What phenomenon is indicated when speed appears to disappear and then reappear in RADAR readings?

The phenomenon described, where speed appears to disappear and then reappear in RADAR readings, is best captured by multi-path beam cancellation. This occurs when multiple radar signals reflect off various surfaces before returning to the radar unit, causing interference patterns. In some scenarios, these reflected signals can constructively or destructively interfere with each other, leading to fluctuations in the perceived speed of an object. When the conditions are just right, the resulting signals may cancel each other out at certain points, making it seem like there is no speed reading at all. This is particularly noticeable in environments with a lot of reflective surfaces, such as urban areas.

Understanding this phenomenon is crucial for interpreting RADAR data accurately. It underscores the importance of considering environmental factors and signal paths when analyzing speed readings. Other options, such as multipath fading, signal interference, and range ambiguity, do play roles in RADAR operation, but they describe different issues unrelated to the specific behavior of speed readings disappearing and reappearing in the manner outlined in the question.