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Request CAL/Conv loss info for using 8757D SNA w/2 E8257D PS

Question asked by LIslander on Jan 5, 2011

My team is in the midst of generating LabView code to control two E8257D PSGs in combination with an 8757D SNA in order to perform swept RF to IF conversion measurements. We must use these specific models.
By referencing the E8257D User’s guide (pgs 57 & 58) found at: // along with App Note 1287-7 found at: // as well as info found at: //, since the 8757D SNA is to be measuring the output of our UUT at the IF frequencies and since the SNA obtains it’s Start and Stop frequencies from the Primary PSG, as such the Primary PSG must therefore be set to the desired Start & Stop IF frequencies, while the Secondary PSG would be set to the corresponding Start & Stop RF Input frequencies (as calculated dependent upon the specific LO frequencies that are used in the UUT) which are to be injected into the UUT. The ramp sweep of the PSGs providing the RF and IF frequencies must be synched with each other, hence the need for using the Primary/Secondary configuration. As I understand, to perform swept measurements, this Primary/Secondary configuration will work when using only the ramp sweep setting.


Questions are:
1) With respect to RF to IF conversion loss measurements (inclusive of necessary calibration measurements), do we need to do anything different (from what is shown in Figure 2-8 on pg 58 of User's guide) regarding the equipment configuration?
2) It also seems that the SNA mode needs to be set to DC mode in order to obtain swept trace. Is this correct?
3) To perform the calibration in order to account for and subtract conversion loss correctly, is there a recommended detector(s) and channel(s) configuration that we should be utilizing? For our CAL, we are presently planning on performing a loss measurement (using only one detector) on one channel at the swept RF frequencies and saving that data, and then performing a second loss measurement (using the same detector and channel) at the swept IF frequencies (and saving that data), and then the LabView code would need to perform the proper calculation using the saved data from both swept loss measurements taken in order to account for the conversion loss when calculating the effective reference from which subsequent UUT gain or loss measurements are to be taken against.
a. The issue I am trying to figure out is how do we properly calculate the conversion loss result (that will eventually be accomplished within LabView code) to then display the correct calibrated signal level for the swept IF frequencies on the SNA that is to be used (and saved) as a normalized reference (by effectively saving this SNA trace info into MEM and then performing a MEAS-MEM)?
b. Do we or should we be using two channels somehow? Or more than one detector?
c. While I am aware that Fif= Frf – FLo (and/or Fif=Frf + FLo) and that conversion loss is generally considered as 20 log [magnitude IF/magnitude RF], using these specific pieces of equipment, is there a certain calibration sequence that Agilent would suggest/specify needs to be followed in order to obtain and utilize a correct conversion loss in the process of performing a calibration and normalization? (The link shown above for conversion loss only elaborates what would need to be done when using a PNA, not a SNA)


Also, while the App Note 1287-7 discusses taking two separate power measurements (RF w/o UUT and IF w/UUT), it unfortunately does not address these measurements with respect to equipment configuration (and any necessary measurement steps/sequence involved) using 1 generator to provide the actual RF signal into a UUT while also using another (synched) generator for the IF frequencies that the SNA needs in order to take UUT output measurements at.