# Questions tagged [complex]

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### Complex time domain signals and QAM

Is there an inherent connection between complex time domain signals and QAM? Given a complex time-domain signal is it always implied that this is a QAM-demodulated form of a real time domain signal? ...
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### Extracting positive frequencies of discrete-time signal

Convolution in the time domain is the same as multiplication in the frequency domain. My data is sampled at 200 Hz, which means that the Nyquist frequency is 100 Hz, and all frequency content is <=...
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### Derivative with respect to complex conjugate

I have a real function $C$ of a complex vector $x$. While taking the gradient of the function $C$ for minimising the same, why do we take the derivatives with respect to the complex conjugate of $x$, ...
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### How to extract single side of signal spectrum in SIMULINK

Signal spectrum have two side, positive and negative. I want to make these separate in two signal, by MATALB SIMULINK. But how? I can't find it's block on DSP or communication toolbox. I found a block ...
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### Replacing “e” in Euler's formula with another number

Does Euler's formula remain valid if we use any real number other than the constant $e$? For example replacing $e$ with 5 would make the formula look like this: $5^{it}$. I tried this idea in ...
given: $z^2 + 0.8 \sqrt2 z + 0.64 = 0$ Then, I am using the quadratic equation: $z_{1,2} = \frac{-0.8 \sqrt2 \pm \sqrt{(0.8\sqrt2)^2-4 \cdot 0.64}}{2}$ Wolfram Alpha says it the end there should ...