skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A null-steering viewpoint of interferometric SAR

Abstract

Interferometric synthetic aperture radar (IFSAR) extends the two-dimensional imaging capability of traditional synthetic aperture radar to three-dimensions by using an aperture in the elevation plane to estimate the 3-D structure of the target. The operation of this additional aperture can be viewed from a null-steering point of view, rather than the traditional phase determination point of view. Knowing that IFSAR can be viewed from the null-steering perspective allows one to take advantage of the mathematical foundation developed for null-steering arrays. In addition, in some problems of interest in IFSAR the null-steering perspective provides better intuition and suggests alternative solutions. One example is the problem of estimating building height where layover is present.

Authors:
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
755624
Report Number(s):
SAND99-3220C
TRN: AH200021%%59
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: IEEE Geoscience and Remote Sensing Symposium 2000, Honolulu, HI (US), 07/24/2000--07/28/2000; Other Information: PBD: 2 May 2000
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION; RADAR; INTERFEROMETRY; THREE-DIMENSIONAL CALCULATIONS; DATA ANALYSIS; BUILDINGS; HEIGHT

Citation Formats

BICKEL,DOUGLAS L. A null-steering viewpoint of interferometric SAR. United States: N. p., 2000. Web.
BICKEL,DOUGLAS L. A null-steering viewpoint of interferometric SAR. United States.
BICKEL,DOUGLAS L. 2000. "A null-steering viewpoint of interferometric SAR". United States. doi:. https://www.osti.gov/servlets/purl/755624.
@article{osti_755624,
title = {A null-steering viewpoint of interferometric SAR},
author = {BICKEL,DOUGLAS L.},
abstractNote = {Interferometric synthetic aperture radar (IFSAR) extends the two-dimensional imaging capability of traditional synthetic aperture radar to three-dimensions by using an aperture in the elevation plane to estimate the 3-D structure of the target. The operation of this additional aperture can be viewed from a null-steering point of view, rather than the traditional phase determination point of view. Knowing that IFSAR can be viewed from the null-steering perspective allows one to take advantage of the mathematical foundation developed for null-steering arrays. In addition, in some problems of interest in IFSAR the null-steering perspective provides better intuition and suggests alternative solutions. One example is the problem of estimating building height where layover is present.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2000,
month = 5
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • A brief theoretical review of adaptive null steering is presented. The basic theory is first outlined in the context of sidelobe cancellation systems as well as general antenna arrays. Various approaches to the practical implementation of adaptive null steering are then discussed. These fall into the two main categories of closed-loop methods and direct-solution methods. The closed-loop methods are very cost-effective and suitable in principle, for either analog or digital processing. However, their rate of convergence is fundamentally limited and too slow for some applications. The direct-solution methods do not suffer from this problem, but tend to be suitable onlymore » for digital processing and are more expensive from the computational point of view. However, they are well suited to parallel processing and now provide a very practical alternative due to recent advances in VLSI circuit technology. A brief discussion on the effects of multi-path propagation on adaptive null-steering systems concludes this review.« less
  • We report on interferometric characterization of a deep parabolic mirror with a depth of more than five times its focal length. The interferometer is of Fizeau type; its core consists of the mirror itself, a spherical null element, and a reference flat. Because of the extreme solid angle produced by the paraboloid, the alignment of the setup appears to be very critical and needs auxiliary systems for control. Aberrations caused by misalignments are removed via fitting of suitable functionals provided by means of ray tracing simulations. It turns out that the usual misalignment approximations fail under these extreme conditions.
  • Relativistic Hamiltonian few-body dynamics [1,2] involves two unitary representations of the Poincare group on the Hilbert space H of physical states, with and without interactions. These two representations, U({Lambda}, a) and U{sub 0}({Lambda},a), coincide for a kinematic subgroup H. The ''Hamiltonians'' are the generators not in the Lie algebra of the kinematic subgroup. The kinematic subgroup of null-plane dynamics leaves the null-plane z {center_dot} x {triple_bond} x{sup 0} + x{sub 3} = 0 invariant. Few-body Hamiltonians satisfying the required commutation relations can be constructed as functions of a mass operator and kinematic quantities. For more than two particles there aremore » nontrivial problems in satisfying cluster separability. [3] Consistency of electro-weak interactions with strong interactions also involves significant problems: Poincare covariance of current operators requires the construction of appropriate interaction currents.« less
  • The role of neutrals in triggering the H-L back transition in high density ELMing H-mode plasmas is explored in double-null (DN) and single-null (SN) divertors. The authors propose that the neutral particle buildup below the X-point may play an important role in triggering the H-L transition at high density. Neutral pressure in the private flux region is, in fact, significant near the H-L backtransition. High density formation inside the separatrix near the X-point may also be a factor in triggering the H-L backtransition. They have observed that the ELMing H-mode density limit in SN divertors normally occurred at or nearmore » the H-L back transition. The radiated power coming from inside the separatrix at the H-L transition did not appear sufficient by itself to produce this back transition, since it is only {approximately}15--30% of P{sub in}. Poloidally-localized neutrals may explain two important differences in SN and double-null (DN) plasmas near their respective H-L backtransitions. First, electron pressure along the separatrix between the X-point and the outboard strike point decreased only modestly for DN divertors, even at densities comparable to the Greenwald density limit {bar n}{sub e,G}, in contrast to SN plasmas. Second, no divertor (or core) MARFEs were detected in the DNs as {bar n}{sub e} approaches {bar n}{sub e,G}, in contrast to SNs, where divertor MARFEs can form at {bar n}{sub e}/{bar n}{sub e,G} as low as {approximately}0.6. High X-point DNs achieved density limits well above those of comparably-prepared SNs, e.g., {bar n}{sub e}/n{sub e,G} {approx} 0.9--1.0 for DNs versus 0.75--0.80 for SNs. These differences result from a lower neutral pressure in the private flux regions of DNs than in comparable SNs at the same {bar n}{sub e}, since neutrals impact both pressure balance and MARFEing behavior.« less
  • Tokamak plasma performance generally improves with increased shaping of the plasma cross section, such as higher elongation and higher triangularity. The stronger shaping, especially higher triangularity, leads to changes in the magnetic topology of the divertor. Because there are engineering and divertor physics issues associated with changes in the details of the divertor flux geometry, especially as the configuration transitions from a single-null (SN) divertor to a marginally balanced double-null (DN) divertor, we have undertaken a systematic evaluation of the plasma characteristics as the magnetic geometry is varied, particularly with respect to (1) energy confinement, (2) the response of themore » plasma to deuterium gas fueling, (3) the operational density range for the ELMing H-mode, and (4) heat flux sharing by the diverters. To quantify the degree of divertor imbalance (or equivalently, to what degree the shape is double-null or single-null), we define a parameter DRSEP. DRSEP is taken as the radial distance between the upper divertor separatrix and the lower divertor separatrix, as determined at the outboard midplane. For example, if DRSEP=O, the configuration is a magnetically balanced DN; if DRSEP = +1.0 cm, the divertor configuration is biased toward the upper divertor. Three examples are shown in Fig. 1. In the following discussions, VB drift is directed toward the lower divertor.« less