and (b) a direct step mode in which the gain signal adjustment subcircuit increases the periods of time and adjusts the gain signal at a second rate as a function of a deviation of the average peak value from a target average peak value, the first rate being faster than the second rate, the analyzing circuit thereby applying a two-stage gain determination process to the digital signal to approach the target average peak value.
129 Citations
27 Claims
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1. For use in an automatic gain control that receives a digital signal from a digital circuit having a given dynamic range and develops therefrom a gain signal to be applied to a variable gain amplifier, an analyzing circuit for determining a magnitude of said gain signal, comprising:
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a peak sampling subcircuit that samples peak values of said digital signal over variable length sampling periods; and a gain signal adjustment subcircuit, coupled to said peak sampling subcircuit, that operates in a selected one of; a search mode in which said gain signal adjustment subcircuit adjusts said variable length sampling periods to a first interval length and adjusts said gain signal at a first rate until a first one of said sampled peak values falls within said dynamic range of said digital circuit; and a direct step mode in which said gain signal adjustment subcircuit adjusts said variable length sampling periods to a second interval length and adjusts said gain signal at a second rate as a function of a deviation of an average of a plurality of sampled peak values from a target average peak value, said analyzing circuit thereby applying a two-stage gain determination process to said digital signal to approach said target average peak value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. For use in an automatic gain control that receives a digital signal from a digital circuit having a given dynamic range and develops therefrom a gain signal to be applied to a variable gain amplifier, a method of determining a magnitude of said gain signal, comprising the steps of:
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sampling peak values of said digital signal during each of at least one variable length period of time; and operating a gain signal adjustment subcircuit in a selected one of; a search mode in which said gain signal adjustment subcircuit adjusts said vaiable periods of time to a first interval length and adjusts said gain signal at a first rate until a first one of said sampled peak values falls within said dynamic range of said digital circuit; and a direct step mode in which said gain signal adjustment subcircuit adjusts said variable periods of time to a second interval length and adjusts said gain signal at a second rate as a function of a deviation of an average of a plurality of sampled peak values from a target average peak value, said analyzing circuit thereby applying a two-stage gain determination process to said digital signal to approach said target average peak value. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A digital radio receiver, comprising:
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a power supply; a radio signal reception circuit, coupled to said power supply, that receives radio signals; a demodulation circuit, coupled to said radio signal reception circuit, that removes a carrier wave from said radio signals to yield a modulating wave; a variable gain amplifier, coupled to said demodulation circuit, that amplifies said modulating wave as a function of a gain signal received into said variable gain amplifier to produce an amplified modulating wave; an analog to digital converter, coupled to said variable gain amplifier and having a given dynamic range, that quantizes said amplified modulating wave to produce a digital signal; and an automatic gain control, coupled to said analog to digital converter, that receives said digital signal and develops therefrom a gain signal to be applied to said variable gain amplifier, said automatic gain control having an analyzing circuit for determining a magnitude of said gain signal, including; a peak sampling subcircuit that samples peak values of said digital signal over variable periods of time; and a gain signal adjustment subcircuit, coupled to said peak sampling subcircuit, that operates in a selected one of; a search mode in which said gain signal adjustment subcircuit adjusts said variable periods of time to a first interval length and adjusts said gain signal at a first rate until a first one of said sampled peak values falls within said dynamic range of said analog to digital converter; and a direct step mode in which said gain signal adjustment subcircuit adjusts said variable periods of time to a second interval length and adjusts said gain signal at a second rate as a function of a deviation of an average of a plurality of said sampled peak values from a target average peak value, said analyzing circuit thereby applying a two-stage gain determination process to said digital signal to approach said target average peak value. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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Specification