1240 results about "Cross polarization" patented technology

An ultra-wideband magnetic antenna includes a planar conductor having a first and a second slot about an axis. The slots are substantially leaf-shaped having a varying width along the axis. The slots are interconnected along the axis. A cross polarized antenna system is comprised of an ultra-wideband magnetic antenna and an ultra-wideband dipole antenna. The magnetic antenna and the dipole antenna are positioned substantially close to each other and they create a cross polarized field pattern. The present invention provides isolation between a transmitter and a receiver in an ultra-wideband system. Additionally, the present invention allows isolation among radiating elements in an array antenna system.

An apparatus and method to reduce the size of a microstrip antenna without sacrificing antenna efficiency too much are described. The antenna structure includes discontinuity of strip width in the middle of the antenna patch to reduce the size of the antenna at a given resonant frequency. The antenna structure further includes a plurality of patches of differing widths connected to each other at junctions. The junctions are placed symmetrically to ensure maximum radiation at the boresight and also to further reduce cross-polarization levels. A coaxial feed is connected at a predetermined location near the center of a patch, having a narrower width, in order to match the input impedance of the antenna to the coaxial feed.

A dual polarized three-sector base station antenna with variable beam tilt in each sector. The invention advantageously provides a variable phase shifter with very small lateral dimensions which significantly reduces the diameter of a three-sector antenna. The feed network is located on both sides of the antenna ground plane, and the combination of the cable, microstrip and airstrip lines further reduces the lateral size of the antenna. Metal rings on the radome and double-bended ground plane are providing antenna with better cross-polarization and port-to-port isolation.

Overlay measurements for a semiconductor wafer are obtained by forming a periodic grating on the wafer having a first set of ridges and a second set of ridges. The first and second sets of ridges are formed on the wafer using a first mask and a second mask, respectively. After forming the first and second sets of gratings, zero-order cross polarization measurements of a portion of the periodic grating are obtained. Any overlay error between the first and second masks used to form the first and second sets of gratings is determined based on the obtained zero-order cross polarization measurements.

Substantial improvements in frequency reuse in microwave communications systems is achieved by canceling co-channel interference and transmitter leakage. Interferometric beam-narrowing reduces beamwidth without reducing peak magnitude of the beam pattern. Frequency-dependent beam-shaping compensates for frequency-dependent distortions of the beam pattern thereby improving bandwidth. A spatial demultiplexing technique utilizes spatial gain distributions of received signals to separate signals, even from co-located transmit sources, and uses microwave lensing to enhance received spatial gain distributions. Predetermined cross-polarization interference is used to separate differently-polarized receive signals. A reference branch provides a cancellation signal to a receiver to cancel transmitter leakage signals. An error signal controls an impedance-compensation circuit that is responsive to changes in antenna impedance but not to receive signals. A dc bias magnetic field applied to a magnetic permeable material adjusts non-linear distortion in a cancellation circuit for canceling distortion in a transmitter leakage signal. Discreet impedance elements approximate a circuit having distributed impedance.

Instead of constructing a full multi-dimensional look up table as a model to find the critical dimension or other parameters in scatterometry, regression or other optimized estimation methods are employed starting from a “best guess” value of the parameter. Eigenvalues of models that are precalculated may be stored and reused later for other structures having certain common characteristics to save time. The scatterometric data that is used to find the value of the one or more parameter can be limited to those at wavelengths that are less sensitive to the underlying film characteristics. A model for a three-dimensional grating may be constructed by slicing a representative structure into a stack of slabs and creating an array of rectangular blocks to approximate each slab. One dimensional boundary problems may be solved for each block which are then matched to find a two-dimensional solution for the slab. A three-dimensional solution can then be constructed from the two-dimensional solutions for the slabs to yield the diffraction efficiencies of the three-dimensional grating. This model can then be used for finding the one or more parameters of the diffracting structure in scatterometry. Line roughness of a surface can be measured by directing a polarized incident beam in an incident plane normal to the line grating and measuring the cross-polarization coefficient. The value of the one or more parameters may then be supplied to a stepper or etcher to adjust a lithographic or etching process.

A structure formed on a semiconductor wafer is examined by directing an incident beam at the structure at an incidence angle and a azimuth angle. The incident beam is scanned over a range of azimuth angles to obtain an azimuthal scan. The cross polarization components of diffracted beams are measured during the azimuthal scan.

A dual band, dual pole, variable downtilt, 90 degree azimuth beamwidth antenna (10). The antenna includes dipole elements (12, 14) forming both a PCS band and a cellular band antenna. The PCS band antenna has two sections disposed each side of the cellular band antenna, the elements of each being positioned 90° with respect to the other. A microstrip feed network formed upon a common PC board (18) feeds the respective dipole elements, and has serpentine portions with a corresponding dielectric member slideable thereover to establish the phase of the associated dipole antennas and achieve a linear downtilt of the respective antenna array. A slide rod adjustment assembly (100) provides unitary movement of the dielectric members between two different slide rods. These dielectric members are secured with adhesive to the respective slide rods to achieve good dielectric control and no use of hardware. The radiating dipole elements are capacitively coupled to each microstrip, and are also capacitively associated reflector element. One arm of the reflector element is offset at least 45 degrees with respect to the other arm to improve cross polarization.