# OFDM Query : Why In Phase and Quadrature Phase RF Conversion is needed? [duplicate]

OFDM Basic Query- x[n] produced at output of IFFT is in discrete time, so we can use DAC and then RF Upconversion (multiply it with LO Frequency say f) and send it, why are we doing RF up conversion in Inphase and Quadrature phase then adding it and sending it? Can someone please explain.

• isn't Dan's rather excellent explanation of exactly that in the answer to your last question about what real and imaginary parts in an IFFT have to do with OFDM? Dec 30, 2021 at 22:05
• also, you haven't accepted a single answer to your several questions on this site – that's not good style, unless none of these answers actually answered your question. Dec 30, 2021 at 22:28
• Thanks, will keep the suggestions handy, apologies missed out correlating the two questions. Dec 31, 2021 at 1:29

However, you can map a complex number onto an RF carrier by multiplying the real part by $$\cos \omega t$$, and the imaginary part by $$\sin \omega t$$. This is I/Q modulation. The result is not complex -- it's all real. But the resulting arithmetic that you do on it, at the transmit and the receive end, is the same as if it were a complex number.