ALFA IF/ LO system

21apr10- system block diagram (dana)
     (old....18feb04- system block diagram (lisa wray)
05apr08- System Temperature/powerLevels (bsisk)
05apr08- Eddie's down conversion box
05apr08- Fiber Span AC231, Fiber Optic Xmtr/Rcvr measurements by bsisk

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05apr08   Eddies down conversion box:

    Eddies down conversion box takes the output of the alfa filter bank, amplifies, downconverts, filters, amplifies, and then sends the IF signal down the fiber.
  

Specs for Eddies down conversion box.

Component	Make	GAIN db	CumGain db	NF db	Compression (1db)	Level@1db compression	Notes
RF amp	MGA-86576 (avago)	+21(20)	20	2.2	+6 dBm	-27	amp bias
mixer	IAM-8 (avago)	+15	35	19	+8dBm	+7
Filter	P7LP507 (coil craft)	-.5	34.5			6.5	500Mhz Lowpass.
IF amp	MAV-11SM (mini circuits)	+12(11)	45.5	3.6	+17dBm	16.5	AmpBias
Fiber Modulator	AC231 (Fiber Span)	-.8	44.7	39 (-135dBm Hz)	+15dBm		See fiber TX notes

• Fiber Tx Notes (from fiber span rep:)
• For a clean(i.e., very linear) signal, we recommend staying 10 dB or more below the 1dB compression point, putting the "peak linear power" at +5 dBm.
  
• The damage threshold for these devices is an input power of +20 dBm. Please do not exceed this maximum, even for very short durations.
• Amp bias:
• The RF and IF amps are not properly biased (according to the data sheets). Proper biasing caused oscillations in the board. Ganesh thinks that the actual biasing may decrease the gain of the combined amps by up to 3db.
• Input Levels for compression:
• -27Dbm at input to RF amp will cause 1 db compression at mixer output (assuming 20 db gain for misbiased RF amp).
• Input Levels for damage to fiber Optic transmitter.
• A peak level of +20dBm will damage the fiberOpticTx.
• With +45 db gain
  
• a -25 dBm signal would cause problems if No compresssion.
• a -27 dBm signal will be 1db compresses at the mixer output.