Method of and circuit for automatic gain control in electronic equipments

Claim 2

1) Method of automatic gain control in an electronic equipment and more particularly in a telecommunications equipment, in which a variable-amplitude signal is controlled and is locked to a fixed and pre-determined reference level by multiplying it by a control variable, characterized in that at any instant the value of said control variable is obtained by an iterative updating process comprising the steps of: - determining an error signal as difference between the reference level and the actual level of the controlled signal; - multiplying said error signal by the value reached by the control variable at the previous instant; - normalizing said product with respect to the reference value; - adding the signal resulting from said normalization with said previous value of the control variable.

Claim 3

2) Method according to claim 1, characterized in that said controlled signal undergoes a saturation with respect to its maximum or minimum values before the determination of the error signal.

Claim 4

3) Circuit for the realization of the method according to claims 1 and 2, characterized in that it comprises: - a first multiplier (M1) that multiplies the signal to be controlled (S) by the control variable (X) and supplies a controlled signal; - a detecting and sampling device (RC) supplying a signal proportional to the level of the controlled signal at pre-determined instants; - a first adder (SM 1), that receives the output signal of said detecting and sampling device (R C) and a signal at the reference level and supplies an error signal as difference between said two signals; - a second multiplier (M2), that multiplies said error signal by the value reached by the control variable at the previous instant, said previous value being supplied to the multiplier by a delay element (RT); - a normalization circuit (NR) that receives the output signal of said second multiplier (M2), divides it by the value (R) of the reference level and effects a reduction of the value of said signal for stability reasons, the output signal of the normalization circuit forming an updating signal for the control variable; - a second adder (SM2) that adds the updating signal to said previous value of the control variable and supplies a new value of the variable itself, the updated value being sent through said delay element (RT) to said first multiplier (Ml).

Claim 5

4) Circuit according to claim 3, characterized in that between said first multiplier and said detecting and sampling device there is inserted a saturation circuit (SA) able to effect a control on the maximum and minimum values of the controlled signal, the output of that saturation circuit being also connected to utilization devices of the controlled signal.

Claim 6

5) Circuit according to claim 3, characterized in that the output of said delay element is connected to a detector (RS) of the presence or absence of the signal to be controlled, said detector supplying enabling or disabling signals respectively/for utilization devices of the controlled signal.

Claim 7

6) Method of and circuit for the automatic gain control, basically as herein described with reference to the annexed drawing.

Claim 8

6) Method of and circuit for the automatic gain control, basically as herein described with reference to the annexed drawing.