Showing papers on "Moving target indication published in 1985"

Two-port synthetic aperature radar system for radar detection of targets

Abstract: Doppler signals from a two-port radar system are spectrally processed and searched for a pattern of points wherein clutter at a first instant of time is subsequently replaced by low-level returns indicating the movement of a target. The rate of change of the low-level signals, along the same range bin but different Doppler bins, is indicative of target azimuth position relative to the boresight of the radar antenna. The difference between the total Doppler detected from the target and the Doppler for the azimuth position of the black hole detection is the Doppler for the relative radial velocity of the target. Not only is the black hole and shadow (lack of detection) detectable but more measurable and detectable is the clutter signal difference with the target motion.

Point clutter threshold determination for radar systems

Abstract: An adaptive detection threshold system for moving target detector and moving target indicator radar systems. The threshold system uses data from the echo input signal to reconstruct a threshold level closely resembling the output clutter residue in doppler filters due to point clutter sources. At least three azimuth data values are used, with the values being from adjacent coherent processing intervals and separated in azimuth a distance approximately equal to the beamwidth of the antenna system. The data at the same range from the three azimuths is combined to form an estimate of the residue at the output of a doppler filter, assuming that the echo is caused by point clutter. Compensation for radar instability and changes in scan rate or interpulse period is included. Data from conventional constant false alarm rate processing designed to control alarms from distributed interference, such as weather echoes, is also used to compensate the residue estimate.

Moving target indication system

Abstract: A system comprising a scanning detector for rapidly scanning a field of view through appropriate optical means, and with a linear infrared detector array, there being electronic apparatus for converting the detector signals to digital signals and for storing such information for comparison with like information from another or many additional scans. The system further includes electronic apparatus for processing such detector signals from a first scan as well as from second or succeeding scans to determine the amount of misalignment between the frames of such scans to develop a correction signal which is applied to adjustment apparatus to correct such misalignment to insure that the frames of succeeding scans are accurately aligned with frames from previous scans.

Moving target indicator

Abstract: A Doppler pulse-radar system has a moving target indicator (MTI) in which stationary clutter is removed from I and Q components of the radar received signals by two conventional MTI clutter filters (11, 12) whose outputs are corrected in respective corrector circuits (13, 14) so that two further MTI clutter filters (15, 16) can remove the remaining clutter from moving clutter sources. The corrector circuits (13, 14) produce respective signals with constant amplitude and phase. An operator observing a visual display driven by the I/Q combiner (18) adjusts the output from a presumptive moving clutter average Doppler frequency generator (18) to reduce observed clutter. A phase-correcting data generator (19) generates a phase variation signal for each trigger repetition, which is integrated (21) and drives a sin & cos converter (22). An amplitude-correcting data generator (20) generates amplitude correcting values for each trigger state. A correcting data generator (23) forms product signals from the outputs of the converter (22) and generator (20) and supplies these signals to the converter circuits (13, 14).

An Experiment Quantifying The Effect Of Clutter On Target Detection

Abstract: Experiments were conducted to determine the influence of background clutter on target detection criteria. The experiment consisted of placing observers in front of displayed images on a TV monitor. Observer ability to detect military targets embedded in simulated natural and manmade background clutter was measured when there was unlimited viewing time. Results were described in terms of detection probability versus target resolution for various signal to clutter ratios (SCR). The experiments were preceded by a search for a meaningful clutter definition. The selected definition was a statistical measure computed by averaging the standard deviation of contiguous scene cells over the whole scene. The cell size was comparable to the target size. Observer test results confirmed the expectation that the resolution required for a given detection probability was a continuum function of the clutter level. At the lower SCRs the resolution required for a high probability of detection was near 6 lines pairs per target (LP/TGT), while at the higher SCRs it was found that a resolution of less than 0.25 LP/TGT would yield a high probability of detection. These results are expected to aid in target acquisition performance modeling and to lead to improved specifications for imaging automatic target screeners.

Moving target indicator using a surface acoustic wave device

Abstract: A surface acoustic wave (SAW) device in a pseudo-coherent moving target indicator uses a common input transducer to delay both reference and signal inputs to a mixer by varying amounts. The mixer produces a Doppler signal which is processed within a single range cell. The SAW device may contain additional delay paths which drive other range cells. Power splitting and amplification sections of the moving target indicator are minimized through use of the SAW device.

Comparing the radar clutter-suppression performances of lattice prediction error filters using three variations of Burg's algorithm

Abstract: An adaptive technique is presented for suppressing clutter in a moving target indicator radar signal processor. The technique is based on the assumption that radar clutter can be modeled as a Mth-order auto-regressive (AR) process and employs a lattice prediction error filter structure to suppress clutter without significantly distorting the target signal. Filter coefficients are the reflection coefficients determined using one of the three variations of Burg's AR parameter estimation algorithm due to Andersen, Makhoul and Marple. These filter designs are applied to second-order Butterworth-shaped spectra representing both ground and storm clutter, and their performances are compared with each other and with more conventional methods in terms of improvement in signal-to-clutter ratio between filter input and output. Results are presented which show the dependence upon such factors as sample size, filter order, and doppler frequency.