摘要:
The invention proposes a novel method for using the signals provided by an airborne FM/CW radio altimeter, allowing to perform an analysis of the ground overflown by an aircraft for the purpose of, for example, identifying it, or alternatively of recognizing it. The method of the invention consists in analyzing, in the frequency domain, the shape of the spectrum of the beat signal generated by said radio altimeter to characterize said ground so as to extract from it information relating to the reflectivity of said ground.
摘要:
A method of receiving pulses of the M.L.S. type and a system for implementing this method. The method comprises a dividing stage for dividing the received pulse into zones (Z1, . . . Z8). A mean value is determined of the samples within each zone in order to obtain the points PI(1) . . . PI(8). The straight line DR at best passing through these points provides the instant (tMAX) which is the "time" of the pulse.
摘要:
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.
摘要:
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.