During the last two decades, our research group has actively contributed to the development and validation of numerical and asymptotic methods for characterizing radar scattering from complex targets. In 1985, we helped pioneer the shooting and bouncing ray (SBR) technique for predicting radar returns from realistic aerospace vehicles. Through our research efforts, the concept of SBR was realized for predicting radar signatures of complex air and ground targets described by three-dimensional computer models. In the 1990s, our research group devised a number of fast algorithms that led to order-of-magnitude improvements in the speed and accuracy of the SBR technique.
Our research in SBR theory has directly contributed to the development of the industry-standard signature prediction code Xpatch (link). Today, Xpatch is considered one of the premier high-frequency signature codes, with a user community of over 450 governmental and industrial organizations in the United States. Xpatch was the enabling technology in several DoD target identification programs, including the Air Force Non-Cooperative Target Identification Program and DARPA's Moving and Stationary Target Acquisition and Recognition Program.
In radar feature extraction, our group successfully applied joint time-frequency (JTF) representations to radar signature analysis and radar image formation. In radar signature analysis, we gained a new understanding of the various scattering mechanisms on complex targets. The resulting insight greatly bridged the gap between the traditional time domain and frequency domain interpretations. In radar image formation, the use of JTF analysis to deal with complex target motions such as articulating aircraft or ships on the ocean was found to be very useful for inverse synthetic aperture radar (ISAR) image formation. Dr. Ling is the co-author (with V. C. Chen) of a 2002 book Time-Frequency Transforms for Radar Imaging and Signal Analysis.
H. Ling, R. Chou and S. W. Lee, "Rays versus modes: pictorial display of energy flow in an open-ended waveguide," IEEE Trans. Antennas Propagat., vol. AP-35, pp. 605-607, May 1987.
S. W. Lee, H. Ling and R. Chou, "Ray-tube integration in shooting and bouncing ray method," Microwave Optical Tech. Lett., vol. 1, pp. 286-289, October 1988.
H. Ling, R. Chou and S. W. Lee, "Shooting and bouncing rays: calculating the RCS of an arbitrarily shaped cavity," IEEE Trans. Antennas Propagat., vol. AP-37, pp. 194-205, February 1989.
H. Ling, S. W. Lee and R. Chou, "High-frequency RCS of open cavities with rectangular and circular cross sections," IEEE Trans. Antennas Propagat., vol. AP-37, pp. 648-654, May 1989.
H. Ling, H. Kim, G. A. Hallock, B. W. Birkner and A. Zaman, "Effect of arcjet plume on satellite reflector performance," IEEE Trans. Antennas Propagat., vol. AP-39, pp. 1412-1420, September 1991.
H. Kim and H. Ling, "Electromagnetic scattering from an inhomogeneous body by ray tracing," IEEE Trans. Antennas Propagat., vol. AP-40, pp. 517-525, May 1992.
R. Bhalla and H. Ling, "ISAR image formation using bistatic data computed from the shooting and bouncing ray technique," J. Electromag. Waves Applications, vol. 7, pp. 1271-1287, September 1993.
R. Bhalla, H. Ling, S. W. Lee and D. J. Andersh, "Dynamic simulation of Doppler spectra of targets with rotating parts," Microwave Optical Tech. Lett., vol. 7, pp. 840-842, December 1994.
R. Bhalla and H. Ling, "A fast algorithm for signature prediction and image formation using the shooting and bouncing ray technique," IEEE Trans. Antennas Propagat., vol. AP-43, pp. 727-731, July 1995.
R. Bhalla and H. Ling, "Image-domain ray-tube integration formula for the shooting and bouncing ray technique," Radio Science, vol. 30, pp. 1435-1446, September-October 1995.
R. Bhalla, H. Ling and H. Nussbaum, "Multi-aspect range profile extrapolation for the shooting and bouncing ray technique," J. Electromag. Waves Applications, vol. 10, pp. 249-268, February 1996.
