Wakeup messaging for backscatter communication system node

1. A backscatter communication system, comprising:

a backscatter node, comprising:

an antenna circuit; and

a wake-up circuit coupled to the antenna circuit, the wake-up circuit comprising:

an envelope detection circuit coupled to the antenna circuit that receives a radio frequency (RF) signal from a transmitter;

a pattern correlation circuit coupled to the envelope detection circuit; and

a receiver circuit coupled to the pattern correlation circuit and configured to receive message data from the RF signal,

wherein the pattern correlation circuit is configured to identify at least one predefined waveform within the RF signal and in response to the identification, enable the receiver circuit, wherein the envelope detection circuit comprises a rectifier coupled to a low pass filter (LPF) via a node, wherein the LPF comprises a capacitor and a nonlinear resistor.

2. The system of claim 1 , wherein the nonlinear resistor comprises a first resistor coupled between the node and ground, a first diode-resistor pair coupled between the node and ground, and a second diode-resistor pair coupled between the node and ground.

3. The system of claim 2 , wherein the backscatter node further comprises a controller circuit coupled to the wake-up circuit and a backscatter circuit coupled to the controller circuit, wherein the controller circuit is configured to enable the backscatter circuit when the pattern correlation circuit identifies the at least one predefined waveform.

4. The system of claim 3 , wherein enabling the backscatter circuit further comprises switching from a low power mode to an active mode.

5. The system of claim 1 , further comprising a receiver and the transmitter, wherein, the backscatter node is configured to provide a backscatter signal to the receiver in response to receiving the RF signal from the transmitter.

6. The system of claim 1 , further comprising a backscatter circuit coupled to the antenna circuit, wherein the backscatter circuit is configured to operate in a selectable backscatter channel mode.

7. The system of claim 6 , further comprising a controller circuit coupled to the envelope detection circuit and the backscatter circuit, wherein the controller circuit comprises: at least one processor and memory that stores one or more instructions executable by the at least one processor, wherein the one or more instructions comprise to: receive from the transmitter a message indicating a backscatter channel to be used by the backscatter node.

8. A method, comprising:

receiving, at a backscatter node, a radio frequency (RF) signal that comprises a wake-up message from a transmitter or a receiver; and

in response to receiving the wake-up message, changing from a low power mode to an active mode, wherein the wake-up message comprises a predefined waveform, wherein the envelope detection circuit comprises a low pass filter that is insensitive to whether the RF signal is relatively weak or relatively strong.

9. The method of claim 8 , further comprising: receiving the wake-up message via an antenna circuit of the backscatter node; and extracting the wake-up message from the RF signal via an envelope detection circuit which is coupled to the antenna circuit.

10. The method of claim 9 , wherein the wake-up message is extracted when a signal strength of the RF signal is greater than a first predetermined threshold, when the signal strength of the RF signal less than a second predetermined threshold, or both.

11. The method of claim 8 , wherein the low pass filter comprises a capacitor coupled to a nonlinear resistor.

12. The method of claim 11 , wherein the nonlinear resistor comprises a first resistor coupled between a node and ground, a first diode-resistor pair coupled between the node and ground, and a second diode-resistor pair coupled between the node and ground, wherein the capacitor also is coupled between the node and ground.

13. The method of claim 8 , further comprising: receiving, from the transmitter or the receiver, a set of link parameters for use in backscatter communication.

14. The method of claim 8 , further comprising: using a set of link parameters and power scavenged from the RF signal, sending a backscatter communication to the receiver.

15. The method of claim 8 , further comprising: after sending a backscatter communication using a set of link parameters, receiving from the transmitter an updated set of link parameters; and using the updated set of link parameters, sending another backscatter communication.

16. The method of claim 14 , further comprising: receiving data from a sensor coupled to an apparatus and the backscatter node, wherein the backscatter communication comprises at least a portion of the data received from the sensor.

17. The method of claim 8 , further comprising: receiving from the transmitter or the receiver an indication of a backscatter channel; and using the RF signal of the transmitter, sending a backscatter communication to the receiver via the backscatter channel.

18. A non-transitory computer-readable medium, comprising a plurality of instructions stored thereon, the plurality of instructions comprising to:

receive, at a backscatter node, a radio frequency (RF) signal that comprises a wake-up message from a transmitter or a receiver; and

in response to receiving the wake-up message, change from a low power mode to an active mode, wherein the wake-up message comprises a predefined waveform, wherein the low pass filter comprises a capacitor coupled to a nonlinear resistor.