Digital Modulation: Different Types and Their Differences

Modulation is one type of process used to change the properties of a periodic signal which is known as carrier signal with a modulating signal that normally contains data to be transferred. This technique is frequently used in electronics as well as telecommunications. In the 20th century, most of the radio systems used AM or FM for broadcasting. This article discusses how the data can be communicated in digital form by modulating a carrier waveform. Even though, this method is called as DM (Digital Modulation). Generally, it involves AM (or) FM (or) PM. Therefore digital modulation must be observed the three modulation techniques how they communicating the information in the form of bits. In the rule, the same types of modulator otherwise demodulator can be used as these modulations are used to transmit analog pattern.

What is Digital Modulation?

The term DM stands for digital modulation, and it is a common term for the techniques of modulation. This modulation uses discrete signals for modulating a carrier wave. Indifference, both the amplitude modulation and frequency modulation techniques are analog. Digital modulation removes communication noise as well as provides enhanced strength for the signal intrusion. But, it is not rare to digital modulation schemes for introducing time delay because of the required process. To avoid this, a comfort SST (Secure Stream Technology) audio is designed.

Digital Modulation (DM) gives more capacity of data, high information security, and accessibility of a faster system by enormous quality communication. Therefore, DM techniques have a huge demand due to their capacity for communicating superior amounts of information than AM (analog modulation) techniques.

Types of Digital Modulation

There are several kinds of digital modulation techniques are available based on the requirement which includes the following.

  • ASK or Amplitude shift Key
  • FSK or Frequency shift key
  • PSK or Phase shift key

1) ASK (Amplitude Shift Keying)

In amplitude shift keying, once the instant amplitude of the carrier signal is changed in quantity toward m(t) message signal. For instance, if we have the modulated carrier (m(t) coswct) then the carrier signal will be coswct. Because the data is an ON/OFF signal, and the output is also an ON/OFF signal wherever the carrier is there when data is 1, as well as the carrier, is not present when data is 0. Therefore this modulation scheme is called as OOK or on/off keying (OOK) otherwise amplitude shift keying or ASK. The applications of ASK mainly include IR remote controls and fiber optic transmitter & receiver.

Amplitude Shift Keying
Amplitude Shift Keying

2) FSK (Frequency Shift Keying)

In frequency shift keying, when the immediate frequency of the carrier signal is changed then the information will be transmitted. In this type of modulation, carrier signal has two pre-defined frequencies namely wc1, and wc2. Whenever the data bit is ‘1’ then the carrier signal by wc1 is transmitted that is coswc1. Similarly, when the data bit is ‘0’ then the carrier signal by wc0 will be transmitted that is coswc0. The applications of frequency shift keying mainly include several modems in telemetry systems and phase shift keying.

Frequency Shift Keying
Frequency Shift Keying

3) PSK Digital Modulation(Phase Shift Keying)

In phase shift keying, the instant phase of the carrier signal is moved for this modulation. If the m(t) baseband signal is =1 then the carrier signal within phase will be transmitted. Similarly, If the baseband signal m(t)=0 then the carrier signal by out of phase is transmitted that is cos(wct+П). If phase shift can be done in four dissimilar quadrants then 2-bit of data will be transmitted at once. This method is an individual case of phase shift keying modulation which is known as Quadrature Phase Shift Keying or QPSK. The applications of phase shift keying include a broadband modem (ADSL), satellite communications, mobile phones, etc.

Phase Shift Keying
Phase Shift Keying

4) M-Ary Digital Modulation

In this modulation technique, two or more bits are made for transmitting at once on a single signal, and then it will help in reducing the bandwidth. These techniques are classified into three types namely M-ary ASK, M-ary FSK, and M-ary PSK.

Difference between Analog and Digital Modulation

The difference between Analog Modulation and Digital Modulation include the following.

 Analog Modulation

Digital Modulation

An AM signal can signify any value in a range.

A DM signal can only signify with a set of discrete values.

 

In analog modulation (AM), the input must be in the form of analog

 

In digital modulation (DM), the input must be the data in the form of digital

 

In AM, the value between the max & min is considered to be applicable.

 

In DM, only two binary numbers are considered applicable such as 1 and 0.

 

Most of the signals that we transmit in nature are analog like voice signal, and  it is much simpler to complete analog modulation compare with digital

But using digital modulation, you require transmitting through an ADC converter before transmission & a DAC at the end of the receiver for recovering the unique signal. The extra phases required to transmit DM (digital modulation) enhances both the price and difficulty of the transmitter as well as receiver.

 

The AM can generate a signal to carry the frequently changing data.

 

The DM generates a signal whose rate changes at particular time intervals.

 

In AM, it is not easy to disconnect the signal from noise. In DM, the signal can simply disconnect from noise.

 

Thus, this is all about an overview of digital modulation methods. This modulation offers more capacity of data, digital data services with compatibility; data security is high, good communication quality, and faster system accessibility. These modulation schemes have a better capacity for conveying a huge amount of data than AM schemes (analog modulation).



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