Showing papers on "Moving target indication published in 1974"

Radar MTI processor with CFAR

Abstract: Disclosed is a radar signal processor providing Moving Target Indicator (MTI) operation with Constant False Alarm Ratio (CFAR) capability. The processor affords substantially reduced incidence of false alarms due to large clutter scatterer returns which exceed normal detection thresholds even after suppression by conventional MTI processing, and at the same time it affords largely unimpaired subclutter visibility. These capabilities are achieved by paralleling the MTI channel with a second processor channel which provides CFAR operation by imposing an additional detection threshold effective to blank the response of the MTI channel to very large clutter scatterers.

Spike enable circuit

Abstract: The elimination of interfering radiation from received radar signals is generally accomplished by side-lobe suppression systems. Large clutter signals, however, can cause a side-lobe suppression system to become almost inoperable. In a high clutter environment the operation of a conventional side-lobe suppression system may also result in a high incidence of false alarms. In the present invention, pulse interference that arrives by way of the main antenna side-lobes that is smaller on the side-lobe suppression channel than the clutter signal appearing on the main radar channel is blanked prior to the implementation of a moving target indication (MTI) channel. A sharply rising interference pulse such as a spike occurring in the auxiliary channel may be detected by a fast time constant (FTC) circuit to provide a sidelobe blanking signal.

Moving target indicating (MTI) radar systems employing vehicle discriminator apparatus

Abstract: There is disclosed a radar system of the type employing a receiver capablef responding to a signal reflected from a moving target, which signal includes a doppler frequency component indicative of target motion. Included therewith are means for responding to an even harmonic component of said returned signal to provide an indication of the magnitude of the same, the magnitude of said even harmonic component indicative of the nature of said vehicle, as, for example, whether said vehicle is a tracked type (tank) or a wheeled type (automobile).

Synthetic aperture radars including moving target indication

Abstract: There is disclosed a synthetic aperture radar arranged to survey a region from a mobile location. Radar pulses are transmitted in sets, the pulses from each set being transmitted from congruent positions. The returned echoes of the pulses of each set are then compared to substantially remove signals relating to static targets. The signals relating to the doppler shifts of returns from moving targets are processed by a correlator covering a frequency band sufficient to include such signals or further signals indicative of them and produced as a result of the sampling nature of the pulsed radar.

Shared pointing for offset target of an adaptive phased array

Abstract: A coherent optical adaptive system employs phase conjugation for locking the beam of a phased array of laser transmitter to a target, focusing the beam on the target and compensating for distortion and disturbances both within the system and in the propagating medium between the system and the target. A first diffraction-limited lobe of the beam is locked on a real target to track the real target. Simultaneously a second diffraction-limited lobe is directed to a location having a predetermined offset with respect to the target and relative energy of the two lobes is selectively adjusted. A signal component representing a fictitious target that is offset by a predetermined amount from the real target is summed with the signal received from the real target, the phase of the sum is compared with the phase of a reference, and the phase of the transmitted signal is adjusted so as to null the difference between the sum and the reference phases for each of a number of channels.

Moving target indicator clutter tracker

Abstract: An improved MTI (Moving Target Indicator) cancelling system that provides cancellation in the first canceller stage of clutter at a first frequency and cancellation in a second or subsequent canceller stage of clutter such as weather or chaff with a substantial doppler frequency offset from that cancelled in the first MTI canceller. The first canceller stage may be a conventional in-phase (I) and in-quadrature (Q) digital MTI unit to develop the I and Q first differences followed by a conversion of these differences into a combined first difference designated as a quantity M and representing an angle times an amplitude multiplier. This M signal is then applied to a second canceller to develop a second difference signal which is then normalized to represent a pure angle term. A computer then determines the average angular error percentage over a selected number of adjacent range bins at each range bin interval and this percent error is then multiplied by the time aligned value of M to provide an actual error and a modified value of M is developed by subtracting the actual error from the value of M. The modified first difference signal is then subtracted from the delayed first difference signal to generate a second difference output signal with the undesired clutter at different doppler frequencies being cancelled.

Processor for discriminating between ground and moving targets

Abstract: A processor adapted for use in conjunction with a monopulse radar system for discriminating between ground and airborne moving targets and comprising: Doppler filter circuits for detecting moving targets; angle measurement circuits which respond to the received sum and elevation difference signals so as to provide an indication of the relative angle of each moving target and of the ground; and means for identifying a detected target as a ground or an airborne target as a function of whether the angle of the target is substantially the same as or different from that of the ground.

MTI Clutter Locking for Arbitrary Clutter Spectral Shapes

Abstract: Clutter-locking criteria for various types of cancellers and clutter spectra are discussed. It is shown that the proper locking criterion for general asymmetric clutter spectra is different from that applicable to those spectra which have even symmetry or are very narrow.

Target Detection Assessment Using an Orthogonal Mixed-Factor Central-Composite Design

Abstract: Target detection performance on a time-compressed radar display with both spatial and temporal cues was investigated. The effects of six variables (frame duration, noise level, clutter level, number of stored frames, target speed, and target direction) were examined using an orthogonal mixed-factor central-composite response surface experimental design. Results are discussed in terms of the contributions of spatial and temporal cues to detection performance. A methodological discussion of the experimental design is also included.

A method for optimising radar signal waveforms for clutter rejection

Abstract: In the case of radar targets embedded in a strong 2-dimensional clutter field in the range-Doppler space, the clutter rejection property of rectangular pulse bursts, expressed as the signal-to-interference power ratio, is known to depend on the parameters of the pulse train and the probability density of clutter in the range-Doppler field. In this paper a systematic quantitative study is made of the effect of signal parameters like pulse spacing and pulse train length on the signal-to-interference ratio. The processing of the range-and-Doppler-shifted signal in the matched filter receiver is simulated on a digital computer to obtain the ambiguity function for any given pulse train. The volume under the ambiguity function weighted by the clutter probability density yields the signal-to-interference ratio. This ratio has been computed for trains of 2 to 10 pulses with varying pulse spacing for four different types of clutter distribution and the results are presented in this paper. This analysis provides va...