Power Management for an Active RFID Tag in Credit Card Form Factor

1 . A computer-implemented method for managing power in a dual frequency Active Radio Frequency Identification (RFID) transponder in a form factor substantially conforming to a credit card or smaller, the method comprising:

operating in a sleep mode, the sleep mode comprising a listen-only non-transmitting state of the transponder;

receiving, during the sleep mode, an activation signal from an activator at a distance of at least 10 feet from the transponder, the activation signal for activating the transponder from the sleep mode and controlling the transponder to operate in a beacon mode;

while operating in the beacon mode, transmitting an identifier signal identifying the transponder, the identifier signal detectable at a range of at least 20 feet from the transponder; and

responsive to ending operation in the beacon mode, re-entering the sleep mode.

2 . The method of claim 1 , wherein the transponder draws power from a thin film battery having a storage capacity of at least 25 mAH (milli-ampere-hours).

3 . The method claim 1 , wherein the transponder operates with a nominal terminal voltage of approximately 3 Volts.

4 . The method of claim 1 , wherein the transponder has a minimum operational threshold voltage of approximately 2.2 Volts.

5 . The method of claim 1 , further comprising:

controlling the transponder to operate in a bootstrap mode after an initial power-on of electronics of the transponder.

6 . The method of claim 5 , wherein transponder remains in the bootstrap mode for a fixed time duration.

7 . The method of claim 5 , wherein the transponder cannot be activated to enter the beacon mode while in the bootstrap mode.

8 . The method of claim 5 , further comprising:

detecting connection of battery terminals of the transponder to electronics of the transponder; and

entering the bootstrap mode responsive to the detection.

9 . The method of claim 5 , wherein controlling the transponder to operate in the bootstrap mode further comprises:

(a) entering a sleep state for a fixed time duration;

(b) generating a reset pulse after the fixed time duration of the sleep state;

(c) incrementing a reset count responsive to the reset pulse; and

(d) repeating steps (a)-(c) responsive to the reset count being less than a programmed count.

10 . The method of claim 9 , further comprising:

exiting the bootstrap mode when the reset count reaches the programmed count.

11 . The method of claim 1 , further comprising:

controlling the transponder to operate in a transition mode following completion of a bootstrap mode executed upon an initial power-on of the transponder, wherein at least one function of the transponder is limited in the transition mode.

12 . The method of claim 11 , wherein controlling the transponder to operate in the transition mode further comprises:

(a) entering a listen state for a fixed time duration;

(b) generating a reset pulse after the fixed time duration of the listen state;

(c) incrementing a reset count responsive to the reset pulse; and

(d) repeating steps (a)-(c) responsive to the reset count being less than a programmed count.

13 . The method of claim 12 , further comprising:

receiving the activation signal while the transponder is in the listen state; and

transmitting the identifier signal representing the identifier of the transponder responsive to the receiving the activation signal during the listen state.

14 . The method of claim 1 , further comprising:

controlling the transponder to operate in a normal mode following completion of a bootstrap mode and a transition mode, the bootstrap mode initiated upon an initial power-on of the transponder, and the transition mode initiated upon completion of the bootstrap mode, wherein operating in the normal mode comprises cycling between operating in the sleep mode and operating in the beacon mode.

15 . The method of claim 14 , wherein the transponder operates in the sleep mode for substantially more time than the transponder operates in the beacon mode over a lifetime of the transponder.

16 . The method of claim 15 , wherein operating in the sleep mode comprises:

consuming less than 173 micro-ampere-hour per week of operation in the sleep mode.

17 . The method of claim 15 , wherein operating in the sleep mode comprises:

cycling between a deep sleep state and a listen state, wherein the transponder can detect the activation signal in the listen state and does not detect the activation signal in the deep sleep state.

18 . The method of claim 17 , wherein the deep sleep state consumes 420 nano-amperes or less of current per cycle.

