Current-mode receivers for induction-based communication and related methods
View Patent ↗A transceiver for use in induction-based communication protocols, such as radio-frequency identification (RFID) and near field communication (NFC), is described. The transceiver may be arranged such that the transmitter and the receiver share a common input/output (I/O) terminal. The transceiver may be configured to interrogate a transponder to which it is inductively coupled, and to wait for the transponder's response. Data transmitted back by the transponder may be detected by sensing an impedance modulation at the I/O terminal or at a node whose impedance varies with the I/O terminal. The impedance modulation may be sensed by allowing a current to be modulated by the impedance variation and by converting the current into a voltage. The corresponding voltage modulation may be sensed by a receiver.
1. A method comprising:
generating a current with a transmitter of an integrated circuit (IC) and coupling the current to an inductor via an input/output (I/O) terminal of the IC; and
sensing information received at the IC through the inductor by sensing a variation in impedance seen at the I/O terminal, wherein sensing the variation in impedance comprises:
sensing the current coupled to the inductor;
converting the sensed current into a voltage; and
sensing a variation in the voltage with a receiver.
2. The method of claim 1 , wherein the information is received at the IC in response to transmitting an interrogation signal with the inductor.
3. The method of claim 2 , further comprising providing the interrogation signal with the transmitter.
4. The method of claim 2 , wherein the interrogation signal is encoded in the current coupled to the inductor.
5. The method of claim 1 , wherein sensing the current coupled to the inductor comprises routing a fraction of the current to a current-to-voltage converter.
6. The method of claim 1 , further comprising decoding the information using a Manchester decoder.
7. An apparatus comprising:
an integrated circuit (IC) comprising:
a transmitter;
a receiver;
an input/output (I/O) terminal connected to the transmitter and configured to be coupled to an inductor;
a current sensor configured to:
sense a current of the transmitter;
convert the sensed current into a voltage; and
provide the voltage to the receiver;
wherein the current is modulated by a variation in impedance seen at the I/O terminal.
8. The apparatus of claim 7 , wherein the inductor comprises a coil.
9. The apparatus of claim 7 , wherein the current sensor comprises a power amplifier.
10. The apparatus of claim 7 , wherein the receiver is connected to the I/O terminal.
11. The apparatus of claim 10 , wherein the receiver is connected to the I/O terminal via a switch.
12. The apparatus of claim 7 , wherein the transmitter comprises an amplitude shift keying (ASK) modulator.
13. The apparatus of claim 7 , further comprising a matching network coupled between the I/O terminal and the inductor and tuned at approximately 13.56 MHz.
14. The apparatus of claim 7 , wherein the receiver comprises a Manchester decoder configured to decode information extracted from the voltage.
15. An electronic device configured to receive, via load modulation, data from a complimentary electronic device magnetically coupled to the electronic device, the electronic device comprising:
an integrated circuit (IC) comprising:
a transmitter;
a receiver;
an input/output (I/O) terminal connected to the transmitter and configured to be coupled to an inductor; and
a current-to-voltage converter coupled to an output of the transmitter at the I/O terminal and to an input of the receiver.
16. The electronic device of claim 15 , wherein the receiver is connected to the I/O terminal.
17. The electronic device of claim 16 , wherein the receiver is connected to the I/O terminal via a switch.
18. The electronic device of claim 15 , wherein the transmitter comprises an amplitude shift keying (ASK) modulator.
19. The electronic device of claim 15 , further comprising a matching network coupled between the I/O terminal and the inductor and tuned at approximately 13.56 MHz.
20. The electronic device of claim 15 , wherein the receiver comprises a Manchester decoder.