• hp8648synth -> bbmBm0A -> pdev
  
• The hp8648 synthesizer generated a 170 MHz sine wave. The pdev mixer LO's were set to 175 and 325 MHz so the sine wave would appear 5 MHz below the center of the lower 170 MHz band.
• The synthesizer power levels were set to: [-35,-25,-15,-10,-5, and 5 dbm].
  
• pnet --sigstat was run to measure the rms voltage in A/D counts.
• Some data was taken to see the sine wave spectrum

• Page 1 top: Sine wave Peak amplitude (in A/D counts) vs input power.
• Page 1 bottom:  (rmsSineWaveAmplitude)^2 vs input power. The vertical scale was changed to db's so the plot should be linear. There is a falloff around -15 bm input power. This had a sine wave with about 850 A/D counts peak.
• Page 2 The spectra of the  sine wave for the different input levels. Most of the spectra have overflows in The table below show the input/output power levels by component for these two inputs:the pfb butterfly stages. The inter mods/ harmonics are probably being created in the mixer chassis (since this was not seen when the sine wave was injected directly into the A/D converters).
  

Measuring the bbm component levels.

• -15 dbm input, 0 dbm attenuation, 2 dbm ouput. Onset of compression.
• 7dbm input, 9 dbm output , 15 dbm attenuation. Full scale A/D sine wave with 15 db attenuators
• A 9 dbm output will generate a sine wave with an amplitude of 2047 A/D  counts.
  
• -8dbm input, 9 dbm output, 0 dbm attenuation. Full scale A/D sine wave with 0 db attenuators.
  

Onset of compression: attn 0,-15 dbm input, 2 dbm output.

Input  Output  Component
-15.0   -19.0  H1 splitter
-19.0   -20.0  LPF1
-20.0   -21.5  H2 ProgAttn set to:  0. db
-21.5     0.5  H3-1 Amp
  0.5    -4.5  U5 Attn
 -4.5    15.5  H3-5 Amp
 15.5    11.5  H1-2 Splitter
 11.5     7.5  U4-Attn
  7.5    -3.5  H4 Mixer
 -3.5   -11.5  U3 Attn
-11.5   -12.5  LPF2
-12.5   -18.5  R2 attn
-18.5     2.0  H5-1 Amp
  2.0    -7.0  U1 Attn
 -7.0     8.0  H6-1 Amp
  8.0     2.0  U2 Attn

A/D full scale:attn 15, 7 dbm input, 9 dbm output.

Input  Output  Component
  7.0     3.0  H1 splitter
  3.0     2.0  LPF1
  2.0   -14.5  H2 ProgAttn set to: 15. db
-14.5     7.5  H3-1 Amp
  7.5     2.5  U5 Attn
  2.5    22.5  H3-5 Amp
 22.5    18.5  H1-2 Splitter
 18.5    14.5  U4-Attn
 14.5     3.5  H4 Mixer
  3.5    -4.5  U3 Attn
 -4.5    -5.5  LPF2
 -5.5   -11.5  R2 attn
-11.5     9.0  H5-1 Amp
  9.0     0.0  U1 Attn
  0.0    15.0  H6-1 Amp
 15.0     9.0  U2 Attn

A/D full scale: attn 0, -8 dbm input, 9 dbm output.

Input  Output  Component
 -8.0   -12.0  H1 splitter
-12.0   -13.0  LPF1
-13.0   -14.5  H2 ProgAttn set to:  0. db
-14.5     7.5  H3-1 Amp
  7.5     2.5  U5 Attn
  2.5    22.5  H3-5 Amp
 22.5    18.5  H1-2 Splitter
 18.5    14.5  U4-Attn
 14.5     3.5  H4 Mixer
  3.5    -4.5  U3 Attn
 -4.5    -5.5  LPF2
 -5.5   -11.5  R2 attn
-11.5     9.0  H5-1 Amp
  9.0     0.0  U1 Attn
  0.0    15.0  H6-1 Amp
 15.0     9.0  U2 Attn

Conclusions:

• The bbmixer chassis starts to compress around -15 dbm input and 0 db attenuation.
• The h3-5 amp is outputting 15.5 dbm
• The pdev A/D digitizers need 9 dbm for a full scale sine wave:
• with 15 db attenuation, the mixer input is 7 dbm,  H3-5 amp needs to output 22.5 dbm
• with 0 db attenuation , the mixer input is -15 dbm, the H3-5 amp needs to output 22.5 dbm.
  
• The mixer chassis is limiting the pdev A/D's to a peak sine wave value of 850 counts which is 9+ bits.
  

• On 13mar08 a sine wave was injected directly into the A/D converters to measure there signal levels.
• The schematic of the bbmixers (.ps)  shows were the components are located.
  

<- page up
home_~phil