Automatic gain control system for an analog to digital converter
AssigneeImagination Technologies Limited
InventorsTaku Yamagata, Adrian John Anderson
Life of this patent
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Abstract
Methods and circuits for controlling an automatic gain control (AGC) circuit wherein the AGC circuit is used to adjust the gain of a signal input to an analog to digital converter. The method includes obtaining a plurality of samples from the output of the analog to digital converter and determining whether the amplitude of each sample is greater than a threshold amplitude value. If the amplitude of a sample is greater than the threshold amplitude value then a counter value is incremented. The target average amplitude of the automatic gain control circuit is then periodically adjusted based on the counter value.
Claims14
A method of controlling an automatic gain control circuit used to adjust gain of a signal input to an analog to digital converter, the method comprising:
- (a) sampling an output of the analog to digital converter to obtain a sample;
- (b) determining whether an amplitude of the sample is greater than a threshold amplitude value, the threshold amplitude value being less than a saturation point of the analog to digital converter;
- (c) in response to determining that the amplitude of the sample is greater than the threshold amplitude value, incrementing a counter value;
- (d) repeating steps (a) to (c);
- and
- (e) periodically adjusting a target average amplitude of the automatic gain control circuit based on the counter value, the automatic gain control circuit being configured to adjust the gain of the signal input to the analog to digital converter to make an average amplitude of the output of the analog to digital converter equal to the target average amplitude, wherein adjusting the target average amplitude comprises comparing the counter value to a first threshold counter value and decreasing the target average amplitude in response to determining the counter value is greater than the first threshold counter value.
A circuit to dynamically control an automatic gain control circuit used to adjust a gain of a signal input to an analog to digital converter, the circuit comprising:
- a comparator circuit configured to:
- obtain a plurality of samples of an output of the analog to digital converter;
- and
- determine, for each sample, whether an amplitude of the sample is greater than a threshold amplitude value, the threshold amplitude value being less than a saturation point of the analog to digital converter;
- and
- in response to determining that the amplitude of a sample is greater than the threshold amplitude value, output an indication that the sample amplitude is greater that the threshold amplitude value;
- a counter circuit coupled to the comparator circuit, the counter circuit configured to receive indications from the comparator circuit and increment a counter value for each indication received;
- and
- a target control circuit coupled to the counter circuit, the target control circuit configured to periodically receive the counter value from the counter circuit and adjust a target average amplitude of the automatic gain control circuit based on the counter value, the automatic gain control circuit being configured to adjust the gain of the signal input to the analog to digital converter to make an average amplitude of the output of the analog to digital converter equal to the target average amplitude, wherein adjusting the target average amplitude comprises comparing the counter value to a first threshold counter value and decreasing the target average amplitude in response to determining the counter value is greater than the first threshold counter value.
Dependencies are inferred from the claim text.