filters

Software

• python program:
  
• /share/megs/phil/svn/aosoft/p12m/wbrcvr/fb/fbprog.sc
• online tcl function:
• /share/megs/phil/svn/aosoft/p12m/tcl/gen/fb.proc
• gpio python code link

230403: S-parameters for filters

• Each page has the 4 sparameters
• Each color is a different filter. For some sets we have 3 filters. For others there are only 2
• the filter names come from the .s2p filenames.
• For the set with 3 filters they are numbers 1,2,3
• for the sets with 2 filters they are labeled polX,polY.
  
• Page 1: Measured s-parameters (wideband)
• Page 2: blowup of s-parameters
• The vertical scale is limited to -20 to +2 db

• The freq ranges is the 3db points from the center of the filter
• the 15GHz lowpass will probably be placed in series with the switchable filters.
• Don't have the xband filters measured yet..
• The xband filters were measured on 1may23
  

230414: s-parameters for filter box.

    On 14apr23 felix measured the s-parameters for the filter bank box. He did a separate measurement for each of the 5 (current) filters.

• Port 1 was the filterbank input.
• Port 2 was the filterbank output.

The first set of plots show  the s-parameter results for filter selections 1-5(.ps)  (.pdf)

• Each page has the parameters for a single filter selected in the switch bank
• There are 4 frames on each page
• top: S21 - box gain
• 2nd: S11- reflection from input to box
• 3rd: S12 - gain looking into the box output
• bottom: S12 - reflection when looking into box output.
  
• The device was scanned 2 to 13.5 GHz
• Black is polX, Red is PolY
• the filter # is the one used to access the filter in the online datataking.
• Page 1: filter 1 - straight thru path selected
  
• a cable connects the input to the output switch
• Page 2: filter 2 -2940 to 4240 bandpass filter selected
  
• Page 3: filter 3 - 2775 to 3475 bandpass filter selected
• This filter has a 5 ghz lowpass filter after it (to remove out of band feed through)
• Page 4: filter 4 - 3180 to 3340 MHz bandpass filter selected
  
• this has a 5 GHz low pass filter after it.
• Page 5: 4800 to 1400 MHz hi pass filter selected
• Page 6: The S11 reflections from the straight thru connection.
• Top: S11 measured
• 2nd: acf of S11 showing that the ringing is 1.8  nanoseconds.
• bottom: acf of S11 plotted vs distance
• the x axis is in inches.
• I assumed the velocity is .7*c
• 7.5 inches separates the 2 surfaces causing the reflection
• This ringing was see in all 5 of the filters.

• the s-parameters results for filter selection 6 (xband filters).  (.ps)  (.pdf)
• These were measured separately on 1may23.
  

Summary

• The s-parameters  for the filter box was were measured.
• A separate measurement was done for each of the 5 installed filters/cable
• The gain through the box varied from 9db (4-14GHz hipass at 13.4 GHz) to 15 db (straight thru cable at 2 GHz)
• The gains measured thru the box are a few db higher than the values computed using the single components.
  
• This might be the 0-14GHz hipass filter in front of the switch. The schematic shows 2db insertion loss while the s-parameters for the filter by itself were closer to 0 db.
• When computing the contributions of Tsys for the box, we still need to use the individual components since we don't have a separate noise figure measurement for the box at each filter position.