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A hologram based compact antenna test range (CATR) is designed, constructed, and used to test a 15-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. [ABSTRACT FROM AUTHOR]

Transmittance and monostatic reflectivity of different radar absorbing materials at 650 GHz are presented. The reflectivity was measured in plane-wave conditions in a radar cross-section (RCS) range with vertical polarization. The lowest reflectivity level (-70 dB) was achieved with commercial absorbers TK THz RAM and Firam-500 with oblique incidence angles. Floor carpets were also studied, and the reflectivity level of those was found to be sufficiently low (from -50 to -60 dB) for use in antenna test ranges. Results agree with earlier studies and indicate the applicability of the RCS method in reflectivity measurements also at 650 GHz. [ABSTRACT FROM AUTHOR]

This paper presents monostatic reflectivity measurements of radar absorbing materials at 310 GHz in a phase-hologram-based compact range. The radar cross-section method was used and the backscattered reflection was measured with horizontal and vertical polarizations in plane-wave conditions. Transmission was also studied. The reflectivity was measured over an incidence angle of 0°-.45°. The reflectivity of Thomas Keating Terahertz RAM at normal incidence was found to be -56 dB-the smallest of the studied materials. The reflectivity of carpet material measured was also below -40 dB and it was found to be suitable for use as an absorber. The results are in line with those available from previous studies of reflectivity and complement them with new materials, frequency, and angle information. [ABSTRACT FROM AUTHOR]

A compact radar cross section (RCS) test range based on a phase hologram has been developed for scale-model measurements. The phase hologram converts the feed-horn radiation to a plane wave needed for RCS determination. The measurements are performed at 310 GHz using continuous-wave operation. A monostatic configuration is realized using a dielectric slab as a directional coupler. The main advantage of a scale-model RCS range is that the dimensions of radar targets are scaled down in proportion to the wavelength. Therefore, RCS data of originally large objects can be measured indoors in a controlled environment. Test objects such as metal cylinders and simplified targets have been measured. The feasibility of the phase-hologram RCS range has been verified. The operation and measurement results of the monostatic measurement range are reported here. A comparison with simulated results is also included [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

Computer-generated holograms can be used as collimating elements in compact antenna test ranges (CATR5). Recently, a 1.5 m parabolic antenna, the ADMIRALS representative test object (RTO), was tested at 322 GHz using a hologram-based CATR that was built specifically for these tests. The construction of the compact range is discussed in this paper. A 3 m hologram was used to realize a 1.8 m diameter quiet zone. The measured quiet-zone field amplitude and phase and the measured H-plane radiation pattern cut of the representative test object are presented. The measured -3 dB beam width of the antenna was 0.0500 in the H plane. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper studies the feasibility of a hologram-based compact antenna test range (CATR) for submillimeter-wave frequencies. In the CATR, a hologram is used as a collimating element to form a plane wave for antenna testing. The hologram is a computer-generated interference pattern etched on a thin metal-plated dielectric film. Two demonstration holograms of approximately 1 m in diameter were designed for 650 GHz, and they were manufactured on two different Mylar films. The holograms were illuminated with a horn, and the plane-wave field was probed at 644 GHz. The measured amplitude and phase ripples were 2 dB and 15° peak-to-peak for one of the holograms. A higher quiet-zone field quality can be achieved by increasing the manufacturing accuracy by further manufacturing tests. After this, the hologram-based CATR should have a potential for high-quality antenna tests at frequencies up to 650 GHz. [ABSTRACT FROM AUTHOR]