a5/a6

a5.md

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+# Suppressed  Carrier Wave
+Derive expressions from which it will be evident whether the
+communication channel has more power as an AM signal with
+a suppressed carrier wave or as an AM signal with the carrier
+wave present. Assume the voltage signal, $v(t)$ and $m(t)$, as in
+the previous figure. Modulating (LF) sinusoidal signal has
+amplitude $A$ and frequency $f_{LF}$ Hz, cosine wave RF carrier has
+amplitude $1$ and frequency $f_{VF}$.
+
+
+According to $P_t = P_c + P_{USB} + P_{LSB} $ the total transmitting power has to be split among carrier, upper and lower side band.
+With the carrier wave suppressed, the modulating signal will take up all of the available transmission power instead.
+
+For a standard AM signal with the above requirements, the formula is:
+$$ s(t) = (1+A \cos(2\pi f_{LF}t)) \cdot \cos(2\pi f_{VF} t)$$
+
+With the power of a wave signal given by $P=\frac{(v_m/\sqrt{2})^2}{2}$ (where $v_m$ is max of cosine signal),
+our sideband power is $2* \frac{(A/\sqrt{2})^2}{2} = \frac{A^2}{2}$ 
+and our carrier power $\frac{1}{2}$, equal to the power gained in DSB-SC.

a6.md

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+# Time Synchronization
+Time sync between sender and receiver is important because the carrier wave has to be used to demodulate the signal in the receiver.
+If there is a time shift, there will be a phase error introduced by the demodulation, resulting in a distorted signal.