Abstract: A receiver system using antennas which may be effected by reflections or multipath propagation errors wherein the antennas are placed at spaced apart locations and produce outputs which differ due to the difference of locations and which may differ due to the multipath propagation errors, wherein the system corrects for the position differences and eliminates a signal which contains multipath errors to provide a corrected signal.

Abstract: The improved direction finder of the instant invention has three orthogonal antenna elements or an array of antenna elements consisting of antennas in three dimensions. Amplitude and phase difference measurements are made on various combinations of antennas, and they are compared to a data base of antenna relationships that correspond to three dimensional angles. The spacial angle of arrival of electromagnetic signals are determined by the fit between the measured parameters and the stored relationships. This apparent direction of arrival is compensated for any motion of the antenna by an error signal representative of antenna motion with respect to inertial space. The apparent direction of arrival is thereby compensated to provide true direction of arrival determinations. The motion compensated direction finding system of the invention has especial utility for buoys released from undersea vessels released to sea surface.

Abstract: A method for recapturing a satellite at the highest elevation angle as quickly as possible with a GPS receiver having a plurality of receiving channels when a state of receiving satellite signals recovers to normal after having been interrupted by obstacles like a tunnel, wherein a search range of satellite signal receiving frequency is divided into a plurality of frequency bands and each of which is assigned to the plurality of receiving channels in a one-to-one relationship, a search frequency of each receiving channel is changed in step wise for searching a satellite signal simultaneously in the receiving channels, and further, by providing a time difference for a step wise change-over timing of the search frequency between receiving channels, a time required for recapturing the satellite is greatly reduced by increasing a change to lock up one of the receiving channels with the satellite signal receiving frequency, since there are as many chances as a number of receiving channels within one cycle of the s

Abstract: A system is disclosed in which a direction-finding system (12) employed on an aircraft (20) receives RF transmissions from a remote signal source (16). Amplitude and phase data concerning the transmission are used for direction finding but are perturbed by the various surfaces of the aircraft. To minimize the influence of such perturbations, a database (14) including model data subject to the same perturbations is employed by the system and incoming transmissions from signal source (16) are correlated to the database data to determine the proper azimuth and elevation associated with said transmissions. Several embodiments of a database production system (18) used in creating the database are also disclosed.

Abstract: A direction finding receiving system for use on a protected aircraft in which a signal from an ATCRABS transponder on an intruder aircraft is received has been described incorporating a four element interferometer type antenna array, reversing switches, individual receivers, a phase detector and a processor for processing the outputs of the phase detector. The invention overcomes the problem of correcting for the difference in phase delay of signals passing through the receivers.

Abstract: An attitude sensing system which incorporates the precision in attitude sensing of a satellite navigation system with the dynamic tracking capabilities of an inertial measurement unit. Optimally estimated attitude and system error signals are combined with the outputs of an inertial measurement unit to control the phase differences of signals received on an interferometer array from a navigation satellite. The outputs from the inertial measurement unit and the phase differences are processed in an optimal estimator filter to produce periodically updated attitude and system error signals. This permits inertial attitude sensing to benefit from the long term accuracy of attitude estimation based upon signals from the satellite navigation system.