Leung Tsang

Leung Tsang
University of Michigan | U-M · Department of Electrical Engineering and Computer Science (EECS)

About

656
Publications
33,582
Reads
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19,099
Citations
Introduction
Additional affiliations
September 2001 - June 2004
City University of Hong Kong
Position
  • Professor Chair
September 1983 - December 2014
University of Washington Seattle
Position
  • Professor (Full)

Publications

Publications (656)
Article
In this paper, we apply the BBGF-KKR-MST (Broadband Green's function-KKR-Multiple Scattering Theory) to calculate Band Structures and Band Field Solutions in topological acoustics. A feature of BBGF is that the lattice Green's functions are broadband, and the transformations to cylindrical waves are calculated rapidly for many frequencies for speed...
Preprint
Full-text available
Seasonal snow cover is the largest single component of the cryosphere in areal extent, covering an average of 46 million square km of Earth's surface (31 % of the land area) each year, and is thus an important expression of and driver of the Earth’s climate. In recent years, Northern Hemisphere spring snow cover has been declining at about the same...
Article
In this article, we study wave propagation in vegetation at multiple frequencies using a hybrid method. First, the multiple scattering within a single plant is captured using the high-frequency structure simulator (HFSS) for extracting the T-matrix of the plant in vector cylindrical waves (VCW). Second, the Foldy-Lax equations (FLE) are applied wit...
Article
—In this paper, we derived Analytical Kirchhoff Solutions (AKS) for bistatic scattering near the specular directions at P band and L band for applications in Signals of Opportunity (SoOp). The land surface profiles are divided into three scales: microwave roughness f1, fine scale topography f2, and coarse scale 30-meter DEM f3 . The microwave rough...
Article
We apply the broadband Green’s function-KKR-multiple scattering theory (BBGF-KKR-MST) to calculate normalized band-field solutions of magneto-optic crystals. The advantage of the method is that the matrix eigensystem equations are of low order. For the first three bands, a total of three cylindrical waves is sufficient to characterize the eigensyst...
Article
Full-text available
This paper implements a newly developed combined active and passive algorithm for the retrieval of snow water equivalent (SWE) by using three-channel active and two-channel passive observations. First, passive microwave observations at 19 and 37 GHz are used to determine the scattering albedo of snow. An a priori scattering albedo is obtained by av...
Article
Full-text available
Microwave radiometry has provided valuable spaceborne observations of Earth's geophysical properties for decades. The recent SMOS, Aquarius, and SMAP satellites have demonstrated the value of measurements at 1400 MHz for observing surface soil moisture, sea surface salinity, sea ice thickness, soil freeze/thaw state, and other geophysical variables...
Article
In this paper, we develop a hybrid method for studying wave scatterings and propagation in a vegetation field. The coherent multiple scatterings among the plants and the gaps in the vegetation field are considered through a two-step hybrid method. First, the T-matrix of a single plant is calculated using the Huygens principle and the vector cylindr...
Article
Wheat, canola, and pasture are three of the major vegetation types studied during the Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12) conducted to support NASA's Soil Moisture Active Passive (SMAP) mission. The utilized model structure is integrated in the SMAP baseline active retrieval algorithm. Forward lookup tables (data-cub...
Article
Ice sheet subsurface temperature is important for understanding glacier dynamics, yet existing methods to obtain the temperature of the ice sheet column are limited to in situ sources at present. The ultrawideband software-defined microwave radiometer (UWBRAD) has been developed to investigate the remote sensing of ice sheet internal temperatures....
Article
The Ultra-Wideband Software Defined Microwave Radiometer (UWBRAD) is a wideband radiometer operating from 0.5 to 2 GHz for remote sensing of polar ice sheet temperature profiles. Small-scale (cm to m) fluctuations in firn density in the upper portion of the ice sheet significantly impact observed brightness temperatures. Previously, a fully coheren...
Article
In this paper, we develop a method of simulations of using the broadband Green’s function (BBGF) in the Korringa Kohn Rostoker (KKR) method. The merit of the method is broadband such that once the initial setup is completed, the calculation at every frequency is calculated rapidly. The broadband Green’s function consists of a frequency-independent...
Conference Paper
Accurate calculations of electromagnetic scattering and emission from ocean surfaces with large sizes and root-mean-square (RMS) heights are still a challenge for the full-wave numerical methods. The widely used sparse matrix canonical grid (SMCG) method is only efficient for small and moderate roughness surfaces. This is because of the limitation...
Article
A novel method is developed in this paper to characterize the band diagram and band modal fields of gyromagnetic photonic crystals that support topological one-way edge states. The proposed method is based on an integral equation formulation that utilizes the broadband Green's function (BBGF). The BBGF is a hybrid representation of the periodic lat...
Article
In near-infrared imaging and spectroscopy, high-fidelity modeling of photon transport for dense polydisperse colloidal suspensions is crucial. We developed photon transport models using the radiative transfer equation (RTE) with the dependent scattering theory (DST) at volume fractions up to 20%. The polydispersity and interference effects strongly...
Article
