W.V.T. Rusch’s research while affiliated with University of Southern California and other places

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Publications (104)


Characteristics of Millimeter-Wave Imaging Optics Using a Single Offset Paraboloidal Reflector
  • Article

January 1995

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10 Reads

Electromagnetics

Aluizio Prata Jr

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Willard V. T. Rusch†

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Herbert G. Pascalar

All-reflective systems with focal–plane arrays of monolithic elements promise major improvements in millimeter wave imaging applications. In this work high resolution, diffraction limited, wide–field imaging performance is investigated for a single offset paraboloidal reflector. Using accurate electromagnetic vector diffraction analysis, off-axis image degradation is computed for progressively larger field-of-view. Comparisons validate the estimates obtained from the closed-form expressions used to initiate the design process. As a practical example of the design process, a system with an unobstructed 500 wavelengths entrance aperture diameter is designed and its imaging performance, at various locations within a 6048 elements image plane, is computed. The offset reflector dimensions result in a less than 0.2 degree half-power beamwidth and about 50 percent directivity loss at the edges of a rectangular 13 × 6.5 degrees image field of view. Review of these results demonstrate the high–performance capability of millimeter-wave imaging systems using focal plane detector arrays illuminated by offset paraboloidal reflectors.


EFIE Time-Marching Scattering from Bodies of Revolution and Its Applications

April 1994

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7 Reads

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9 Citations

IEEE Transactions on Antennas and Propagation

The authors treat the “entire-tangent” representation of a time-domain electric-field integral equation (TDEFIE) for solving transient scattering problems involving perfectly conducting (PEC) bodies of revolution (BOR). This entire-tangent TDEFIE reduces three-dimensional scattering problems with axial symmetry to two-dimensional problems, thus facilitating the numerical treatment and significantly reducing CPU requirements. Additional refinements and algorithm efficiencies are described. Some numerical results and applications are presented


Time-domain physical-optics

February 1994

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35 Reads

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129 Citations

IEEE Transactions on Antennas and Propagation

The authors extend the concept of the frequency-domain physical-optics approximation to the time domain, and use it to determine some significant properties of large reflector antennas. When this method is used to determine the equivalent surface-current density on the reflector, the effects of time-delayed mutual coupling between points on the surface are ignored. Consequently, many of the numerical limitations found in other conventional time-domain techniques are avoided, e.g. boundary-truncation error, interpolation error, numerical dispersion error, numerical instability, error accumulation with time marching, etc. More significantly, this method requires relatively small amounts of computer memory and CPU time. Several applications to the transient analysis of pulsed radar systems are given


Efficient computation of the time-domain scattering from bodies of revolution

August 1993

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18 Reads

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11 Citations

An approach obtaining the time-domain scattering from metal, dielectric, or dielectric-coated bodies of revolution (BORs) is presented. The axial symmetry of the BORs enables a Fourier mode decomposition in the frequency domain, thereby allowing three-dimensional problems to be treated in two dimensions. By implementing the moment method and inverse discrete Fourier transform techniques, the proposed approach enables the time-domain analysis of more complicated objects, such as multiple metal scatterers and dielectric-coated scatterers. The effects of lossy and dispersive materials can be easily included in the time-domain analysis. Several examples are presented to illustrate the capabilities of the proposed approach


A Synthesis Procedure for Coated Reflector Antennas

October 1992

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5 Reads

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1 Citation

IEEE Transactions on Antennas and Propagation

A procedure is presented for the synthesis of coated axially symmetric reflector antennas to provide specified far-field radiation patterns. The technique stems from ray tracing from the feed to the aperture plane via reflection from the reflector surface. The coating profile required to attenuate the aperture fields is determined based on the reflection of plane waves from metal-backed slabs. The procedure involves two steps. Initially the thickness required to produce the proper magnitude aperture distribution is obtained. Then the reflector is shaped to adjust the phase across the aperture. This procedure is demonstrated in the design of a -40 dB Taylor pattern. Comparison of the results with those obtained using a moment method formulation revealed good agreement between the two formulations


Comparison of the slope of the field at the reflection boundary of an edge‐induced and surface‐curvature‐induced microwave shadows

February 1992

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8 Reads

Microwave and Optical Technology Letters

Using diffracted-field formulas the slope of the field is evaluated at the reflection boundary of an edge-induced shadow. Retaining high-frequency terms the wavelength dependency is (λ)−1/2. Using a formula for the field near the turning point of an inflected surface the slope of the field at the reflection boundary is evaluated. Retaining high-frequency terms, the wavelength dependency is (λ)−5/6 in this case. That is, the shadow for the surface-curvature-induced case gets sharper nearly twice as fast as for the edge-induced case as the frequency increases. This slope is a measure of spillover into the shadow region.


