Reference signal design for passive wireless devices

An apparatus for wireless communication at a first wireless device, comprising:

• at least one processor;
• and
• memory coupled with the at least one processor, the memory storing instructions executable by the at least one processor to cause the first wireless device to:
• transmit, via a continuous radio frequency waveform that activates a second wireless device, a trigger message to the second wireless device, the trigger message indicating one or more parameters associated with a reference signal associated with the first wireless device and the second wireless device;
• and
• receive, via a modulated portion of the continuous radio frequency waveform, a message associated with the reference signal based at least in part on the one or more parameters and a capability of the second wireless device.

A method for wireless communication at a first wireless device, comprising:

• receiving, via a continuous radio frequency waveform that activates the first wireless device, a trigger message from a second wireless device, the trigger message indicating one or more parameters associated with a reference signal associated with the first wireless device and the second wireless device;
• modulating the continuous radio frequency waveform based at least in part on the reference signal;
• and
• sending, via a portion of the modulated continuous radio frequency waveform, a message associated with the reference signal based at least in part on the one or more parameters and a capability of the first wireless device.