Amplitude Modulation (AM)（振幅调制）.pdf

Name Date • • EXPERIMENT 6 Amplitude Modulation (AM) OBJECTIVES 1. Demonstrate an amplitude-modulated carrier in the time domain for different modulation indexes and modulating frequencies. 2. Determine the modulation index and percent modulation of an amplitude-modulated carrier from the time domain curve plot. 3. Demonstrate an amplitude-modulated carrier in the frequency domain for different modulation indexes and modulating frequencies. 4. Compare the side-frequency voltage levels to the carrier voltage level in an amplitude- modulated carrier for different modulation indexes. 5. Determine the signal bandwidth of an amplitude-modulated carrier for different modulating signal frequencies. • 6. Demonstrate how a complex modulating signal generates many side frequencies to form the upper and lower sidebands. ~ MATERIALS Two function generators One dual-trace oscilloscope One spectrum analyzer One 1N4001 diode One dc voltage supply One 2.35 nF capacitor One 1 mH inductor Resistors: 100 fl, 2 kfl, 10 kfl, 20 kfl THEORY The primary purpose oia communications system is to transmit and receive information such as audio, video, or binary data over a communications medium or channeL The basic components in a communications system are the transmitter, communications medium or channel, and the receiver. Possible communications media are wire cable, fiber optic • cable, and free space. Before the information can be transmitted, it must be converted into