The limited coverage of wireless communication at the millimeter-wave frequency band due to large free-space path loss, i.e. large signal attenuation, has been a major problem. Furthermore, shadowing and small-scale fading may reduce the received signal even more. An array of rod antennas is designed to tackle those problems by providing high gain, broad scan range, and a shaped beam. Each patch, which couples the electromagnetic wave to the rod, is fed by a coplanar waveguide (CPW) feedline. Each rod antenna demonstrates 18 dBi realized gain and 20° half power beamwidth (HPBW). Moreover, the 4 GHz bandwidth of the antenna provides high data rate for the gigabit wireless application. Furthermore, the Radio Frequency Microelectromechanical System (RF MEMS) switch is used to realize a switched antenna with a broad scan range. The design method and the characterization of the antenna are presented. The proposed antenna system is suitable for a wide range of applications, such as wireless high definition video/audio, USB and firewire replacement, Frequency Modulated Continuous Wave (FMCW) radar, and home/office backhaul application at millimeter-wave frequency.

/pdf/switched-beam-antenna-array-design-for-millimeter-wave-1v6jcrqwjz.pdf

Switched-beam antenna array design for millimeter-wave applications

A scanning probe microscope assembly and corresponding method for making confocal, spectrophotometric, near-field, and scanning probe measurements and forming associated images from the measurements.

Scanning probe microscope assembly and method for making confocal, spectrophotometric, near-field, and scanning probe measurements and associated images

An experimental investigation of dielectric rod as wave guide indicates that the guiding effect is retained even when the rod is only a fraction of a wave‐length in diameter. The greater part of the guided energy is then outside the dielectric, so that a very low loss wave guide results. Measurements of performance made at 1.25 cm indicate attenuations down to 0.004 decibel per meter in polystyrene rod, and show good agreement with theoretical predictions. A resonator utilizing the dielectric‐rod wave guide is described, in which a maximum Q of approximately 53,000 was observed.

An Investigation of Dielectric Rod as Wave Guide

1. lntroduction One of the purposes of this symposium is to dissuss some of the theoretical difficulties involved in the solution of electromagnetic problems. For this reason I believe that the treatment of diffraction problems is an appropriate topic. In particular, the problem of radiation from a horn (acoustic or electromagnetic) has been treated approximately with the aid of one of several formulas suggested by Huygens' physical idea about wave propagation. These formulas are not equally powerful, do not always give equally good approximations, and do not inspire the same a pm'ori confidence in the results. Of course, if no approximations were made in the formulas, it would not matter which formula was used since then the result would always be exact. However, approximations are unavoidable except when the answer is already known and when there is no need for any formula. To understand how Huygens' physical assumption that the conditions at the front of a wave determine the subsequent wave motion suggests various formulas, let us consider a source first in an infinite homogeneous medium and then inside a perfectly rigid horn. In the first case the wavefronts are closed surfaces surrounding the source. In the second case, the wavefronts are open surfaces sliding along the walls of the horn until they reach the aperture. Eventually , the wavefronts will become closed surfaces surrounding the horn as well as the source. Kirchhoff derived an explicit formula for the field outside a closed surface (8) in terms of the wave function and its normal derivative on (8) on the assumption that the source is inside (8) and that the medium outside (S) is homogeneous. In the case of the horn Kirchhoff's surface of integration must enclose the horn as well as the source since the horn introduces a discon-tinuity in the medium. This closed surface may be chosen to consist of an \" aperture surface \" (8.) together with the exterior surface of the horn. In the case of electromagnetic waves the present writer proved another theorem [l, 21 (the \" Induction Theorem \") in which the surface of integration is solely the aperture surface (8J. An obvious analogue of this theorem for scalar waves

Kirchhoof's formula, its vector analogue, and other field equivalence theorems

A new ultrawide-bandwidth dielectric-rod antenna is presented with its application in detecting shallow targets, such as antipersonnel (AP) mines. The lowest hybrid mode is launched and guided along a circular-dielectric waveguide. The end of the waveguide is tapered to a point where electromagnetic waves are radiated out with field behavior similar to that radiated from a Hertzian dipole in the forward direction. The low antenna clutter and weak antenna-ground interaction are two unique features. Its near-field radiation properties are investigated by directly probing the fields and by numerical simulation with a three-dimensional finite-difference time-domain technique. Both measurement and numerical simulation results are presented for the detection of buried AP mines using a prototype dielectric-rod antenna operated at a frequency range from 1 to 6 GHz.

A new ultrawide-bandwidth dielectric-rod antenna for ground-penetrating radar applications

A theory is developed describing the electromagnetic radiation from dielectric rods used as terminations to rectangular wave guides. The radiation patterns are computed from the fields due to equivalent magnetic and electric currents on the surfaces of the rods. These equivalent currents are determined by use of Schelkunoff's equivalence principle applied to approximate fields within the dielectric. Specific calculations are carried out for rods whose average dimensions are 0.9″×0.25″ and whose lengths vary from three to ten wave‐lengths. Experimental patterns are obtained for eight polystyrene rods, some of which are variable in length. Agreement with theory is found for rods from three to six wave‐lengths long; differences between experiment and theory are discussed.

C. W. Horton

Papers

The Radiation Patterns of Dielectric Rods—Experiment and Theory