Showing papers on "Moving target indication published in 1967"

Clutter attenuation analysis

Abstract: : The performance of moving target indication (MTI) systems for combat surveillance radars depends to a large extent on the clutter spectrum, which is especially important when the radar attempts to detect slowly moving ground targets. This spectrum has long been assumed to be Gaussian shaped. However, MTI system performance predicted by this assumption was not achieved in practice. This report describes the results of an investigation conducted to determine the performance to be expected from an MTI system. The approach used was to measure the clutter rejection ratios afforded by various high-pass filters. The signal was taken from the boxcar demodulator of an X-band radar observing different clutter targets under varying wind conditions. Clutter rejection ratios of 10 to 40 db were measured. These results were then used to obtain a theoretical expression for the clutter power spectrum. This expression differs from the usual Gaussian assumption. Some credence is given to the results by a direct spectral analysis performed on a clutter signal. Two methods of filtering clutter signals which will result in acceptable MTI performance are suggested in this report. The results of this investigation are significant in that they have led to establishing criteria for a better MTI system design.

Dual channel adaptable moving target processor

Abstract: An airborne moving target indicator system which includes, in combination with a pulsed radar system, a digital moving target processor comprising a digital ground clutter rejection filter which is programmed to adapt to the varying frequency characteristics of received radar clutter signals. The rejection filter superimposes with alternate signs a minimum number of optimumly weighted digitized signal returns, for each of a plurality of discrete range intervals, so as to achieve a desired level of clutter signal rejection. The processor further includes a digital video integrator that is programmed as a function of the predicted time on target so as to optimize the target-tonoise ratio of the output signal from the rejection filter. A digital mean-level threshold detector is coupled to the output circuit of the integrator and is programmed as a function of the number of integrated filter outputs to maintain a selected false alarm rate.

Adaptable moving target processor

Abstract: An airborne moving target indicator system which includes, in combination with a pulsed radar system, a digital moving target processor comprising a digital ground clutter rejection filter which is programmed to adapt to the varying frequency characteristics of received radar clutter signals. The rejection filter superimposes with alternate signs a minimum number of optimumly weighted digitized signal returns, for each of a plurality of discrete range intervals, so as to achieve a desired level of clutter signal rejection. The processor further includes a digital video integrator that is programmed as a function of the predicted time on target so as to optimize the target-tonoise ratio of the output signal from the rejection filter. A digital mean-level threshold detector is coupled to the output circuit of the integrator and is programmed as a function of the number of integrated filter outputs to maintain a selected false alarm rate.

Continuous wave radar with means for indicating moving target direction

Abstract: A continuous wave radar set in which the transmitted wave is periodically gradually reversed in phase by frequency modulating the microwave oscillator thereof. The target echoes are heterodyned with a sample of the transmitted wave and applied in parallel to an all-range channel and a ranging channel. Doppler frequency signals from all moving targets within the radar beam appear in the all-range channel, whereas in the ranging channel Doppler frequency signals at any range can be selected by means of range gates. By correlating Doppler signals from the two channels, or a pair of signals from the ranging channel, target range and directivity information may be obtained.

Moving target indicator with automatic clutter residue control

Abstract: A radar system for eliminating effects of varying backgrounds in combination with an MTI. The output of a phase detector with an IF input is fed to an MTI canceller producing a video signal which is fed to a logarithmic amplifier followed by a high-pass FTC filter and then an antilog device.

Doppler wave recognition with high clutter rejection

Abstract: : A Doppler Radar is described which makes it possible to detect moving targets deeply embedded in clutter noise. The system is based on the use of quadrature detection and a new low level correlator. Most of the required amplification takes place after correlation and integration so that amplifier overloading can be avoided.

Efficiency of attenuation of moving clutter

Abstract: The Doppler-frequency shift resulting from clutter motion degrades the efficiency of moving target indication (m.t.i.) radar systems. Although the degradation is much less when some compensation methods are used, it still exists because of the finite tolerances of the Doppler-compensation frequency shift. This effect is analysed for single- and double-delay-line m.t.i. cancellers and fluctuating clutter.

Radar-waveform design for detecting targets in clutter

Abstract: The waveform dependence of matched-filter systems is investigated for detecting signals in nonstationary clutter, including the range dependence of the clutter power return. As is normally the case for microwave radars with moderate waveform durations, it is assumed that the r.m.s. clutter Doppler-shift spread is less than the signal Doppler-shift resolution. General expressions are derived for the output S/C ratio, as a function of the radar ambiguity function, the target range delay and the Doppler shift, and specific examples are evaluated. It is shown, for example, that, owing to the nonstationarity of the clutter return, long waveforms which resolve the mean Doppler-shift difference between target and clutter may result in a worse S/C ratio than that achieved with a short waveform which has no Doppler-shift resolution.