FM-CW Radar ranging system with automatic calibration

Claim 1

In a frequency modulated continuous wave ranging system of the type including: first means for generating a continuous wave interrogation signal, said interrogation signal being frequency modulated in accordance with a desired waveform and having predetermined parameters enabling measurement of the range R of a target of interest, at least one of said parameters being subject to undesired change in value, causing the measured range to be incorrect; second means for transmitting said interrogation signal to a target of interest and receiving reflected signals from said target of interest; third means responsive to said interrogation signal for producing a reflected signal indicative of a target at known range, X,; fourth means for deriving difference signals indicative of the frequency difference of said reflected signals of said target of interest and known range target from the instantaneous frequency of said interrogation signal, said difference signals being indicative of said ranges R and X, respectively; and fifth means responsive to said difference signals from said fourth means for scaling said signals indicative of range R by said signals indicative of range X; wherein the improvement comprises: sixth means coupled between said first means and second and third means for alternatively coupling said first and second means and said first and third means such that said fourth means alternatively produces signals indicative of range R and range X; and seventh means responsive to signals from said fourth means for storing one of said indications of range X and range R and wherein said fifthe means is responsive to said difference signals stored by said seventh means representing one of ranges R and X and said signals from said fourth menas, representing the one of ranges R and X not stored by said seventh means, for scaling said signals indicative of range R by said signals indicative of range X.