Types Of Amplitude Modulation
Amplitude Modulation can be categorized into three main domains:
Double sideband-suppressed carrier modulation (DSB-SC): In this, the frequency spectrum of the modulating signal is symmetrically below and above that of the carrier signal. Sidebands are represented by the incoming information signal’s lower and upper frequencies. Higher frequency components are found in upper sidebands compared to lower sidebands and lower frequency components in carrier frequencies.
Modulation of a single sideband ( SSB): Amplification of single sideband refers to the transmission of only one sideband through an antenna. It has a sideband on either the top or lower half.
Modulation of the Vestigial Sideband (VSB): It is a solution to the problem of distracting noises created as a result of bandpass filter not having the capacity to block off frequencies outside of the cut off zone. In this instance, one of the sidebands ( upper or lower) is transmitted but a part of the other is not.
ITU type designations
In the year of 1982, the International telecommunication Union (ITU) designated the types of amplitude modulation as given in the table below:
|
Designation |
Description |
|---|---|
|
A3E |
DOUBLE-SIDEBAND A FULL CARRIER |
|
R3E |
SINGLE-SIDEBAND REDUCED-CARRIER |
|
H3E |
SINGLE-SIDEBAND FULL-CARRIER |
|
J3E |
SINGLE-SIDEBAND SUPPRESSED-CARRIER |
|
B8E |
INDEPENDENT-SIDEBAND EMISSION |
|
C3F |
VESTIGIAL-SIDEBAND |
|
LINCOMPEX |
LINKED COMPRESSOR AND EXPANDER |
Linear Modulation and Over Modulation
There are two categories of amplitude modulated wave determined from the value of modulation index μ.
Linear Modulation: Linear modulation is observed when the modulation index μ is less than 1.
Over Modulation: Over modulation is observed when the modulation index μ is greater than 1.
Linearly modulated waves are preferred over overly modulated ones. This is due to the fact that the overmodulated wave’s amplitude eventually drops to zero. It indicates that the amplitude is not changed in accordance with the message signal at that point. hence, the signal will be distorted.
Amplitude Modulation – Definition, Types, Expression
Amplitude Modulation or AM, is a modulation technology mainly used for radio carrier wave-based message transmission which modifies the carrier wave’s amplitude (signal intensity) in accordance with the message signal, such as an audio signal, i.e., a modulating signal.
In this article, we will learn what amplitude modulation is, its definition, historical overview, equations to explain the process , its applications in telecommunication, and some related methodologies. We will also solve some numerical problems based on amplitude modulation and attempt to answer FAQs regarding this topic