Download
sofie signal gain analysis mark hervig gats n.
Skip this Video
Loading SlideShow in 5 Seconds..
SOFIE Signal Gain Analysis Mark Hervig GATS PowerPoint Presentation
Download Presentation
SOFIE Signal Gain Analysis Mark Hervig GATS

SOFIE Signal Gain Analysis Mark Hervig GATS

91 Vues Download Presentation
Télécharger la présentation

SOFIE Signal Gain Analysis Mark Hervig GATS

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. SOFIE Signal Gain AnalysisMark HervigGATS

  2. SOFIE Analog Signal Path Weak Channel Balance Attenuator attenuation = BAw A/D 14 bits -3V to 3V -213 to 213 counts 1 count = 366 V Vin,w Differential Amp gain = GV Strong Channel Balance Attenuator attenuation = BAs Vin,s • Vin is the signal into the balance attenuator, after synchronous rectification: • Vin = VA/Dmax * margin • set margin to 1.2, so Vin = 3V * 1.2 = 3.6V • we’ll get Vw and Vs below 3V using the BA’s • for example to get Vexo = 2.95V requires BA = 0.82 • The difference signal: • V = (Vin,w * BAw – Vin,s* BAs) * GV

  3. Balance attenuator setting vs. V balance voltages • Difference signal balance voltage, Vbal: • Vbal = (Vin,w * BAw – Vin,s* BAs) * GV • Solve for BAw We can balance at various voltages to increase dynamic range in V Little impact on Vw These curves apply to all channels

  4. V precision vs. V gain and balance attenuator settings count precision, CPV = (214 BAsGV)-1 These curves apply to all channels

  5. V precision vs. balance attenuator setting Count precision, CPV = (214 BA)-1 Lowering BA reduces precision These curves apply to all channels

  6. Recommended V Gain Settings Assumes 14 bit A/D, -3 to 3V. V balance voltage was –2.5V for all channels. Upper altitude is where the 1st 10 count change occurs. Lower altitude is where V reaches 0.8214 counts. Note that the CBE 1-count precisions are not CBE system noise. Required V precisions are taken as the strong band requirements. Signals were based on atmospheric transmissions calculated using a climatology for summer at 60°N. The analyses that lead to the above results are shown on the following pages.

  7. (Chad) SOFIE Radiometric Measurement End-to-End Required SNRs

  8. SOFIE PC Radiometric Electronics Overview • Carrier Frequency = 1kHz, Modulation = 2 Hz, Effective Sync Rect Q = 500 • Nominal Equal System-wide Phasing: Butterworth and Bessel Filters

  9. 1) O3 channel profiles Balance V at –2.5V BAs = 0.819 BAw = 0.613 GV = 3.3 V saturates at 60 km, or 0.8*214 counts

  10. 1) O3 Channel useful altitude Useful altitude of V signals is determined by the V gain and balance attenuator settings. Baseline altitude range will be determined by GV Adjusting the BA settings changes the altitude range very little in this case

  11. 2) SW particle channel profiles Balance V at –2.5V BAs = 0.819 BAw = 0.814 GV = 300 V useable through typical PMC

  12. 3) H2O channel profiles Balance V at –2.5V BAs = 0.819 BAw = 0.812 GV = 96 V saturates at 50 km, or 0.8*214 counts

  13. 3) H2O Channel useful altitude Useful altitude of V signals is determined by the V gain and balance attenuator settings. Baseline altitude range will be determined by GV We can adjust the BA settings to change our altitude range

  14. 3) H2O channel useful altitude The V gain to saturate at 50 km altitude changes with V balance voltage Decreasing the V balance voltage increases the dynamic range With increased dynamic range, we can tolerate an increase in the V gain The figure shows the V gain that saturates V at 50 km vs. Vbal Decreasing Vbal allows us to get more precision and dynamic range

  15. 4) 2.8 m CO2 channel profiles

  16. 4) 2.8 m CO2 channel useful altitude Useful altitude of V signals is determined by the V gain and balance attenuator settings. Baseline altitude range will be determined by GV Adjusting the BA settings changes the altitude range

  17. 5) IR particle channel profiles Balance V at –2.5V BAs = 0.819 BAw = 0.814 GV = 120 V useable through typical PMC

  18. 6) CH4 channel profiles Balance V at –2.5V BAs = 0.819 BAw = 0.816 GV = 202 V saturates at 40 km, or 0.8*214 counts

  19. 6) CH4 Channel useful altitude Useful altitude of V signals is determined by the V gain and balance attenuator settings. Baseline altitude range will be determined by GV Adjusting the BA settings changes the altitude range

  20. 7) 4.3 m CO2 channel profiles

  21. 7) 4.3 m CO2 channel useful altitude Useful altitude of V signals is determined by the V gain and balance attenuator settings. Baseline altitude range will be determined by GV Adjusting the BA settings changes the altitude range

  22. 8) NO channel profiles Balance V at –2.5V BAs = 0.819 BAw = 0.817 GV = 300 V never saturates, but the signal is dominated by atmospheric interference below 80 km.