Diameter Reflector Antenna Research Articles

A Dual Circular-Polarized Extremely Thin Monopulse Feeder at <italic>W</italic>-Band for Prime Focus Reflector Antenna

A thin monopulse feeder is very important in a radar system with strict profile limitation. Besides, to implement polarization-agile radar, a monopulse feeder with two orthogonal polarizations is required to synthesize an arbitrary polarization. To achieve these requirements, a dual circular-polarized extremely thin monopulse feeder at W-band is investigated and realized for a prime focus reflector antenna, which can be used in a tri-mode seeker. To begin with, two kinds of the 2 × 2 substrate integrated waveguide (SIW) slot antenna array topologies are discussed based on the standard of circular polarization efficiency. After that, the better one integrated with a compact and single-layer SIW comparator is used to feed the reflector antenna. The total thickness of the developed feeder is only 0.56 mm. For a prime focus 140 mm diameter reflector antenna with the blockage of a diameter of 40 mm, the measured gain of the entire antenna system is 35.6 dBi at 94 GHz. The DIFF-beam null depth is -20.1 dB in xoz plane and -20.5 dB in yoz plane. The gain ratios of the SUM- and DIFF-pattern are 3.5 dB in xoz plane and 4 dB in yoz plane. The results show that this type of antenna has great prospects in a monopulse tracking system with polarization agile function.

Analysis of Aperture Phase Errors Using Interval Method

This paper studies the aperture phase errors of reflector antenna based on the interval method. Through the interval matrix perturbation algorithm and the interval truncation algorithm, the effect of surface nodal displacement intervals on the aperture phase errors is obtained. The numerical example of an 8m diameter reflector antenna shows that the method is rational and feasible.

Reflector Antenna Distortion Analysis Using MEFCM

The impact of random errors and systematic errors due to reflector surface distortions is discussed by using Ruze formula in conjunction with the mechanical-electromagnetic-field coupling model (MEFCM). Ruze formula demands too rigorous reflector precision and manufacturing accuracy due to not taking the systematic error into consideration. The best-fitting method treats the systematic error, but not random error. The MEFCM takes both systematic error and random error into account. Numerical examples of 7.3 m and 40 m diameter reflector antenna validate the method proposed. The proposed MEFCM method integrates the mechanical design with electromagnetic analysis in order to optimize the reflector antenna design.

Efficient 3-D moment-method analysis for reflector antennas using a far-field approximation technique

A full 3-D moment-method analysis is used to model the radiation patterns of 10-15 /spl lambda/ diameter reflector antennas. The moment-method is made computationally efficient by a far-field approximation technique which dramatically reduces the demands of computer memory and CPU time by over 90%, and 80%, respectively. The reflector dishes are discretised with an unstructured 3-D finite-element-type mesh of triangles. The moment-method is applied to rotationally symmetric dishes in order to compare the accuracy of the analysis with results from a more conventional body-of-revolution type moment-method analysis.

The Very Long Baseline Array

The VLBA is a new radiotelescope dedicated to research in astronomy and astrometry/geodesy using the techniques of VLBI. The array comprises ten 25 m diameter reflector antennas located so as to give optimum coverage of baselines up to 8600 km. Instrumentation provided at each antenna includes receivers for nine frequency bands between 327 MHz and 43 GHz, a hydrogen maser frequency standard and a tape recorder system capable of a peak data rate of 512 Mb/s and unattended operation for a day recording at 128 Mb/s. The antennas are controlled and monitored by a single operator located in the Array Operations Center (AOC) in Socorro, New Mexico. The AOC also houses the 20 station correlator which processes the data recorded at the antennas.

Pattern measurements of reflector antennas in the compact range and validation with computer code simulation

The measurements were performed at the University's compact range facility. They demonstrated: (1) the excellent dynamic range that can be achieved with antenna pattern measurements in a compact range facility; and (2) the excellent validation achieved for the calculated patterns of two 8-ft diameter reflector antennas. The compact range has a rolled edge modification to its reflector and uses a pulsed radar system to eliminate the clutter interference such that a dynamic range of more than 80 dB can be obtained. The measured far field patterns of two 8-ft reflector antennas, a prime focus fed antenna and a Cassegrain antenna, at 11 GHz were compared with those calculated by Ohio State University's Reflector Antenna Code. The computer code simulation's approach is also briefly described. >

A small dipole-fed resonant reflector antenna with high efficiency, low cross polarization, and low sidelobes

The computer-aided optimization of a small five-wavelength diameter reflector antenna with a center-supported dipole-disk feed is described. The primary radiation is controlled by using a patented beamforming ring to give low cross polarization and low sidelobes due to spillover. The efficiency is maximized by controlling and taking advantage of the multiple reflections between the feed and the reflector. This has inspired the name resonant reflector antenna. The gain from the feed reflector resonances is so large that it compensates almost completely for the about 1 dB loss due to center blockage of the aperture.