Patent ID: 6140982
Filing Date: 2000-10-31
Classification: G01S

Abstract:
A method of identifying a target as a friend or foe, wherein:(a) a querying electromagnetic wave is transmitted to a target to be identified by an interrogator,(b) provided that the target to be identified a transponder matched to the querying electromagnetic wave, the target receives the querying electromagnetic wave, if necessary, and the transponder transmits an electromagnetic wave in response; and(c) the responding electromagnetic wave transmitted by the transponder is received and evaluated by the interrogator such that, if a predeterminable transponder response code is present, the associated target to be identified is classified as a friendly target,(d) the interrogator transmits the querying electromagnetic wave in the millimeter-wavelength range, with a predeterminable, average wavelength, a predeterminable directional characteristic, a predeterminable maximum range and a predeterminable coding, directly to the target to be identified;(e) the querying electromagnetic wave is received by the transponder by means of a receiving antenna essentially having a non-directional receiving characteristic, and the responding electromagnetic wave is then transmitted essentially non-directionally, and lies in the same millimeter-wavelength range as the querying electromagnetic wave;(f) the responding electromagnetic wave transmitted by the transponder is received by the interrogator by means of a receiving antenna that is directed at the target to be identified and has a predeterminable directional receiving characteristic;(g) in the interrogator, the received responding electromagnetic wave is supplied to a first mixer by way of a first limiter, a low-noise preamplifier and a second limiter, then converted by the first mixer and a signal generated by a local oscillator, with a predeterminable frequency, into a predeterminable intermediate-frequency range, and demodulated in a quadrature demodulator after a predeterminable low-pass filtering, resulting in orthogonal signals in the video range;(h) the orthogonal signals are converted into an analog signal by means of a matched filter matched to the coding of the responding wave, and subsequently converted into a digital signal by an analog/digital converter; and(i) the digital signal is decoded by at least a decoder and a controller and evaluated such that it is possible to identify a target as a friend or foe based on the coding.