Digital automatic gain control circuit
First Claim
1. Digital automatic gain control apparatus of the type including a first variable attenuator (106, 107) responsive to a first control signal (105) for applying controlled attenuation to an analog input signal (101) and a second variable attenuator (108) for applying controlled attenuation to a digital representation (103) of an output signal from the first attenuator (106, 107) to generate a gain adjusted output signal (104),digital control means (60) responsive to the gain adjusted output signal (104) for generating the first control signal (105) and for generating a second control signal (G) to cause incremental adjustment of the attenuation applied by the second attenuator (108) when the first control signal (105) maintains the attenuation applied by the first attenuator (106, 107) nominally constant and to cause a substantial adjustment of the attenuation applied by the second attenuator (108) to a prescribed intermediate setting (G0) between predetermined maximum and minimum attenuation settings (THI,TLO) for the second attenuator (108) counteracting the simultaneous attenuation adjustment of the first attenuator (106, 107).
1 Assignment
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Accused Products
Abstract
A digital automatic gain control (AGC) circuit in a digital communication receiver generates a gain adjusted output signal (104) having nominally constant output power by controllably attenuating an input signal (101). Attenuation is accomplished by employing a coarse analog attenuator (106, 107) and a fine digital attenuator (108) under control of a digital control circuit (60). Attenuation adjustments to the analog attenuator (106, 107) alone perturb the gain adjusted output signal (104) causing processing errors in the digital receiver. The digital attenuator (108) is controllably adjusted, in a predetermined manner, to minimize the number of subsequent adjustments made to the analog attenuator (106, 107) following a first adjustment. Adjusting the digital attenuator to a prescribed intermediate attenuation setting (GO) between predetermined maximum and minimum attenuation settings (THI,TLO) for the digital attenuator (108) counteracts the effect of a simultaneous attenuation adjustment to the analog attenuator (106, 107) and also substantially reduces the likelihood of subsequent analog attenuator adjustments. This minimizes perturbations in the gain adjusted output signal (104) and processing errors in the digital receiver.
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Citations
10 Claims
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1. Digital automatic gain control apparatus of the type including a first variable attenuator (106, 107) responsive to a first control signal (105) for applying controlled attenuation to an analog input signal (101) and a second variable attenuator (108) for applying controlled attenuation to a digital representation (103) of an output signal from the first attenuator (106, 107) to generate a gain adjusted output signal (104),
digital control means (60) responsive to the gain adjusted output signal (104) for generating the first control signal (105) and for generating a second control signal (G) to cause incremental adjustment of the attenuation applied by the second attenuator (108) when the first control signal (105) maintains the attenuation applied by the first attenuator (106, 107) nominally constant and to cause a substantial adjustment of the attenuation applied by the second attenuator (108) to a prescribed intermediate setting (G0) between predetermined maximum and minimum attenuation settings (THI,TLO) for the second attenuator (108) counteracting the simultaneous attenuation adjustment of the first attenuator (106, 107).
Specification