The Current State of the Reflector Antenna Art—Entering the 1990’s

February 1992

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16 Reads

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36 Citations

Proceedings of the IEEE

Modern reflector theory and practice, with emphasis on the recent past are reviewed. Included are a brief historical review and performance definitions for the nonspecialist. Special sections are devoted to shaped multiple reflectors, reflector surface metrology, and reflectors for the next decade and beyond. In spite of decreasing budgets for scientific, commercial, and military space programs, the 1990s promise to be a true golden age for the reflector antenna art



Low-Sidelobe Reflector Synthesis and Design using Resistive Surfaces

October 1991

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16 Reads

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9 Citations

IEEE Transactions on Antennas and Propagation

A procedure is presented for determining the resistivity of a paraboloid's reflecting surface to obtain a desired sidelobe level. The only requirement is that the normalized aperture distribution due to the feed be greater than the corresponding normalized low sidelobe distribution at every point on the reflector (i.e. the reflection coefficient of the surface ⩽1). In the synthesis procedure, blockage is ignored and an ideal feed is assumed. In spite of this, computation of the secondary radiation patterns of a resistively corrected antenna including the feed using the method of moments shows that a -40-dB sidelobe level is achievable. In principal, there is no limit to the sidelobe reduction for the field scattered from the reflector. In practice, blockage, feed illumination errors, errors in the surface resistivity, and the feed backlobe will limit the sidelobe level


Analysis of rim loaded, axially-symmetric reflector antennas using integral equation techniques

July 1991

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6 Reads

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1 Citation

The application of integral equations to the analysis of thinly coated perfect electric conductors, in particular coated reflector antennas, is examined with emphasis upon the controllability of the far-field radiation patterns. A set of coupled-field integral equations, derived from enforcing boundary conditions and equivalence principle, represents the fields exterior and interior to the coating region and accounts for all of the scattering mechanisms associated with the problem. Results using integral equation techniques are presented which demonstrate the effectiveness that rim loading has in the control of the far-field patterns


Citations (39)


... Software profiling is the investigation of program behavior using information collected during program execution, as opposed to by analyzing the source code prior to execution [28]. It allows performance analysis, by determining which functions or sections of an application could benefit from optimization. ...

Reference:

Design and Implementation of a PTX Emulation Library
III. Performance Analysis
  • Citing Chapter
  • December 1970

... (D is for the size of the antenna aperture, λ is for antenna operating wavelength, R is for the minimum distance of the antenna test) testing conditions are very harsh. In fact, the past CATR system has defects on test band, the quiet area size and test performance, so a brand new millimeter compact range is willing to come into being[1][2][3]. This paper describes the detection of a Ka-band quiet area in a millimeter compact range. ...

A millimeter-wave compact range using an axially-symmetric paraboloid in a Gregorian configuration
  • Citing Conference Paper
  • January 1991

... To improve this scan loss, one can reshape the surface of the lens to remove the higher order phase terms on the lens CFO. Specifically, the difference between the phase of the elliptical lens CFO spectrum and the translated nonsymmetric Gaussian lens feed, referred to as the hologram phase, is approximated by a Zernike expansion [34], [35]. The surface of the elliptical lens is then modified using the following expression: ...

A quadrature formula for evaluating Zernike polynomial expansion coefficients (antenna analysis)
  • Citing Conference Paper
  • January 1989

... There are two solution schemes for the transient electromagnetic scattering analysis, namely the marching-on-in-time (MOT) method [4], [5] and marching-on-in-degree (MOD) method [6]–[8]. However, for BORs, the MOT method cannot make use of the axial symmetry of them since the subdomain temporal basis functions are adopted [9]. The MOD method does not have this limitation because the weighted Laguerre polynomials are used as the global temporal basis functions. ...

