lec10_modul

lec10_modul - Modulation Modulation - Carrier Systems...

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ME365 Modulation Slide 1 Modulation Modulation - Carrier Systems Amplitude Modulation Demodulation
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ME365 Modulation Slide 2 Modulation - Carrier Systems Modulation Using a low frequency or base-band signal (voice, distance measurement, …) to modify a high frequency carrier signal . Advantages: Telemetry signal transmission Multiplexing - multiple signals may be transmitted on the same channel. Capacitive or inductive devices require high frequency AC input (carrier) to operate. Stability and noise rejection
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Modulation - Carrier Systems No wires Good for rotating machinery Long wires act as a low-pass filter Long wires can enhance coupling to power lines High frequency avoids some environmental noise sources Lower frequency needs larger devices Co-located sensor and transmitter can be small Large device can mechanically load system
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ME365 Modulation Slide 3 Modulation - Carrier Systems Types of Modulation In the modulation process, some characteristic of a high- frequency sinusoidal carrier signal, V ( t ), is changed in direct proportion to the instantaneous amplitude of the information (baseband) signal, x ( t ). Carrier signal: V ( t ) = V C sin( w C t + f ) where: V C = Carrier amplitude C = Carrier frequency (rad/sec) f = Carrier phase at t = 0 sec. Three properties can be changed: AM (A mplitude M odulation): changes the amplitude ( V C ). FM (F requency M odulation): changes the frequency ( C ).
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lec10_modul - Modulation Modulation - Carrier Systems...

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