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The main difference between both modulations is that in frequency modulation, the carrier wave frequency is modified as per the transmit data. In contrast, in amplitude modulation, the carrier wave is modified according to the data.
Figure 9.5.1 9.5. 1: Amplitude-modulated wave. The amplitude of the carrier wave (blue, traveling at phase velocity vw = ω/k v w = ω / k) is changed over time, resulting in an envelope (red) which travels at the lower group velocity vg v g.
Modulation. December 1, 2011. Applications of signals and systems in communication systems. Example: Transmit voice via telephone wires (copper) mic. amp. telephone wire. amp. speaker. Works well: basis of local land-based telephones. In cellular communication systems, signals are transmitted via elec tromagnetic (E/M) waves. mic. amp. E/M wave.
For example, if the value of \( f_2 \) is 1Hz, the volume should go to zero once every second. The \( y_2\) waveform is acting as a modulator and creates an amplitude envelope. This means its magnitude is determining the magnitude of \( y_{1\times2} \).
Modulation means variation of the amplitude or the phase (or both) of an otherwise constant sinusoidal RF carrier wave in order that the signal carry information: digital data or analog waveforms such as audio or video. In this chapter we look at pure amplitude modulation (AM) and pure frequency modulation (FM).
An AM signal has the mathematical form. s(t) = Ac[1 + kam(t)] cos ωct. where. m(t) is the baseband message. c(t) = Ac cos ωct is called the carrier wave. The carrier frequency, fc, should be larger than the highest spectral component in m(t). The parameter ka is a positive constant called the amplitude sensitivity of the modulator.
Pros and Cons of AM-DSB-SC. Straightforward. Sensitive to frequency and phase error of the reference signal (coherent demodulation) Bandwidth inefficient ( AM-DSB-SC=50%)
