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directivity degradation

Question asked by e4411a on Jun 15, 2007
Latest reply on Jun 16, 2007 by Dr_joel
Hi,

When we add an attenuator to the o/p of a coupler, the directivity of the coupler  would degrade by twice the amount of attenuator that we add. 

I need to test amplifers that have o/ p power ranges greater than 30dBm and this is beyond the i/p range of the PNA. So I need to use attenuators at the o/p of the device. i calibrate out the attenuators and so for the S22 measurements the attenuator is at the o/p of the coupler. If I were to use a 10dB pad, would this not degrade the directivity by 20dB.

Could somebody please clarify on this and explain the meaning of raw diectivity.

Rgds  

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