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Spirent KB Article
Doc ID: FAQ14704
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GNSS Positioning Simulator: Should I expect to see exactly the same spectrum for image rejection as shown in the calibration procedure?
Environment/Versions
STR4730 / 4750 / 4760 / 4780 / 4790
GSS7700 / 7735 / 7790 / 7800 / 7900
GSS8000
Answer
It is very unlikely that you'll get a spectrum on the analyser that looks exactly like the example figure for image rejection shown in the Customer Calibration Procedure document
See
FAQ10505
Indeed that figure is somewhat exaggerated to make it more obvious where those three main signals might appear in relation to one another
In most cases you'll find that only the wanted signal is immediately clear and that the carrier or image are not present above the analyser noisefloor at all (see Note)
Which is the ideal case
NOTE
This is based on the typical analyser settings most commonly used for the image rejection part of the calibration procedure:-
- Attenuation = 0dB
- Reference Level = -40dBm (adjust this as necessary)
- Centre Freq = in accordance with values given in calibration procedure
- Span = 200kHz
- Res BW = 300Hz (adjusted to give the lowest possible noisefloor without the sweep taking a long time, e.g. sweep < 5s)
Version
2.0
Publish Date
2014-07-29
Categories
Product : Calibration,STR4790,STR4780,STR4760,STR4750,STR4730,GSS7790,GSS7735,GSS7700,GSS7800
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