Daniel J. Hoppe

Bio: Daniel J. Hoppe is an academic researcher from California Institute of Technology. The author has contributed to research in topics: Antenna (radio) & NASA Deep Space Network. The author has an hindex of 16, co-authored 77 publications receiving 1046 citations. Previous affiliations of Daniel J. Hoppe include Jet Propulsion Laboratory.

Starshade optical edge modeling, requirements, and laboratory tests

Abstract: In conjunction with a space telescope of modest size, a starshade can be used as an external occulter to block light from a target star, enabling the detection of exoplanets in close orbits. Typically, the starshade will be placed some 50,000 km from the telescope and the system oriented so that the sun is on the opposite side of the shade to the telescope, but somewhat away from the line of sight. A small amount of sunlight can scatter from the edges of the shade directly into the telescope. Since the photon rate from an earthlike exoplanet might be only a few photons per minute, it is desirable that the scattered sunlight is also near this level. We have built an analytical model of the performance of starshade edges for both specular and Lambertian surfaces and derived requirements for properties such as reflectivity and radius of curvature. A computer model was also developed to show the appearance of the sunlight from the starshade and assess the contrast with the exoplanet. A commercial electromagnetism code was also used to investigate aspects of the results. We also constructed a scatterometer with which various test edges were measured and derived the likely performance if used in a starshade. We discuss these models and give the principal results.

System and method for controlling the phase of an antenna array

Abstract: A system and method for controlling power transferred to an aircraft. The system includes a master antenna and a plurality of slave antennas on the ground. Each slave antenna transmits an uplink signal of a unique phase modulated frequency. The master antenna transmits a master uplink signal. The aircraft receives all the uplink signals and modulates a composite of those signals to produce a downlink beacon that has multiple phase components, each of which corresponds to one of the slave antennas and has a unique frequency. Each of the slave antennas receives the downlink beacon and uses the corresponding phase component to adjust the phase of the slave uplink signal relative to the master uplink signal.

Beam-forming concentrating solar thermal array power systems

Abstract: The present invention relates to concentrating solar-power systems and, more particularly, beam-forming concentrating solar thermal array power systems. A solar thermal array power system is provided, including a plurality of solar concentrators arranged in pods. Each solar concentrator includes a solar collector, one or more beam- forming elements, and one or more beam-steering elements. The solar collector is dimensioned to collect and divert incoming rays of sunlight. The beam-forming elements intercept the diverted rays of sunlight, and are shaped to concentrate the rays of sunlight into a beam. The steering elements are shaped, dimensioned, positioned, and/or oriented to deflect the beam toward a beam output path. The beams from the concentrators are converted to heat at a receiver, and the heat may be temporarily stored or directly used to generate electricity.

A hybrid finite-element method for axisymmetric waveguide-fed horns

Abstract: A new method for finding radiation patterns and the reflection coefficients associated with an axisymmetric waveguide fed horn is presented. The approach is based on a hybrid finite element method (FEM) wherein the electromagnetic fields in the FEM region are coupled to the fields outside by two surface integral equations. Because of the local nature of the FEM, this formalism allows for the presence of inhomogeneities to be included in the problem domain. The matrix equation which results from the application of this method is shown to be complex-symmetric. Comparisons of calculated and measured data for two different horns show good agreement.

Polarization compensating protective coatings for TPF-Coronagraph optics to control contrast degrading cross polarization leakage

Abstract: We describe here the design approaches and performance analysis of the OTA in the wavelength band of interest. Coronagraph performance at 600nm wavelength based on a particular coating and occulting focal plane mask is also presented.

Nanoscale wires and related devices

Abstract: The present invention relates generally to sub-microelectronic circuitry, and more particularly to nanometer-scale articles, including nanoscale wires which can be selectively doped at various locations and at various levels. In some cases, the articles may be single crystals. The nanoscale wires can be doped, for example, differentially along their length, or radially, and either in terms of identity of dopant, concentration of dopant, or both. This may be used to provide both n-type and p-type conductivity in a single item, or in different items in close proximity to each other, such as in a crossbar array. The fabrication and growth of such articles is described, and the arrangement of such articles to fabricate electronic, optoelectronic, or spintronic devices and components. For example, semiconductor materials can be doped to form n-type and p-type semiconductor regions for making a variety of devices such as field effect transistors, bipolar transistors, complementary inverters, tunnel diodes, light emitting diodes, sensors, and the like.

Doped elongated semiconductors, growing such semiconductors, devices including such semiconductors, and fabricating such devices

Abstract: A bulk-doped semiconductor that is at least one of the following: a single crystal, an elongated and bulk-doped semiconductor that, at any point along its longitudinal axis, has a largest cross-sectional dimension less than 500 nanometers, and a free-standing and bulk-doped semiconductor with at least one portion having a smallest width of less than 500 nanometers. Such a semiconductor may comprise an interior core comprising a first semiconductor; and an exterior shell comprising a different material than the first semiconductor. Such a semiconductor may be elongated and may have, at any point along a longitudinal section of such a semiconductor, a ratio of the length of the section to a longest width is greater than 4:1, or greater than 10:1, or greater than 100:1, or even greater than 1000:1. At least one portion of such a semiconductor may a smallest width of less than 200 nanometers, or less than 150 nanometers, or less than 100 nanometers, or less than 80 nanometers, or less than 70 nanometers, or less than 60 nanometers, or less than 40 nanometers, or less than 20 nanometers, or less than 10 nanometers, or even less than 5 nanometers. Such a semiconductor may be a single crystal and may be free-standing. Such a semiconductor may be either lightly n-doped, heavily n-doped, lightly p-doped or heavily p-doped. Such a semiconductor may be doped during growth. Such a semiconductor may be part of a device, which may include any of a variety of devices and combinations thereof, and a variety of assembling techniques may be used to fabricate devices from such a semiconductor. Two or more of such a semiconductors, including an array of such semiconductors, may be combined to form devices, for example, to form a crossed p-n junction of a device. Such devices at certain sizes may exhibit quantum confinement and other quantum phenomena, and the wavelength of light emitted from one or more of such semiconductors may be controlled by selecting a width of such semiconductors. Such semiconductors and device made therefrom may be used for a variety of applications.

IEEE Transactions on Microwave Theory and Techniques and Antennas and Propagation Announce a Joint Special Issue on Ultra-Wideband (UWB) Technology

Abstract: Before the emergence of ultra-wideband (UWB) radios, widely used wireless communications were based on sinusoidal carriers, and impulse technologies were employed only in specific applications (e.g. radar). In 2002, the Federal Communication Commission (FCC) allowed unlicensed operation between 3.1–10.6 GHz for UWB communication, using a wideband signal format with a low EIRP level (−41.3dBm/MHz). UWB communication systems then emerged as an alternative to narrowband systems and significant effort in this area has been invested at the regulatory, commercial, and research levels.

Electromagnetic Modeling of Composite Metallic and Dielectric Structures

Abstract: Starting from the equivalence theorem any composite metallic and dielectric structure can be analyzed by using SIE (surface integral equations). Such integral equations are usually solved by MoM (method of moments). Most of the existing MoM methods for solving SIE are developed for BORs (bodies of revolution). There are only few such methods that can handle structures of arbitrary shape. These methods use sub-domain basis functions defined over triangles, requiring a very large number of unknowns even for the simplest problems. This paper presents a new MoM method for electromagnetic modeling of composite metallic and dielectric structures. The method uses entire-domain basis functions defined over bilinear surfaces, resulting in a remarkably small number of unknowns.