Advances in Radio Science www.adv-radio-sci.net 1684-9965 1684-9973 5 Kleinheubacher Berichte 2006 2007 10.5194/ars-5-43-2007 http://www.adv-radio-sci.net/5/43/2007/ http://www.adv-radio-sci.net/5/43/2007/ars-5-43-2007.html http://www.adv-radio-sci.net/5/43/2007/ars-5-43-2007.pdf 43 48 2007-06-12 A comparison of software- and hardware-gating techniques applied to near-field antenna measurements M. M. Leibfritz M. D. Blech blech@ihf.uni-stuttgart.de F. M. Landstorfer T. F. Eibert Institute of Radio Frequency Technology (IHF), Universität Stuttgart, Germany It is well-known that antenna measurements are error prone with respect to reflections within an antenna measurements test facility. The influence on near-field (NF) measurements with subsequent NF to far-field (FF) transformation can be significantly reduced applying soft- or hard-gating techniques. Hard-gating systems are often used in compact range facilities employing fast PIN-diode switches (Hartmann, 2000) whereas soft-gating systems utilize a network analyzer to gather frequency samples and eliminate objectionable distortions in the time-domain by means of Fourier-transformation techniques. Near-field (NF) antenna measurements are known to be sensitive to various errors concerning the measurement setup as there have to be mentioned the accuracy of the positioner, the measurement instruments or the quality of the anechoic chamber itself. Two different approaches employing soft- and hard-gating techniques are discussed with respect to practical applications. Signal generation for the antenna under test (AUT) is implemented using a newly developed hard-gating system based on digital signal synthesis allowing gate-widths of 250 ps to 10 ns. Measurement results obtained from a Yagi-Uda antenna under test (AUT) and a dual polarized open-ended waveguide used as probe antenna are presented for the GSM 1800 frequency range. Christ, J.: Korrektur prinzipbedingter und durch die Meßumgebung verursachter Fehler bei der Nahfeld-Fernfeld-Transformation, Dissertation, Universität Stuttgart, Shaker-Verlag, Aachen, 1995. Hansen, J E.: Spherical Near-Field Antenna Measurements, Institution of Electrical Engineers, London, 1988. Harris, F J.: On the Use of Windows for Harmonic Analysis with the Discrete Fourier Transform, Proceedings of the IEEE, vol 66, no 1, January, 1978. Hartmann, J.: Grenzen der Störstrahlungsunterdrückung bei der Vermessung von Mikrowellen- und Millimeterwellenantennen in kompensierten Doppelspiegel-Compact-Range-Meßanlagen, Dissertation, Universität der Bundeswehr, München, 2000. Leibfritz, M M.: Effiziente Methoden zur Diagnose bei Gruppenantennen unter Verwendung der sphärischen Nahfeldmesstechnik, Fortschrittsbericht, Universität Stuttgart, 2006. Marple~Jr., S L.: Computing the Discrete-Time "Analytic" Signal via FFT, IEEE Transactions on Signal Processing, vol 47, no 9, September, 1999. Oppenheim, A V., Schafer, R W., and Buck, J R.: Zeitdiskrete Signalverarbeitung, Pearson Studium, München, 2004.