Abstract: This radar system for measuring the nearest distance "h" comprises transmitting means (9, 7, 5) for transmitting towards an object a frequency-modulated wave, receiving means (15, 17) for receiving the wave after reflection by the object, mixing means (20) for producing a beat-frequency wave between the transmitted wave and the received wave, high-speed digital processing means (30) for effecting a time-frequency transformation operation of the beat-frequency wave; it further comprises management means (50) for providing the user with the value "h" by influencing more specifically the transmitting means and the high-speed digital processing means.

Abstract: An auto-correlation apparatus for producing N auto-correlation values R(k), (k=0, . . . N-1) of an auto-correlation function of a sequence of digital samples x(n), (n=-.infin. . . . 0, . . . p) of an input signal, each sample being encoded as words of "b" binary bits, each value R(k) being defined by the formula: ##EQU1## wherein M is the number of digital samples. The apparatus comprises a random access memory for storing at respective addresses therein words (X,R) each of which is a concatenation of a word representing the value of a signal sample (X) and a word representing an auto-correlation value (R). A multiplier cooperating with an adder performs multiplying and summing operations on the M most recent signal sample words in accordance with the formula for R(k). A memory addressing and sequencing member supplies an addressing cycle to the memory for each received signal sample words, and controls the operations of the multiplier and adder.

Abstract: This radar device for measuring the distance h of the device to a surface (2) includes transmission means (5) for transmitting to the surface a frequency-modulated wave E(t) provided by an oscillator (14) having a frequency control, receiving means (7) for receiving this wave R(t) reflected from the surface, a mixer circuit (10) for producing a beat wave between the transmitted and received waves and a processing circuit (20) including a beat-wave-digitizing circuit (25) and a time-frequency transform operator (27) for supplying frequency components from which the distance h is determined. This processing circuit (20) further includes an auto-correlation operator for effecting an auto-correlation of the beat wave digitized by the circuit (25) and also spectrum processing means (32) for finally determining the distance h.