R. Bhalla and H. Ling, "3D scattering center extraction using the shooting and bouncing ray technique," IEEE Trans. Antennas Propagat., vol. AP-44, pp. 1445-1453, November 1996.
R. Bhalla and H. Ling, "Cross range streaks in ISAR images generated via the shooting and bouncing ray technique: cause and solutions," IEEE Antennas Propagat. Mag., vol. 39, pp. 76-80, April 1997.
R. Bhalla, J. Moore and H. Ling, "A global scattering center representation of complex targets using the shooting and bouncing ray technique," IEEE Trans. Antennas Propagat., vol. AP-45, pp. 1850-1856, December 1997.
R. Bhalla and H. Ling, "A fast algorithm for simulating Doppler spectra of targets with rotating parts using the shooting and bouncing ray technique," IEEE Trans. Antennas Propagat., vol. AP-46, pp. 1389-1391, September 1998.
R. Bhalla, H. Ling, J. Moore, D. J. Andersh, S. W. Lee and J. Hughes, "3D scattering center representation of complex targets using the shooting and bouncing ray technique," IEEE Antennas Propagat. Mag., vol. 40, pp. 30-39, October 1998.
C. Ozdemir, R. Bhalla, L. C. Trintinalia and H. Ling, "ASAR - antenna synthetic aperture radar imaging," IEEE Trans. Antennas Propagat., vol. AP-46, pp. 1845-1852, December 1998.
C. Ozdemir and H. Ling, "ACSAR - antenna coupling synthetic aperture radar imaging algorithm," J. Electromag. Waves Applications, vol. 13, pp. 285-306, March 1999.
R. Bhalla and H. Ling, "Near-field signature prediction using far-field scattering centers extracted from the shooting and bouncing ray technique," IEEE Trans. Antennas Propagat., vol. AP-48, pp. 337-338, February 2000.
C. Ozdemir, R. Bhalla and H. Ling, "A radiation center representation of antenna radiation pattern on a complex platform," IEEE Trans. Antennas Propagat., vol. AP-48, pp. 992-1000, June 2000.
T. Su, C. Ozdemir and H. Ling, "On extracting the radiation center representation of antenna radiation patterns on a complex platform," Microwave Optical Tech. Lett., vol. 26, pp. 4-7, July 2000.
Y. Zhou and H. Ling, "On the multiplaten z-buffer algorithm for ray tracing in high-frequency electromagnetic scattering computations," Microwave Optical Tech. Lett., vol. 43, pp. 298-301, November 2004.
H. Ling, "RCS of waveguide cavities: a hybrid boundary-integral/modal approach," IEEE Trans. Antennas Propagat., vol. AP-38, pp. 1413-1420, September 1990.
T. M. Wang, A. Cuevas and H. Ling, "RCS of a partially open rectangular box in the resonant region," IEEE Trans. Antennas Propagat., vol. AP-38, pp. 1498-1504, September 1990.
T. M. Wang and H. Ling, "A connection algorithm on the problem of EM scattering from arbitrary cavities," J. Electromag. Waves Applications, vol. 5, pp. 301-314, April 1991.
T. M. Wang and H. Ling, "Electromagnetic scattering from three-dimensional cavities via a connection scheme," IEEE Trans. Antennas Propagat., vol. AP-39, pp. 1505-1513, October 1991.
J. Moore, H. Ling, U. U. Graf and D. T. Jaffe, "A boundary integral approach to the scattering from periodic gratings," Microwave Optical Tech. Lett., vol. 5, pp. 480-483, September 1992.
H. Kim and H. Ling, "On the application of fast wavelet transform to the integral equation solution of electromagnetic scattering problems," Microwave Optical Tech. Lett., vol. 6, pp. 168-173, March 1993.
J. Moore and H. Ling, "Scattering by gaps in coated structures," J. Electromag. Waves Applications, vol. 7, pp. 325-344, March 1993.
