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Multi-Carrier IM measurement

Question asked by Leyo on Nov 8, 2010
Latest reply on Nov 9, 2010 by Leyo
This is regarding Multi-crrier IM measurement for GSM Base station.
I am using MXA (N9020A) for this measurement. ACP mode under spectrum Analyzer is used  for this measurement. Noticed thata there two methods for the ACP measurment, IBW method and RBW method. What are the differnce between them. Can somebody point me some literature on this?. Is this ACP method valid only for WCDMA and LTE?. I mean is this ACP screen is valid for measuring GSM multi-carrier IM?.
For the following configuration
6  GSM carriers  and the offset is 2.8 MHz. IBW method with IBW of 100 KHz, RBW/VBW 100 KHz Span 25 MHz.
I am sseeing a spike in the 2.8 MHz offset (around 5 dB higher than nornal IM signal) with ACP screen. But with normal swept  SA method  with above seetings, the spike is not there. Just wondering is this ACP method adding anything.