Efficient computation of the time-domain scattering from bodies of revolution
  • Citing Conference Paper
  • August 1993

... Various designs of different antenna surface coating to generate radiator surface impedance were attempted. The results prove mostly a drop of front to back radiation ratio and an increase of the back radiation level [5][6][7][8]. In this research an attempt is made to investigate the influence of perturbing the parabolic surface geometry on the standard antenna characteristics like directivity, beam width, back radiation level and level of side lobes and first null. ...

Analysis of rim loaded, axially-symmetric reflector antennas using integral equation techniques
  • Citing Conference Paper
  • July 1991

... This known angular variation reduces the number of unknowns from being proportional to the surface area to depending only on the object's generating arc length, as discussed by Bennett (1971). Sun and Rusch (1991) also partially used this property in their TDIE modeling of reflector antennas. Although problem symmetries have been quite widely exploited in FD models, apparently more can be done to use symmetries for reducing solution time in TD modeling. ...

EFIE time-domain scattering from bodies of revolution
  • Citing Conference Paper
  • July 1991

... Despite their straightforward nature, these techniques were often computationally expensive and prone to numerical instability. Over time, more sophisticated methods have emerged, such as the use of recurrence relations [15,16,17,18,19,20,21]. These studies successfully addressed instability issues for higher mode numbers and provided fast algorithms for calculating Zernike polynomials. ...

Algorithm for computation of Zernike polynomials expansion coefficients
  • Citing Article
  • Publisher preview available
  • February 1989

... When linearly polarized radiation transverses magnetized plasmas, it undergoes rotation in its polarization plane. This effect, dubbed Faraday Rotation (FR) has been used for decades to remotely probe coronal and heliospheric structures (e.g., Levy et al. 1969 [8]; Kooi et al. 2017 [9]; and Figures 4 and 5). FR is a particularly promising remote sensing technique to derive not only the strength but also the 3D configuration of the magnetic field in CMEs while they are still in the corona. ...

Pioneer 6: Measurement of Transient Faraday Rotation Phenomena Observed during Solar Occultation
  • Citing Article
  • November 1969

Science

G S Levy

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T Sato

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B L Seidel

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[...]

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W. V. T. Rusch

... Observations of FR require a background transmitter of at least partially linearly polarized light. Early observations used natural radio sources [e.g. the Crab nebula - Golnev et al. 1964;Sofue et al. 1972Sofue et al. , 1976Soboleva & Timofeeva 1983] as well as spacecraft transmitters [Levy et al. 1969;Stelzried et al. 1970;Volland et al. 1977;Bird 1982;Pätzold et al. 1987]. Modern observations have involved radio galaxies [Mancuso & Spangler 1999, 2000Spangler 2005;Ingleby et al. 2007;Mancuso & Garzelli 2013;Kooi et al. 2014Kooi et al. , 2017Kooi et al. , 2021, pulsars [Ord et al. 2007;You et al. 2012], and continued use of spacecraft transmitters [Jensen et al. 2013[Jensen et al. , 2018Wexler et al. 2017Wexler et al. , 2019Wexler et al. , 2021. ...

The quasi-stationary coronal magnetic field and electron density as determined from a Faraday rotation experiment
  • Citing Article
  • November 1970

Solar Physics

... HE PRESENCE of long thin mechanical support structures in front of a constant-phase aperture, such as that of a focused paraboloid, has generally defied rigorous attempts to analyze their effects upon the R F performance of the aperture. However, as a good first approximation, it has been proposed [l]-[4] that the strut currents are the same currents that would flow on an infinite cylindrical structure of the same cross section in free-space immersed in an infinite linearly polarized plane wave with the same polarization and direction of incidence as the local geometrical ray incident upon that part of the strut as it emerges from the aperture (transmit mode). This approximation is known as the " IFR-hypothesis. ...

Analysis of blockage effects on gain and sidelobes by struts of arbitrary cross-section in a dual-reflector antenna
  • Citing Conference Paper
  • October 1971