REMOTE COMMUNICATION DEVICE BY INDUCTIVE COUPLING WITH MULTI-LEVEL MODULATION

摘要

The remote communication device comprises a portable object (1) with an antenna coil (3), inductively coupled to an antenna coil on a fixed station (2). The charge impedance of the antenna coil (3) on the portable device is modulated to k different levels by means of a multi-level modulation circuit (10). The above acts on the voltage level at the input to a control circuit, the output of which controls a variable impedance (Ze), connected to the antenna coil (3) connectors of the portable device. In a first embodiment the multi-level modulation circuit applies k different values (Vref 1 ... Vrefk) to a reference voltage (Vref) in the control circuit (6). In other embodiments the above applies a drop in voltage or inserts a voltage, which may have k different values, between the output (VDD) of a rectifying circuit (5) and an input of the control circuit.