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niRFSG write arb waveform I/Q

What does it mean when you have an in input I data, but no Q input data? Is it really possible that a waveform has no Q data? Thank you.

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Hello Margarette,

 

Thank you for bringing this issue to the forums. So, here is a document we provide which goes over the basics of IQ Data and why we use it to modulate signals.

 

To answer your question, if an input signal has only I data, or no Q data, this means it is using more of a Phase-Shift Keying (PSK) modulation scheme, more specifically Binary Phase-Shift Keying (BPSK). In BPSK the system is designed so that the carrier can assume only two different phase angles, each change of phase carries one bit of information. So, in your case the phase could shift from 0 degrees to 180 degrees, this will allow no Q data. Hence, 0 degrees could be used to encode a "0" and 180 degrees could be used to encode a "1."

 

Please let me know if I answered your question correctly. 

 

Thank you,

Vimal Fernandez

Applications Engineer
National Instruments
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