J. Moore, H. Ling and C. S. Liang, "The scattering and absorption characteristics of material coated periodic gratings under oblique incidence," IEEE Trans. Antennas Propagat., vol. AP-41, pp. 1281-1288, September 1993.
J. Moore and H. Ling, "Boundary integral solution to the diffraction and surface wave mechanisms in the coated edge," J. Electromag. Waves Applications, vol. 7, pp. 1221-1237, September 1993.
H. Ling and H. Kim, "On the application of Kirchhoff's approximation to scattering from discontinuities in large waveguide ducts," Microwave Optical Tech. Lett., vol. 7, pp. 168-172, March 1994.
L. C. Trintinalia and H. Ling, "Electromagnetic scattering from 3-D arbitrary coated cavities via a connection scheme using triangular patches," J. Electromag. Waves Applications, vol. 8, pp. 1411-1423, November 1994.
H. Kim and H. Ling, "On the efficient representation of Green's function using multiresolution wavelet concepts," Microwave Optical Tech. Lett., vol. 9, pp. 183-187, July 1995.
H. Kim and H. Ling, "A fast multiresolution moment method algorithm using wavelet concepts," Microwave Optical Tech. Lett., vol. 6, pp. 317-319, December 1995.
H. Kim, H. Ling and C. Lee, "A fast moment method algorithm using spectral domain wavelet concepts," Radio Science, vol. 31, pp. 1253-1261, September-October 1996.
H. Deng and H. Ling, "Moment matrix sparsification using adaptive wavelet packet transform," Elect. Lett., vol. 33, pp. 1127-1128, June 1997.
Y. Wang, H. Ling, J. Song and W. C. Chew, "A frequency extrapolation algorithm for FISC," IEEE Trans. Antennas Propagat., vol. AP-45, pp. 1891-1893, December 1997.
H. Deng and H. Ling, "Efficient representation of moment matrix with pre-defined wavelet packet basis," Elect. Lett., vol. 34, pp. 440-441, March 1998.
Y. Wang and H. Ling, "A model-based angular extrapolation technique for iterative method-of-moments solvers," Microwave Optical Tech. Lett., vol. 20, pp. 229-233, February 1999.
H. Deng and H. Ling, "Fast solution of electromagnetic integral equations using adaptive wavelet packet transform," IEEE Trans. Antennas Propagat., vol. AP-47, pp. 674-682, April 1999.
Y. Wang and H. Ling, "Radar signature prediction using moment method codes via a frequency extrapolation technique," IEEE Trans. Antennas Propagat., vol. AP-47, pp. 1008-1015, June 1999.
H. Deng and H. Ling, "Preconditioning of electromagnetic integral equations using pre-defined wavelet packet basis," Elect. Lett., vol. 35, pp. 1144-1146, July 1999.
H. Deng and H. Ling, "On a class of pre-defined wavelet packet bases for efficient representation of electromagnetic integral equations," IEEE Trans. Antennas Propagat., vol. AP-47, pp. 1772-1779, December 1999.
T. Su and H. Ling, "Determining the equivalent impedance boundary condition for corrugated coatings based on the genetic algorithm," IEEE Trans. Antennas Propagat., vol. AP-48, pp. 374-382, March 2000.
Y. Wang and H. Ling, "A frequency-aspect extrapolation algorithm for ISAR image simulation based on two-dimensional ESPRIT," IEEE Trans. Geo. Science and Remote Sensing, vol. 38, pp. 1743-1748, July 2000.
B. Jiang, T. Su and H. Ling, "Frequency interpolation of electromagnetic scattering data using a hybrid model," Microwave Optical Tech. Lett., vol. 27, pp. 307-312, December 2000.
H. Deng and H. Ling, "Wavelet-based preconditioner for three-dimensional electromagnetic integral equations," Elect. Lett., vol. 36, pp. 2063-2065, December 2000.
T. Su, Y. Wang and H. Ling, "A frequency extrapolation technique for computing antenna-platform radiation problems," J. Electromag. Waves Applications, vol. 15, pp. 865-883, July 2001.
