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Abstract

A radio frequency distance measuring system and method where two continuous wave carrier signals, derived from a stable frequency source, are radiated from a known reference point. The frequency of the first continuous wave carrier signal is displaced from the frequency of the second continuous wave carrier signal by a selected difference frequency. When received at the unknown point, the two continuous wave carrier signals are mixed to provide a difference or beat frequency marker signal, delayed in arrival at the unknown point from the known point by the speed of light. A locally generated marker signal is derived from a stable frequency source at the unknown point, and has the same frequency as the difference frequency signal. The leading or trailing edge of the difference frequency signal can be compared with the locally generated marker signal, and the time difference or phase difference between them can be displayed using a phase meter or time interval indicator and corresponds to determine directly the distance between the known transmitter reference point and the unknown receiver point. Multiple known reference point transmitters, each transmitting two continuous wave carrier signals displaced in frequency by a selected difference frequency, can be used to obtain two or more distance measurements at the unknown point to determine the position of the unknown receive point with respect to the known transmitter points. A chart shows the relationship of the selected difference frequency to the distance that can be measured without ambiguity.

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First Claim