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I got a problem about AGC

Question asked by sarah on Mar 14, 2011
Latest reply on Mar 14, 2011 by Jim

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hi, i have a question about AGC loop (using ADL5330 and AD8318)

 

i'm making the circuit about AGC, you can see the figure1

 

i want the constant power about -30dBm

 

so i was changed input power level of VGA(ADL5330) when i fixed setpoint voltage

 

but power was not fixed

 

i think in situation of fixing setpoint voltage, even though vga input power level is change, vga out power have to be fixed, is it right?

 

but it's changable

 

the VGA(*adl5330) has the gain range of -30 ~ 16 dBm at 2200MHz

 

and i'm using the 20 dB coupler. so i need detector range of -50~04 dBm, so i select AD8318

 

but important thing is that the loop is not fixed (for changing the input level & fixing setpoint voltage)

 

so how can i get this condition

No.1 ) constant power level of -30dBm,

No.2 ) VGA input power level -40~0 dBm (it's changeable)(tell me what range needed)

 

here's my question

No.1) What's the problem about my circuit?

No.2) what setpoint voltage needed when i get -30dBm of VGA power out level?

No.3) what range of VGA input level needed? how can i decide it?

No.4) R divider value (412/1Kohm) is nesessary?

No.5) i need more specific answer, so tell me more about this solution

 

please reply quickly

 

i'm waiting for your answer,

 

thank you!

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