A hybrid spatial-spectral method for rapid and broadband calculation of the vector potential normal modes and dyadic Green's function (GF) inside the cavity of irregular shape is presented. In the broadband method of simulation, the normal modes of the irregular cavity, which are independent of operation frequency, are first computed through a line...
Article
A partially coherent approach for computing the electromagnetic response of a layered medium having random rough interfaces and a random dielectric profile is presented as an alternative to the full-wave solution of the problem. The statistical nature of this problem, in particular, the random dielectric profile, introduces randomness in the phase...
Article
A semi-analytical approach for rapid calculation of the Green's function inside the cavity of irregular shape over a broad range of frequency is presented. The method is based on the extraction of the Green's function at an imaginary wave number from itself to obtain a rapidly convergent hybrid spatial-spectral expansion of the Green's function. Th...
Conference Paper
Sea surface salinity (SSS) is an important ocean dynamic parameter, which plays a crucial role in the studies of global climate change, global water cycle forecast, marine environment monitoring, etc.[1-3]. Especially in polar region, SSS becomes a sensitive indicator of climate change. However, the accuracies of retrieved SSS using the popular L-b...
Article
We use full wave simulations of rough surfaces to calculate the emissivities of polar ocean between 0.5 GHz to 2 GHz for applications in ocean salinity. High accuracy is required because the emissivity variations between flat and rough surfaces are at the order of magnitude of 10-3. In addition, the changes of emissivity due to salinity change are...
Article
Full-text available
The increased availability of spaceborne radar data projected over the next decade provides a great opportunity for operational soil moisture mapping with high spatial (< 50 m) and temporal (< 3 days) resolution, by combining the data from multiple SAR missions. Accordingly, a multi-frequency soil moisture retrieval framework has been proposed, bei...
Article
In this paper, we develop a hybrid method to calculate the propagation of microwaves in randomly distributed dielectric cylinders. The hybrid method combines off-the-shelf techniques for single object and our developed techniques of Foldy-Lax method that include extracting the T-matrix for single object, vector translation addition theorem and solv...
Article
In this article, we apply the broadband Green's function for fast full-wave simulations of the radiated emissions from the printed circuit boards (PCBs) of irregular shape. Changes were made on the previous version that improve the computational efficiency and accuracies of the solutions. The improvements include imaginary wavenumber extractions fo...
Article
An ultrawideband radiometer was used to measure microwave brightness temperature spectra over Arctic sea ice in the Lincoln Sea near the north coast of Greenland. Spectra over the range of 0.5-2 GHz were compared to thermal infrared images collected during the airborne campaign and also compared to nearly concurrent Sentinel-1 C-band synthetic aper...
Article
Full-text available
Multi-angular and multi-temporal methods have been developed and accepted as two promising strategies for reliable soil moisture retrieval from radar data. However, the way to combine time series multi-angular data acquired from both descending and ascending orbits with different imaging modes (e.g., ScanSAR and Stripmap) remains unresolved. Conseq...
Article
A distinct feature of GNSS-R land reflectometry is that random rough surfaces are superimposed on many levels of elevations. The rms elevations are in tens of meters which are many times larger than the microwave wavelengths at GNSS frequencies. Such multiple elevations were not considered in the coherent model nor the incoherent model. In this pap...
Article
The method of broadband Green's functions with low wavenumber extractions (BBGFL) is used to calculate Green's function for inhomogeneous waveguides filled with different dielectrics and with irregular boundaries. To construct the BBGFL modal solutions, we derive governing equations of the linear eigen-matrix problem and orthonormalization conditio...
Article
This essay is on the theories of multiple scattering of waves by discrete scatterers and rough surfaces. Applications of the theories are illustrated with emphasis on the remote sensing of the earth. A historical background is provided. The basic theories are based on solving Maxwell equations. We describe the physical results, analytical approache...
Article
The Translation Matrix (T-Matrix) solution to the 3D problem of scattering of the electromagnetic waves from a dielectric layered medium with random rough interfaces is presented. The solution is based on the coupled vector integral equation of the electric field using the dyadic periodic Green's function as a kernel. It is shown that the T-Matrix...
Conference Paper
The studies of electromagnetic scattering and emission by ocean surfaces are crucial for remote sensing of ocean dynamic parameters, e.g., sea surface wind (SSW) and sea surface salinity (SSS). Analytic approximation models have been proposed to simulate the ocean scattering and emission [1-5]. Numerical methods using surface integral equations imp...
Article
In this paper, we develop a radar snow water equivalent (SWE) retrieval algorithm based on a parameterized forward model of bicontinuous dense media radiative transfer (Bic-DMRT). The algorithm is based on retrieving the absorption loss of the snowpack which is directly proportional to the SWE. In the algorithm, Bic-DMRT is first applied to generat...
Article
An efficient optimization methodology is developed and exemplified for electromagnetic scattering problem of structures with multi-scale features. We have developed a scheme to efficiently derive the exact full-wave scattering solution from a large scatterer with localized modifications by using the Green's function of the original scatterer. The G...