Maintaining ADC input magnitude from digital par and peak value
Automatic gain control in a receiver. A method for controlling operating range of an analog-to-digital converter (ADC) by an automatic gain control circuit includes estimating a peak-to-average ratio corresponding to an analog signal from digital samples of the analog signal. The method includes determining a peak value corresponding to the analog signal based on the peak-to-average ratio. Further, the method includes maintaining magnitude of the analog signal at an input of the ADC and gain of the receiver based on the peak value.
1. A process of controlling an operating range of an analog to digital converter in a receiver comprising:
A. receiving a radio frequency signal at an antenna;
B. amplifying the radio frequency signal received at the antenna in a radio frequency amplifier;
C. mixing a signal from a local oscillator with the amplified radio frequency signal to produce an intermediate frequency signal;
D. filtering the intermediate frequency signal;
E. amplifying the filtered intermediate frequency signal in an intermediate frequency amplifier;
F. converting the amplified filtered intermediate frequency signal to digital samples in an analog to digital converter; and
G. in an automatic gain control circuit:
i. estimating a peak-to-average ratio from the digital samples;
ii. determining a peak value based on the peak-to-average ratio; and
iii. maintaining magnitude of the amplified filtered intermediate frequency signal by providing the peak value to the radio frequency amplifier and the intermediate frequency amplifier.
2. The process of claim 1 , in which estimating the peak-to-average ratio includes: determining a second order norm of the digital samples, the second order norm representing root-mean-square voltage of the digital samples; and determining a fourth order norm of the digital samples, the fourth order norm being a statistical representation of peak amplitude characteristics of the digital samples.