Abstract: A multilateration location system (12) includes a locatable unit (16) and any number of known-position locators (14). A time of arrival detector (22) determines instants in time when a location signal (20) transmitted by the locatable unit (16) arrives at various known-position locators (14). For each combination of two known-position locators (14) that receive the location signal (20), a pre-estimation process (32) determines whether the difference in arrival times is less than or equal to a maximum propagation duration for the locator pair. The maximum propagation duration is based upon the distance between the locators (14) in the locator pair. If the difference is greater than the maximum propagation duration, the difference is omitted from the data set processed by a multilateration calculation process (34). A post estimation filtering process (36) screens out location estimates that are too distant from a predicted position.

Abstract: A transmitter (12) broadcasts a PN encoded message (16). A receiver (14) includes a SAW correlator (38) configured to autocorrelate with the PN sequence used in the broadcast signal. A preamble of the message (16) conveys two successive bits (18) that are each encoded with the PN sequence. After the correlator (38) has been preloaded with the PN sequence from the first bit (18), its non-correlation output exhibits reduced amplitude time sidelobes. A timing comparison circuit (60) compares a correlation signal (46) with a timing threshold (72). The timing threshold (72) is established at a very low level to minimize the influence of multipath. False triggering on noise is prevented by disabling the timing comparison circuit (60) until after the first bit (18). At this point in time the correlator (38) has been preloaded with its PN sequence, is again being loaded with its PN sequence, and outputs reduced amplitude time sidelobes.

Abstract: Timing signals are transmitted from reference transmitters through antenna/receivers (antenna preamplifier nodes) to collector nodes (C-Nodes) and to a central computer. The times of arrival of the signals at the various C-Nodes are measured by the C-Nodes, relative to each C-Node's clock. The time of arrival signals at each C-Node must be based upon a common time reference to be useful for positioning. Therefore, the central computer determines the offsets of clocks relative to a selected reference C-Node clock. The time of arrival signals are then calibrated against one another and used to adjust the time of arrival signals so that all time-of-arrivals are relative to the same reference and can be used for position determination and the clocks of the collection nodes are effectively synchronized.

Abstract: An optical target detector utilizes a star coupler to achieve automatic alignment of "pencil" laser beams. A number of "pencil" beams of laser light are deployed from the surface of a projectile in order to detect a target. The laser light is transmitted to the target and reflected back from the target to the optical target detector. The light tramsmitted, in the form of a number of "pencil" beams, and the light being reflected by the target are transmitted through a star coupler device in order to maintain alignment for the transmission of maximum light signal strength and simultaneously to minimize aerosol backscatter.

Abstract: A spectral filter for use in optical systems receiving field-of-view (FOV) optical beams at differing angles refracts all FOV beams onto a single plane focal surface. The spectral filter comprises a combination of lens having varied thicknesses incorporated into a single filter unit. Each thickness, or step, of the spectral filter corresponds to a different one of the received FOV beams.