IEE Proceedings F (Radar and Signal Processing)
Volume 138, Issue 2, April 1991
Volumes & issues:
Volume 138, Issue 2
April 1991
Radar clutter and multipath propagation
- Author(s): S. Watts
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 73 –74
- DOI: 10.1049/ip-f-2.1991.0011
- Type: Article
- + Show details - Hide details
-
p.
73
–74
(2)
Statistical properties of multifrequency high-range-resolution sea reflections
- Author(s): T. Hair ; T. Lee ; C.J. Baker
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 75 –79
- DOI: 10.1049/ip-f-2.1991.0012
- Type: Article
- + Show details - Hide details
-
p.
75
–79
(5)
The statistical properties of multifrequency high-range-resolution, low-grazingangle measurements of sea clutter are presented. It is shown that the compound form of the K-distribution provides an excellent description for measurements made at S, X and J bands for all the radar range resolutions employed (0.375 m to 15 m). It is also shown that the K-distribution shape parameter tends to decrease as the illuminated patch is made smaller, corresponding to an increase in spikiness of the backscatter. This change in shape parameter appears to be a function of the underlying modulation with the speckle component remaining largely unchanged.
Canadian East coast radar trials and the K-distribution
- Author(s): T.J. Nohara and S. Haykin
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 80 –88
- DOI: 10.1049/ip-f-2.1991.0013
- Type: Article
- + Show details - Hide details
-
p.
80
–88
(9)
The use of the K-distribution to describe the amplitude statistics of sea clutter collected with an instrument-quality X-band radar off the East Coast of Canada is investigated. It is shown that the K-distribution is suitable for modelling the amplitude statistics of both likepolarised and crosspolarised radar configurations. The amplitude statisitcs of small ice targets (growlers) in spiky clutter are also examined; the results obtained indicate that using only long-term amplitude statistics is not sufficient for the reliable detection of such targets in the presence of sea clutter. Furthermore, it is shown that the crosspolarised channel does not offer any added benefit to small target detection when considering only long-term amplitude statistics. We also consider the phase statistics of sea clutter and show them to be uniformly distributed on 2Π.
K-distributed coherent sea clutter
- Author(s): C.J. Baker
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 89 –92
- DOI: 10.1049/ip-f-2.1991.0014
- Type: Article
- + Show details - Hide details
-
p.
89
–92
(4)
The properties of coherently detected high-range-resolution radar sea clutter are examined with reference to those properties observed noncoherently. It is shown here how the non-Gaussian characteristics of noncoherently detected sea clutter manifest themselves in the coherent domain and how these characteristics require a thorough understanding in order to optimise any detection processing, especially if integration techniques are utilised. In particular it is demonstrated how the compound form of the K-distribution may be employed to model the amplitude statistics in individual range-Doppler cells and how such a description is necessary to take into account their correlation properties.
Millimetre-wave backscatter from desert terrain
- Author(s): L.D. Williams ; R.P. Kirby ; M.A. Summerfield ; D.J. Rust ; S. Astbury ; P.A. Lee
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 93 –98
- DOI: 10.1049/ip-f-2.1991.0015
- Type: Article
- + Show details - Hide details
-
p.
93
–98
(6)
The association of millimetric radar clutter and terrain characteristics measured on a variety of desert surfaces is reported. Close-up photogrammetric analysis provided digitised profile data from which measures of surface roughness have been obtained, and the dielectric properties of surface materials and vegetation are estimated empirically with data obtained from field samples. The data are used to obtain empirical multiple regression models, which suggest that for 94 GHz backscatter from desert terrain copolar backscatter is dominated by surface scattering, apparently so much so that it is reduced by the presence of vegetation (which is volumescattering), the latter contrary to what has been found at lower microwave frequencies. The methods also suggest that crosspolar backscatter is dominated by volume scattering and appears to be unaffected by sparse vegetation.
Gross spatial structure of land clutter
- Author(s): S.P. Tonkin and R.A. McCulloch
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 99 –108
- DOI: 10.1049/ip-f-2.1991.0016
- Type: Article
- + Show details - Hide details
-
p.
