Simulation of Radar Range and of Doppler Effect by Means of a Stationary Target

The subject of this correspondence is relevant to a type of passive electronic countermeasure known under the code name of "confusion chaff." It consists of metal strips or wires dispensed in a proper place in space so as to produce radar echoes similar to those of real targets of interest to the defense. We wish to concentrate here on the phase where medium in which chaff is deposited is dense, and where chaff becomes ineffective since it either burns up or slows down, thus either disappearing altogether or becoming susceptible to easy discrimination. In the following discussion, we wish to outline a method which will remedy the situation. In the proposed arrangement, chaff is deposited in the atmosphere from a dispenser in such a manner as to have negligible velocity with respect to the medium (air), which prevents it from burning up. It is then irradiated by an airborne transponder, located on the vehicle dispensing chaff, so as to simulate desired radar echoes in range and Doppler, making returns undistinguishable from echoes from the main target.