The digital signal is coded so a low becomes a sine wave of one frequency, while a high becomes a sine wave of another frequency. Either that, or it alternates between less and greater amplitude of one sine wave frequency.
For such data transmission we perform Digital modulation such as QAM, BPSK,QPSK, FSK, ASK etc etc. After which they are demodulated back to 1s and 0s.
These values represent the amplitude and phase of a modulated signal. If it is digitally modulated then we have 16 digital possibilities in this case of 16QAMwhat are these numbers really and how are they related to the analog signal produced by modulation???
Thank you
Are you referring to frequency modulation here?
I am also confused with transmission of bits through radio channels, after the bits are converted to symbols, how are the symbols transmitted in the air as analog signal? Or if my understanding there is wrong please correct me.
i understand that part of modulation, what i meant was the complex number representation of each symbol...
as for the MATLAB simulation, hmod = modem.qammod(16);
tx = randint(500,1,16); % producing random numbers to be transmitted
qamSig = modulate(hmod,tx);
the result of modulation, qamSig is a vector of complex numbers... That is where i stumbled...
thanks
oh that yes well those complex numbers are a way to plot the signal on the Real Imaginary axis.
I am lost here, how does a complex number = signal?
Thanks
I see! THANK YOU!!! So that's how the complex number represents the Amplitude and phase of each of M signals?
And that signal is the result after M-QAM right?
Use ADS which has a wonderful array of communication systems (in examples) and you can design urself as well , as actually what is happening when we transmit using QAM or QPSK etc.
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