L. C. Trintinalia and H. Ling, "First order triangular patch basis functions for electromagnetic scattering analysis," J. Electromag. Waves Applications, vol. 15, pp. 1521-1537, November 2001.
Y. Wang and H. Ling, "Efficient radar signature prediction using a frequency-aspect interpolation technique based on adaptive feature extraction," IEEE Trans. Antennas Propagat., vol. AP-50, pp. 122-131, February 2002.
H. Deng and H. Ling, "An efficient preconditioner for electromagnetic integral equations using pre-defined wavelet packet basis," IEEE Trans. Antennas Propagat., vol. AP-50, pp. 1633-1640, November 2002.
H. Deng and H. Ling, "An efficient wavelet preconditioner for iterative solution of three-dimensional electromagnetic integral equations," IEEE Trans. Antennas Propagat., vol. AP-51, pp. 654-660, March 2003.
H. Choo, H. Ling and C. S. Liang, "Shape optimization of corrugated coatings under grazing incidence using a genetic algorithm," IEEE Trans. Antennas Propagat., vol. AP-51, pp. 3080-3087, November 2003.
L. C. Trintinalia and H. Ling, "Integral equation modeling of multi-layered doubly-periodic lossy structures using periodic boundary condition and a connection scheme," IEEE Trans. Antennas Propagat., vol. 52, pp. 2253-2261, September 2004.
A. M. Raynal, J. T. Moore and H. Ling, "Broadband scattering data interpolation based on a relaxed adaptive feature extraction algorithm," Progress in Electromag. Research, vol. 64, pp. 99-116, September 2006.
H. Choo, H. Ling and C. S. Liang, "Design of planar absorbers with periodic resistive patches using a Pareto genetic algorithm," IEEE Trans. Antennas Propagat., vol. AP-56, pp. 2127-2130, July 2008.
D. J. Mar, J. P. Marsh, C. P. Deen, H. Ling, H. Choo and D. T. Jaffe, "Micromachined silicon grisms for infrared optics," Applied Opt., vol. 48, No. 5, pp. 1016-1029, February 2009.
N. Whitelonis and H. Ling, "Investigation of circular pipes as propagation channel for through-wall radar," IEEE Antennas Wireless Propagat. Lett., vol. 9, pp. 145-148, 2010.
H. Kim and H. Ling, "Wavelet analysis of electromagnetic backscattering data," Elect. Lett., vol. 3, pp. 279-281, January 1992.
H. Ling and H. Kim, "Wavelet analysis of backscattering data from an open-ended waveguide cavity," IEEE Microwave and Guided Wave Letters, vol. 2, pp. 140-142, April 1992.
H. Kim and H. Ling, "Wavelet analysis of radar echo from finite-size targets," IEEE Trans. Antennas Propagat., vol. AP-41, pp. 200-207, February 1993.
J. Moore and H. Ling, "Time-frequency analysis of the scattering phenomenology in finite dielectric gratings," Microwave Optical Tech. Lett., vol. 6, pp. 597-600, August 1993.
H. Ling, J. Moore, D. Bouche and V. Saavedra, "Time-frequency analysis of backscattered data from a coated strip with a gap," IEEE Trans. Antennas Propagat., vol. AP-41, pp. 1147-1150, August 1993.
J. Moore, L. C. Trintinalia, H. Ling and G. Xu, "Super-resolved time-frequency processing of wideband radar echo using ESPRIT," Microwave Optical Tech. Lett., vol. 9, pp. 17-19, May 1995.
J. Moore and H. Ling, "Super-resolved time-frequency analysis of wideband backscattered data," IEEE Trans. Antennas Propagat., vol. AP-43, pp. 623-626, June 1995.
J. Moore and H. Ling, "Super-resolved time-frequency processing of surface wave mechanisms contained in wideband radar echo," Microwave Optical Tech. Lett., vol. 9, pp. 237-240, August 1995.