19 . The method of claim 17 , wherein cycling between the deep sleep state and the listen state comprises operating in the deep sleep state for 182 microseconds or less per cycle.

20 . The method of claim 17 , wherein cycling between the deep sleep state and the listen state comprises operating in the listen state for 46 microseconds or less per cycle.

21 . The method of claim 17 , wherein operating in the beacon mode comprises executing a series of beacon frames, wherein executing each beacon frame comprises:

operating in a beacon delay state for a delay duration randomly generated for each beacon delay state;

executing a beacon transmit comprising transmitting a packet representing the identifier of the transponder; and

operating in a beacon sleep period for a fixed duration.

22 . The method of claim 21 , wherein each beacon frame has a duration less than or equal to 13.614 seconds.

23 . The method of claim 21 , wherein the series of beacon frames during one cycle of the beacon mode comprises 274 or fewer frames.

24 . The method of claim 1 , wherein operating in the beacon mode comprises 10.17 micro-ampere-hours or less per week.

25 . The method of claim 1 , wherein further comprising consuming 183.17 micro-ampere-hours or less per week and achieving a battery life of at least two years.

26 . A computer-readable storage medium storing computer-executable program instructions for execution by one or more processors, the instructions when executed causing the one or more processor to perform steps including:

controlling a transponder to operate in a sleep mode, the sleep mode comprising a listen-only non-transmitting state of the transponder;

receiving, during the sleep mode, an activation signal from an activator at a distance of at least 10 feet from the transponder, the activation signal for activating the transponder from the sleep mode and controlling the transponder to operate in a beacon mode;

while controlling the transponder to operate in the beacon mode, transmitting an identifier signal identifying the transponder, the identifier signal detectable at a range of at least 20 feet from the transponder; and

responsive to ending operation in the beacon mode, controlling the transponder to re-enter the sleep mode.

27 . The computer-readable storage medium of claim 26 , further comprising instructions for controlling the transponder to operate in a bootstrap mode following initial power-on of the transponder, the instructions for controlling the transponder to operate in the bootstrap mode including instructions for:

(a) entering a sleep state for a fixed time duration;

(b) generating a reset pulse after the fixed time duration of the sleep state;

(c) incrementing a reset count responsive to the reset pulse; and

(d) repeating steps (a)-(c) responsive to the reset count being less than a programmed count.

28 . The computer-readable storage medium of claim 26 , further comprising instructions for controlling the transponder to operate in a transition mode following completion of a bootstrap mode executed upon initial power-on of the transponder, the instructions for controlling the transponder to operate in the transition mode comprising instructions for:

(a) entering a listen state for a fixed time duration;

(b) generating a reset pulse after the fixed time duration of the listen state;

(c) incrementing a reset count responsive to the reset pulse; and

(d) repeating steps (a)-(c) responsive to the reset count being less than a programmed count.

29 . The computer-readable storage medium of claim 26 , further comprising instructions for controlling the transponder to operate in a normal mode following completion of a bootstrap mode executed upon initial power-on of the transponder and a transition mode executed upon completion of the normal mode, the instructions for controlling the transponder to operate in the normal mode comprising instructions for: cycling between operating in the sleep mode and operating in the beacon mode.

30 . A dual frequency Active Radio Frequency Identification (RFID) transponder in a form factor substantially conforming to a credit card or smaller, the transponder including:

a processor; and

a computer-readable storage medium storing computer-executable program instructions for execution by the processor, the instructions for:

operating in a sleep mode, the sleep mode comprising a listen-only non-transmitting state of the transponder;

receiving, during the sleep mode, an activation signal from an activator at a distance of at least 10 feet from the transponder, the activation signal for activating the transponder from the sleep mode and controlling the transponder to operate in a beacon mode;

while operating in the beacon mode, transmitting an identifier signal identifying the transponder, the identifier signal detectable at a range of at least 20 feet from the transponder; and

responsive to ending operation in the beacon mode, re-entering the sleep mode.