Abstract: In accordance with the USB specifications, an accuracy of 0.25% is required for the data transmission rate. To generate a clock signal that allows this accuracy, the invention uses a clock generator unit that does not require a crystal. The clock generator unit includes an internal clock generator, a pulse counter that is connected to the internal clock generator, a pulse number memory, and a pulse filter. The pulse counter counts the number of internally generated clock pulses between two pulses of the synchronization signal, which are transmitted in accordance with the USB specification. The difference between the ascertained pulse number and a nominal pulse number is evaluated and is used for controlling the pulse-suppressing pulse filter. This results in a stabilized clock signal.

Abstract: In accordance with the USB specifications, an accuracy of 0.25% is required for the data transmission rate. To generate a clock signal that allows this accuracy, the invention uses a clock generator unit that does not require a crystal. The clock generator unit includes an internal clock generator, a pulse counter that is connected to the internal clock generator, a pulse number memory, and a pulse filter. The pulse counter counts the number of internally generated clock pulses between two pulses of the synchronization signal, which are transmitted in accordance with the USB specification. The difference between the ascertained pulse number and a nominal pulse number is evaluated and is used for controlling the pulse-suppressing pulse filter. This results in a stabilized clock signal.

Abstract: The method of cryptological authentification in a scanning identification system comprising a base station, which supplies energy via the alternating field to a transponder connected to the object to be identified, includes the following method steps. For essentially the entire communication between the base station and the transponder, the base station generates an inquiry signal. Upon receiving the inquiry signal transmitted by the base station, the transponder responds with an identification number stored in its memory. The base station then encodes a first bit sequence it has generated by using a key bit sequence that is allocated to the identification number of the transponder, and transmits the second bit sequence obtained in this manner to the transponder. When the second bit sequence is received, the transponder generates a checking bit sequence from the second bit sequence, and, following the complete reception of the second bit sequence, transmits this checking bit sequence to the base station.

Abstract: In a method of transferring data from a transponder to a reading device in a scanning identification system through load-modulation of an inquiry signal emitted by the reading device, with the transponder being initialized at the beginning of the reception of the inquiry signal and responding with the emission of the response signal, first a predetermined number of data bits that are not part of the response signal are transmitted, and a terminator sequence followed by the response signal are repeatedly transmitted, until the inquiry signal is interrupted. The time required by the reading device for building up the inquiry field is bridged by the predetermined number of data bits and, at the same time, the reading device is synchronized to the clock of the response signal. Through the terminator sequence, which indicates the beginning of a valid response signal, the response signal is already recognized correctly by the reading device during the first transfer.

Abstract: The invention relates to a method for transmitting data in a system comprising a reader that creates an interrogation field which contains at least two transponders that, after a start signal has been given in the interrogation field, transmit through load modulation of the interrogation field a uniquely assigned bit sequence back to the reader.

Abstract: The invention relates to a method for calibrating an oscillating receiver circuit of a transponder in an RFID system to resonance to the frequency of an inquiry signal transmitted by a reader, the oscillating receiver circuit comprising at least one inductive resistor and at least one capacitor. Immediately after the start of reception of the inquiry signal, capacitors are connected in increments to the capacitance of the oscillating receiver circuit until such time as the rectified, smoothed inquiry signal assumes a maximum voltage value. This active self-calibration is performed upon each initialization of the transponder but can also be addressed by having the reader send a special sequence to the transponder.

Abstract: The invention relates to a method for operating a contactless and batteryless chip card. The chip card is supplied with energy via an alternating field by a write/read unit. The bidirectional data transfer is achieved by modulation of the energy-transmitting alternating field. The chip card includes, inter alia, an antenna coil for receiving the alternating field, an input circuit generating the supply voltage from the coil current, and a voltage detector for detecting blanking gaps in the alternating field. By the method in accordance with the invention the voltage detector compares the two voltages at the coil ends with one another and then supplies an output signal, provided both the voltages are substantially equal in size for longer than a predetermined period. Furthermore, a chip card is described that contains a voltage detector permitting operation according to the method described.

Abstract: The invention relates to a contactless and batteryless chip card having an antenna coil, a transmission and reception stage which via an electromagnetic alternating field generated by a write/read unit on the one hand supplies the chip card with energy and on the other hand ensures bidirectional data transmission to the write/read unit. The chip card in accordance with the invention has a detector for determining the field strength of the electromagnetic alternating field transmitting energy to said chip card. The functions of the user part, which have a high energy requirement to implement them, are only implemented advantageously when the detector has detected a sufficient field strength. This prevents defective or incomplete implementation of energy-consuming functions of the chip card before they are begun. The field strength detector consists of a switch and load in parallel to the coil with the switch controlled by a control circuit to cause the switch to be on only during a measurement cycle.