L. C. Trintinalia and H. Ling, "Super-resolved time-frequency parameterization of electromagnetic scattering mechanisms due to structural dispersion," Microwave Optical Tech. Lett., vol. 10, pp. 82-84, October 1995.
L. C. Trintinalia and H. Ling, "Interpretation of scattering phenomenology in slotted waveguide structures via time-frequency processing," IEEE Trans. Antennas Propagat., vol. AP-43, pp. 1253-1261, November 1995.
L. C. Trintinalia and H. Ling, "Extraction of waveguide scattering features using joint time-frequency ISAR," IEEE Microwave and Guided Wave Letters, vol. 6, pp. 10-12, January 1996.
A. Filindras, U. O. Larsen and H. Ling, "Scattering from the EMCC dielectric slabs: simulation and phenomenology interpretation," J. Electromag. Waves Applications, vol. 10, pp. 515-535, April 1996.
Y. Wang and H. Ling, "Extraction of higher order modes in open microstrip lines via FDTD and joint time-frequency analysis," Microwave Optical Tech. Lett., vol. 13, pp. 319-321, December 1996.
L. C. Trintinalia and H. Ling, "Joint time-frequency ISAR using adaptive processing," IEEE Trans. Antennas Propagat., vol. AP-45, pp. 221-227, February 1997.
C. Ozdemir and H. Ling, "Joint time-frequency interpretation of scattering phenomenology in dielectric-coated wires," IEEE Trans. Antennas Propagat., vol. AP-45, pp. 1259-1264, August 1997.
L. C. Trintinalia, R. Bhalla and H. Ling, "Scattering center parameterization of wide-angle backscattered data using adaptive Gaussian representation," IEEE Trans. Antennas Propagat., vol. AP-45, pp. 1664-1668, November 1997.
Y. Wang, H. Ling and V. C. Chen, "ISAR motion compensation via adaptive joint time-frequency technique," IEEE Trans. Aerospace Electronic Sys., vol. AES-34, pp. 670-677, April 1998.
V. C. Chen and H. Ling, "Joint time-frequency analysis for radar signal and image processing," IEEE Signal Processing Mag., Special Issue on Joint Time-Frequency Analysis, vol. 16, pp. 81-93, March 1999.
Y. Wang and H. Ling, "Adaptive ISAR image construction from unevenly undersampled data," IEEE Trans. Antennas Propagat., vol. AP-48, pp. 329-331, February 2000.
H. Deng and H. Ling, "Clutter reduction for synthetic aperture radar imagery based on adaptive wavelet packet transform," Progress in Electromag. Research, vol. 29, pp. 1-23, March 2000.
J. Li and H. Ling, "3D ISAR image reconstruction of a target with motion data using adaptive feature extraction," J. Electromag. Waves Applications, vol. 15, pp. 1571-1587, November 2001.
Y. Zhou and H. Ling, "Electromagnetic inversion of Ipswich objects using the genetic algorithm," Microwave Optical Tech. Lett., vol. 33, pp. 457-459, June 2002.
H. Deng and H. Ling, "Application of adaptive local cosine transform to detection and estimation of ultra-wideband signals through dispersive propagation channels," Microwave Optical Tech. Lett., vol. 35, pp. 150-153, October 2002.
V. C. Chen and H. Ling, Time-Frequency Transforms for Radar Imaging and Signal Analysis, Artech House, Norwood, MA, ISBN No. 1-58053-288-8, 2002.
J. Li, H. Ling and V. C. Chen, "An algorithm to detect the presence of 3D target motion from ISAR data," Multidimensional Systems and Signal Processing, special issue on Radar Signal Processing and Its Applications, vol. 14, pp. 223-240, January-July 2003.
J. Li and H. Ling, "Use of genetic algorithms in ISAR imaging of targets with higher order motions," IEEE Trans. Aerospace Electronic Syst., vol. AES-39, pp. 343-351, January 2003.
Y. Zhou, J. Li and H. Ling, "Shape inversion of metallic cavities using a hybrid genetic algorithm combined with a tabu list," Elect. Lett., vol. 39, pp. 280-281, February 2003.
