Amazon patents radar system that triggers cameras only on real motion

1. A method comprising: transmitting, by a radar sensor of an electronic device, a first signal representing a first frame; receiving, at a first receiver of the radar sensor, a second signal representing a reflected signal; determining, at the radar sensor based on mixing together the first signal and the second signal, a third signal representing an intermediate frequency signal; determining, at the radar sensor based on the third signal and using an analog to digital converter, a first set of values corresponding to the first frame, each value of the first set of values being associated with a respective time; determining, at the radar sensor based on the first set of values and using a fast Fourier transform algorithm, a second set of values corresponding to the first frame, each value of the second set of values being associated with a respective frequency; determining, at the radar sensor based on the second set of values corresponding to the first frame and a third set of values corresponding to a second frame, a fourth set of values representing differences between a reflection of the first frame and a reflection of the second frame, each value of the fourth set of values being associated with a respective frequency; comparing, at the radar sensor, one or more values of the fourth set of values to a first threshold; based on the comparing, sending, from the radar sensor to a controller of the electronic device, a signal indicating that a first radar detection event has occurred; based on the signal indicating that the first radar detection event has occurred, determining at the controller whether a configured first number of radar detection events have occurred within a configured first time interval; determining, using the fourth set of values, a first set of amplitude values representing highest amplitude values for a plurality of frequency bins, wherein a size of the first set of amplitude values is determined based on a configured value; determining using the fourth set of values, an amplitude ratio between a highest amplitude value of the first set of amplitude values and a lowest amplitude value of the first set of amplitude values; determining, at the controller and using the fourth set of values, a signal characteristic score for the first radar detection event based on the amplitude ratio; comparing, at the controller, the signal characteristic score to a second threshold; and based on the comparing of the signal characteristic score to the second threshold, generating image data using a camera of the electronic device.