A method and apparatus for providing a constant scale factor in azimuth and synchronism of data blocks for a second stage fast Fourier transform in a synthetic aperture radar having two stages of FFT by varying the sampling rate at the output of the first stage FFT as an inverse function of range.

A system for detecting the presence of clutter utilizing an area overlap technique that effectively rejects scintillating position clutter near the boundaries of the area clutter map ACM cells. A first area clutter-mapper system is provided with its area ACM cells at a first position and a second clutter-mapper system is provided with its ACM cells in a second position with each cell displaced by about one-half ACM cell dimension in range and azimuth to overlap the original ACM cell boundaries. All of the clutter returns which were divided among the original set of ACM cells occur in one of the area overlap ACM cells so that when the clutter scintillates between ACM cells for any selected detection criterion, it is identified as clutter rather than a moving target. Separate detection history counts for clutter-identification and inhibit code for clutter rejection are provided in both the first and second clutter overlap map units. A clutter rejection code or condition in either area map unit will determine that clutter is present and the control gate samples either the clutter amplitude or a cluster code in both the first and second ACM cell units and rejects target signals if clutter has been determined in either of the units. In one modeling of the concept of invention, it was found that the area overlap method increased the amount of clutter rejected by 55% over a conventional single ACM mapping system unit.

A missile guidance system in which a synthetic array radar antenna control system correlates the phase and doppler frequency information contained in signals received by a four quadrant antenna from an illuminated section of terrain, so as to compute the velocity components of the antenna. The velocity components are utilized, in conjunction with the earth rate supplied from a terrestrial navigation system, to maintain the azimuth null plane of the antenna in alignment with a selected target designated by means of a synthetic array map of the illuminated terrain. A missile command system controls the flight path of missile along the azimuth null plane to the target.

A radar tracking system 100 adapted for use with existing radar tracking systems. The inventive system includes a radar target detection system 106, 108 for detecting radar targets in clutter using magnitude and angular position information obtained from return signals. A tracking algorithm 104 is used to track and update the positions of said targets with respect to the position of the radar system. The tracking algorithm includes a true target angle estimator 110 for maintaining accurate target angle information when the target is clutter and when the target is out of clutter. The tracking algorithm maintains accurate target distance information when the target is in clutter and when the target is out of clutter. In a specific embodiment, accurate distance information is maintained in a track file 122 where the amplitudes of return signals are stored once a target is detected by the detection system 100.

An apparatus for detecting clutter blocks and an interference source for dynamically establishing a clutter map includes a clutter block detecting module accumulates a plurality of range cell data of each detecting area, and compares the accumulated value with a clutter block level to define the position of a clutter block; a interference source detecting module accumulates all range cell data in each radar beam area, and compares the accumulated value with an interference source reference level to detect whether any interference source exists; and a clutter map establishing module saves the clutter maps on different beam areas in three memory blocks. When one clutter map cell is extracted, the clutter map cells on different beam areas neighboring with the beam area saving extracted clutter map cell are also extracted. The largest value among the extracted clutter map cells is being a clutter threshold value of a detected target.