A detailed study on the amplitude modulation using Multisim softwareFull description
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Amplitude Modulation lab reportFull description
Modulation d Amplitude CPF0708
Laporan Praktek Teknik Transmisi Jobsheet PAM
Laporan Praktek Teknik Transmisi Jobsheet PAM
AM Radio Simulator
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AM
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LAB REPORT AMPLITUDE MODULATION
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STU. ID No
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Output Wave forms.
Fm(t) signal
Fc(t) signal
Output wave foms observed by oscilloscope
Output wave foms observed by spectrum analyzer
CONCLUSION
Observed how the Timedomain signal and the frequency donation signal of Amplitude Modulated signal behaved.
DISCUSSION
Modulation indices are described for various forms of modulation. The amplitude modulation, AM, modulation index can be defined as the measure of extent of amplitude variation about an un-modulated carrier. As with other modulation indices, the modulation index for amplitude modulation, AM, indicates the amount by which the modulated carrier varies around its static un-modulated level. A complementary figure to modulation index is also used for amplitude modulation signals. Known as the modulation depth, it is typically the modulation index expressed as a percentage. Typically the modulation index of a signal will vary as the modulating signal intensity varies. However some static values enable the various levels to visualized more easily.
Amplitude modulated index of 0.5 When the modulation index reaches 1.0, i.e. a modulation depth of 100%, the carrier level falls to zero and rise to twice its non-modulated level.
Amplitude modulated index of 1.0 Any increase of the modulation index above 1.0, i.e. 100% modulation depth causes over-modulation. The carrier experiences 180° phase reversals where the carrier level would try to go below the zero point. These phase reversals give rise to additional sidebands resulting from the phase reversals (phase
modulation) that extend out, in theory to infinity. This can cause serious interference to other users if not filtered.
Amplitude modulated index of more than 1.0 i.e. over-modulated Broadcast stations in particular take measures to ensure that the carries of their transmissions never become over modulated. The transmitters incorporate limiters to prevent more than 100% modulation. Hover they also normally incorporate automatic audio gain controls to keep the audio levels such that near 100% modulation levels are achieved for most of the time.Single sideband modulation can be viewed as an amplitude modulation signal with elements removed or reduced. In order to see how single sideband is created, it is necessary to use an amplitude modulated signal as the starting point.
An amplitude modulated carrier showing sidebands either side of the carrier From this it can be seen that the signal has two sidebands, each the mirror of the other, and the carrier. To improve the efficient of the signal, both in terms of the power and spectrum usage, it is possible to remove the carrier, or at least reduce it, and remove one sideband - one is the mirror image of the other. A single sideband signal therefore consists of a single sideband, and often no carrier, although the various variants of single sideband are detailed below.
Single sideband modulation showing upper and lower sideband signals It can be seen that either the upper sideband or lower sideband can be used. There is no advantage between using either the upper or lower sideband. The main criterion is to use the same sideband as used by other users for the given frequency band and application. The upper sideband is more commonly used for professional applications.