Advertisements
Advertisements
Question
I-V characteristics of four devices are shown in Figures.
 |
 |
 |
|
| (i) | (ii) | (iii) | (iv) |
Identify devices that can be used for modulation.
Options
'i’ and ‘iii’.
only ‘iii’.
‘ii’ and some regions of ‘iv’.
All the devices can be used.
Advertisements
Solution
‘ii’ and some regions of ‘iv’.
Explanation:
A square law modulator is a device which can produce modulated waves by the application of the message signal and the carrier wave.
A square law modulator is used for modulation purposes. Characteristics shown by (i) and (iii) correspond to linear devices.
And by (ii) corresponds to the square law device which shows non-linear relations. Some parts of (iv) also follow square law.
Hence, (ii) and (iv) can be used for modulation.
APPEARS IN
RELATED QUESTIONS
The process of superimposing a low frequency signal on a high frequency wave is_______ .
Define modulation and transducer
Define modulation index.
State three important factors showing the need for translating a low frequency signal into a high frequency wave before transmission
A carrier wave of peak voltage 12 V is used to transmit a message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of 75%?
Explain the need for modulation related to the size of antenna (aerial).
What is the role of a bandpass filter?
A carrier wave of peak voltage 15 V is used to transmit a message signal. Find the peak voltage of the modulating signal in order to have a modulation index of 60%
In a communication system, what is meant by modulation?
The carrier wave of a signal is given by C(t) = 3 sin (8πt) volt. The modulating signal is a square wave as shown. Find its modulation index.
Define the term modulation. Draw a block diagram of a simple modulator for obtaining AM signal ?
Given modulation index physical significance .For an amplitude modulated wave, the maximum amplitude is found to be 10 V while the minimum amplitude is 2 V. Determine the modulation index μ ?
Answer the following question.
Why a signal transmitted from a TV tower cannot be received beyond a certain distance? Write the expression for the optimum separation between the receiving and the transmitting antenna.
A 100 m long antenna is mounted on a 500 m tall building. The complex can become a transmission tower for waves with λ.
A male voice after modulation-transmission sounds like that of a female to the receiver. The problem is due to ______.
A TV transmission tower antenna is at a height of 20 m. How much service area can it cover if the receiving antenna is (i) at ground level, (ii) at a height of 25 m? Calculate the percentage increase in area covered in case (ii) relative to case (i).
A carrier wave Vc(t) = 160 sin(2π × 106t) volts is made to vary between Vmax = 200 V and Vmin = 120 V by a message signal Vm(t) = Am sin(2π × 103t) volts. The peak voltage Am of the modulating signal is ______.
