Abstract: A phase reference navigation system and method employs a plurality of fixed narrow beamwidth antennas arranged to cover a predetermined angular sector and such that the patterns of adjacent antennas crossover one another at their half-power points. Each antenna radiates an RF carrier which is amplitude modulated by a reference phase signal and by one of two different frequency subcarriers. Adjacent antennas radiate different frequency subcarriers. Each subcarrier is frequency modulated by a variable phase signal which has a phase relative to the reference signal which corresponds to the direction of orientation of the antenna from which that subcarrier radiates. A receiver simultaneously receives the RF energy radiated by two adjacent antennas. Upon demodulation, the two variable phase signals are recovered and combined to produce a resultant signal which has a phase that varies as a function of angle between the two antennas.

Abstract: A measurement system for determining the groundspeed of an aircraft during final approach and landing, by measuring at the aircraft the Doppler shift of a radio signal, and/or its modulation components, transmitted by a fixed ground station. The carrier signal is allowed to drift; it is provided with a modulated tone on the carrier having a frequency signature that identifies the direction and magnitude of this carrier frequency drift. In a second embodiment the Doppler cycles are not counted directly, but rather fixed increments of a cycle wavelength are measured; the time period of each segment is inverted to obtain a value proportional to the Doppler frequency.