Gain control method and apparatus
First Claim
1. A gain controller comprising:
- a first low pass filter configured to generate a filtered in-phase (I) signal;
a second low pass filter configured to generate a filtered quadrature (Q) signal;
a normalization circuit coupled to outputs of the first and second low pass filters, the normalization circuit comprising;
a first circuitry that determines the combined signal strength of the I and Q signals;
a second circuitry coupled to the first circuitry that outputs the averaged combined signal strength measurements from both the I and Q signals; and
a third circuitry coupled to the second circuitry that outputs the inverse of averaged combined signal strength measurements.
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Abstract
An analog/digital gain control device avoid some of the requirements associated with the nature of a closed-loop AGC circuits and which meets the remaining requirements without much difficulty uses an analog to digital conversion method that increases the number of effective ADC bits by compressing the baseband input analog signal using a logarithmic circuit. After the compressed analog signal is converted into a digital signal, a digital anti-log process or look-up table (LUT) is used to expand the digital signal back to the original linear scale. The word size of the output of the anti-log process is larger than the input word size due to the nature of the anti-log function. To reduce the word size of the digital signal an open loop normalization technique can be applied.
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Citations
15 Claims
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1. A gain controller comprising:
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a first low pass filter configured to generate a filtered in-phase (I) signal; a second low pass filter configured to generate a filtered quadrature (Q) signal; a normalization circuit coupled to outputs of the first and second low pass filters, the normalization circuit comprising; a first circuitry that determines the combined signal strength of the I and Q signals; a second circuitry coupled to the first circuitry that outputs the averaged combined signal strength measurements from both the I and Q signals; and a third circuitry coupled to the second circuitry that outputs the inverse of averaged combined signal strength measurements. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A gain control method employed in a communication system, the method comprising:
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filtering a digital in-phase (I) signal to generate a filtered I signal; filtering a digital quadrature (Q) signal to generate a filtered Q signal; determining the combined signal strength of the I and Q signals; determining the averaged combined signal strength measurements from both the I and Q signals; and determining the inverse of the averaged combined signal strength measurements. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification