Junction range finder

Claim 1

Apparatus for locating an electrically nonlinear object comprising: A. means for generating a frequency modulated exciting signal of a predetermined fundamental frequency; B. a transmitting means for transmitting said exciting signal in the vicinity of said nonlinear object for causing a signal of a higher harmonic to be reflected by said nonlinear object; C. a means located in close proximity to said nonlinear object for receiving said higher harmonic reflected signal; D. filter means coupled to said receiving means for passing a predetermined harmonic portion of said received signal; E. means coupled to said generating means for multiplying said exciting signal to produce a signal of the same frequency as said signal reflected by said nonlinear object and filtered by said filter means; F. a first mixer for mixing said multiplied excited signal with said filtered reflected signal producing a combined signal; G. amplifier means for amplifying said combined signal, H. a discriminator coupled to the output of said amplifying means for producing a signal having an amplitude directly proportional to the distance to said nonlinear object, and I. a limiter interposed between said first mixer and said discriminator for reducing unwanted amplitude modulations.