Module 4: Quadrature Amplitude Modulation

[@chudi7175]

This lecture made me to know the difference between PSK and QAM. Thank you

[@kapoon]

Exactly that I was want to see! Thanks from Kazakhstan! I was wondering about sine wave modulated but at least square is good too

[@davidricketts7975]

The 1.6 comes from the fact that the radius on the right has to be bigger for the same distance red than the square on the right. The a actual number just comes from the geometry of a circle and a square.

[@rdramser]

Thank you for this great series.

[@muhammadkhizar3659]

Awesome explanation !!

[@hermandragland]

Thanks David, this was a good explanation :)

[@TheSuperGamerPro]

Thank you mr David

[@michaelcoletti6217]

thank you~! very good explanation!

[@muhannadak8087]

Thanks a lot! I have a question. So if the data in QAM relies on the amplitude, and waves change amplitude with the distance. How do make sure we don't lose the data?

[@yusufgorkemmatyar2114]

Sir, QAM modulator transmitter capable of transmitting PAM signals ?

[@mihaiferent2456]

Thank you

[@nagarajuparicherla2961]

yes, it is very good explanation, I have question How the value 1.6dB came? Can please give answer

[@michaelcoletti6217]

the radius in the circle is represent the amplitude require for 16psk to get to this amplitude it cost more power. so probably someone calculate it and it was 1.6db

[@p07a]

For QAM 16: Distance between symbols = 1 --> Maximum distance from origin = sqrt( (1.5)^2 + (1.5)^2 ) = 3sqrt(2)/2 For PSK 16: Maximum distance from origin (i.e., radius) = 1 → Distance between symbols = 2pi/16 (subtract error, since arc is longer than chord) = pi/8 (- error) So for max distance between symbols to be 1 → radius will be 8/pi. Now, we have QAM-16_maxAmp = 3sqrt(2)/2 = 2.121 and PSK-16_maxAmp = 8/pi = 2.546 Ratio = QAM-16_maxAmp / QAM-16_maxAmp = (3sqrt(2)/2) / (8/pi) = 3*pi*sqrt(2)/16 = 0.833 To Decibels = 20*log10(Ratio) = -1.59 dB ( + error ) Disclaimer: I am not an electrical engineer.

[@WonYYang]

kzbin.info/www/bejne/gZWvoICfYst8i5Y for simulation of QAM passband signaling with Simulink

[@WonYYang]

kzbin.info/www/bejne/apS0dJufadNki7s for simulation of QAM passband signaling with MATLAB