Patent ID: 6366164
Filing Date: 2002-04-02
Classification: G06K

Abstract:
Circuit layout for the contactless data transmission between a transponder and a base unit to acquire a low frequency signal which was modulated onto a carrier signal by means of AM modulation,comprising a serial oscillating circuit (L, C, R), which is excited by transistors (T1-T4), connected in the form of two circuit branches (T2, T3, and T1, T4) as an H bridge, with the two circuit branches (T2, T3, and T1, T4) of the H bridge being respectively driven by a control circuit each (S1, S2), and the H bridge being connected to a voltage supply source (VB), and, respectively, one resistor each (R1, R2) being connected in series with a circuit branch (T2, T3, and T1, T4) of the H bridge, wherein the first control circuit (S2) for the first H bridge circuit branch (T2, T3) is pulsed with the carrier signal, the second control circuit (S1) for the second H bridge circuit branch (T1, T4) is pulsed with the inverted carrier signal, at least one controllable current source (Q1, Q2) is connected in parallel to at least one resistor (R1, R2), and the resistor (R1, R2) is connected to the AM demodulator (AM) which is itself pulsed with the carrier signal.