METHOD AND CIRCUIT OF AN ACTIVELY TRANSMITTING TAG

• US 20150347892A1
• Filed: 01/14/2014
• Published: 12/03/2015
• Est. Priority Date: 01/15/2013
• Status: Active Grant

• Current Assignee: STMicroelectronics International N.V. (STMicroelectronics NV)
• Original Assignee: ams AG (Ams-Osram AG)
• Inventors: KUNC, Vinko, STIGLIC, Maksimiljan, KOVACIC, Kosta, PEVEC, Albin, STERN, Anton
• Granted Patent: US 9,760,822 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0705 the battery being connected to a power saving arrangement
• 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: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• CPC Class Codes: G06K 7/10297 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 Class Codes: H04B 5/24 Inductive coupling
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/77 for interrogation

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.

Claims

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 circuit of an actively transmitting tag, comprising

an antenna,

a digitizer comprising an input coupled to the antenna,

a voltage-controlled oscillator,

an output amplifier, wherein an output of the voltage-controlled oscillator is coupled via the output amplifier to the antenna,

a phase-displacement detector, wherein an output of the digitizer and an output of the output amplifier are coupled to input terminals of the phase-displacement detector, and

a regulator, wherein an output of the phase-displacement detector is coupled via the regulator circuit to the voltage-controlled oscillator.

18. The circuit according to claim 17, comprising

a phase-frequency comparator, wherein an output of the digitizer is coupled via the phase-frequency comparator to the voltage-controlled oscillator.