Identity each statement below as either True on False and explain. 1. The primar

Question

Identity each statement below as either True on False and explain.

1. The primary purpose of modulation is to increase the power of a signal for transmission.

2. The autocorrelation function of a power signal is the inverse Fourier transform of the power spectral density of that signal.

3. An envelope detector cannot be successfully used to demodulate AM signals with modulation index >1.

4. A 1st-order PLL can perfectly match both the frequency and phase of an incoming signal.

5. In NTsc television, the color information is transmitted as individual messages for Red,Green, and Blue components.

Explanation / Answer

1.FALSE

The primary purpose of modulation is used to reduce the power of a transmitted signal and increase the efficiency for transmission.

2.TRUE

For a real power signal f (t) the power spectral density by Sff (w) is by definition the
Fourier transform of the autocorrelation function.

Sff (w) = F [rff (t)] = Rff (jw).
Since rff (t) is real and even its transform Sff (w) is real and even.

The autocorrelation function of a power signal is the inverse Fourier transform of the power spectral density of that signal.

3.TRUE

For modulation index lessthan or equal to 1 message signal is completly stored in the form of positive envelope so that envelope detection is possible

4.FALSE

First order PLL will automatically tend to recover phase lock if the input is displaced by a constant phase. This is clearly a very desirable loop characteristic.

consider the PLL steady-state response to a frequency step at the input.A frequency step can approximate the effect of a frequency Doppler shift in the incoming signal due to the relative motion between the transmitter and the receiver.

5.FALSE

A color signal conveys picture information for each of the red, green, and blue components of an image.However, these are not simply transmitted as three separate signals, because these signal is not compatible with monochrome receivers.Instead, the RGB signals are converted into YUV form, where the Y signal represents the lightness and darkness (luminance) of the colors in the image and the U and V signals are "color difference" signals.

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