Analog Modulation Systems

 Introduction

Analog modulation systems are of 3 types .They are

Amplitude modulation(AM)

Pulse modulation

Angle modulation

and again the angle modulation is divided into two types they are Frequency modulation (FM), Phase modulation(PM).

Amplitude Modulation(AM)

In amplitude modulation method, the carrier is a sinewave with frequency fc. The carrier  frequency is much higher than the frequency of the modulating signal(fm). The amplitude of the  carrier varies in proportion to the amplitude of the modulating signal. The amplitude modulated(A.M) signal is transmitted by a transmitter. The  information is contained in its amplitude variation. The frequency of the carrier remains constant. AM is used in radio and TV broadcasting applications.

Frequency Modulation(FM)

In frequency modulation method, the frequency of the carrier is changed in proportion with the amplitude of the modulating signal. Thus, the frequency compression and expansion will take place. The FM signal is transmitted by the transmitter and it carries the information in the frequency variation. The amplitude of the carrier remains constant. Also, FM is used for TV, sound and radio broadcasting and police wireless transmission.

Phase Modulation(PM)

In PM the phase shift of the carrier signal is varied in proportional with the amplitude of the modulating signal. The amplitude of the carrier remains constant. Thus, the information is carried in the phase

variations of the modulated signal. The phase modulated signal is shown. phase modulation is very similar to the frequency modulation. The only difference is that the phase of the carrier is varied instead of varying the frequency. The amplitude of the carrier remains constant. Also, PM is used for generation of FM.