Method for determining a RFID backscatter link frequency and RFID tag

A method for determining a backscatter link frequency (BLF) value in a radio frequency identification (RFID) tag device, the method comprising:

• continuously evaluating incoming waveforms to determine receiving of a query command, wherein the query command comprises a start of a T→R calibration (TRCAL) symbol, an end of the TRCAL symbol, and a divide ratio (DR) parameter;
• upon determining the receiving of the start of the TRCAL symbol, initializing a first and a second counter, wherein the counters are clock driven, and wherein the first counter is associated with a first divide ratio and the second counter is associated with a second divide ratio;
• until determining the receiving of the end of the TRCAL symbol, incrementing the first counter every first incremental number of oscillator clock cycles and the second counter every second incremental number of oscillator clock cycles;
• upon determining the receiving of the DR parameter, determining the divide ratio based on the DR parameter and selecting, from the first and the second counter, the counter associated with the determined divide ratio as applicable counter;
• and
• storing the current counter value of the applicable counter as BLF indicator value;
• and
• wherein the BLF is 1/(BLF indicator value*oscillator clock cycle length).

A radio frequency identification (RFID) tag device, comprising:

• connection means configured to connect the RFID tag device to an antenna;
• an analog demodulator, configured to continuously evaluate incoming waveforms;
• a clock device, configured to drive a first and a second counter, wherein the first counter is associated with a first divide ratio and the second counter is associated with a second divide ratio;
• and
• a digital processing unit configured to
• determine, based on the evaluated waveforms, reception of a query command, wherein the query command comprises a start of a T→R calibration (TRCAL) symbol, an end of the TRCAL symbol, and a divide ratio (DR) parameter
• initialize the first and the second counter upon determination of the reception of the start of the TRCAL symbol;
• increment the first counter every first incremental number of oscillator clock cycles and the second counter every second incremental number of oscillator clock cycles until determination of the reception of the end of the TRCAL symbol;
• determine a reception of a DR parameter,
• determine the divide ratio based on the DR parameter after reception of the query command, and select, from the first and the second counter, the counter associated with the determined divide ratio as applicable counter;
• and
• store the current counter value of the applicable counter as BLF indicator value;
• and
• wherein the BLF is 1/(BLF indicator value*oscillator clock cycle length).

A non-transitory computer-readable medium comprising a computer program comprising executable instructions that, when executed, cause a processor to determine a backscatter link frequency (BLF) value in a radio frequency identification (RFID) tag device, the executable instructions to cause the processor to:

• continuously evaluate incoming waveforms to determine receiving of a query command, wherein the query command comprises a start of a T→R calibration (TRCAL) symbol, an end of the TRCAL symbol, and a divide ratio (DR) parameter;
• upon determining the receiving of the start of the TRCAL symbol, initialize a first and a second counter, wherein the counters are clock driven, and wherein the first counter is associated with a first divide ratio and the second counter is associated with a second divide ratio;
• until determining the receiving of the end of the TRCAL symbol, increment the first counter every first incremental number of oscillator clock cycles and the second counter every second incremental number of oscillator clock cycles;
• upon determining the receiving of the DR parameter, determine the divide ratio based on the DR parameter and selecting, from the first and the second counter, the counter associated with the determined divide ratio as applicable counter;
• and
• store the current counter value of the applicable counter as BLF indicator value;
• and
• wherein the BLF is 1/(BLF indicator value*oscillator clock cycle length).