Showing papers on "Moving target indication published in 1979"

Optimum antenna polarizations for target discrimination in clutter

Abstract: The concept of Stokes vectors and Stokes target operators is used to obtain optimum antenna polarizations for target discrimination in the presence of background clutter. The analysis involves a constrained maximization of the ratio of two bilinear forms, representing the signal-to-interference power ratio.

Infrared radar system

Abstract: An infrared radar system. The system includes an infrared laser and associated controller which are adapted to provide a succession of transmit pulses having a relatively high intensity spike portion followed by a relatively low intensity quasi-CW portion. An optical system directs the transmit pulses to a target scene and collects infrared radiation reflected from the scene. The collected radiation is imaged on a heterodyne detector array together with a locally generated reference infrared beam. A range network is responsive to signals from the detector array to provide signals representative of the range of objects in the target scene. A moving target indicator network is responsive to signals from the detector to provide signals representative of the velocity of objects in the target scene.

Helicopter rotating blade detection system

Abstract: An airborne pulse doppler radar set generally includes a moving target indicator (MTI) system for detecting moving aircraft within its scanning purview. To avoid processing undesirable clutter, the MTI system includes a clutter cancelling type filter for rejecting doppler shift frequency signals reflected from objects moving at velocities below a predetermined minimum velocity value. Unfortunately, the doppler shift frequencies representative of the body velocity of most helicopters fall within this clutter repetition band and may go undetected by the MTI system. To detect these helicopters, a helicopter detection system which operates on the specular flash energy of the doppler shift frequency signals reflected from the rotating blades of a helicopter is provided. The helicopter detection system passes substantially the received reflected radar signals that have doppler shift frequencies representative of the helicopter rotating blade velocities, derives a threshold value based on the values of the passed signals, and generates detection signals at times corresponding to the passed signal values which are at least that of the derived threshold value. In addition, the helicopter detection system is capable of inhibiting the generation of the detection signals at time corresponding to the reception of interference type radar signals by the radar set. Furthermore, an unambiguous range of each detected helicopter may be computed. Moreover, the helicopter detection system has the capability of distinguishing between detected targets having even and odd numbers rotating blades.

Target discrimination apparatus

Abstract: The target discrimination apparatus utilizes logic circuit which is positioned between the detection window and the clutter averaging cells of a conventional constant false alarm rate (CFAR) radar detector to provide better estimation of the clutter average and therefore better target detection in the multiple target environment.

Moving target indicator system utilizing charge coupled device

Abstract: A time change or moving target indication system utilizing charge-coupled devices (CCD's) for signal processing in which successive integrated samples from individual detectors are loaded into adjacent CCD storage buckets and then clocked to an output device. The output device is any suitable differencing arrangement which samples the charge stored in adjacent buckets and gives an output proportional to the difference. The system of the invention allows the successive signals from individual detectors to pass through virtually identical elements in the signal processing chain so as to reduce the effects of transfer inefficiency on the accuracy of the MTI subtraction process. Further, the signal spectrum from an individual detector output may be shifted to higher frequencies during the readout process so as to reduce the effects of any 1/f noise that may be present in the output device. The concept, in accordance with the invention, may be implemented off the focal plane as well as on the focal plane and may be implemented for a single row of detectors or for a detector array. In the off-focal plane configuration in accordance with the invention, the detectors are sampled at a rate much higher than the system field time to provide a high signal bandwidth which permits additional signal processing such as noise spike suppression and background subtraction to be performed before subsequently integrating the samples from individual detectors over the desired field time.

High speed adaptive clutter filter

Abstract: Method and apparatus for eliminating the effects of clutter in a coherent pulsed Doppler radar including determining the center frequency of the clutter and periodically moving the local oscillator frequency so that the clutter is shifted out of the Doppler filter passband, leaving only targets in the passband.

Radar signal processors

Abstract: Radar signal processor utilizing a technique for detecting targets moving slowly and clutter. The technique comprises dividing the clutter spectrum into a large number of narrow bands and in each band measuring the power ratio between upper and lower side bands. When this ratio exceeds a fixed threshold, the target is declared and, if necessary, its velocity signature can be detailed.

Noncoherent radar moving target indicator using fiber optic delay lines

Abstract: A prime candidate for detection of low flying targets over the sea surface is high resolution radar with a noncoherent delay line canceller. Fiber optic delay lines are capable of providing the required large timebandwidth (TB) product. Optimum information capacities in the spectral region around 1.3 {\mu} m are estimated theoretically to correspond to timebandwidth products of 10^8 and 10^6 for single-mode (based on 1-nm source spectral width) and graded-index multimode fibers, respectively. Pulse-to-pulse subtraction with 17-dB cancellation has been experimentally demonstrated using a 940- m graded-index multimode fiber as delay line. Higher cancellation ratios are anticipated from the use of wider bandwidth fibers.

Sense and inject moving target indicator apparatus

Abstract: A moving target indicator apparatus utilizing charge injector device (CID) sensors to detect the presence or absence of a moving target. A signal from a possible target site in the sensor array is measured during a flow scan and is processed with the signal return from a second scan to determine absence or presence and direction.

Design of MTI Radar on the Basis of Detection Probability

Abstract: A single (quadrature) channel moving target indicator (MTI) radar system employing a tapped delay line filter is analyzed. The point of view taken is that of optimal clutter rejection in conjunction with subsequent receiver decision operations. The random nature of the spread of target Doppler shifts is taken into account. Based on the above, a procedure is presented by means of which the detection probability can be numerically evaluated for an optimized filter frequency response.

Charge-Coupled Device (CCD) Radar Signal Processors

Abstract: CCD/NMOS analog sampled data signal processing technology is becoming sufficiently mature to warrant consideration for many signal processing functions. Similarly the desire for improved radar system performance has led to the development of many sophisticated radar signal processing techniques. The design and implementation of two types of CCD based radar processors are discussed in this paper. A moving target indicator capable of processing 1800 range bins of video with a 4 pole Butterworth filter characteristic has been developed for use with an AN/APS-94 radar. A.250 range bin chirp Z transform processor utilizing a CCD/NMOS integrated circuit has also been developed for the AN/PPS-5 radar.

On Increasing Usable MTI Filter Bandwidth by Removing Linear-Phase Constraint

Abstract: It has been shown in the literature that the linear-phase constraint of finite-duration impulse-response (FIR) digital filters can, under certain circumstances, be effectively traded either for a better filter amplitude response or a reduction in the number of filter coeficients. It is shown that such a tradeoff can be exploited for moving target indicator (MTI) radar signal processors to increase the usable bandwidth for target detection. Although it is demonstrated that the increase is significant for narrowband (ground) clutter, it is negligible for wideband (weather) clutter.