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From: | Roee Bar |
Subject: | [Discuss-gnuradio] USRP Complex Demodulation |
Date: | Fri, 13 Nov 2015 18:25:47 -0800 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 |
Hello,I am trying to understand how the USRP performs the modulation/demodulation to/from higher frequencies.
Let's say I have a complex signal s(t). When I feed it to the USRP block, my understanding is that the USRP performs something like s(t)*exp(i*w*t), and transmit the real part of it, i.e.,
r(t) = 1/2 * (s(t)*exp(i*w*t) + s_c(t)*exp(-i*w*t)), where s_c is the complex conjugate of s(t).However, I couldn't find any explanation how the receiver brings the signal back to its original representation. My experiments show that it's not just multiplication with exp(-i*w*t) followed by low pass filter, but something else. The USRP source complex output is not the original s(t). Can someone please clarify this issue?
Thanks in advance! Roee
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