The motive for the sensor is to
1. sense a robot within range of around 20 meters..
2. use a fixed frequency to detect it.
3. should detect the robot in only limited field.. means all the usual sensors transmit wave in spherical wavefront but i need something like ir sensor or something that will have a conical or semi-spherical waveform that would help me in not detecting the other robots within the range of 20 mt... because all the robots are operated at same frequency... but the direction of conical waveform should decide which robot to drive.
