Showing papers on "Moving target indication published in 1988"
Patent•
29 Aug 1988TL;DR: In this article, a method of operating a pulse Doppler radar to increase the probability of detection of an airborne target is presented, which consists of transmitting interrogating pulses with a high pulse repetition frequency and processing received signals using any conventional pulse doppler technique for echo signals.
Abstract: A method of operating a pulse Doppler radar to increase the probability of detection of an airborne target is shown to consist of transmitting interrogating pulses with a high pulse repetition frequency and processing received signals using any conventional pulse Doppler technique for echo signals having a Doppler shift frequency outside the spectrum of Doppler shift frequencies of clutter and using a DPCA technique at a submultiple of the pulse repetition frequency for echo signals having a Doppler shift frequency within the spectrum of Doppler shift frequencies of clutter.
27 citations
Patent•
10 Feb 1988
TL;DR: In this paper, the rotational velocity of a chaff piece is calculated by offset 45 degree angle fins at the base of the chaff foil pieces so as to present a doppler complication to the reflected radar wave.
Abstract: The limited advantage of chaff when the radar detection system to be confused has moving target indication (MTI) to screen out such 'slow moving' targets, is countered by the use of offset 45 degree angle fins at the base of the chaff foil pieces so as to present a doppler complication to the reflected radar wave. The rotational velocity of the foil could show up just as readily as a linear velocity of a target such as an aircraft. With many of this type of foil aloft, and each having somewhat different rotational velocities, the doppler system can conceivably be confused. At the same time, the rotation of these units help to increase the target area making a cluster of such units seem larger than actual in terms of the radar signature. The design geometry of the blade coupled with the angular displacement of the fins, serve to govern the rotational velocity of the unit in flight, thus presenting each reflecting surface for a slightly longer exposure than if the blade were pointed and the edges streamlined. Prototypes have proved the aerodynamic stability of the units, and the added advantage of compacted stowage in a limited space is readily observed.
10 citations
Patent•
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TL;DR: In this paper, a moving target indication (MTI) radar with TACCAR circuitry was used for shifting the frequency of the transmitter/local oscillator, which includes a main directional antenna, and subordinate antenna elements for detecting returns from sidelobe directions.
Abstract: A moving target indication (MTI) radar which includes TACCAR circuitry or similar means for shifting the frequency of the transmitter/local oscillator, includes a main directional antenna, and subordinate antenna elements for detecting returns from sidelobe directions. The signals from the subordinate antenna elements are modulated, and modulated return pulses are identified and employed to eliminate false pseudo moving target signals which would otherwise be received from the side lobes of the main antenna.
7 citations
Patent•
03 Oct 1988
TL;DR: In this paper, the phase variation φri is memorized and used during the course of each of the periods of repetition of the next burst to modify the phase of the signal received from the clutter from the same range cell in a maner.
Abstract: In a doppler radar, in order to compensate for the speed of moving clutter, one first establishes during a burst of order (i) the phase variation φri from one period to the next and which is due to clutter in a given range cell Then, this phase variation φri is memorized and is used during the course of each of the periods of repetition of the next burst to modify the phase of the signal received from the clutter from the same range cell in a maner as to displace its Doppler frequency towards the zero frequencies band, and band which corresponds to the rejection zone of the fixed echoes eliminating filter
7 citations
Patent•
20 Jan 1988TL;DR: In this article, the target data such as specific frequencies with a narrow width of frequency lines contained in the target signal, the speed and course of the target and range of the targets from the receiving location are determined.
Abstract: of EP0253277The target water sound signals, e.g. propulsion noises, are received at a receiving location distant from the target in at least one target-locating selective receiving direction. From the received signal, the frequency spectrum is formed and characteristic Doppler echo frequencies are read out in a high-frequency spectral range. From these Doppler echo frequencies, the target data such as specific frequencies with a narrow width of frequency lines contained in the target signal, the speed and course of the target and range of the target from the receiving location are determined.
4 citations
20 Apr 1988
TL;DR: A statistical model is reported that describes the radar backscatter characteristics of a point target located in a non-Rayleigh, correlated, sea clutter environment and the extension of the model to include pulse-to-pulse and scan- to-scan correlation effects in both target and clutter signals is discussed.
Abstract: The development of a statistical model is reported that describes the radar backscatter characteristics of a point target located in a non-Rayleigh, correlated, sea clutter environment. The model is based on the analysis of experimental observations of forward and backscattering from the sea surface, and hence, has the attractive feature of being related to the physical mechanisms governing the scattering processes. Numerical computations involved in calculating the distribution of electric field (of the signal in clutter) are described and sets of representative results pertaining to the single pulse detection are presented. The extension of the model to include pulse-to-pulse and scan-to-scan correlation effects in both target and clutter signals is also discussed. >
3 citations
Patent•
20 Apr 1988
TL;DR: In this article, a coherence is realized by multiple convolution processing the echo signal with transmiting signal sample, which may eliminate or decrease the influence of pulse-to-pulse frequency fluctuation and of power fluctuation in a transmiter.
