A method for tracking a satellite in a land mobile satellite communications system is disclosed. A rate gyro is provided for use in the event that an automatic satellite tracking is prevented. The satellite is automatically tracked using a receive signal level if the receive signal level equals or exceeds a threshold. An output of the rate gyro is constantly compensated while automatically tracking the satellite. When the receive signal level falls below the threshold and the automatic satellite tracking becomes unable, the satellite is tracked using the compensated output of the rate gyro.

Antenna beam pointing method for satellite mobile communications system

This scanning array scans an area around the array for nearby objects, collision obstructions, and terrain topography. The scanning array can scan for sounds emitted by objects in the vicinity of the scanning array, passive energy receipt sources, or it can also send out an energy beam and scan for reflections from objects within the energy beam. The energy beam can be optical, laser, radar or other energy emitting sources. The scanning array of the invention can be used for helicopter detection and avoidance of collision risk and can be used for other scanning purposes. Scanning of an entire hemisphere or greater is accomplished by manipulating the scanner platform through the coordination of either linear actuators or gimbals so as to produce nutation without rotation. This motion allows transceivers to be directly coupled to transmitting and sensing modules without the losses associated with slip rings and other coupling devices.

Scanning array for obstacle detection and collision avoidance

A multi-loop control system for a gimballed antenna that employs devices for measuring both absolute line-of-sight (an autotrack receiver or beacon tracker) and relative angular position (a resolver). The control system uses both signals simultaneously, thereby increasing the performance and pointing accuracy capability. Two control loops operate simultaneously to provide for optimum performance. The first loop is an inner high-bandwidth control loop that uses the relative gimbal angle measurement to control pointing of the antenna along a precommanded profile. The inner loop may run alone to provide for coarse pointing. When available, the line-of sight measurement is used in a low-bandwidth outer loop to provide corrections to the command profile of the inner loop. Control logic is provided that allows switching between several control modes. By using the present invention, antenna tracking control performance is maximized, especially in the presence of attitude disturbances of a spacecraft or significant flexible interactions.

Gimbal control system

A technique for boresighting an antenna mounted on a moving platform is described. The technique uses a concurrently moving calibration target. Target navigation data and platform navigation data are used to compensate for movement of the target and the platform. The antenna pointing direction is biased in a direction which provides a best signal quality, and the bias used to determine antenna boresight calibration factors. The boresight correction factors can be used for open loop pointing.

Method and device for boresighting an antenna on a moving platform using a moving target

Disclosed is a conically scanning antenna emitting a beam of radiation which is modulated in phase but not in amplitude. In certain embodiments the antenna comprises a source of radiation including a horn illuminating a reflector, the horn being either inclined to the reflector axis or juxtaposed with a prism imparting such inclination to its direction of maximum radiation. The inclined horn or the prism is rotated about the axis by drive means supplying a reference scanning signal to a processor.

Conical scan antenna for tracking radar

Apparatus for generating elevation and azimuth reference signals for use in demodulating a tracking error signal to provide elevation and azimuth error components for use in adjusting the position of a tracking conical scan radar antenna, includes a template ring having a notched periphery and being attached to a rotatable nutator of the antenna such that its peripheral notches are in a predetermined angular phase relationship with a reference position on a feed horn attached on the nutator, during rotation of the feed horn with the nutator. The apparatus further includes an optical transducer and electronic circuitry coupled thereto for producing the reference signals from a signal generated by the transducer in response to rotation of the ring with the nutator. As the ring rotates with the nutator, its notched periphery makes or breaks a photon path between light beam generating and sensing elements of the transducer. The sensing element then generates the signal which is received by the electronic circuitry. In addition to the two reference signals produced by the circuitry, a sync signal is generated and used internally within the circuitry to insure that the reference signals produced are in a proper phase relationship to the reference position on the feed horn of the nutator during rotation thereof.

Reference signal generating apparatus

An antenna tracking system in which attenuation of gain in the azimuth tracking circuit as a function of the angle of elevation of the antenna is compensated. A correction circuit is provided in the servo loop for amplifying the azimuth error signal and rate gyro signal by an amount equal to the secant of the elevation angle.

Vernal Wynn Thompson

Papers

Reference signal generating apparatus

Secant correction circuit