Abstract: A frequency modulated continuous wave altimeter and method of detecting the presence of an object in a predetermined area. The altimeter is generally comprised of an antenna for receiving and radiating microwave energy, a transmitter for generating frequency modulated microwave energy, a mixer for generating a sinusoidal resulting signal from the communication of transmitted and reflected microwave energy, and a receiver for processing the resulting signal and generating an output signal indicative of distance. The transmitter includes a Gunn diode for generating a carrier signal, modulating means for varying the frequency of the carrier signal, and a high frequency oscillator for impressing a tone on the modulating means.