Self-powered autonomous reconfigurable intelligent surfaces using wide radio frequency power range harvesting circuit
The technology described herein is directed towards a reconfigurable intelligent surface (RIS) that harvests RF energy from incoming signals. In one implementation, there are two types of RIS elements (unit cells), one type engineered to capture and wirelessly harvest energy from incoming electromagnetic waves, while the other type redirects the incoming signals towards a predetermined direction. The harvested energy is combined and converted to DC power using a harvesting circuit. In one implementation, a dual-mode energy harvesting circuit employs a higher power rectifier sub-circuit and a lower power rectifier subcircuit, with a multiport circulator and switch that self-actuates to use one or the other rectifier subcircuit based on the combined RF input power captured by the energy harvesting elements. A multiple battery approach is described, in which one battery is charging based on the converted DC power, another, previously-charged battery is powering the reconfigurable intelligent surface components.
1 . A system, comprising:
a reconfigurable intelligent surface that redirects an incoming electromagnetic signal as a redirected electromagnetic signal;
respective first unit cells of the reconfigurable intelligent surface, the respective first unit cells comprising respective variable tuning devices that are controllable to determine at least one of: a shape, a direction, or an amplitude of the redirected electromagnetic signal;
respective second unit cells of the reconfigurable intelligent surface, the respective second unit cells comprising:
respective substrate integrated waveguides configured to capture respective portions of energy of the incoming electromagnetic signal,
respective electrical contacts, and
respective coupling probes that extend into the respective substrate integrated waveguides to transfer harvested electrical energy to the respective electrical contacts based on the respective portions of energy captured in the respective substrate integrated waveguides; and
electrical charging circuitry coupled between the respective electrical contacts and an energy storage device, the electrical charging circuitry configured to convert the harvested electrical energy from the respective electrical contacts to direct current that charges the energy storage device,
wherein the electrical charging circuitry comprises a wide power range rectifier circuit, comprising a power-dependent radio frequency switch that self-actuates at a defined high radio frequency power level, resulting in coupling a first higher power rectifier subcircuit to the harvested electrical energy to output the direct current that charges the energy storage device, and self-de-actuates below the defined high radio frequency power level, resulting in coupling a second lower power rectifier subcircuit to the harvested electrical energy to output the direct current that charges the energy storage device, and
wherein the harvested electrical energy is combined and coupled to a first port of a multi-port device circulator, the multi-port device circulator having a second port coupled to the power-dependent radio frequency radio switch for coupling the first higher power rectifier subcircuit to the harvested electrical energy in response to the power-dependent radio frequency radio switch self-actuating, and a third port coupled to the second lower power rectifier subcircuit for coupling the second lower power rectifier subcircuit to the harvested electrical energy in response to the power-dependent radio frequency radio switch self-de-actuating.
2 . The system of claim 1 , wherein the first higher power rectifier subcircuit comprises a first multistage rectifier subcircuit having an even number of stages, and wherein the second lower power rectifier subcircuit comprises a second multistage rectifier subcircuit having an odd number of stages.
3 . The system of claim 1 , wherein the power-dependent radio frequency switch comprises vanadium dioxide.
4 . The system of claim 1 , wherein the energy storage device comprises a first battery, and further comprising a second battery, a controller, and a switch that is operational in a first state to couple the first battery to the electrical charging circuitry, in conjunction with the second battery providing power to the controller and to the respective variable tuning devices of the respective first unit cells, the respective variable tuning devices controllable by the controller to determine the at least one of: the shape, the direction, or the amplitude of the redirected electromagnetic signal.
5 . The system of claim 4 , wherein the switch is operational in a second state to couple the second battery to the electrical charging circuitry, in conjunction with the first battery providing power to the controller and to the respective variable tuning devices of the respective first unit cells.
6 . The system of claim 5 , further comprising a power management unit that toggles the switch between the first state and the second state based on at least one of: a first level of charge of the first battery, or a second level of charge of the second battery.
7 . The system of claim 1 , wherein the electrical charging circuitry comprises a radio frequency power combiner comprising inputs electrically coupled to the respective electrical contacts.
8 . The system of claim 7 , wherein the electrical charging circuitry comprises an impedance matching circuit electrically coupled to an output of the radio frequency power combiner.
9 . The system of claim 1 , wherein the first higher power rectifier subcircuit comprises ten stages, and wherein the second lower power rectifier subcircuit comprises seven stages.
10 . The system of claim 1 , wherein the energy storage device comprises at least one of: a battery, or a capacitor.
