Doppler frequency analysis of ground clutter for space-air based bistatic radar

2015 ◽  
Author(s):  
Zhongyan Huang Zhongyan Huang ◽  
Libao Wang Libao Wang ◽  
Junquan Yuan Junquan Yuan ◽  
Hui Rao Hui Rao ◽  
Xiaoyan Ma Xiaoyan Ma
Keyword(s):  
Frequency Analysis ◽  
Doppler Frequency ◽  
Bistatic Radar ◽  
Ground Clutter

scholarly journals Statistical Analysis of Bistatic Radar Ground Clutter for Different German Rural Environments

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3311
Author(s):  
Michael Kohler ◽  
Daniel W. O’Hagan ◽  
Matthias Weiss ◽  
David Wegner ◽  
Josef Worms ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Measurement Data ◽  
Distribution Functions ◽  
Statistical Properties ◽  
Cumulative Distribution ◽  
Center Frequency ◽  
Rural Environment ◽  
Bistatic Radar ◽  
Ground Clutter ◽  
Rural Environments

This article presents the statistical analysis of bistatic radar rural ground clutter for different terrain types under low grazing angles. Compared to most state-of-the-art analysis, we present country-specific clutter analysis for subgroups of rural environments rather than for the rural environment as a whole. Therefore, the rural environment analysis is divided into four dominant subgroup terrain types, namely fields with low vegetation, fields with high vegetation, plantations of small trees and forest environments representing a typical rural German environment. We will present the results for both the summer and the winter vegetation. Therefore, bistatic measurement campaigns have been carried out during the summer 2019 and the winter of 2019/20 in the aforementioned four different rural terrain types. The measurements were performed in the radar relevant X-band at a center frequency of 8.85 GHz and over a bandwidth of 100 MHz according to available transmit permission. The distinction of the rural terrain into different subgroups enables a more precise and accurate clutter analysis and modeling of the statistical properties as will be shown in the presented results. The statistical properties are derived from the calculated clutter amplitudes probability density functions and corresponding cumulative distribution functions for each of the four terrain types and the corresponding season. The data basis for the clutter analysis are the processed range-Doppler maps from the bistatic radar measurements. According to the authors’ current knowledge, a similar investigation based on real bistatic radar measurement data with the division into terrain subgroups has not yet been carried out and published for a German rural environment.

scholarly journals Low-Altitude and Slow-Speed Small Target Detection Based on Spectrum Zoom Processing

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Xuwang Zhang ◽  
Songtao Lu ◽  
Jinping Sun ◽  
Wei Shangguan
Keyword(s):  
Target Detection ◽  
Doppler Frequency ◽  
Real Data ◽  
Detection Algorithm ◽  
Clutter Suppression ◽  
Slow Speed ◽  
Small Target Detection ◽  
Ground Clutter ◽  
Radar Systems ◽  
Low Altitude

This paper proposes a spectrum zoom processing based target detection algorithm for detecting the weak echo of low-altitude and slow-speed small (LSS) targets in heavy ground clutter environments, which can be used to retrofit the existing radar systems. With the existing range-Doppler frequency images, the proposed method firstly concatenates the data from the same Doppler frequency slot of different images and then applies the spectrum zoom processing. After performing the clutter suppression, the target detection can be finally implemented. Through the theoretical analysis and real data verification, it is shown that the proposed algorithm can obtain a preferable spectrum zoom result and improve the signal-to-clutter ratio (SCR) with a very low computational load.

scholarly journals Features of Usіng Pulse-Doppler Radars for Determіnatіon Low-Altіtude Targets

2019 ◽  
pp. 62-66
Author(s):  
G. Baranov ◽  
R. Gabruk ◽  
I. Gorishna
Keyword(s):  
Doppler Frequency ◽  
Local Oscillator ◽  
Main Beam ◽  
Limiting Factor ◽  
Transmitted Power ◽  
Moving Targets ◽  
Ground Clutter ◽  
Pulse Doppler ◽  
Range Rate ◽  
The Look

In this paper, we analyzed the features of Doppler processing in radars. In ground based radars, the amount of clutter in the radar receiver depends heavily on the radar-to-target geometry. The amount clutter is considerably higher when the radar beam has to face toward the ground. Furthermore, radars employing high PRFs have to deal with an increased amount of clutter due to folding in range. Clutter introduces additional difficulties for airborne radars when detecting ground targets and other targets flying at low altitudes. This is illustrated in Fig. 10.5. Returns from ground clutter emanate from ranges equal to the radar altitude to those which exceed the slant range along the main-beam, with considerable clutter returns in the side-lobes and main-beam. The presence of such large amounts of clutter interferes with radar detection capabilities and makes it extremely difficult to detect targets in the look-down mode. This difficulty in detecting ground or low altitude targets has led to the development of pulse Doppler radars where other targets, kinematics such as Doppler effects are exploited to enhance detection. Pulse Doppler radars utilize high PRFs to increases the average transmitted power and rely on target's Doppler frequency for detection. The increase in the average transmitted power leads to an improved SNR which helps the detection process. However, using high PRFs compromise the radar's ability to detect long range target because of range ambiguities associated with high PRF applications. Techniques such as using specialized Doppler filters to reject clutter are very effective and are often employed by pulse Doppler radars. Pulse Doppler radars can measure target Doppler frequency (or its range rate) fairly accurately and use the fact that ground clutter typically possesses limited Doppler shift when compared with moving targets to separate the two returns. Clutter filtering is used to remove both main-beam and altitude clutter returns, and fast moving target detection is done effectively by exploiting its Doppler frequency. In many modern pulse Doppler radars the limiting factor in detecting slow moving targets is not clutter but rather another source of noise referred to as phase noise generated from the receiver local oscillator instabilities.  

