Frequency modulation telemetry system

Claim 1

A frequency modulation telemetry system comprising: a. scanning means for causing an alternating scanning signal having an adjustable frequency to be propagated towards a target capable of sending an alternating response signal, whose frequency reproduces the variations in the frequency of the scanning signal, back to the telemetry system; b. modulation generator means for controlling said scanning means by a modulation signal for creating a variation in the frequency of said scanning signal according to a predetermined pattern as a function of time, said predetermined pattern being a succession of two types of ramps, increasing and decreasing, which cause the frequency of the scanning signal to vary between a low and high frequency in a predetermined time interval called the ''''pseudo period,'''' the succession comprising at least two consecutive ramps of the same type and at least two consecutive ramps of the opposite type, and for supplying a start signal having a predetermined time relationship with the pattern; c. receiving means, sensitive to a variation in the frequency of the response signal according to the predetermined pattern, for supplying a return signal having a predetermined time relationship with the pattern; d. chronometer means for receiving the start and return signals and measuring the time interval between these two signals, and for providing a distance indicating signal, determined by the interval which represents the distance of said target, wherein said receiving means comprises: e. frequency discriminator means for supplying a pass signal each time the frequency of the response signal is equal to a predetermined reference frequency; f. time comparator means for receiving the pass signals and supplying a comparison signal which has a first value each time the time interval between two successive pass signals is between two predetermined values, one value higher and one lower than the pseudo period, and which has a second value each time the time interval is not between the two predetermined values; and g. sequence comparator means for recording the succession order of the first and second values of the comparison signal, and supplying the return signal as soon as a thus recorded sequence of the first and second values is identical to a predetermined sequence corresponding to the predetermined pattern, wherein the first value signal corresponds to a succession of two ramps of the same type and the second value signal corresponds to a succession of two ramps of the two different types.