- 21st February 2006, 08:34 #1

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## Insertion Loss & Return Loss [hlp]

Hello everyone;

Suppose a two-port network with scattering parameters. Please express**Return Loss & Insertion Loss**by scattering parameters.

- 21st February 2006, 08:34

- 21st February 2006, 10:27 #2

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## Re: Insertion Loss & Return Loss [hlp]

Hi,

Insertion loss is S21 [dB]

Return Loss(es) are -S11 [dB] and -S22 [dB] (minus sign, they are expressed as positive values)

flyhigh

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- 21st February 2006, 10:27

- 21st February 2006, 12:19 #3

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## Re: Insertion Loss & Return Loss [hlp]

Just a small correction.

Insertion loss is -S21 [dB]

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- 21st February 2006, 12:19

- 21st February 2006, 17:14 #4

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## Re: Insertion Loss & Return Loss [hlp]

Hi,

yes, of course, S21 comes with minus sign as well.

flyhigh

- 21st February 2006, 19:20 #5

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## Re: Insertion Loss & Return Loss [hlp]

S21 is the Gain of the two port device! Pout/Pin

If it is a lossy or passsive device the gain will be zero or negative (Insertion Loss).

If it is an active device it should have some gain, making it a Positive S21

S11 is the Input ReturnLoss Looking in to Port 1 Pin(forward)/ Pin(reflected Back)

S22 is the Output Returnloss Looking in to Port 2 P(forward)/ P(reflected Back)

When S11 & S22 are Very Negative (dB) That means that none of the power going

in to the port get reflected out!

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- 21st February 2006, 21:40 #6

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## Re: Insertion Loss & Return Loss [hlp]

S11 is the Input Return Loss and S22 is the Output Return Loss ONLY if S12=0 !!!