Patent ID: 7171172

Claim:
A method for calibrating a signal receiver comprising a plurality of serially connected automatic gain control circuits, from which at least two of said gain circuits have unknown gain characteristics, the method comprising the following steps: (a) inputting a signal receiver output signal to a calibration block; (b) generating control signals for each automatic gain control circuit to set a required level of the signal receiver output signal; (c) individually measuring a gain characteristic of at least one automatic gain control circuit of unknown characteristic by using a first procedure comprising: (i) initializing the calibration block to set a required constant level of the signal receiver output signal throughout the whole first procedure; (ii) setting constant gains of the remaining automatic gain control circuits; and (iii) performing a series of measurements in at least one measurement loop controlling the calibration block, where for each measurement in the series, the parameters of a signal receiver input signal (S_ 1 ) are changed by programmably-calculated values within a predefined range; (d) storing the gain characteristic of the circuit of unknown characteristic under measurement in the memory block as a calibration table, which specifies a series of pairs of values describing the input signal level and the value of the control signal of the circuit under measurement; (e) individually measuring the gain characteristics of the remaining automatic gain control circuits of unknown characteristics by the use of a second procedure that comprises: (i) initializing the calibration block to set a requited constant level of the signal receiver output signal throughout the whole procedure, (ii) connecting to the signal receiver an input signal (S_ 1 ) of predetermined parameters; (iii) performing a series of measurements in at least one measurement loop controlling the calibration block, where for each measurement the gains of automatic gain control circuits of known characteristics are changed by programmably-calculated values within a predefined range; (f) calculating the relative level of the input signal as the difference between the signal receiver input signal level and gains of the circuits of known characteristics; and (g) storing the gain characteristic of the remaining circuit of unknown characteristic under measurement in the memory block as a calibration table, which specifies a series of pairs of values describing the relative level of the input signal and the value of the control signal of the circuit under measurement.