Device and/or method for power-dependent tuning for energy harvesting
Subject matter disclosed herein may relate to wireless energy harvesting and may relate more particularly to power-dependent tuning at energy-harvesting devices.
1 . An apparatus, comprising: an energy-harvesting device to include:
an antenna;
a converter circuit;
a variable reactance circuit electronically coupled to the converter circuit, wherein the variable reactance circuit is to vary a reactance characteristic in accordance with a bias signal provided by a bias signal generator circuit such that a combined reactance of the variable reactance circuit and the converter circuit substantially matches an inductive reactance of the antenna, wherein the bias signal is varied in accordance with a power level of a wireless signal received at the energy-harvesting device; and
circuitry to vary an output impedance of the converter circuit at least in part in accordance with the power level of the wireless signal received at the energy-harvesting device.
2 . The apparatus of claim 1 , wherein the variable reactance circuit to include circuitry to vary a capacitance characteristic.
3 . The apparatus of claim 1 , wherein the variable reactance circuit is to vary the reactance characteristic to compensate at least in part for an impedance mismatch between the antenna and the converter circuit to arise at least in part from a variation of the power level of the wireless signal received at the energy-harvesting device.
4 . The apparatus of claim 3 , wherein the variable reactance circuit to comprise a diode-coupled metal-oxide semiconductor field-effect transistor (MOSFET).
5 . The apparatus of claim 3 , wherein the variable reactance circuit to comprise a varactor.
6 . The apparatus of claim 1 , wherein the converter circuit to comprise at least one charge pump to provide the bias signal to the variable reactance circuit.
7 . The apparatus of claim 6 , wherein the at least one charge pump to comprise a multi-stage charge pump.
8 . The apparatus of claim 1 , wherein the wireless signal to comprise a radio- frequency signal.
9 . The apparatus of claim 8 , wherein the energy-harvesting device to comprise a radio-frequency identification (RFID) device.
10 . The apparatus of claim 9 , wherein the RFID device to comprise a computational RFID (C-RFID) device.
11 . A method, comprising:
receiving a wireless signal at an antenna of an energy-harvesting device;
varying a reactance characteristic of a variable reactance circuit of the energy-harvesting device in accordance with a bias signal provided by a bias signal generator circuit of the energy-harvesting device such that a combined reactance of the variable reactance circuit and a multi-stage converter circuit of the energy-harvesting device substantially matches an inductive reactance of the antenna, wherein the bias signal is varied in accordance with a power level of the wireless signal; and
varying an output impedance of the converter circuit in accordance with the power level of the wireless signal.
12 . The method of claim 11 , wherein the varying the reactance characteristic of the variable reactance circuit includes varying a capacitance characteristic.
13 . The method of claim 11 , wherein the varying the reactance characteristic of the variable reactance circuit includes varying the reactance characteristic to compensate at least in part for an impedance mismatch between the antenna and the converter circuit arising at least in part from a variation of the power level of the wireless signal.
14 . The method of claim 13 , wherein the varying the reactance characteristic includes varying the reactance characteristic at least in part via a diode-coupled metal-oxide semiconductor field-effect transistor (MOSFET) of the variable reactance circuit.
15 . The method of claim 13 , wherein the varying the reactance characteristic includes varying the reactance characteristic at least in part via a varactor.
16 . The method of claim 11 , wherein varying the reactance characteristic includes providing the bias signal from at least one charge pump of the converter circuit to the variable reactance circuit.
17 . The method of claim 16 , wherein the at least one charge pump comprises a multi-stage charge pump.
18 . The method of claim 11 , wherein the wireless signal comprises a radio-frequency signal.
19 . The method of claim 18 , wherein the energy-harvesting device comprises a radio-frequency identification (RFID) device.
20 . The method of claim 19 , wherein the RFID device comprises a computational RFID (C-RFID) device.