Intro

    On 15may23  Felix measured the s-parameters for:

• The  fiber optic chassis down in the pedestal
• the 36" cable that goes from the dewar to the filter box.
  

    

---

The fiber optic chassis in pedestal.

• port 1: box input
• port 2: box output
• The box contains:
• zva-183gx-s+ (.pdf) wideband rcvr. amp before fo transmitter.
• 3db pad
• zudc10-02183-S+ 10db coupler before foTx wb rcvr  (.pdf)

Plots show the

• The s-parameters: s21 s11,s22,s12  
  
• The acf computed from each sparameter spectra
• The acf was computed as:  abs(fft(spc))[0:lenfft/2-1] (since it is symmetric)
• I then divided by acf[0] (the 0 lag which is the integral of the power across the spectra)
• May be off by a factor of 2 since the negative lags were ignored.
• The lag axis was:
• max Bw:14-2 GHz = 12GHz
• shift rate: 1/12GHz (.083 ns resolution)
• max lagdelay: .083*500=41 ns.
  

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

• Black is polX, red is polY
• Page 1: S21 : gain: box input to foTransmitter.
  
• Top S21 gain:
• the box has about 33db gainh
  
• 
  
• Bottom: acf of S21
• 
  
• Page 2: S11: reflections at box input.
• Top: spectra of S11
• The level stays below -10 except for some of the ripples from 11 to 12 GHz
• Bottom: acf of S11
• has a reflection at about 2 ns
• Page 3: S12: looking into the output of the box
  
• nothing interesting.
• Page 4: S22: reflections looking at the box output
  
• Top spectra
• < -20db
• Bottom: acf
• a few reflections at 2,3 and 4ns
  
• Page 5: plot ACF's for all parameters on 1 page.
• I plotted the Acf on 1 page to compare the freq ripples
• I converted the x axis to distance using vel=.7 C (.7*.15 m/ns)
• S11 and S22 show ripples around .2 meter= 7 inches. this is the cable at the input.
  

   

SUMMARY:

• The sparameters from the cal input to the lna output were measured.
• Ripples were seen (especially in S11 and S22)
• the times for the ripples were longer than expected (if just looking at the cable lengths)
• You would have though that the 10db pad between the sma input and the coupler would have done a better job cutting down the ripples.
  

processing: x101/230515/sparmswbrcv.pro

---

Cable dewar to filter box

• The cable is about 36 inches long
• we use the cable loss S21 when computing the cable contribution to tsys

sparameters for cable dewar to filter box (.ps) (.pdf)