J. Li, Y. Zhou and H. Ling, "Sparse parameterization of electromagnetic scattering data using a genetic algorithm with adaptive feeding," Elect. Lett., vol. 39, pp. 1104-1105, July 2003.
J. Li and H. Ling, "ISAR feature extraction from non-rigid body targets using adaptive chirplet signal representation," IEE Proc. - Radar, Sonar and Navigation, special issue on time-frequency analysis for synthetic aperture radar and feature extraction, vol. 150, pp. 284-291, August 2003.
C. Ozdemir, S. Lim and H. Ling, "A synthetic aperture algorithm for ground-penetrating radar imaging," Microwave Optical Tech. Lett., vol. 42, pp. 412-414, September 2004.
S. S. Ram and H. Ling, "Application of the reassigned joint time-frequency transform to wideband scattering from waveguide cavities," IEEE Antennas Wireless Propagat. Lett., vol. 6, pp. 580-583, December 2007.
N. Whitelonis and H. Ling, "Radar signature analysis using a joint time-frequency distribution based on compressed sensing," IEEE Trans. Antennas Propagat., 2014.
R. Bhalla and H. Ling, "IFSAR modeling of terrains and targets using a ray-based electromagnetic technique," IASTED International Conference on Antennas, Radar and Wave Propagation, paper 425-082, 5 pp., Banff, Canada, July 2004.
R. Bhalla and H. Ling, "Multi-baseline IFSAR study using a SBR based simulator," SPIE Defense and Security Symposium, Algorithms for Synthetic Aperture Radar Imagery XII, vol. 5805, pp. 102-111, Orlando, FL, April 2005.
R. Bhalla, J. Li and H. Ling, "3D SAR image formation from sparse aperture data using 3D target grids," SPIE Defense and Security Symposium, Algorithms for Synthetic Aperture Radar Imagery XII, vol. 5805, pp. 44-53, Orlando, FL, April 2005.
R. Bhalla, H. Ling, J. Moore and V. J. Velten, "Angular tracking of 3D scattering centers using an optical flow algorithm," International IEEE AP-S Symposium, paper no. S001p03a, 4 pp., Washington, DC, July 2005.
R. Bhalla, A. Raynal, H. Ling, J. Moore and V. J. Velten, "Angular description for 3D scattering centers," SPIE Defense and Security Symposium, Algorithms for Synthetic Aperture Radar Imagery XIII, vol. 6237, 10 pp., Orlando, FL, April 2006.
A. M. Raynal, R. Bhalla, H. Ling and V. J. Velten, "Efficient algorithms for target validation using 3D scattering features," SPIE Defense and Security Symposium, Algorithms for Synthetic Aperture Radar Imagery XIV, Orlando, FL, April 2007.
N. Whitelonis and H. Ling, "Beamforming through a circular pipe for target location," IEEE Antennas Wireless Propagat. Lett., vol. 9, pp. 417-420, 2010.
N. Whitelonis and H. Ling, "Beamforming through a circular pipe with two open ends," 2010 International IEEE AP-S Symposium, Toronto, Canada, July 2010. (Finalist, student paper contest)
N. Whitelonis and H. Ling, "Imaging through a circular pipe using synthetic aperture radar," 2011 International IEEE AP-S Symposium, Spokane, WA, July 2011.
N. Whitelonis and H. Ling, "Compressed sensing through a pipe," 2012 International IEEE AP-S Symposium, Chicago, IL, July 2012. (Honorable mention, student paper contest)
N. Whitelonis and H. Ling, "Application of a compressed sensing based time-frequency distribution for radar signature analysis," 2012 International IEEE AP-S Symposium, Chicago, IL, July 2012.
N. Whitelonis and H. Ling, "High-resolution radar imaging through a pipe via MUSIC and compressed sensing," IEEE Trans. Antennas Propagat., vol. AP-61, pp. 3252-3260, June 2013.