On Mon, Dec 15, 2008 at 4:41 PM, Aadil V. [email protected] wrote:

Hi, I have read this information regarding the USRP ADC

“The full range on the ADCs is 2V peak to peak, and the input is 50 ohms

differential. This is equates to 40mW, or 16dBm.”

Please may someone enlighten me, how the 40mW and 16dBm values were

calculated?

I am not sure where those numbers came from directly, but the 50 Ohms

differential might be wrong. From the datasheet here:

```
http://www.analog.com/static/imported-files/data_sheets/AD9860_9862.pdf
```

Page 2 shows the differential input resistance to be 200 Ohms with the

maximum differential input being 2Vp-p.

Regardless (and assuming the 50 Ohms), the equations are only Ohms Law

and conversion into dBm.

P = V^2 / R

P = 1.0V^2 / 50 Ohms

P = 20mW

Since there are two inputs, we double that to be 40mW of power used up.

10*log10( P / 1mW )*

10log10( 40mW / 1 mW )

16.02 dBm

Hope this helped.

Brian