METHOD AND CIRCUIT OF AN ACTIVELY TRANSMITTING TAG
First Claim
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,whereinthe 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, andwherein 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.
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Accused Products
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.
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Citations
18 Claims
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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.
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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.
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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.
Specification