Search

We modified and justified the radar equation for ground penetration by including the backscattering effect. We propose a strawman system on an orbiter 50 km above the surface based on lunar conditions. The Tightly coupled dipole arrays antenna substantially reduces the size and mass and consists of an array with 8 × 8 cells on a light weight plate that is 1.62‐m2 wide with cells 0.25‐m high providing increased directionality and beam‐steering capability. The system includes 8 transmitters and 16 receivers that are able to measure wave polarization so that it is sensitive to subsurface water/ice. The system is controlled by central computers with transceivers all programmable providing more functionalities and flexibilities enabling systems of an even larger number of transceivers. It uses the synthetic aperture radar method to enhance the spatial resolution along the orbit track and has phase steering capability to increase the resolution in the cross‐track direction. The total transmitted power is 160 W. The radar is able to operate in three modes: a fine‐resolution mode that provides the full Multiple‐Input Multiple‐Output ultrawideband (MIMO UWB) capability with vertical range resolution up to 0.2 m, a deep penetration mode that is able to penetrate 100 m for high attenuation targets or over few kilometers for low attenuation targets, and a survey mode that provides overall characterization of the planet economically. This system can provide internal properties and structures of a target and detailed information about most useful resources such as ice, water, minerals, and shelter caves, for human space exploration on the Moon, Mars, and asteroids. Key Points: We present and verify the radar equation for ground penetration radarWe design a system on an orbiter which is able to penetrate deeper than 100 m with vertical resolution up to 0.2 mThe system is based on new technologies with a matrix of transceivers and matching compact antenna arrays [ABSTRACT FROM AUTHOR]

The design and characterization of a simple, flexible wideband antenna using polydimethylsiloxane (PDMS) composite are presented. Conductive fibers are used to construct the metallic parts on a PDMS composite. To characterize the performance, two identical antennas are designed, one using the PDMS composite while the other on conventional dielectric materials. It was observed that both antennas behave well in terms of the matched bandwidth; however, the radiation towards the broadside direction is reduced when using the PDMS composite as substrate, particularly at higher frequencies. The antenna exhibits a matched bandwidth of 59.9%, ranging from 3.43 to 11.1 GHz. Moreover, the bending analysis carried out for different scenarios show that the wideband behavior of the antenna is well preserved and the variation reaches a maximum of 1% variation. [ABSTRACT FROM AUTHOR]

A bandpass filter resonating at ∼1.4 μm and based on a dual-frequency-selective surface design is fabricated and characterized on a silicon substrate. The filter consists of square apertures arranged in a square lattice and separated by magnesium-fluoride dielectric layers. Simulations indicate minimal change in spectral reflectance versus overlay misalignment. The measured reflectance shows almost zero minima and a sharp roll-off. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 95–98, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20387 [ABSTRACT FROM AUTHOR]

In this paper, a method is presented for analyzing very large finite arrays of tapered-slot antenna elements. The Toeplitz matrix property of regularly spaced arrays, combined with a parametrically truncated coupling radius, generates fixed matrix storage based on the coupling radius rather than array size, thus allowing very large problem analysis. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 323–328, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11050 [ABSTRACT FROM AUTHOR]

Generating accurate, high-resolution time-frequency distributions (TFD) is a critical aspect of dynamic radar scattering analysis. Well-formed TFD's can be used for target identification, target acquisition in high-noise environments, or extending the range of radar systems. In this paper, we diverge from traditional methods employing complex signal-processing methods and propose a simple approach for constructing the TFD for computational electromagnetic (CEM) targets based on the physics of the problem. The proposed method allows for an arbitrarily high resolution at any single look angle. Several examples are presented to validate the method. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 186–189, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10552 [ABSTRACT FROM AUTHOR]

Hybrid finite element methods (FEM) which combine the finite element and boundary integral methods have been found very successful for the analysis of conformal finite and periodic arrays embedded on planar or curved platforms. A key advantage of these hybrid methods is their capability to model inhomogeneous and layered material without a need to introduce complicated Green's functions. Also, they offer full geometrical adaptability and are thus of interest in general-purpose analysis and design. For the proposed hybrid FEM, the boundary integral is only used on the aperture to enforce the radiation condition by employing the standard free space Green's function. The boundary integral truncation of the FEM volume domain, although necessary for rigor, is also the cause of substantial increase in CPU complexity. In this paper, we concentrate on fast integral methods for speeding-up the computation of these boundary integrals during the execution of the iterative solver. We consider both the adaptive integral method (AIM) and the fast multipole method (FMM) to reduce the complexity of boundary integral computation down to &Oscr;(Nα) with α<1.5. CPU and memory estimates are given when the AIM and FMM accelerations are employed as compared to the standard &Oscr;(N2) algorithms. In addition, several examples are included to demonstrate the practicality and application of these fast hybrid methods to planar finite and infinite arrays, frequency selective surfaces, and arrays on curved platforms. Copyright © 2000 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The first part of the paper presents the implementation and performance of a new absorbing boundary condition (ABC) for truncating finite element meshes. This ABC can be applied conformally to the surface of the structure for scattering and antenna radiation calculations. Consequently, the computational domain is reduced dramatically, thus allowing the simulation of much larger structures, and results are presented for three-dimensional bodies. The latter part of the paper discusses optimization issues relating to the solver's CPU speed on parallel and vector processors. It is shown that a jagged diagonal storage scheme leads to a four-fold increase in the FLOP rate of the code, and a standard matrix profile reduction algorithm substantially reduces the inter-processor communication. [ABSTRACT FROM AUTHOR]

The finite element method (FEM) with local absorbing boundary conditions has been recently applied to compute electromagnetic scattering from large 3-D geometries. In this paper, we present details pertaining to code implementation and optimization. Various types of sparse matrix storage schemes are discussed and their performance is examined in terms of vectorization and net storage requirements. The system of linear equations is solved using a preconditioned biconjugate gradient (BCG) algorithm and a fairly detailed study of existing point and block preconditioners (diagonal and incomplete LU) is carried out. A modified ILU preconditioning scheme is also introduced which works better than the traditional version for our matrix systems. The parallelization of the iterative sparse solver and the matrix generation/assembly as implemented on the KSR1 multiprocessor is described and the interprocessor communication patterns are analysed in detail. Near-linear speed-up is obtained for both the iterative solver and the matrix generation/assembly phases. Results are presented for a problem having 224,476 unknowns and validated by comparison with measured data. [ABSTRACT FROM AUTHOR]

An absorbing boundary condition of second order is derived for mesh terminations conformal to the shape of the radiator or scatterer. The boundary condition is expressed entirely in terms of the principal curvatures of the termination surface and results in a symmetric system of equations when incorporated into the finite-element functional. [ABSTRACT FROM AUTHOR]

Presents a correction to the article "Conformal Absorbing Boundary Conditions for the Vector Wave Equation," which was published in the December 1993 issue of the journal "Microwave & Optical Technology Letters."