Automatic Gain Control Loop Based on Threshold Crossing Rate Measurement

In a mobile telecommunication system the received signal envelope has a very large dynamic range. A gain control is then required to adjust the signal amplitude at the input of the Analog to Digital Converter, ADC. The Automatic Gain Control, AGC, must control such amplitude to avoid (or limit) ADC saturation and, at the same time, to ensure an efficient usage of its dynamic range. In the state of art approach, the AGC loop adjustment is based on the measurement of the received signal power. This measurement can be made directly from the RF unit or after the ADC. In this contribution, we describe an approach based on indirect power measurement with low complexity circuitry. Shortly, this method measures the signal probability of exceeding a properly defined threshold, allowing power estimate.