Internal spurious are normal in many receivers, including spectrum analyzers.
Input related and also not input related spurs.
Here example from Rohde&Schwarz FSC
https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_common_library/dl_brochures_and_datasheets/pdf_1/FSC_dat-sw_en_5214-3330-22_v0200.pdfSome characters can not show... if need, read pdf.
Image frequencies
fin – 2 × 21.4 MHz < –70 dBc, typ. –80 dBc
fin – 2 × 831.4 MHz < –70 dBc, typ. –90 dBc
fin – 2 × 4881 MHz –60 dBc
Intermediate frequencies
21.4 MHz, 831.4 MHz, 4881.4 MHz –60 dBc, typ. –80 dBc
8931.4 MHz –50 dBc
Other interfering signals,
signal level – RF attenuation < –20 dBm
f ? 3.6 GHz
spurious at fin – 2440.7 MHz < –60 dBc
3.6 GHz < f ? 6 GHz
spurious at fin – 4465.7 MHz < –60 dBc
Other interfering signals,
related to local oscillators
f ? 3.6 GHz
?f < 300 kHz –60 dBc
?f ? 300 kHz < –60 dBc
f > 3.6 GHz
?f < 300 kHz –54 dBc
?f ? 300 kHz < –54 dBc
f = receive frequency
Residual spurious response
input matched with 50 ohm,
without input signal, RBW < 30 kHz,
f ? 3 MHz, RF attenuation = 0 dB,
tracking generator = OFF
< –90 dBm
Siglent SSA3000X specifications
Residual response (= Residual spurious response)
input terminated = 50 ohm, attenuation = 0 dB
<-90 dBm,typ.
And afaik they are well below (better) than specified (typical) limit.
Just simplified, and there can be much more than just these named...
http://rf-design.blogspot.fi/2008/07/spectrum-analyzer-residual-spurious.htmlSpectrum Analyzer Residual Spurious Response
When the RF input is terminated, the spectrum analyzer may still show discrete responses while the LO's are sweeping. This occurs because at certain LO frequencies, the harmonics of the first and second LO mix together forming a product that is equal to an IF frequency. If this "spurious" IF frequency gets into the IF path, the detector will see a signal and therefor the display will show a blip at the RF frequency where m*LO1-n*LO2 = +/-IF. IF can be any of the IF frequencies in the instrument.
Using Google there can find lot of reading for whole rest of life about spurs, in theory and in practice. Spectrum analyzer IS just one kind of heterodyne receiver.
Of course it is important to reduce these spurs as far as reasonable but if need really clean all we do not have enough money for buy these.
I can not see any serious issue in SSA3000Xrelated to internal spurs. But, user is good to know these scatter spur frequencies just as example 1540MHz, 1905MHz etc. Oh and 20nVrms level 1GHz in my test SA. Is it 10 fW (0.01pW) in 50ohm system?
It is nice if Siglent can attenuate/reduce these but many times it is hard (and some times also hard core) rf-designers hardware work.
There is many other much more important things to do.In all T&M instruments, all what you see are errors and lies mixed with illusions of reality.
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Topic: Siglent SSA3000X and SSA3000X-Plus Spectrum Analyzers (Read 626228 times)