Frequency modulated continuous wave altimeter

Claim 1

A frequency modulated continuous wave altimeter, comprising: (a) antenna means for receiving and radiating microwave energy; (b) transmitting means for generating frequency modulated microwave energy, including first oscillating means for generating a carrier signal, modulating means for varying the frequency of said carrier signal, and second oscillator means for impressing a tone on said modulating means; (c) mixer means, coupled between said antenna means and said transmitting means, for generating a resulting signal from the communication of transmitted and reflected microwave energy; (d) receiving means for receiving said resulting signal and generating an output signal indicative of distance, and receiving means including amplifier means, tuned to the frequency of said tone, for selectively amplifying said resulting signal, detector means for generating a signal responsive to said selectively amplified resulting signal, and counting means for generating an output indicative of distance from the number of signals generated from said detector means.

Claim 10

A method of detecting the presence of an object in a predetermined area using a frequency modulated continuous wave altimeter having an antenna, a transmitter, a mixer, and a receiver, the steps comprising: (a) generating a linearly varying voltage waveform in said transmitter: (b) generating a tone and impressing said tone on said linearly varying voltage waveform; (c) generating a microwave carrier signal in said transmitter; (d) frequency modulating said carrier signal in response to said linearly varying voltage waveform, such that said transmitter produces frequency modulated microwave energy; (e) transmitting said microwave energy to said antenna through said mixer; (f) radiating said microwave energy from said antenna into said predetermined area; (g) receiving a portion of said microwave energy reflected from a surface in said predetermined area; (h) generating a resulting signal from said mixer comprising two sinusoidal waveforms displaced in time by said tone, said resulting signal being indicative of a distance between said antenna and said surface reflecting said microwave energy; (i) selectively amplifying said resulting signal at the frequency of said tone to generate an envelope waveform with cusps occuring concomitantly with the inflection points on said resulting signal; and (j) determining the presence of said object from the number of said cusps in said envelope waveform.

Claim 11

A method of detecting the presence of an object in a predetermined area using a frequency modulated continuous wave altimeter having an antenna, a transmitter, a mixer, and a receiver, the steps comprising: (a) generating a linearly varying voltage waveform in said transmitter: (b) generating a tone and impressing said tone on said linearly varying voltage waveform; (c) generating a microwave carrier signal in said transmitter; (d) frequency modulating said carrier signal in response to said linearly varying voltage waveform, such that said transmitter produces frequency modulated microwave energy; (e) transmitting said microwave energy to said antenna through said mixer; (f) radiating said microwave energy from said antenna into said predetermined area; (g) receiving a portion of said microwave energy reflected from a surface in said predetermined area; (h) generating a resulting signal from said mixer comprising two sinusoidal waveforms displaced in time by said tone, said resulting signal being indicative of a distance between said antenna and said surface reflecting said microwave energy; (i) selectively amplifying said resulting signal at the frequency of said tone to generate an envelope waveform with cusps occuring concomitantly with the inflection points on said resulting signal; and (j) determining the presence of said object from the number of said cusps in said envelope waveform.