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difference between analog modulation and digital modulation | analog modulation vs digital modulation

This page compares analog modulation vs digital modulation and describes difference between analog modulation and digital modulation.

Before jumping to difference between analog and digital modulation types let us understand about modulation basics. Modulation makes it possible to transmit analog or digital signal over the air or through the wired medium from one end to the other.

Any modulation block consists of input signal, carrier signal and output signal. Input signal is information either in analog form or digital form which need to be transmitted. Input signal is designated as modulating waveform or modulating signal. Carrier signal is usually high frequency signal. The output signal is designated as modulated waveform or modulated signal.

Analog Modulation


Analog modulation-amplitude modulation Fig.1 Analog Modulation (AM example)

Analog modulation is the term refers to modulation of the analog signals. The figure-1 depicts this type of modulation with AM as example. As shown here input signal and carrier signal both are analog in nature. The parameters of carrier i.e. amplitude or frequency or phase is varied according to the input frequency signal.

Examples:
• AM (Amplitude Modulation): Ampitude of the carrier varies according to amplitude of analog input signal.
• FM (Frequency Modulation): Frequency of the carrier varies according to frequency of analog input signal.
• PM (Phase Modulation): Phase of the carrier varies according to phase of analog input signal.
Refer


Digital Modulation

Digital modulation-ASK modulation
Fig.2 Digital Modulation (ASK example)

Digital modulation is the term refers to modulation of the digital signals. The figure-2 depicts this type of modulation with ASK as example. As shown here input signal is digital while carrier signal is in analog form. Here, based on digital signal input i.e. logic 1 or logic 0, carrier frequency is manipulated before transmission.

Examples:
ASK (Amplitude Shift Keying): The carrier signal with constant amplitude and frequency is present when binary 1 digital signal is being transmitted. No carrier during binary 0 transmission period.
FSK (Frequency Shift Keying): The carrier signal with different frequencies are transmitted during binary 1 and binary 0 periods.
PSK (Phase Shift Keying): The carrier signal with different phases are transmitted during binary 1 and binary 0 period.

The other examples of digital modulation techniques include BPSK, QPSK , QAM, 8PSK etc.

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