Helo on getting data with its description of an AGC example

[ruwan2]

Hi,

I read the following link on AGC:


https://www.eetimes.com/document.asp?doc_id=1272474

I can not get the data on the below picture. For example, I don't see how the 4 dB sensitivity degradation.
gain change: 75 - 54 = 21 dB
input level change: -67 - (-45)=-22 dB
How to get '4'?

Thanks,


To demonstrate how the AGC can be used to extend dynamic range, Figure 3 shows the receiver error vector magnitude (EVM) vs. input power for various gain settings. The best sensitivity is achieved at the maximum gain setting of 75 dB, but the EVM falls below –15 dB with a –67 dBm signal. Reducing the gain to 54 dB, for example, increases the maximum signal power to –45 dBm, at the expense of a 4 dB sensitivity degradation.



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It looks like it is the reading of the horizontal difference at the left side. Thanks,

 

[D.A.(Tony)Stewart]

The vertical difference in Rx EVM differs by as much as 4dB for the two gain settings over the entire range of Pin. This occurs around -70dB in.

A rise in Error Vector Magnitude at low signal levels means a loss in sensitivity.

 

[ruwan2]

Thanks, SunnySkyguy! Great answer.