Patent ID: 8233867

Claim:
A method for obtaining field strength information from a received electromagnetic signal via a receiver unit, generating an input voltage for an operational amplifier from the received signal in the receiver unit via an input resistance; generating an output voltage by the operational amplifier via a fixed amplification factor; changing the input voltage until the output voltage lies within a predefined interval that includes a value of the reference voltage; tapping the input voltage at a divider node of a voltage divider; changing a gate voltage of a MOS transistor that is operating within a nonlinear range and connected to the divider node to adjust the output voltage to the reference voltage such that a forward resistance of the MOS transistor is changed in a nonlinear manner; generating the gate voltage via a controllable current source and a controllable current sink such that a storage element connected to the gate of the MOS transistor is discharged or charged; and determining a field strength value received by the receiver unit from a comparison of the value of a present gate voltage with quantities assigned to the gate voltage values in a storage element.