Showing papers by "Daniel J. Hoppe published in 1994"
TL;DR: In this paper, a new symmetric formulation of the hybrid finite element method (HFEM) is described which combines elements of the electric field integral equation (EFIE) and the magnetic field integral equations (MFIE) for the exterior region along with the finite element solution for the interior region.
Abstract: A new symmetric formulation of the hybrid finite element method (HFEM) is described which combines elements of the electric field integral equation (EFIE) and the magnetic field integral equation (MFIE) for the exterior region along with the finite element solution for the interior region. The formulation is applied to scattering by inhomogeneous bodies of revolution. To avoid spurious modes in the interior region a combination of vector and nodal based finite elements are used. Integral equations in the exterior region are used to enforce the Sommerfeld radiation condition by matching both the tangential electric and magnetic fields between interior and exterior regions. Results from this symmetric formulation as well as formulations based solely on the EFIE or MFIE are compared to exact series solutions and integral equation solutions for a number of examples. The behaviors of the symmetric, EFIE, and MFIE solutions are examined at potential resonant frequencies of the interior and exterior regions, demonstrating the advantage of this symmetric formulation. >
53 citations
20 Jun 1994
TL;DR: In this paper, the use of a ferrite circulator was discussed in the context of the JPL/NASA Deep Space Network (DSN) in order to avoid the heat dissipation, waveguide loss, and arcing problems aggravated by high average power.
Abstract: Transmitters of the JPL/NASA Deep Space Network (DSN) typically operate at power levels in excess of 100 kW. This causes heat dissipation and loss problems even in the conventional DSN transmit frequencies of the S and X bands. These problems are compounded by operation in continuous mode, rather than in pulsed operation where the average power is low. In an effort to avoid the heat dissipation, waveguide loss, and arcing problems aggravated by high average power, the DSN has helped pioneer the development of beam waveguide antennas. These beam waveguide antennas use quasi-optical techniques to confine the fields, eliminating waveguide usage and their associated losses. The development of quasi-optical, non-reciprocal devices is natural to the beam waveguide environment. The present paper discusses the use of a ferrite circulator in this context.
2 citations
20 Jun 1994
TL;DR: In this paper, the authors describe a system of mode converters used to transform a TE/sub 0N/mode into a Gaussian beam through the use of several different modes.
Abstract: Future plans call for increasing the uplink and downlink frequencies used for communication with deep space probes from the present 2 GHz and 8 GHz bands into the millimeter band, 32-35 GHz. High power transmitters, of the order of several hundred kilowatts CW will be required in the millimeter band. The only sources presently capable of producing this power level are gyro devices. In order to produce these power levels gyro devices employ unconventional interaction cavities. These cavities resonate in higher order waveguide modes, and typically deliver the output signal into an oversize circular waveguide in a higher order waveguide mode, such as a TE/sub 0N/ mode. If the power is to be used constructively, for example to illuminate a reflector antenna, a Gaussian beam is typically required. Transformation of the TE/sub 0N/ mode into a Gaussian beam is achieved through the use of several mode converters. One possible system of mode converters is depicted. The mode converters used to generate the TM/sub 11/ mode required for testing the TM/sub 11/-HE/sub 11/ mode converter are described.