11 . A system, comprising:
a reconfigurable intelligent surface of unit cells, wherein at least some of the unit cells comprise respective substrate integrated waveguides that obtain respective portions of energy from an impinging radio frequency (RF) electromagnetic signal, and couple the respective portions of energy to respective energy harvesting contacts through respective via probes extending into the respective substrate integrated waveguides;
electrical charging circuitry, comprising:
RF power combiner circuitry coupled to the respective energy harvesting contacts to combine the respective portions of energy harvested from the respective energy harvesting contacts into combined RF input, and
a wide power range rectifier circuit, comprising:
a switch that self-actuates into a closed state at a defined high RF power level, and self-de-actuates into an open state below the defined high RF power level;
a circulator comprising a first input port coupled to the combined RF input, a second output port coupled to the switch, and a third output port coupled to a lower power multistage rectifier, wherein
in the closed state, the circulator routes the combined RF input through the switch to a higher power multistage rectifier that outputs first direct current (DC) power to a DC power combiner, and
in the open state, the circulator routes the combined RF input to the lower power multistage rectifier that outputs second DC power to the DC power combiner; and
an energy storage device coupled to the DC power combiner to charge the energy storage device based on the respective portions of energy harvested from the respective energy harvesting contacts.
12 . The system of claim 11 , wherein the higher power multistage rectifier comprises a first multistage rectifier subcircuit having ten stages, and wherein the lower power multistage rectifier comprises a second multistage rectifier subcircuit having seven stages.
13 . The system of claim 11 , wherein the at least some of the unit cells are respective first unit cells, wherein the energy storage device is a first energy storage device, wherein the switch is a first switch, and further comprising a controller, and a second switch that is operational in a first state to couple the first energy storage device to the electrical charging circuitry, in conjunction with a second energy storage device providing power to the controller and to respective variable tuning devices of respective second unit cells of the reconfigurable intelligent surface of unit cells, the respective variable tuning devices controllable by the controller to determine at least one of: a shape, a direction, or an amplitude of a redirected instance from the respective second unit cells of the impinging RF electromagnetic signal.
14 . The system of claim 13 , wherein the switch is operational in a second state to couple the second energy storage device to the electrical charging circuitry, in conjunction with the first energy storage device providing power to the controller and to the respective variable tuning devices of the respective second unit cells.
15 . The system of claim 11 , wherein the energy storage device comprises at least one of: a battery, or a capacitor.
16 . A method, comprising:
obtaining, by a system comprising a controller coupled to a reconfigurable intelligent surface, an incoming electromagnetic wave impinging on the reconfigurable intelligent surface;
redirecting, by the system via respective first unit cells of the reconfigurable intelligent surface, a redirected instance of the impinging electromagnetic wave as a beam, the beam comprising beam characteristics corresponding to respective variable phase shifts, as controlled by the controller, of respective variable tuning elements of the respective first unit cells;
capturing, by the system via respective second unit cells of the reconfigurable intelligent surface, respective radio frequency (RF) electrical energy portions from the impinging electromagnetic wave;
combining, by the system, the respective electrical energy portions into combined RF electrical energy;
coupling, by the system, the combined RF electrical energy to a first higher power multistage rectifier via a switch of a wide power range rectifier circuit, wherein the switch:
in response to the combined RF electrical energy being determined to satisfy a power crossover level, self-actuates into a closed state to couple the combined RF electrical energy to the first higher power multistage rectifier, or
in response to the combined RF electrical energy being determined not to satisfy the power crossover level, self-de-actuates into an open state to decouple the combined RF electrical energy from the first higher power multistage rectifier;
rectifying the combined RF electrical energy, that has been routed via a circulator, of the wide power range rectifier circuit, comprising a first input port coupled to the combined RF electrical energy, a second output port coupled to the switch, and a third output port coupled to a second lower power multistage rectifier, into direct current,
via the first higher power multistage rectifier that outputs first direct current (DC) power to a DC power combiner, through the switch in a closed state, in response to the combined RF electrical energy being determined to satisfy the power crossover level, or
via the second lower power multistage rectifier that outputs second DC power to the DC power combiner, through the switch in an open state, in response to the combined RF electrical energy being determined not to satisfy the power crossover level;
charging, by the system, a first battery with the direct current; and
powering, by the system, the controller and the respective variable tuning elements of the respective unit cells from a second battery previously charged based on previous combined RF electrical energy obtained from the respective second unit cells and previously rectified into previous direct current.
17 . The method of claim 16 , further comprising switching, by the system, to charge the second battery based on the direct current, and to power the controller and respective variable tuning elements of the respective first unit cells from the first battery.
18 . The method of claim 17 , further comprising determining, by a power management device of the system, whether to perform the switching based on at least one of: a first level of charge of the first battery, or a second level of charge of the second battery.
19 . The method of claim 16 , wherein the respective second unit cells comprise respective substrate integrated waveguides, wherein the capturing of the respective RF electrical energy portions via the respective second unit cells comprises coupling respective electrical harvesting contacts to respective via probes that extend into the respective substrate integrated waveguides of the second unit cells to obtain the respective RF electrical energy portions, and wherein the combining of the respective electrical energy portions into the combined RF electrical energy comprises coupling the respective harvesting contacts to at least one RF power combiner.
20 . The method of claim 16 , wherein the first higher power multistage rectifier comprises a first multistage rectifier subcircuit having ten stages, and wherein the second lower power multistage rectifier comprises a second multistage rectifier subcircuit having seven stages.