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https://designers-guide.org/forum/YaBB.pl Measurements >> RF Measurements >> SFDR and Reference Level of Spectrum Analyzer https://designers-guide.org/forum/YaBB.pl?num=1290665142 Message started by ywguo on Nov 24th, 2010, 10:05pm |
Title: SFDR and Reference Level of Spectrum Analyzer Post by ywguo on Nov 24th, 2010, 10:05pm Hi Guys, When I measured a sine wave with spectrum analyzer. I am curious that the reference level impacts the harmonics. For ref level = 0 dBm, SFDR ≈ 72 dBc. For ref level = 10 dBm, SFDR ≈ 81 dB. I thought the reference level is used to adjust the display only. I am reading a few documents of Agilent about spectrum analyzer. However, I have not find the answer until now. Would you please comments this phenomina? Best Regards, Yawei |
Title: Re: SFDR and Reference Level of Spectrum Analyzer Post by ywguo on Nov 24th, 2010, 10:06pm Reference Level = 0 dBm |
Title: Re: SFDR and Reference Level of Spectrum Analyzer Post by ywguo on Nov 24th, 2010, 10:07pm Reference Level = 10 dBm |
Title: Re: SFDR and Reference Level of Spectrum Analyzer Post by currant on Nov 25th, 2010, 12:22am Hi, ywguo. I think answer is simple. You overload internal circuits of spectrum analyzer (SA). As it can sees in your pictures, when You modify refLevel - value of internal attenuator also modify, and input signal attenuate before it come on SA's internal circuits. This is bad for noise (SNR) measurment, but good for HD measurment. Best regards. |
Title: Re: SFDR and Reference Level of Spectrum Analyzer Post by ywguo on Nov 25th, 2010, 7:42pm Hi Currant, I have not noticed the change of ATTN. Thanks Yawei |
Title: Re: SFDR and Reference Level of Spectrum Analyzer Post by ssahl on Dec 31st, 2010, 2:04am Hi, I agree with Currant. Changing the reflvl will change the internal signal level in the analyser, it does not only change the display. The spectrum analyser is a radio receiver! /ssahl |
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