Method and apparatus utilizing time-expanded pulse sequences for distance measurement in a radar

DETAILED DESCRIPTION We claim: 1.
A method of processing radar echo pulse sequences having steep pulse flanks and a predetermined sequence frequency, comprising the steps of: generating an auxiliary pulse sequence of a sequence frequency that differs slightly from said predetermined sequence frequency; multiplying the pulses of a radar echo pulse sequence by the pulses of said auxiliary pulse frequency; integrating the product signal produced by the multiplying step and thereby suppressing high frequency signal components and obtaining time-expanded radar signals, and utilizing said time-expanded radar signals for control of indicator means as if said time-expanded signals were directly detected radar signals.
2.
A method as defined in claim 1, in which the step of generating an auxiliary pulse sequence is carried out by generating auxiliary pulses at a frequency which differs from said predetermined frequency so little that at recurring intervals a plurality of successive pulses of said radar echo pulse sequence are overlapped in time by successive pulses of said auxiliary pulse sequence.
3.
A method as defined in claim 2, in which the step of generating an auxiliary pulse sequence is carried out by generating pulses of an individual pulse duration that does not exceed the duration of the radar pulses of said radar echo pulse sequence.
4.
A method as defined in claim 2, in which there are also performed the steps of: differentiating the individual pulses of said time-expanded radar signals produced by the integrating step; producing a pulse amplitude selection gate signal by reference to first positive and negative threshold voltages whenever one of said differentiated time-expanded signals exceeds both said first threshold voltages; producing a null passage pulse for each of said differentiated time-expanded signals by reference to second positive and negative threshold voltages closer to zero voltage than said first threshold voltages, whenever one of said differentiated time-expanded signals exceeds both said second threshold voltages, and selecting for processing only those of said null passage pulses which occur during the presence of one of said pulse amplitude selection gate signals