scholarly journals Graceful Degradation An Airborne Surveillance Radar Perspective

2019 ◽  
Vol 69 (4) ◽  
pp. 389-395
Author(s):  
Rajesh Ramachandran ◽  
Reena Sharma ◽  
Suma Varughese
Keyword(s):  
Single Channel ◽  
Doppler Frequency ◽  
Side Lobe ◽  
Graceful Degradation ◽  
Ground Clutter ◽  
Desirable Feature ◽  
Systematic Failure ◽  
Array Performance ◽  
Random Failures ◽  
Zero Frequency

Active electronically scanned antenna (AESA)-based radars imbibe the desirable feature of ‘graceful degradation’. Such radars use miniaturised transmit-receive (TR) modules and a failure of few modules does not lead to failure of the mission. For example, in AESA-based ground MTI radar, failure of a few modules does not affect the array performance. In such a case, the static ground clutter is centred on zero frequency does not have a motion dependent Doppler spread. However, in airborne AESA radars, the ground clutter has an angle dependent Doppler frequency due to the platform motion and clutter leaking in through antenna side-lobes. Hence, the antenna side lobe levels dictate the side lobe clutter against which target detection is to be performed. The detection performance is governed by the signal to interference plus noise ratio (SINR). For Airborne surveillance radar the effect of random and systematic failures of TR modules and their effect on SINR is characterised. It is shown that single channel processing does not effectively provide the graceful degradation feature as the SINR loss due to failures is significant. However, the effect of systematic failure on SINR loss is less as compared to random failures. An effective scheme for feeding the array is also proposed.

scholarly journals A SEMI-RIGOROUS SENSOR MODEL FOR PRECISION GEOMETRIC PROCESSING OF MINI-RF BISTATIC RADAR IMAGES OF THE MOON

2016 ◽  
Vol XLI-B4 ◽  
pp. 425-429
Author(s):  
R. L. Kirk ◽  
J. M. Barrett ◽  
D. E. Wahl ◽  
I. Erteza ◽  
C. V. Jackowatz ◽  
...  
Keyword(s):  
Doppler Shift ◽  
Doppler Frequency ◽  
Bistatic Radar ◽  
Data Sets ◽  
Essential Difference ◽  
Trajectory Data ◽  
Rigorous Approach ◽  
Radar Images ◽  
Recorded Image ◽  
Phase Angles

The spaceborne synthetic aperture radar (SAR) instruments known as Mini-RF were designed to image shadowed areas of the lunar poles and assay the presence of ice deposits by quantitative polarimetry. We have developed radargrammetric processing techniques to enhance the value of these observations by removing spacecraft ephemeris errors and distortions caused by topographic parallax so the polarimetry can be compared with other data sets. Here we report on the extension of this capability from monostatic imaging (signal transmitted and received on the same spacecraft) to bistatic (transmission from Earth and reception on the spacecraft) which provides a unique opportunity to measure radar scattering at nonzero phase angles. In either case our radargrammetric sensor models first reconstruct the observed range and Doppler frequency from recorded image coordinates, then determine the ground location with a corrected trajectory on a more detailed topographic surface. The essential difference for bistatic radar is that range and Doppler shift depend on the transmitter as well as receiver trajectory. Incidental differences include the preparation of the images in a different (map projected) coordinate system and use of “squint” (i.e., imaging at nonzero rather than zero Doppler shift) to achieve the desired phase angle. Our approach to the problem is to reconstruct the time-of-observation, range, and Doppler shift of the image pixel by pixel in terms of rigorous geometric optics, then fit these functions with low-order polynomials accurate to a small fraction of a pixel. Range and Doppler estimated by using these polynomials can then be georeferenced rigorously on a new surface with an updated trajectory. This “semi-rigorous” approach (based on rigorous physics but involving fitting functions) speeds the calculation and avoids the need to manage both the original and adjusted trajectory data. We demonstrate the improvement in registration of the bistatic images for Cabeus crater, where the LCROSS spacecraft impacted in 2009, and describe plans to precision-register the entire Mini-RF bistatic data collection.

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