Circularly Polarized Compact Range Feed with 30 dB Polarization Isolation

Author: German Cortes-Medellin
Publication: APS 2018
Copyright Owner: NSI-MI Technologies

NSI-MI Technologies has developed a dual polarized compact range feed with a cross-polarization level of -30 dB from 10.7 GHz to 13 GHz.

Controlling the Gain of Wide Band Open Quad Ridge Antennas

Author: German Cortes-Medellin
Publication: EuCAP 2018
Copyright Owner: NSI-MI Technologies

We present a methodology to precisely control the gain of an open quad-ridge horn (OQRH) without impacting the input match over the wide band frequency of operation characteristic of this type of horns.

Further Refining and Validation of RF Absorber Approximation Equations for Anechoic Chamber Predictions

Author: Vince Rodriguez
Publication: EuCAP 2018
Copyright Owner: NSI-MI Technologies

Indoor antenna ranges must have walls, floor and ceiling treated with RF absorber. The normal incidence performance of the absorber is usually provided by the manufacturers of the materials; however, the bi-static or off angle performance must also be known. In a recent paper [1], a polynomial approximation was introduced that gave a prediction of the reflected energy from pyramidal absorber. In this paper, the approximations are used to predict the quiet zone (QZ) performance of several anechoic chambers. These predictions are compared with measurements performed per the free space VSWR method of four different chambers. Among the chambers analyzed are a 7.3m by 3.65m by 3.65m range with a 24-inch absorber, operating from 1 to 6 GHz with a 91 cm spherical QZ and a 5.18 m path length. Another chamber is 7 m long by 3.3 m wide with a 2.4 m height. 12-inch absorber is used to treat the internal surfaces and the QZ changes from 63 cm to 20 cm from 2 GHz to 18 GHz. The path length is 5.18m. While performing the comparison, changes are made to the calculations to further improve the predictions of the computations. A chamber previously analyzed is computed again after the changes to see whether there are improvements in the prediction. The results show that the polynomial approximations can be used to give a reasonably accurate and safe prediction of the QZ performance of anechoic chambers and improve some of the previous comparisons especially at lower frequencies where the ray tracing is not that accurate.

Near-Field Antenna Measurements using a Lithium Niobate Photonic Probe

Authors: Vince Rodriguez, Brett Walkenhorst, and Jim Toney
Publication: EuCAP 2018
Copyright Owners: NSI-MI Technologies, Srico

Recently, a paper was presented in which a lithium niobate (LiNbO3) crystal electric field sensor was characterized as a possible probe for near-field antenna measurements. In the present paper, some preliminary measurements are presented. A standard gain horn operating in the X-band was measured in a spherical near-field range using the LiNbO3 probe as the near-field probe. The results are compared to computed data for said horn. An additional flat– plate, slotted array antenna operating in the X-band was also measured. The data was transformed to the far field and compared with previous measurements of said antenna performed using a traditional open-ended-waveguide (OEWG) probe. Additionally, the transform was used to backproject to the aperture of the antenna and the data show the two slots in the array that are covered with metallic tape. The transforms and back-projection suggest that these probes could be used as near-field probes in antenna measurements if some stability issues are corrected.


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