99
–108
(10)
The performance of a ground-based surveillance radar system against a particular target depends critically on whether land clutter is important within the region covered, and on the path of the aircraft relative to that clutter. Often the land clutter is very strong over parts of the region surveyed, but essentially nonexistent elsewhere. In such cases, the detailed clutter characteristics can have a much smaller effect on detectability than the gross spatial distribution of the clutter. For any given site, it is possible to produce a binary clutter map and examine several different aircraft paths to find the system performance for that site. However, often the performance for a given class of sites rather than one particular site is required. Repeating the sitespecific calculation for a reasonable sample of different sites is very time-consuming. A more powerful approach is to use a statistical characterisation of the gross structure of clutter visibility (e.g. as a function of terrain type). The paper describes the development of such a statistical representation for use in radar performance modelling, using the theory of binary Markov random fields.
Polarimetric radar signatures of precipitation at S and C-bands
- Author(s): V.N. Bringi ; V. Chandrasekar ; P. Meischner ; J. Hubbert ; Y. Golestani
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 109 –119
- DOI: 10.1049/ip-f-2.1991.0017
- Type: Article
- + Show details - Hide details
-
p.
109
–119
(11)
Polarimetric radar measurements in precipitation at S and C-band frequencies are considered. Time series data were obtained from three advanced radars: the National Center for Atmospheric Research (NCAR) CP-2 radar, the National Severe Storms Laboratory's (NSSL) Cimarron radar, and the C-band Poldirad radar operated by the German Aerospace Research Establishment (DLR). Measurements of radar reflectivity, differential reflectivity ZDR, differential propagation phase (φDP, and the crosscorrelation between horizontal and vertical polarised waves are derived from time series data in rain, rain mixed with ice, and in the stratiform ice phase of convective storms. Raindrops are modelled as oblate in shape with a gamma form for their size distribution. The gamma parameters (No, Do, m) are varied over an entire range encompassing a wide variety of rainfall types. The radar rain measurements are shown to be in good general agreement with the model rain simulations. By combining ZDR and(φDP it is possible to identify regions of mixed particle types, e.g. raindrops and hail, or ice crystals and snowflakes. The differential phase upon backscatter may be identified by examining the range profile of φDP, giving additional clues as to the type and size of particles responsible for the backscatter.
Modelling and simulation of non-Rayleigh radar clutter
- Author(s): E. Conte ; M. Longo ; M. Lops
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 121 –130
- DOI: 10.1049/ip-f-2.1991.0018
- Type: Article
- + Show details - Hide details
-
p.
121
–130
(10)
As the undesired echo from a radar environment (clutter) is often not Rayleigh-distributed, problems arise in specifying the clutter as a non-Gaussian random process and in computer-generating realisations of clutter for simulation purposes. The paper shows that modelling the clutter as a compound Gaussian or a spherically invariant random process allows a complete specification of the clutter suitable for use in radar design. It also lends itself readily to computer simulation procedures. Specific procedures for generating clutter realisations with assigned correlation properties and with K or Weibull amplitude distributions are suggested, and are validated by statistical tests. Then the issue of resolving between the Weibull and K distributions is considered, and empirical operative characteristics of the associated hypothesis test are computed.
Radar detection of signals with unknown parameters in K-distributed clutter
- Author(s): E. Conte ; M. Longo ; M. Lops ; S.L. Ullo
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 131 –138
- DOI: 10.1049/ip-f-2.1991.0019
- Type: Article
- + Show details - Hide details
-
p.
131
–138
(8)
The detection of signals with unknown parameters in correlated K-distributed noise, using the generalised Neyman-Pearson strategy is considered. The a priori uncertainty on the signal is removed by performing a maximum likelihood estimate of the unknown parameters. The resulting receivers can be regarded as a generalisation of the conventional detector, but for a zero-memory nonlinearity depending on the amplitude probability density function of the noise as well as on the number of integrated pulses. It is shown that the performance for uncorrelated observations is unaffected by the specific signal pattern, but depends only on the signal-to-noise ratio; moreover, the effect of the clutter correlation on the performance can be accounted for simply by a detection gain. A performance assessment, carried out by computer simulation, shows that the proposed receivers significantly outperform conventional ones as the noise amplitude probability density function markedly deviates from the Rayleigh law. It also shows that the generalised Neyman-Pearson strategy is a suitable means of circumventing the uncertainty on wanted target echos since the operating characteristics of the receivers for the case of signals with unknown parameters closely follow those of the receiver for a completely known signal.
