Basically, I want to detect an ultrasonic beacon in a radius around the robot. The beacon would have a separate ultrasonic emitter while the robot would have the spinning receiver.
Are there any existing ultrasonic sensors that would meet this use case or am I stuck hacking one together myself?
Is ultrasonic even the best choice? I was hoping that the beacon would be kept in a pocket, so I figured optical sensors were out.
Edit: The beacon and robot will both be mobile so fixed base stations are not an option.