Antenna Tests With a Hologram-Based CATR at 650 GHz

A hologram-based compact antenna test range (CATR) is designed, constructed, and used to test a 1.5-m antenna at 650 GHz. The CATR is based on a 3.16-m-diameter hologram as the collimating element. So far, this is the highest frequency at which any CATR has been used for antenna tests. The quiet zone is measured and optimized before the antenna tests. The measured antenna pattern results at 650 GHz are analyzed and compared to the simulated patterns. Feed scanning antenna pattern comparison technique is used to correct the antenna pattern. These tests show the hologram CATR to be promising for antenna measurements up to 650 GHz.     

BinEHO: a new binary variant based on elephant herding optimization algorithm

One of the new optimization techniques proposed in recent years is elephant herding optimization (EHO) algorithm. Despite its short history, EHO has been used to solve many engineering and real-world problems by attracting researcher attention with its advantages such as efficient global search ability, having fewer control parameters and ease of implementation. However, there is no remarkable binary variant of EHO algorithm in the literature. A new binary approach based on EHO algorithm is proposed in this study. The newer binary variant of EHO named as BinEHO is binarized with preserving the search ability of basic EHO. The main purpose of the study is to present a simple, efficient and robust binary variant which copes with different binary problems. Therefore, the proposed method is tested on three important binary optimization problems, 0–1 knapsack, uncapacitated facility location and wind turbine placement, in order to show its performance and accuracy. In addition, the BinEHO is compared with various binary variants on these problems. Experimental results and comparisons show that the BinEHO algorithm is a robust and efficient tool for binary optimization.

     

Test results of 310 GHz hologram compact antenna test range

The quiet-zone field test results of a submillimetre-wave compact antenna test range (CATR) based on a 60 cm diameter hologram are presented. The instrumentation setup based on a dedicated millimetre-wave vector network analyser is also briefly described. The presented test results at 310 GHz show the potential of the hologram CATR for submillimetre-wave antenna testing     

Testing of a 1.5-m reflector antenna at 322 GHz in a CATR based on a hologram

Hologram-based compact antenna test range (CATR) is a potential method for testing large antennas at submillimeter wavelengths. This paper describes testing of a 1.5-m single offset parabolic reflector antenna with a 3-m-diameter hologram-based CATR. This is the first time such a measurement is carried out at submillimeter wavelengths. The antenna tests were done in a CATR that was specifically designed and constructed for these tests. The measured radiation pattern at the frequency of 322 GHz is presented. The measured pattern corresponds reasonably well to the simulated pattern of the antenna. The effect of the quiet-zone field nonidealities on the measurement results and the reasons for the discrepancies in the measured antenna beam are discussed.     

How to deal with unbelievable assertions

We tackle the problem that arises when an agent receives unbelievable information. Information is unbelievable if it conflicts with the agent’s convictions, that is, what the agent considers knowledge. We propose two solutions based on modifying the information so that it is no longer unbelievable. In one solution, the source and the receiver of the information cooperatively resolve the conflict. For this purpose we introduce a dialogue protocol in which the receiver explains what is wrong with the information by using logical interpolation, and the source produces a new assertion accordingly. If such cooperation is not possible, we propose an alternative solution in which the receiver revises the new piece of information by its own convictions to make it acceptable.     

Hologram-based compact range for submillimeter-wave antenna testing

A hologram-based compact antenna test range (CATR) is being developed to overcome challenges met in antenna testing at submillimeter wavelengths. For the first time, this type of CATR has been built for testing of a large reflector antenna at submillimeter wavelengths. The CATR is based on a 3-m computer-generated hologram as the focusing element. This paper discusses the design and the construction of the CATR, and the verification of the CATR operation with quiet-zone tests done for the CATR prior to the antenna testing. Assembly of the CATR, testing of the 1.5-m reflector antenna at 322 GHz, and the disassembly were all done within two months in 2003. The quiet-zone field measurement results are analyzed in this paper. The CATR was concluded to be qualified for antenna testing. The antenna testing is described in a separate paper.     

A feed scanning based APC technique for compact antenna test ranges

The measurement accuracy of a compact antenna test range (CATR) depends on the level of spurious signals. To improve the measurement accuracy, several error compensation methods have been developed, but most of them are not feasible at submillimeter wavelengths. This paper introduces an error compensation technique for compact antenna test ranges, which is especially suitable at submillimeter wavelengths. The method is based on antenna pattern comparison (APC). In the original APC technique the antenna pattern is recorded several times at different positions of the quiet-zone field, and the corrected pattern is obtained by averaging the measured patterns. In the proposed method, the lightweight transmitter is moved instead of moving the heavy combination of the antenna under test (AUT) and the rotation stage. The feasibility of the method is studied and the method is tested with measurements in a hologram based compact antenna test range at 310 GHz. The accuracy provided by the proposed method is compared to the accuracy provided by the conventional APC. The accuracies provided by both methods are practically equal.     

Millimetre-wave Bessel beams using computer holograms

A computer-generated binary amplitude hologram is used to transform an initial Gaussian electromagnetic field with spherical phase front at 310 GHz into a nondiffracting Bessel beam. The beam profile is measured with the help of a near field scanner. In contrast to the situation in the optical region, both amplitude and phase information is readily obtainable from the generated field     

Dual reflector feed system for hologram-based compact antenna test range

Manufacturing of large computer-generated submillimeter wave holograms with high pattern accuracy has been the main challenge in the development of hologram based compact antenna test ranges (CATRs). Illumination of the hologram with a shaped beam produced by a dual reflector feed system (DRFS) simplifies the hologram manufacturing by eliminating the narrow slots in the hologram pattern. In this paper, the design of a shaped dual reflector feed for a hologram CATR is described. The simulated and measured illumination field amplitude and phase at 310 GHz are presented and compared to the desired hologram illumination. The measured amplitude is within /spl plusmn/0.5 dB from the design objective in the most significant central region of the illuminating beam. Measurement results of the quiet-zone field of a demonstration CATR illuminated by the DRFS are presented and compared to the measured quiet-zone amplitude and phase of a hologram fed directly with a corrugated horn. The quiet-zone diameters of the both holograms are over 0.25 meters and the measured root mean squared (rms) amplitude and phase ripples are below /spl plusmn/0.4 dB and /spl plusmn/5/spl deg/, respectively. Further improvements to the hologram CATR, such as greater tolerance to manufacturing errors, are also discussed.