Calculate output signal for a 50 Ohm terminator [NI USRP-2930]

[EtuelDue]

Hello,

I have a question regarding the my output signal properties for a 50 Ohm terminator (In this case an oscilloscope). My output signal (Real OFDM-Signal for optical application, no Q-Component) calculated in LabVIEW is shown in the this figure:

You can see that this signal has a Peak-to-Peak ratio of 0.5 and a RMS value of 47.69m. From this I want to calculate the Peak-to-Peak ratio of the signal if I terminate the USRP device with a 50 Ohm resistor (or any other resistor). I did this with an oscciloscope (impedance 50 Ohm) and got the following result:

Do you have any idea in which way I can calculate the signal properties from the oscilloscope with the known information from the figure above? Is this even possible without having any more information about the I-Q-Mixer and the ADC?

Thanks and regards!

[ErikL]

Do you want an RF output or a baseband output from the device?  The 2930 will give you a mixed RF output.  A 'real' OFDM signal transmitted on I with no Q component will likely not give you the desired result.  Most optical applicaitons would use a connection directly to the DAC or ADC to the LED or light sensor using the baseband daugherboard such as the LFRX or LFTX  http://www.ettus.com/product/details/LFRX

[EtuelDue]

Tahnks for your answer. I want the properties from the RF output. I am pretty sure it will give me desired results, although I have to use an additional mixer in order to transmit in the 1-100 MHz range. I agree with you that for most optical application the other daughterboards would me more suitable but in our case we want to use the 120 MHz USRP RIO Boards for maximum bandwidth and least computional processes on the host pc. So my question remains: Is it possible to calculate the signal properties?