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High-Resolution Step-Frequency Radar
Published in James D. Taylor, Ultra-wideband Radar Technology, 2018
reduction of clutter, which is achieved in two steps—first, by limiting the amount of clutter entering the radar receiver and, second, by cancelling the clutter in the signal processor. The amount of clutter entering the radar receiver can be reduced by decreasing the effective pulse width. Effective short pulse width is normally achieved by employing standard techniques of pulse compression, which compress long coded transmit pulses required for adequate average power. However, pulse compression increases the instantaneous bandwidth, which requires wider bandwidth components and higher AID sampling rates. The hardware and bandwidth requirements will increase signifi- cantly for conventional pulse compression for very high range resolution systems, which are required for very low clutter in the radar receiver. These disadvantages can be avoided with the step-frequency waveform and still achieve high range resolution.
Digital Interperiod Signal Processing Algorithms
Published in Vyacheslav Tuzlukov, Signal Processing in Radar Systems, 2017
Although such technological developments are able to augment the moving-target indication radar capabilities substantially, there are still no perfect solutions to all problems encountered with using moving-target indication radars, and the design of moving-target indication radar systems is still as much an art as it is a science. Examples of current problems include the fact that when receivers are built with increased dynamic range, limitations arising out of systemic instability will cause increased clutter residue (relative to system noise), leading to false detections. Clutter maps, which are used to prevent false detections from clutter residues, work quite well on fixed radar systems but are difficult to implement on, for example, shipboard radars, because as the ship moves, the aspect angle and range to each clutter patch changes, creating increased residues after the clutter map. A decrease in the resolution of the clutter map to counter the rapidly changing clutter residue will preclude much of the inter-clutter visibility, which is one of the least appreciated secrets of successful moving-target indication radar operation. The moving-target indication radar must work in the environment that contains strong fixed clutter; birds, bats, and insects; weather; automobiles; and ducting. The ducting is also referred to as anomalous propagation; it causes radar return signals from clutter on the surface of the Earth to appear at greatly extended ranges, which in turn exacerbates the problems with birds and automobiles, and can also cause the detection of fixed clutter hundreds of kilometers away.
Radar Clutter
Published in Bassem R. Mahafza, Introduction to Radar Analysis, 2017
Clutter is a term used to describe any object that may generate unwanted radar returns that may interfere with normal radar operations. Parasitic returns that enter the radar through the antenna’s mainlobe are called mainlobe clutter; otherwise they are called sidelobe clutter. Clutter can be classified into two main categories: surface clutter and airborne or volume clutter. Surface clutter includes trees, vegetation, ground terrain, man-made structures, and sea surface (sea clutter). Volume clutter normally has a large extent (size) and includes chaff, rain, birds, and insects. Surface clutter changes from one area to another, while volume clutter may be more predictable.
Coherent Linear Detection of Slow Fluctuating Radar Targets in a K-Distributed Clutter
Published in IETE Journal of Research, 2022
V. Afsharnaderi, N. Parhizgar, A. Mosalehe
During the detection process, clutter is considered one of the most important destructive factors. The clutter, as an unwanted echo, is typically used for returns from barriers such as the surface of the earth, the sea, the buildings, etc. These returning signals are combined with those received from the target which, in turn, lead to disturbances on the returned target signals in the radar. The clutter has a random nature. Therefore, it is modeled by various statistical distribution models considering the condition and nature of the problem. There are different statistical distributions, including Gaussian, Rayleigh, Weibull, and K-distribution, which are determined depending on the problem conditions and parameters such as the type of propagation environment, resolution, oblique radiation angle, and among others. In the past, the Gaussian distribution was used widely to investigate sea clutters [3,4]. However, with the advancement of radar technology, it was found out that sea clutter modeling based on the Gaussian distribution was not appropriate for high-resolution or low-oblique radiation angle radars. Thus, models based on the Gaussian distribution have not higher ability to differentiate the clutter from target signals. Therefore, non-Gaussian complicated models replaced the Gaussian models that could largely meet the conditions imposed in theory and practice. One of the most important distributions used for clutter description, especially sea clutter, is the K-distribution [1]. Studies have shown that the simulated data generated by the K-distribution is very similar to the actual data of the sea clutter in real conditions [5].