Hello all, In this forum, a lot of discussion have been made on NSA measurement. Today, I would like to have your opinion on antenna factors to be used to performed such measurement.
In our laboratory, we have one Open Area test Site (3, 10 and 30m) (OATS) and a semi anechoic room at 3m (SAR). We use CHASE CBL6112A bilog antenna. (30MHz - 2GHz). My main problem is to perform the NSA measurement in the SAR, following ANSI C63.4 and/or EN55022 requirements. Which antenna factor must be used ? I have some possibilities, and the results differ depending the one I choose. 1st choice : Use the antenna manufacturer factor, which are done at 10m. 2nd choice : Use our antenna factors. These ones have been calculated on our OATS at 3m, following the ANSI C63.5 requirements, and using the 3 antenna method. In this case, the antenna are determined in horizontal polarization only. 3rd choice : Use our antenna factors, determined following ANSI C63.5 requirements, but using the 2 antenna method (chapter 5.2 of ANSI C63.5:1998) 4th choice : Use our room manufacturer method. This method consists to perform measures in the exact geometric configuration which will be used in the chamber. For example, antenna factor are determined in Vertical polarization, at 3m distances, and 1m height for the transmit antenna and 1-4m height for the receive antenna. We perform a Vdirect measurement (VD), a VSite measurement (VS) and the antenna factor is calculated with the following : Af = (VD - VS - ThNSA) / 2, where ThNSA = theoritical NSA. Following our room manufacturer, this last method is used by most of the people who are performing NSA measurement. It's not easy for me to understand why we use the theoritical NSA in this case, because our OATS is not the perfect one, and it seems to me that we introduce an error in this calculation. Depending the method used, the NSA is OK or NOT. So, I'm very interesting to know : - which factor are you using ? - does it exist some literature on this matter ? - Have you been facing this problem, and how do you solve it ? Thanks a lot for your contribution, best regards ============================================== Pierre SELVA Safety Lab manager NCE EMC, Radio and safety lab. 19 rue François BLUMET Phone : 33 4 76 27 83 83 ZI de l'Argentière Fax : 33 4 76 27 77 00 38360 SASSENAGE e-mail : [email protected] ==============================================
