Method and circuit of an actively transmitting tag

Patent metadata

Field	Value
Publication number	US-9760822-B2
Application number	US-201414761291-A
Country	US
Kind code	B2
Filing date	Jan 14, 2014
Priority date	Jan 15, 2013
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

An actively transmitting tag detects a shift of a phase of an antenna signal (as) with regard to a phase of a transmitted signal (ts) in time intervals with a length of one half-period of a subcarrier, in which time intervals it transmits high-frequency wave packets with their phase being inverted according to a communication protocol at the ends of said half-periods. Generation of said wave packets is controlled by said phase shift in a way that said phase shift retains its absolute value at transitions into subsequent half-periods. Synchronizing the tag's transmission to a received interrogator signal carried out even during tag's transmitting enables the tag to transmit according to protocol ISO 14443 B by inverting a phase at transitions between said half-periods. Said synchronizing is carried out although no time window without a tag transmitting exists within the transmitted data frame.

First claim

The invention claimed is:

1. A method for high-frequency communication between an interrogator and an actively transmitting tag, which, before it starts transmitting a data frame, first observes a phase of an antenna signal due to an interrogator's radiation field and then starts transmitting the data frame in the form of a sequence of high-frequency bursts by exciting, through a matching circuit, its own antenna with a transmitted signal initially having said observed phase of the antenna signal, wherein the actively transmitting tag transmits the data frame by transmitting the high-frequency bursts, each of them having a length of one subcarrier half-period of the transmitted signal and their phase being inverted according to a communication protocol each time at the end of the subcarrier half-period, wherein, in time intervals with the length of one subcarrier half-period during transmitting the data frame, the actively transmitting tag detects a shift of the phase of the antenna signal with regard to a phase of the transmitted signal, and wherein each time after transition into a subsequent subcarrier half-period, the actively transmitting tag controls generating the high-frequency burst according to said detected shift of the phase.

2. The method as recited in claim 1 , wherein the actively transmitting tag controls generation of high-frequency bursts in a way that said shift of the phase retains a constant absolute value at the transitions into the subsequent subcarrier half-periods.

3. The method as recited in claim 2 , wherein said shift of the phase remains zero at the transitions into the subsequent subcarrier half-periods.

4. The method as recited in claim 1 , wherein the actively transmitting tag calculates a difference between said shift of the phase for the current subcarrier half-period and said shift of the phase for the previous subcarrier half-period and wherein the actively transmitting tag controls generation of high-frequency bursts in a way that the difference between said shifts of the phase retains a constant absolute value at the transitions into the subsequent subcarrier half-periods.

5. The method as recited in claim 4 , wherein said difference between said shifts of the phase remains zero at the transitions into the subsequent subcarrier half-periods.

6. The method according to claim 1 , wherein said communication protocol is any communication protocol, according to which the phase is inverted at the transitions between the subcarrier half-periods.

7. The method as recited in claim 6 , wherein said communication protocol is a communication protocol ISO 14443 B, according to which the phase is inverted at the transitions between the subcarrier half-periods.

8. The method as recited in claim 6 , wherein said communication protocol is a communication protocol ISO 14443 A, according to which the phase is inverted at the transitions between the subcarrier half-periods and bit rates for the transmission are 212 kb/s, 424 kb/s or 848 kb/s.

9. A circuit for high-frequency communication between an interrogator and an actively transmitting tag, whose antenna signal (as) is conducted from an antenna into a digitizer, whose output is connected to an input of a phase-frequency comparator, which, before the actively transmitting tag starts transmitting a data frame, first observes a phase of the antenna signal due to an interrogator's radiation field in order that the actively transmitting tag starts transmitting the data frame in the form of a sequence of high-frequency bursts in a way that a voltage-controlled oscillator starts generating a transmitted signal initially having said observed phase of the antenna signal and in the form of said high-frequency bursts being conducted to the antenna through an output amplifier and a matching circuit, wherein the actively transmitting tag transmits the data frame by transmitting the high-frequency bursts each of them having a length of one subcarrier half-period of the transmitted signal and their phase being always inverted according to a communication protocol at the end of the subcarrier half-period, wherein an output of the digitizer and an output of the output amplifier are connected to input terminals of a phase-displacement detector, which, in time intervals with said length of one subcarrier half-period, detects a shift of the phase of the antenna signal with regard to a phase of the transmitted signal, and wherein a phase-displacement signal from an output of the phase-displacement detector is conducted to a regulator circuit, which, while the high-frequency bursts are transmitted, controls the voltage-controlled oscillator in order to generate the high-frequency bursts according to said detected shift of the phase.

10. The circuit as recited in claim 9 , wherein a phase-inverting signal controls a controlled inverter stage in a way to invert the phase of the transmitted signal according to a communication protocol.

11. The circuit as recited in claim 9 , wherein the phase-displacement detector is a mixing circuit.

12. The circuit according to claim 9 , wherein the regulator circuit controls the voltage-controlled oscillator in a way that said shift of the phase retains a constant absolute value at the transitions into the subsequent subcarrier half-periods.

13. The circuit according to claim 9 , wherein said shift of the phase remains zero at the transitions into the subsequent subcarrier half-periods.

14. The circuit according to claim 9 , wherein the phase-displacement signal from the output of the phase-displacement detector is conducted to an input of a controlled circuit for a phase-displacement change determination, which circuit is controlled by said phase-inverting signal and calculates a difference between said shift of the phase for the current subcarrier half-period and said shift of the phase for the previous subcarrier half-period, and wherein an output of the controlled circuit for the phase shift change determination is connected to the regulator circuit, which controls the voltage-controlled oscillator in a way that the difference between said shifts of the phase retains a constant absolute value each time at the transitions into the subsequent subcarrier half-periods.

15. The circuit as recited in claim 14 , wherein said difference between said shifts of the phase remains zero at the transitions into the subsequent subcarrier half-periods.

16. The circuit according to claim 9 , wherein said communication protocol can be any communication protocol, according to which the phase is inverted at the transitions between the subcarrier half-periods.

17. A method for high-frequency communication between an interrogator and an actively transmitting tag, the method comprising: determining, by the actively transmitting tag and prior to transmitting a data frame, a phase of an antenna signal due to a radiation field of the interrogator; exciting, through a matching circuit, an antenna of the actively transmitting tag with a transmitted signal, wherein the transmitted signal initially has a phase equal to the phase of the antenna signal; generating, by the actively transmitting tag, a sequence of high-frequency bursts corresponding with the data frame; transmitting, by the actively transmitting tag, the sequence of high-frequency bursts, wherein each high-frequency burst has a length of one subcarrier half-period of the transmitted signal and a phase inverted according to a communication protocol at an end of each subcarrier half-period; detecting, by the actively transmitting tag and during the transmitting of the data frame, a shift

Assignees

• St Microelectronics Int Nv

Inventors

• Kunc Vinko
• Stiglic Maksimiljan
• Kovacic Kosta
• Pevec Albin
• Stern Anton

Classifications

• G06K19/0705

  the battery being connected to a power saving arrangement · CPC title

• G06K19/0723

  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 title

• G06K7/10297

  arrangements for handling protocols designed for non-contact record carriers such as RFIDs NFCs, e.g. ISO/IEC 14443 and 18092 (cryptographic protocols H04L9/00; network security protocols H04L63/00; real-time communication protocols in data switching networks H04L65/00; network protocols for data switching network services H04L67/00) · CPC title

• G06K19/0726 Primary

  the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier · CPC title

• H04B5/0056

  Electricity · mapped topic