Abstract: The present invention relates to the field of rader system and radar signal processing, By digit correction.a coherence is realized by multiple- convolution processing the echo signal with transmiting signal sample. The system may eliminate or decrease the influence of pulse-to-pulse frequency fluctuation and of power fluctuation in a transmiter,It also may eliminate the influence of coherent oscillator and improve the stability of pulse-to-pulse frequency in a transmiter, The improvement factor of the system may be over 40 dB.The system is flexible and may be used to replace the moving target display system with phase-locked coherence, It can be used in an existing or a newly developed full coherent pulse radar and the cosl of it may be lowered, while the performance will be improved.
1 citations
11 Apr 1988
TL;DR: A new approach to a near optimum MTI filter design using adaptive techniques is presented, consisting of an adaptive whitening filter for radar clutter followed by a likelihood ratio test (LRT) for target signal in white noise.
Abstract: Presents a new approach to a near optimum MTI filter design using adaptive techniques. The resulting scheme consists of an adaptive whitening filter for radar clutter followed by a likelihood ratio test (LRT) for target signal in white noise. A complete procedure is developed for the whitening filter design. The LRT may operate either with or without a clutter power map. The detection performance of the new scheme is evaluated using real radar data. When operating with a clutter map, it provides 7.5 dB average performance improvement over the innovations-based detection algorithm (IBDA) for ground clutter-dominated data and 5 dB improvement for weather clutter. And the latter has been demonstrated to be superior to the classical moving-target-detection (MTD) by 3 to 5 dB. >
1 citations
29 Jan 1988
TL;DR: This report describes the algorithms used to generate and use the clutter residue editing system and preliminary experimental results using a clutter residue map editing system are presented.
Abstract: : The Terminal Doppler Weather Radar (TDWR) system is designed to provide high quality low altitude Doppler radar data near airports. Ground clutter suppression will be a major challenge to supplying such high quality Doppler data. To confront this challenge the FAA has specified stringent clutter suppression requirements in the TDWR technical specifications. These specifications are designed to provide an effective clutter suppression system. In particular, the specifications require an antenna with narrow beam width and low side-lobes to minimize ground target illumination. Also, a high pass frequency filter (with a stop attenuation in excess of 50 dB) is required to reduce stationary clutter. Finally, a clutter residue map editing system is used to remove remaining clutter. This report describes the algorithms used to generate and use the clutter residue editing system. The major issues are discussed followed by a description of the algorithms designed to address these issues. Finally, preliminary experimental results using a clutter residue map are presented.
1 citations
11 Apr 1988
TL;DR: Two finite-impulse response filter design techniques that find the optimum finite-wordlength (FWL) coefficients to meet an arbitrary frequency-domain criterion to the design of moving-target indicator filters are applied and are truly optimum in the weighted-least-square sense.
Abstract: The authors apply two finite-impulse response (FIR) filter design techniques that find the optimum finite-wordlength (FWL) coefficients to meet an arbitrary frequency-domain criterion to the design of moving-target indicator filters. These FWL FIR filters are truly optimum in the weighted-least-square sense. Examples show that discrete optimization increases the signal-to-clutter improvement ratio (I/sub SC/) by up to 20 dB, compared to simple rounding. The designer has the choice of increasing performance for the specified wordlength or of minimizing wordlength (minimum cost, maximum speed) for the specified performance. In addition, these techniques provide the flexibility to handle stationary and moving clutter simultaneously. >
11 Apr 1988
TL;DR: In this paper, the authors proposed a method to cancel the clutter signal by a filter adapted in real time to each antenna sweep and to each radar resolution cell, which is designed to have a transfer function almost equal to the inverse of the clutter spectral density as observed in a selected area.
Abstract: Radar detection of targets moving at ground level or at low altitude requires some specific signal processing schemes. These include clutter filtering and adaptive thresholding to maintain a constant false alarm rate. The clutter is then assumed to both locally homogeneous and extended. On practice, these hypotheses are only partially true because the surveyed area contains clutter edges (forest edges, coasts, etc.). Signal processors ignoring discontinuities and parameter variations of the model encounter false alarm in the neighbourhood of clutter edges and loss of detection sensibility. A method is presented which minimizes the limitations described above by precisely analysing the clutter characteristics in real time. Cancellation of the clutter signal by a filter adapted in real time to each antenna sweep and to each radar resolution cell is performed. This filter is designed to have a transfer function almost equal to the inverse of the clutter spectral density as observed in a selected area. >
06 Jun 1988
TL;DR: In this article, a pulsed energy maximization method for target identification is presented. Butts et al. used a procedure in which the energy received from the target within a specified time duration is maximized, yielding a waveform that produces an aspect-independent zero response in the late time.
Abstract: Possible applications of pulsed energy maximization to target identification are investigated. The analysis uses a procedure in which the energy received from the target within a specified time duration is maximized. The maximization, if performed for an appropriate target angle and duration, yields a waveform that produces an aspect-independent zero response in the late time. This waveform can then be used to discriminate targets with a nonzero late-time response without the need to determine target singularities. As an illustration of the method, the procedure is formulated for a canonical radar system and a thin-cylinder target, and numerical results are presented. >