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Message ID: 2477     Entry time: Mon Nov 11 20:42:49 2019     In reply to: 2476     Reply to this: 2479
 Author: anchal Type: DailyProgress Category: FSS Subject: FSS Diagnostics - Two Tone Test

Method

• RFPD of the FSS loops were tested through there Test input ports (Updated schematics: South SN010, North SN009)
• I first took transfer function from the Test input port to the RF out port. Ideally, the transfer function of RFPD should be 100kOhm times this transfer function.
• Moku is used to generate two RF signals with a different frequency equivalent to RFPD's resonant frequency.
• These two outputs are combined with ZFSC-2-1W-S+ two-way splitter/combiner.
• I switched around the voltage amplitude of these frequencies and took a spectrum from AG4395A near difference frequency.
• The configuration file for spectrum measurement is present with data.
• This measurement was made through twoToneTest script present in the data folder.

Inferences:

• In first plot of each measurement set, I simply plotted the measured spectrum at the different signal voltage levels.
• In second plots, I have done some back calculations, but I'm not sure if this is a good of estimating non-linearity.
• I have used following formula to calculate ratio of total power in the difference frequency to the GM of powers of probe signals.
$\LARGE Ratio = \frac{ ASD_{@f2-f2} \sqrt{IFBW} } { \sqrt{ V_1\ TF_{@f1} V_2\ TF_{@f2}}}$
• This ratio I have plot in dB in the second plot.
• It seems that the spectrum level generated is not dependent on how strong the probe signals are.
• This can be seen as along the diagonal, instead of remaining the same ratio, the ratio decreases by 20 dB in each step which is an increase in the denominator above.
• Lastly, I just connected the two ends of cable between which DUT goes and repeated the measurement.
• The non-linearity of the measurement setup itself is safely 50 dB below the measured values.

But what now?

• I need more time to make sense of these measurements. So that will come tomorrow.

Data

 Attachment 1: NFSS_RFPD_SN009_TF_11-11-2019_183131.pdf  28 kB
 Attachment 2: SFSS_RFPD_SN010_TF_11-11-2019_203310.pdf  26 kB
 Attachment 3: FSStwoToneTest.pdf  109 kB
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