Modulation refers to the properties of a periodic waveform (that repeats itself over a certain period), named as the carrier signal and the modulating signal. The Carrier signal is a high-frequency signal as compared to the message signal. The modulated signal is the original message signal that contains the information transmitted from the transmitter to the receiver through the communication channel.
For Example:
1. Audio signal
2. Television
In AM, the amplitude of the carrier varies with the amplitude of the message signal. Amplitude Modulation techniques are used to improve the transmission medium's bandwidth utilization and total transmission power.
Modulation in AM
Let's discuss some methods that perform AM modulation:
Types of AM
AM is further categorized as:
In Pulse Modulation, the pulse carries the information. The amplitude, width, and position of the pulse vary with the message signal.
Modulation: Natural Sampling and Flat top sampling are the modulation techniques used in PAM (Pulse Amplitude Modulation). In such types of modulation, the input signal is samples at regular intervals. In PWM (Pulse Width Modulation), a comparator is used to generate a PWM signal. A PPM signal is generated by using a PWM output signal as the input signal.
Types of Pulse Modulation
Pulse Modulation is further categorized as:
Angle Modulation is the combination of frequency and phase modulation. Here, the frequency or phase of the carrier varies with the instantaneous value of the message signal.
Types of Angle Modulation
Angle Modulation is further categorized as:
The modulation process of PM (Phase Modulation) and FM is the same except the integrator that is an additional requirement to generate the output signal in FM (Frequency Modulation). Parameter variation and Armstrong Indirect methods are the modulation methods used in FM. The function of the parameter variation method depends on the VCO (Voltage Controlled Oscillator) to generate the output signal. The Armstrong Indirect method combines carrier signal source, balanced modulator, 90-degree phase shifter, and an adder.
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