What is a Baseband Equivalent Signal in Communications?

Explains how passband and baseband representations of signals are related in digital communications. Shows how QAM passband signals are generated from lowpass (baseband) constellation points (effectively "up converting" them to the passband), and then shows how the demodulation process at the receiver "cancels out" the up conversion and recovers the baseband signals. This shows that the baseband representation is enough to capture (mathematically) the input-output relationship that results from the modulation/demodulation process.

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[thecarradioandarongtong]

Sir, you deserve many many more views than what you actually do ! Not one word is out of place, which makes me respect it much more !! Great Job !

[ryoko]

Always thanks for your appreciation.
All of your efforts makes me the real engineer.

[jaiho]

Great explanation as always. Low pass equivalent was given by many sites but you connected it with Nyquist and gave the reason. Very thankful.

[houqingliu]

Thank you very much, professor! Your teaching video is really nice and inspiring. I am a junior student majoring in EE, and you make me much closer to the nature of these conceptions.

[MarthaCashh]

Your videos are the best, thanks for making these!

[azzamal-nahari]

Thank you Iain for all these efforts and great explainations. So in practice are all sampling is done on the baseband equivalent signal or actually on the baseband signal before modulation? I mean in normal comm. system we do sampling first then modulation and upconversion and at the Rx downconversion. Complex equivalent is more about facilitating the analysis rather than the sampling itself as I think we do not need to do sampling on the passband signal in practice even if we do not consider the complex baseband equivalant. Is this right?

[atreeinthewoods.]

is the multiplication by 2 on the lowpass signal there to match the 1/2 scale factor on the fourier transform of cosine to fully recreate the original signal?

[sangeshpv]

can you explain baseband in a time series.

[khaledramdan]

hey professor thanks for amazing video.
in digital domain message can be complex and real like BPSK is real and QPSK is complex data.
doubt - can analog message signal be complex because in analog domain what ever we transmit is real only like the voice transmission radio FM etc?

[ahmetserdr]

Sir can you make a video that related to wideband IQ Signal generation at receiver Side and how can we monitor spectrum using this wideband IQ

[mofaelectronics]

hi sometimes we have a rf signal that it's not repeatitive like a sound wave how can we downconvert this signals to sampling with low sample rate analog to digital converters? is there any way?

[ahmetserdr]

Superheterodyne receiver downconverts the incoming RF signal to IF band and samples the IF signal only one ADC. After sampling NCO generate digital oscillator to multiply sampled signal. İ dont understand how can we obtain IQ data at here. Can you help me?