ya, it can be negative because as m=Vm/Vc , the value of Vm if taken in negative then modulation index can be naegative
Modulation index is also called as Modulation depth. The modulation index of a modulation scheme describes by how much the modulated variable of the carrier signal varies around its unmodulated level.
how modulation index varies for FM
it causes over modulation .... that is the phase reversal of carrier signal ..... the modulated wave then exhibits envelope distortion which results in loss of data .....
Advantage - 1. Phase modulation & demodulation is easy compared to Frequency modulation. 2. Phase modulator is used in determining velocity of moving target by extracting Doppler information. Doppler information needs stable carrier which is possible in phase modulation but not in frequency modulation. Disadvantage - 1. Phase ambiguity comes if we exceed its modulation index pi radian(180 degree). 2. we need frequency multiplier to increase phase modulation index. Visit my website http://harshit.org
in order to transmit the video signal amplitude modulation is used. the composite video signal has distinct polarity of black and white levels in the picture.1.positive modulation :- in this type of modulation, increase of brightness toward white causes increase in carrier amplitude peak white has 100% modulation while black and sync level have lower and minimum modulation respectively2.negative modulation :-in this type of modulation,the sync tip level are at 100%.blanking level correspond to black is at 75%and increase in brightness toward white causes decrease in carrier amplitudeNegative modulation is preferred over positive modulation because impulse interference is difficult to deal with and random increase in signal is similar to existing sync pulse.these interference result in generation of black spot and white blobs.
Modulation index is also called as Modulation depth. The modulation index of a modulation scheme describes by how much the modulated variable of the carrier signal varies around its unmodulated level.
how modulation index varies for FM
how modulation index varies for FM
Modulation Index is the ratio of the maximum deviation frequency to the frequency of modulation. In other words it is the ratio of the spread in frequency spectrum to the frequency that was used to modulate the carrier. For FM, modulation index is given by the formula mf= df/f where, mf=modulation index for FM df=difference in carrier frequency f=frequency of the signal
The modulation index in AM can range from zero to any number. But if distortion is to be avoided, then the index must not exceed 100%.
The values of amplitude modulation index is categorized as an objective type.
fc>2fm
frequency modulation..
the modulation system is of FM
It can be anything at all, from yoctowatts to terawatts. You must state the power output at some modulation index before I can calculate it for some other modulation index. By the way . . . the answer also depends on the method of modulation, which you have not mentioned. For example, with pure FM, the transmitted power doesn't change, regardless of the mod-index.
a measure of the degree of frequency modulation expressed numerically for a pure tone modulation as the ratio of the frequency deviation to the frequency of the modulating signal.
mf=(K*Am)/fm where K: is a proprtionality coefficient Am: is amplitude of the message fm=frequency of modulation