Frequency modulator for high-precision range measurements

摘要

A range measuring apparatus of the linear frequency modulation type is disclosed which comprises a measuring control loop for rendering the beat frequency between the transmitted and received frequencies equal to a fixed frequency. The apparatus further includes means for forming a permanent second beat signal between two signals derived from the generator supplying the frequency modulated signal, one of these signals being delayed by means of the delay line. A phase detector receives this second pulsed signal and the signal of a controlled frequency oscillator and supplies a signal which controls the slope of the frequency modulation. The error signal of the measuring control loop controls the frequency of the signal from the oscillator. This arrangement results in an increased precision in the range measurements.