Test: Modulation And Detection Of Signals

The abbreviation WWW means world wide web in communication.

The process of impressing information by changing the original signal is called ‘modulation’, and it is done in a variety of ways. In all cases the radio waves simply act as a vehicle for the information, so they are commonly called ‘carrier waves’.

Attenuation is a general term that refers to any reduction in the strength of a signal. Attenuation occurs with any type of signal, whether digital or analog. Sometimes called loss, attenuation is a natural consequence of signal transmission over long distances.

A repeater is an automated radio station that extends the range of communications.To use a repeater, a user's radio is configured to receive on the repeater's transmitting frequency, and when the push-to-talk button is pressed, transmit on the repeater's receiving frequency.

Amplitude modulation, Frequency modulation and Phase modulation are used for the carrier wave which is a continuous wave whereas Pulse amplitude modulation, Pulse width modulation and Pulse position modulation is used if the wave is not a continuous one and is in the form of pulses.

For maximum value modulation index can be greater than 1 or it can take any value depending on the amount of carrier present in the overall modulated signal. Maximum value of modulation index in 1. Above 1 over modulation occurs which cause distortion of signal. Minimum value is 0.

In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted.

Given, peak voltage of the carrier signal is V_c​=10V and 
 peak voltage of the modulated signal is V_m​=2×1=2V (as peak voltage =2× amplitude of voltage)
Modulation index is defined as, μ= V_m /V_c​​=2/10=0.0.2

Power remains constant irrespective of the modulation index in case of F.M. signal.

Velocity modulation is then defined as that variation in the velocity of a beam of electrons caused by the alternate speeding up and slowing down of the electrons in the beam. This variation is usually caused by a voltage signal applied between the grids through which the beam must pass.