Advertisements
Advertisements
प्रश्न
Answer the following question.
If A and B represent the maximum and minimum amplitudes of an amplitude-modulated wave, write the expression for the modulation index in terms of A and B.
Advertisements
उत्तर
Modulation index for an AM wave for which the maximum amplitude is 'a' while the minimum amplitude id 'b'.
Modulation index,
`a_m = (E_m)/(E_c)` ...(1)
The maximum amplitude of the modulated wave, a = Ec + Em ...(2)
The minimum amplitude of the modulated wave, b = Ec - Em ....(3)
From the above equations,
`E_c = (a + b)/2 , E_m = (a - b)/2`
From Equation 1 we get,
Thus, the modulation index is `a_m = E_m/E_c = (((a - b))/2)/(((a + b))/2) = ((a - b))/((a + b))`.
संबंधित प्रश्न
Explain any two factors that justify the need of modulating a low-frequency signal.
A signal of 5 kHz frequency is amplitude modulated on a carrier wave of frequency 2 MHz. What are the frequencies of the side bands produced?
A modulating signal is a square wave, as shown
The carrier wave is given by `c(t) = 2 sin (8pit) "volts"`
(i) Sketch the amplitude modulated waveform
(ii) What is the modulation index?
For an amplitude modulated wave, the maximum amplitude is found to be 10 V while the minimum amplitude is found to be 2 V. Determine the modulation index μ. What would be the value of μ if the minimum amplitude is zero volt?
How is amplitude modulation achieved?
Write three important factors which justify the need of modulating a message signal. Show diagrammatically how an amplitude modulated wave is obtained when a modulating signal is superimposed on a carrier wave.
What is meant by term ‘modulation’? Draw a block diagram of a simple modulator for obtaining an AM signal.
On radiating (sending out) an AM modulated signal, the total radiated power is due to energy carried by ωc, ωc – ωm and ωc + ωm. Suggest ways to minimise cost of radiation without compromising on information.
Draw the plot of amplitude versus ‘ω’ for an amplitude modulated wave whose carrier wave (ωc) is carrying two modulating signals, ω1 and ω2 (ω2 > ω1).
- Is the plot symmetrical about ωc? Comment especially about plot in region ω < ωc.
- Extrapolate and predict the problems one can expect if more waves are to be modulated.
- Suggest solutions to the above problem. In the process can one understand another advantage of modulation in terms of bandwidth?
An audio signal vm = 20sin2π(1500t) amplitude modulates a carrier vc = 80 sin 2π (100,000t). The value of percent modulation is ______.
