Multi-antenna signaling scheme for low-powered or passive radio communications
A multi-antenna signaling scheme, system and method for passive or low-powered RF devices, such as a radio frequency identification tag, are herein described. In one embodiment, the presently disclosed subject matter discloses a Retrodirective Array Phase Modulator which is configured to allow RFID tags to return higher-powered signals with higher data rates back to an RFID interrogator or reader unit. In some configurations, pattern strobing is used which is an array-based transmission technique for stepping or sweeping an RF waveform through space so that passive radio devices may more efficiently harvest energy without increasing transmit power. In some configurations, the presently disclosed subject matter may also use a Staggered Pattern Charge Collector to boost the collection of microwave power.
1. A radio frequency identification tag, comprising:
a retrodirective array phase modulator configured for quadrature phase shift keying comprising:
a retrodirective antenna array comprising at least one antenna pair; and a staggered pattern charge collector for harvesting energy from an incident electromagnetic wave, comprising:
an array of patch antennas; and
a plurality of charge pumps in electrical communication with each of the array of patch antennas, wherein the plurality of charge pumps are configured to collect a charge;
at least one switch configured to selectively engage and disengage the retrodirective array phase modulator, wherein the at least one switch is configured to disengage at least one of the plurality of charge pumps after the at least one of the plurality of charge pumps has collected a predetermined amount of charge, the at least one switch is further configured to engage the retrodirective array phase modulator after the at least one switch disengage at least one of the plurality of charge pumps; and
a memory for storing data.
2. The radio frequency identification tag of claim 1 , wherein the quadrature phase shift keying is higher-order M-ary phase shift keying modulation configured to reduce a transmission time of data.
3. The radio frequency identification tag of claim 1 , wherein a main pattern lobe is spatially strobed.
4. The radio frequency identification tag of claim 3 , wherein the antenna array of the retrodirective array phase modulator is spatially strobed by sweeping, rotating or stepping the main pattern lobe.
5. The radio frequency identification tag of claim 1 , further comprising a plurality of 4 throw switches configured to change a phase length of a transmission line between the at least one antenna pair.
6. The radio frequency identification tag of claim 1 , further comprising at least one microcontroller for controlling a plurality of switches that change a phase length of a transmission line between the at least one antenna pair.
7. The radio frequency identification tag of claim 1 , wherein the array of patch antennas are configured so that a total peak radiation pattern of each of the array of patch antennas point in different directions.
8. The radio frequency identification tag of claim 1 , wherein at least one of the plurality of charge pumps is configured to engage one or more switches to change a feed point of the remaining plurality of charge pumps to align at least one antenna pattern of at least one charge pump of the remaining plurality of charge pumps towards a direction that provided a predetermined charge-to-threshold time.
9. The radio frequency identification tag of claim 1 , wherein the plurality of charge pumps are configured to be nonlinear to increase the efficiency of the plurality of charge pumps under higher excitation levels with increased duty cycles.
10. The radio frequency identification tag of claim 9 , further comprising at least one low power field effect transistor switch.
11. The radio frequency identification tag of claim 1 , further comprising a data switch configured to switch from a matched load to eliminate reradiation of at least a portion of the energy of an incident wave to an electrical short load to reradiate at least a portion of the energy of the incident wave.
12. The radio frequency identification tag of claim 11 , wherein the data switch is controlled by the retrodirective array phase modulator.
13. A method for multi-antenna signaling, comprising:
receiving, at a radio frequency identification tag, an incident electromagnetic wave comprising an interrogation signal;
changing a phase length of a transmission line between at least one antenna pair of a retrodirective array at the radio frequency identification tag;
spatially strobing a main pattern lobe of at least one antenna of the at least one antenna pair of the retrodirective array;
selectively engaging and disengaging, with at least one switch, the retrodirective array;
when the at least one switch is engaged, harvesting energy from the incident electromagnetic wave by a plurality of charge pumps;
disengaging, by the at least one switch, the least one charge pump of the plurality of charge pumps when a certain charge is harvested; and
engaging a retrodirective array phase modulator after the disengaging of the at least one charge pump of the plurality of charge pumps.
14. The method of claim 13 , further comprising modulating and reradiating the interrogation signal.
15. The method of claim 13 , further comprising aligning at least one antenna pattern of at least one patch antenna in a direction of at least one charge pump of the plurality of charge pumps having the lowest charge-to-threshold time.
16. A multi-channel signaling system, comprising:
a radio frequency identification tag comprising a retrodirective array phase modulator configured for quadrature phase shift keying, comprising:
a retrodirective antenna array comprising at least one antenna pair, wherein the antenna array of the retrodirective array phase modulator is spatially strobed by sweeping, rotating or stepping the main pattern lobe; and
at least one microcontroller for controlling a plurality of switches that change a phase length of a transmission line between the at least one antenna pair;
a staggered pattern charge collector for harvesting energy from an incident electromagnetic wave, wherein the staggered pattern charge collector comprises:
a plurality of arrays comprising a plurality of patch antennas; and
a plurality of charge pumps, wherein at least one of the plurality of charge pumps are in electrical communication with at least one of the plurality of arrays, wherein the plurality of charge pumps are configured to collect a charge;
a memory for storing data; and
a data switch configured to switch between a matched load that substantially eliminates the reradiation of at least a portion of the energy of the incident electromagnetic wave to an electrical short load that causes the reradiation of at least a portion of the energy of the incident electromagnetic wave.
17. The system of claim 16 , wherein the array of patch antennas are configured so that a total peak radiation pattern of each of the array of patch antennas point in different directions.
18. The system of claim 16 , further comprising a plurality of switches to disengage at least one of the plurality of charge pumps after the at least one of the plurality of charge pumps has collected a predetermined amount of charge.
19. The system of claim 16 , wherein the feed point of at least one of the plurality of arrays is configured to point in a plurality of directions.
20. The system of claim 19 , wherein one of the plurality of directions is a direction providing the fastest charge-to-threshold for one of the plurality of charge pumps.