Abstract: Improved non-cooperative radar apparatus locates and type-classifies an agitated, vibrating reflective target (e.g., a vehicle with its engine running)--whether the target is moving or stationary.A homodyne-type receiver with a cooperating band pass filter extracts a reflected, frequency-shifted energy pattern which identifies the incidence of the agitated target. In accordance with further aspects of the instant invention, the particular energy distribution for the returned, reflected wave is then compared with a stored ensemble of such distributions, or target "signatures", to type-catagorize the target.

Abstract: An electronic identification system includes common transceiver and signal processing apparatus, and relative small electronic circuitry, referred to as a "tag", secured to each item of a population to be identified. Each tag is assigned a multi-bit digital code which may or may not be unique.The common equipment determines whether any desired tag-bearing item is nearby by emitting a phase modulated radio frequency wave embodying the requisite tag code, and examining the output of a homodyne mixer, operating on a radar-like recovered reflection signal, for a predetermined signatory response. Such a response will be generated only by a tag circuit responding to a match between its stored encoding and that of the interrogation signal by changing the effective cross sectional reflecting area of the tag antenna.