# What is difference between Phase shift keying (PSK) and Quadrature Amplitude Modulation (QAM) mathematical equation

I went through a literature and found the following expression for PSK signal. On this basis, what will be the equation for **QAM signal **. Also from where i would be able to read about this equation of PSK and QAM. Any help in this regard would be highly appreciated. $$s\left[n \right] = \sqrt{P_s}\exp \left(j \frac{2\pi k}{M} \right)$$

• When you did a web search on "QAM vs PSK", how many other references did you find? Which ones weren't clear? – TimWescott May 21 at 23:49
• Theoretically I had understood, but what will be the mathematical equation similar to that of PSK – charu May 22 at 0:31
• Why do you need an equation? As long as you know the constellation points, I can't think of a reason why you'd need one – Engineer May 22 at 11:25
• Put less strongly, but leading to the same result -- you should be able to look at the constellation points and come up with the equation. Is that where you're having trouble? – TimWescott May 22 at 14:55
• I looked at constellation points and also understood the equations. For e.g., in case of BPSK we get the two equations: S1(t) = AcCos(2*Pifct) for bit 0 and S2(t) = AcCos(2*Pifct+Pi) for bit 1. But these equations are not in the above mentioned form i.e., in the form of exponential. – charu May 22 at 23:49