Intro

    A new set of sband filters were purchased to cut  down on the strong rfi at 2200  and 2350 MHz. On 220309 the sparameters for the filter were measued in the lab using the hp network analyzer.

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The S-parameters

    We purchased 3 filters:

• sn22_01  used in polB
• sn22_02  spare
• sn22_03 using in polA

    The filter consists of a bandpass filter followed by a lowpass filter (that falls off around 6 GHz).

The plots show the measured S-parameters (.ps) (.pdf)

•  Page 1 s-parameters 2070 to 2450MHz.
• The colors show the different filters.
• Top :S21
• this is the bandpass shape
• 2nd: S12
• 3rd: S11
• bottom: S22
• page 2: s-parameters. blowup in db
• top:S21
• the filter has an insertion loss of about 1 db.
• 2nd: S21
• 3rd:S11
• bottom: S22
• Page 3. s- parameters 1 to 10Ghz
• black is the polA filter, red is the polB filter
• The lowpass filter is cutting down the power out at 8 GHz
• Page 4: 7dec21 (oldfilter) spectra showing rfi and how the new filter will reduce it.
• Black trace: 7dec21 spectra with old filter
• The mock spectrometers took 2 172 MHz bands (that overlap)
• The rfi 2340-2350 is an image of the 2350-2360 rfi (it used i,q sampling).
• The red trace applies the new filter to the rfi..
  

Summary

• the 3 db rolloff of the filters is at 2210 and  2343 MHz
• the filters have an insertion loss of about 1 db.
• the filter is down by about 35 db at 2350MHz.    
• It looks like it should do a good job of cutting out the rfi at 2200 and 2350.
  

   

processing: x101/220309/sbfilter.pro