CFAR detection of fluctuating targets in spatially correlated K-distributed clutter
- Author(s): B.C. Armstrong and H.D. Griffiths
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 139 –152
- DOI: 10.1049/ip-f-2.1991.0020
- Type: Article
- + Show details - Hide details
-
p.
139
–152
(14)
The problem of single pulse CFAR detection of Rayleigh fluctuating targets in Kdistributed sea clutter is addressed. The performance of three types of well known CFAR processors, namely the cell averaging (CA), cell averaging greatest of (CAGO), and order statistic (OS) CFAR processors, is examined under varying conditions of clutter spatial correlation for several cases of desired false alarm probability and the number of reference cells used in the CFAR processor. Curves for the detectability loss due to the ‘spikiness’ of the clutter are presented and values for the additional loss due to CFAR thresholding are tabulated. The effects of incorrectly estimating the clutter shape parameter v are investigated. A model is presented to facilitate numerical analysis of detection performance under conditions of partial correlation of the clutter modulation process. Sample results are presented and it is shown that for the CFAR processors analysed here detection performance will not in general be dramatically improved relative to the worst case condition of spatially uncorrelated clutter.
Parabolic equation modelling of the effects of multipath and ducting on radar systems
- Author(s): K.H. Craig and M.F. Levy
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 153 –162
- DOI: 10.1049/ip-f-2.1991.0021
- Type: Article
- + Show details - Hide details
-
p.
153
–162
(10)
The parabolic equation approach to the modelling of clear-air propagation, and in particular to the assessment of radar performance in the presence of multipath and ducting, is described. The derivation and solution of the parabolic equation by means of the split-step algorithm are described. A discussion of the radar equation is given to provide a connection with conventional assessment methods. The model is applied to the problem of anomalous propagation and the influence of the ground. One of the main advantages of the parabolic equation approach over alternative ray and mode methods is its ability to make quantitative predictions for two-dimensional refractiveindex structures without the need for a priori identification of the structures. New applications, such as wideband effects and the influence of refractive-index fluctuations and measurement errors on prediction accuracy, are discussed. Current work on clutter modelling and other extensions to the model are briefly mentioned.
Use of a highly deterministic multipath signal model in low-angle tracking
- Author(s): T. Lo and J. Litva
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 163 –171
- DOI: 10.1049/ip-f-2.1991.0022
- Type: Article
- + Show details - Hide details
-
p.
163
–171
(9)
A maximum-likelihood estimation technique based on deterministic modelling is presented. The algorithm is designed to be used specifically for radar tracking of low-angle targets or radio direction-finding in a naval environment. In this algorithm, a highly deterministic multipath signal model is used for formulating the likelihood function, which is maximised with respect to the angles of arrival. In addition, the Cramer-Rao bounds that apply specifically to this model are derived. It is shown, by using both simulated data and real data, that this technique provides excellent performance in resolving multiple signals. The measured data that are used in this study were recorded using a 32-element sampled aperture antenna on an ‘overwater’ path.
Multipath effects on low-angle tracking at millimetre-wave frequencies
- Author(s): J.A. Bruder and J.A. Saffold
- Source: IEE Proceedings F (Radar and Signal Processing), Volume 138, Issue 2, p. 172 –184
- DOI: 10.1049/ip-f-2.1991.0023
- Type: Article
- + Show details - Hide details
-
p.
172
–184
(13)
The realistic multipath models described provide a powerful method for evaluating the effects of multipath interference at millimetre wave frequencies. The multipath interference simulations predicted that for targets at ranges of greater than 1 km, the use of any single multipath reduction technique will probably not be sufficient to provide the degree of multipath interference rejection required for target track and straight line (constant slope) missile track. The simulations did indicate that a combination of multipath reduction techniques, including elevated missile trajectory, offset angle track, frequency agility and angle averaging, appear to provide sizeable reductions of elevation angular errors due to multipath. While these techniques may provide sufficient angular error reduction for most terrains due to the primarily diffuse nature of multipath interference at millimetre wave frequencies, additional processing may be required when operating over flat surfaces such as asphalt or calm seas.
Most viewed content for this Journal
Article
content/journals/ip-f-2
Journal
5
Most cited content for this Journal
We currently have no most cited data available for this content.
