Encoding of Rfid

• US 20080001750A1
• Filed: 10/13/2005
• Published: 01/03/2008
• Est. Priority Date: 10/22/2004
• Status: Active Grant

• Current Assignee: Wavelogics AB
• Original Assignee: Wavelogics AB
• Inventors: Kurup, Dhanesh
• Granted Patent: US 8,045,641 B2
• Time in Patent Office: Days
• US Class Current: 340/572.1
• CPC Class Codes: G01S 13/751 wherein the responder or reflector radiates a coded signal
• CPC Class Codes: G06K 19/067 Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
• CPC Class Codes: G06K 19/0675 the resonating marks being of the surface acoustic wave [SAW] kind SAW devices per se H03H9/64

Abstract

A method is disclosed for generating data encoded RF (radio frequency) waveform without a separate memory device/chip. The hardware in the proposed method consists of entities performing the operations of time-delay (B), phase shifting (C), attenuation, power dividing (D) and power combining (E). An integral part of the invention is the application of the the method in designing radio frequency identification devices or RFID-tags.

Claims

1. A method for generating a modulated waveform in RFID system tags, characterised by the steps of:

generating K signals S_i^M referred to as mother signals of duration T_i and frequencies F_i, where i=1 to K and K≧

1;

generating from the said K mother signals K further signals of duration T_j referred to as child signals S_j^C, where J=1 to K, and T<sub>j<

Ti</sub>;

dividing each of the said child signal corresponding to each mother signal by means of a powder divider into N_i branches resulting in further N_i child signals where N_i≧

2;

introducing different delays to the said N_i child signals after power division;

forming a signal string by combining the said N_i signals which will be interpreted as a data encoded signal corresponding to the mother signal i carrying an identification information.

2. The method according to claim 1, characterised by the further step of introducing different phase shifting before combining the said N_i;

child signals.

3. The method according to claim 1, characterised by the further step of introducing different attenuation before combining the said N_i child signals.

4. The method according to claim 1, characterised by the further step of making the amplitude of child signals to be zero related to a binary zero and a non-zero amplitude related to binary one in the series 1<

j≦

N_i, thereby forming the signal string as an on/off keyed binary signal of .N_i bits.

5. The method according to claim 1, characterised by the further step of making the phase of child signal corresponding to a binary-value 1 to be 180 degree out of with those corresponding to binary value 0, thereby forming the signal string as a phase shift keyed (PSK) binary coded signal of N_i bits.

6. The method according to claim 1, characterised by the further step of combining child signals corresponding to a binary value 1 to have a different frequency to that of the child signal having binary value 0 to form the child signal string as an a frequency shift keyed (FSK) signal.

7. Method according to claim 1 for encoding RF tags in RFID systems.

17. The method according to claim 2, characterised by the further step of introducing different attenuation before combining the said N_i child signals.

18. The method according to claim 2, characterised by the further step of making the amplitude of child signals to be zero related to a binary zero and a non-zero amplitude related to binary one in the series 1<

j≦

N_i, thereby forming the signal string as an on/off keyed binary signal of .N_i bits.

8. A method for generating a modulated waveform characterised by the steps of;

generating K signals S_I^M referred to as mother signals of duration T_i and frequencies F_i, where i=1 to K and K≧

1;

dividing each of the said K mother signals into signals in N_i branches by means of an N_i-way power divider where N_i≧

2;

introducing different time delays to the said signals after power division;

forming a signal string by combining the said delayed signals and forming a string of N_i signals which will be interpreted as a data encoded signal corresponding to mother signal i carrying an identification information.

9. The method according to claim 8, characterised by the further step of introducing different phase shifting before summing the said delayed mother signals in each branch of an N_i way power divider.

10. The method according to claim 8, characterised by the further step of introducing different attenuation before summing the said mother signals in each branch of an N_i-way power divider.

11. The method according to claim 8, characterised by the further step of combining all the N_i branches using an N_i-way power combiner.

12. The method according to claim 11, characterised by the further step of causing the phase shift of the signals in any branch pair among N_i branches before combining to be 180 degree out of phase with each other resulting in cancellation of signals in certain time intervals resulting in an amplitude modulated signal as in binary ASK modulation.

13. The method according to claim 8, characterised by the further step of connecting an open circuit at the end of each branches where by causing reflection of the signals in each branch at the open circuit.

14. The method according to claim 13, characterised by the further step of causing the phase shift of the reflected signals in any branch pair among N_i branches of the divider to be 180 degree out of phase with each other resulting in cancellation of signals in certain time intervals at the input of the said power divider which act like a power combiner for reflected signals resulting in an amplitude modulated signal as in binary ASK modulation.

15. Method according to claim 9 for encoding RF tags in RFID systems.

19. The method according to claim 9, characterised by the further step of introducing different attenuation before summing the said mother signals in each branch of an N_i-way power divider.

20. The method according to claim 9, characterised by the further step of combining all the N_i branches using an N_i-way power combiner.

16. A method for generating a modulated waveform in RFID system tags, characterised by the step of:

generating from a mother signal of duration T_M, a child signal and a tail signal of duration T_C by means of power dividers and/or power combiners, time delays and phase shifters such that T_C<

T_M.