The phenomenon by which an electromagnetic waveform diffracts, or bends, as it strikes the sharp edge of an obstacle transverse to its direction of propagation.The portion of the signal that is not cut off by the knife edge continues to propagate, but the edge of the signal bends into the line-of-sight (LOS) shadow region as if to fill the void left by the portion of the signal cut off. Knife-edge diffraction can be used to advantage in radio communications when line-of-sight (LOS) cannot be achieved due to the presence of an obstacle, such as a mountaintop or building, that lies in the path of the transmit and receive antennas.
