A receiver system for determining the angle and direction between the longitudinal axis of a vehicle such as an aircraft and the direction of propagation from a source of radiation such as a VHF localizer navigation system. The receiver utilizes a pair of antennas having a mutual spacing determined by the desired accuracy and permitted ambiguities, mounted in the forward section of the aircraft such that one antenna is located on each side of the forward section of the aircraft. The antennas define a baseline therebetween which is substantially perpendicular to the longitudinal axis of the aircraft. The system permits the measurement of the direction of arrival of electromagnetic energy from the localizer system with respect to the baseline of the two antennas by converting the difference in RF phase of the signal respectively received by the pair of antennas to a difference in audio phase from a reference frequency generated by and in the receiver itself.
A monitor located about 100 m from the ILS localizer determines whether the DDM alarm threshold was exceeded due to an equipment error or to an error caused by an overflying aircraft. To accomplish this, either the maximum of the frequency spectrum of the variation with time of the differentiated DDM signal is located, or the frequency spectrum of the variation with time of the DDM signal or of the differentiated DDM signal is compared with one or a plurality of spectra typical of equipment errors or of errors caused by overflying aircraft.
4194244 - Angle sensing system - Owned by The United States of America as represented by the Secretary of the Navy (Washington, DC)
A system for measuring, in conjunction with a GCA radar, the crab angle of n aircraft which is making its landing approach above a runway. A loop antenna mounted on the craft transmits an audio-frequency electromagnetic wave to two sets of crossed receiving loops, each set mounted at one side of the runway. A line joining the centers of the loops makes a 45.degree. angle with the plane of each loop. The outputs of the loops in each set are subtracted from each other, amplified, detected and rectified and then differentiated to provide a pulse output indicating the zero point of the subtraction, i.e., the time when the H-field vector is at an angle of 45.degree. to the plane of each of the loops in the set providing the zero-indicating pulse output. The zero-indicating pulse outputs are fed to a time interval counter which determines the time interval between them. With this information plus the ground speed of the craft (as determined by the GCA radar) and the distance between the receiving-loop sets, the crab angle of the aircraft can be calculated.
An aircraft landing system employs an array of antennas aligned across the runway, and equipment on board the aircraft employs radio interferometry to measure path length differences between the aircraft and selected pairs of the antennas. The antennas each include circuitry for sideband modulation of a basic FM signal so that each antenna radiates a pair of sidebands displaced above and below the basic signal by a respective number of increments. The FM signal can be carried on an X-band carrier of nominally ten GHz, with a frequency deviation of .+-.250 MHz and a modulating frequency of 20 Hz. Further antennas provide taxiing guidance. Data can be communicated on the system.
A method and system for determining an actual location of a sense antenna associated with a phased array communications satellite. A plurality of calibration carrier signals are transmitted at known frequencies. Each of the plurality of calibration carrier signals are received at a second frequency and compared with each of the plurality of transmitted calibration carrier signals. The actual location of the sense antenna is determined based on the comparison between the known frequency and the second frequency. The phased array communications satellite then broadcasts communication signals based on the actual location of the sense antenna rather than a desired location of the sense antenna.
A system for communicating data between an aircraft and ground unit over conventional amplitude modulated (AM) voice radio channels employs a data collection unit for collecting data desired to be transmitted, such as global positioning system (GPS) data, altitude, or aircraft identification information which is encoded by a data encoder. A gating means senses when the microphone of the AM transmitter is keyed, and passes the encoded data and the voice signals to the existing AM modulator of the AM voice transceiver. This results in a transmitted signal received by a receiving unit, such as a ground unit, which separates the received signal into an AM modulated voice signal and a AM data signal. The AM voice signal is demodulated by normal means into an audible signal, with the AM data signal being decoded by a data decoder into data. This data may be used to identify the aircraft symbol on a radar screen, identify the voice signal with a aircraft identification number, or flight number thereby reducing the amount of identification required. In alternative embodiments, avionics equipment may be added to the aircraft responsive to the data being sent from the ground unit, allowing collision avoidance capabilities.
