Reflector (antenna)

About: Reflector (antenna) is a research topic. Over the lifetime, 28730 publications have been published within this topic receiving 212618 citations.

Hybrid PO-MoM analysis of large axi-symmetric radomes

Abstract: Over the last three decades, intensive work has been done to develop techniques aimed at accurate and efficient analysis of antenna radome systems. Some applications involve radar operating in the millimeter wave range and for those cases the radome size can be on the order of one hundred wavelengths or so in length. For practical simulations of such large radomes, a hybrid physical optics-method of moments (PO-MoM) technique is presented for accurate and efficient analysis of electrically large radomes. The procedure combines the method of moments (MoM) for modeling the tip region of the dielectric radome and ray optics in conjunction with physical optics (PO) for treating the flatter smooth section of the radome. Calculated far-field patterns using the new technique agree well with measured data for a reflector antenna radiating in the presence of a large radome. The computational time for simulating the performance of a 46/spl lambda/ reflector in the presence of an 88/spl lambda/ long radome was a mere 4 h on a 233 MHz PC.

Head-up display device

Abstract: A head-up display device includes a display unit for displaying information, a reflector rotatably supported by frame members fixed to a vehicle, and an adjuster for adjusting a rotational position of the reflector by a gearing system. The information displayed on the display unit is reflected by the reflector to a projection area on a vehicle windshield. The adjuster so adjusts the rotational position to allow a vehicle driver to see both a front view through the windshield and a superimposed reflected image of the information. The head-up display device further includes a regulator to allow the reflector to rotate in a rotational direction within a range where the reflector is adjustable by the adjuster, and to prevent the reflector from shifting in a direction other than the rotational direction.

Sensitivity and transient response of microwave reflection measurements

Abstract: Microwave reflection measurements are widely used for the characterization of minority‐carrier lifetimes in semiconductors. A theoretical description of the technique is presented. The approach is based on a dielectric multilayer model that accounts for experimental parameters such as microwave frequency, sample thickness and doping, and the distance to an optional reflector behind the sample. With a new definition of the sensitivity in transient microwave reflection measurements, the most sensitive configuration is investigated for a given semiconductor thickness and conductivity. Good agreement between the theoretical simulation and measurements is demonstrated. The model is also used for calculating microwave reflection transients from the excess carrier decay after pulsed laser excitation. It is found that the reflected microwave power mirrors the carrier decay if three criteria are fulfilled: The carrier generation must be homogeneous; low‐injection conditions are required; and the reflector must be positioned appropriately for linear dependence of the microwave reflection on the carrier density.

Fields in the image space of symmetrical focusing reflectors.

Abstract: The fields scattered by circular symmetric reflector illuminated by a linearly polarised wave incident normally on the aperture are calculated from the induced surface currents. It is shown that the fields in the axial region can be represented by a spectrum of near-spherical hybrid waves propagating along the axis. For large microwave focusing reflectors, the wavefronts are effectively plane in the significant part of the image space. The axial wave fields are linear combinations of the TEln and TMln fields appropriate for circular metal pipes, but can be bounded only by anisotropic-reactance surfaces. Axial-wave theory is used to investigate the characteristics of the fields in the focal region of a paraboloidal reflector, when the incident wave is uniform and plane. For radiotelescope focal ratios, the image structure differs significantly from the classical Airy pattern, deduced by scalar analysis, of optical focusing systems. Energy vortexes circulating about the dark rings influence the efficiency obtainable from aperture-type feeds in the focal plane. Application of axial-wave analysis to spherical reflectors, and the synthesis of high-efficiency low-noise feeds, using hybrid-waves in corrugated guides, are described briefly.