Patent ID: 6922553

Claim:
A method of determining a field strength of an electromagnetic signal received by a receiving unit including an operational amplifier having a fixed gain factor, and an input resistance connected to a first input of said operational amplifier, said method comprising the following steps: a) providing an input signal that corresponds to or is proportional to an amplitude of said electromagnetic signal received by said receiving unit; b) applying said input signal to said input resistance to generate an input voltage, and applying said input voltage to said first input of said operational amplifier; c) amplifying said input voltage by said fixed gain factor in said operational amplifier to produce an output voltage at an output of said operational amplifier; d) comparing said output voltage with a reference voltage; e) changing a resistance value of said input resistance so as to change a voltage value of said input voltage until said output voltage lies within a prescribed voltage range around and including said reference voltage, at which said resistance value is a final adjusted resistance value; and f) determining a field strength value for said electromagnetic signal dependent on said final adjusted resistance value by comparing said final adjusted resistance value with a stored set of nominal resistance values and nominal field strength values respectively allocated thereto.