Transmitting circuit for a contactless communicating communication partner device

• US 20110014883A1
• Filed: 06/30/2005
• Published: 01/20/2011
• Est. Priority Date: 07/06/2004
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Raggam, Peter, Merlin, Erich
• Granted Patent: US 8,494,446 B2
• Time in Patent Office: Days
• US Class Current: 455/91
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: H04B 5/00 Near-field transmission systems, e.g. inductive or capacitive transmission systems
• CPC Class Codes: H04B 5/0012 using capacitive coupling
• CPC Class Codes: H04B 5/0087 with multiple coils at either side
• CPC Class Codes: H04B 5/22 Capacitive coupling
• CPC Class Codes: H04B 5/263 Multiple coils at either side
• CPC Class Codes: H04W 4/80 Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication

Abstract

In a communication partner device (1) intended for the contactless transmission of digital data to be transmitted having a transmission circuit (2), the transmission circuit (2) comprises a modulation circuit (17) for the amplitude modulation of a carrier signal (CS), which modulation circuit (17) comprises a circuit stage (20, 20′) for producing a plurality of different resistance values (RW 1, RW 1′) that act on a signal output (TX1, TX2), which resistance values (RW1, RW1′) can be transformed, by means of a signal processing circuit (3) arranged to transform resistance values that belongs to the communication partner device (1), into transformed resistance values (RW2, RW2′), which transformed resistance values (RW2, RW2′) are responsible for damping a transmission coil (7) of the communication partner device (1) when modulated low-level carrier signal sections are generated in a modulated carrier signal.

Claims

1. transmission circuit for a communication partner device intended for the contactless transmission of data to be transmitted, with which communication partner device a transmitting mode of operation is possible, a carrier signal being subjected, in the transmitting mode, to amplitude modulation of a given degree of modulation in accordance with the data to be transmitted, and a modulated carrier signal having unmodulated carrier signal sections and modulated carrier signal sections being obtained as a result, and which communication partner device has a signal processing circuit connected to the transmission circuit and a transmission coil connected to the signal processing circuit, which signal processing circuit is designed to transform resistance values and which transmission circuit has a carrier-signal generator for generating the carrier signal, a modulation-control circuit for generating modulation-control signals that take account of the data to be transmitted, a modulation circuit for modulating the carrier signal as a function of the modulation-control signals and for generating the modulated carrier signal and a signal output for emitting the modulated carrier signal which signal output is intended to supply the signal processing circuit the modulation circuit containing a circuit stage which circuit stage is designed to produce a resistance value that acts on the signal output and can be transformed by means of the signal processing circuit wherein the circuit stage is designed to be controllable to produce a plurality of different resistance values that act on the signal output wherein the modulation-control circuit is designed to generate different modulation-control signals that are assigned to the different resistance values, and wherein each of the different resistance values is produced as a result of the different modulation-control signals that are assigned to the resistance value concerned being fed to the circuit stage.

2. A transmission circuit as claimed in claim 1, wherein the modulation stage comprises, as a circuit stage for producing a plurality of different resistance values that act on the signal output at least one transistor the main current path of which is connected on the one hand to the signal output and on the other hand to a reference potential (ground) and by means of the main current path of which different resistance values can be produced.

3. A transmission circuit as claimed in claim 2, wherein the circuit stage for producing a plurality of different resistance values that act on the signal output has a plurality of NMOS transistors connected in parallel with one another.

4. A transmission circuit as claimed in claim 3, wherein the plurality of NMOS transistors connected in parallel with one another are connected in series with a plurality of PMOS transistors connected in parallel with one another, which PMOS transistors are intended to produce a plurality of further different resistance values that act on the signal output are connected by their main current paths on the one hand to the main current paths of the NMOS transistors connected in parallel with one another and on the other hand to a source of d.c. voltage and are controllable by means of the modulation-control circuit.

5. A communication partner device having a transmission circuit a transmission coil and a signal processing circuit that is provided between the transmission circuit and the transmission coil and is connected to the transmission circuit which signal processing circuit is designed to transform resistance values wherein the communication partner device contains a transmission circuit as claimed in claim 1.