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.

Expected Changes and Additions to the Antenna Measurement Standard IEEE Std 149TM

Authors: Vince Rodriguez, Lars Foged, Jeff Fordham
Publication: IEEE Conference on Antenna Measurements & Applications, September 3, 2018
Copyright Owner: NSI-MI Technologies, Microwave Vision Italy

The IEEE Standard 149 has not been revised since 1979. Over the years the Standard was reaffirmed without any changes. Recently the IEEE Standards association stopped the practice of reaffirming standards. This change in policy by the IEEE has been the “medicine” that this standard needed. A working group was organized and a project authorization request (PAR) was approved by IEEE for the document to be updated. In this paper, the expected changes to the document are described. The main change is to convert the standard to a recommended practice document. Additionally, some new techniques to measure antennas such as the use of reverberation chambers and compact ranges is discussed in more detail. Most importantly, a discussion on uncertainty is included. The result will be a very useful document for those designing and evaluating antenna test facilities, and those performing the antenna measurements.

   

Recommended Practice for Near-Field Antenna Measurements

Authors: Lars Foged, Vince Rodriguez, Jeff Fordham, Vikass Monebhurrun
Publication: IEEE Conference on Antenna Measurements & Applications, September 3, 2018
Copyright Owner: NSI-MI Technologies, Microwave Vision Italy, Chair IEEE Antennas & Propagation Standards Committee

The IEEE Standards Association Standards Board (IEEE-SASB) approved the IEEE Std 1720™ “Recommended Practice for Near Field Antenna Measurements” in 2012 [1]. More than fourty dedicated people from industry, academia and other institutions contributed to the creation of this new document. The main motivation for a new standard dedicated to near-field measurements was to complement the existing IEEE Std 149-1979™ “Test Procedures for Antennas” [2].

   

On Selecting the Most Suitable Range for Antenna Measurements in the VHF-UHF Range

Author: Vince Rodriguez
Publication: IEEE Conference on Antenna Measurements & Applications, September 3, 2018
Copyright Owner: NSI-MI Technologies

It is desirable to have a single facility to serve all the antenna measurement needs of an organization of company. However, there is not a one-size-fits-all antenna measurement facility to meet all antennas and frequency ranges. Trying to design and operate a Jack-of-all-trades facility is unrealistic. Such facilities may be ideal for testing part of the frequency range and types of antennas but may not be the ideal solution for certain applications. In this papers suggestions and recommendations are given for specific types of antennas mainly operating in the 30 to 3000 MHz range.

   

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