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Am Fm Pm Modulation Comparison Essay

Types of Modulation

Communication is the basic attraction of mankind as it gives the knowledge of what is going on around us. In our daily life, we communicate with many people and use the entertainment media like television, radio, internet and newspaper to get ourselves involved. These entertainment media act as a source of communication. Electronic communication comprises TV, radio, internet, etc. When we want to transmit a signal from one location to another, we have to strengthen the signal. After undergoing strenghthening process the signal travels to a long distance. This is called as modulation, and this article gives an overview of the modulation and types of modulation techniques.

Communication is nothing but, the process of exchanging (two way communication) or passing (one way communication) information from one person to another. The basic electronic communication system consists of these components: transmitter, receiver and communication channel.

Communication System

A transmitter is a group of electronic circuits designed to convert the information into a signal for transmission over a given communication medium.

A receiver is a group of electronic circuits designed to convert the signal back to the original information.

The communication channel is the medium which is designed to transmit the electronic signal from one place to another.

What is Modulation?

Modulation is nothing but, a carrier signal that varies in accordance with the message signal. Modulation technique is used to change the signal characteristics. Basically, the modulation is of following two types:

Modulation Techniques

  • Analog Modulation
  • Digital Modulation

Analog Modulation

In analog modulation, analog signal (sinusoidal signal) is used as a carrier signal that modulates the message signal or data signal. The general function Sinusoidal wave’s is shown in the figure below, in which, three parameters can be altered to get modulation – they are amplitude, frequency and phase; so, the types of analog modulation are:

Analog Modulation

  • Amplitude Modulation (AM)
  • Frequency Modulation (FM)
  • Phase Modulation (PM)

Amplitude Modulation

Amplitude modulation was developed in the beginning of the 20th century. It was the earliest modulation technique used to transmit voice by radio. This type of modulation technique is used in electronic communication. In this modulation, the amplitude of the carrier signal varies in accordance with the message signal, and other factors like phase and frequency remain constant.

The modulated signal is shown in the below figure, and its spectrum consists of the lower frequency band, upper frequency band and carrier frequency components. This type of modulation requires more power and greater bandwidth; filtering is very difficult. Amplitude modulation is used in computer modems, VHF aircraft radio, and in portable two-way radio

Frequency Modulation

In this type of modulation, the frequency of the carrier signal varies in accordance with the message signal, and other parameters like amplitude and phase remain constant. Frequency modulation is used in different applications like radar, radio and telemetry, seismic prospecting and monitoring newborns for seizures via EEG, etc.

This type of modulation is commonly used for broadcasting music and speech, magnetic tape recording systems, two way radio systems and video transmission systems. When noise occurs naturally in radio systems, frequency modulation with sufficient bandwidth provides an advantage in cancelling the noise.

Phase Modulation

In this type of modulation, the phase of the carrier signal varies in accordance with the message signal. When the phase of the signal is changed, then it affects the frequency. So, for this reason, this modulation is also comes under the frequency modulation.

Generally, phase modulation is used for transmitting waves. It is an essential part of many digital transmission coding schemes that underlie a wide range of technologies like GSM, WiFi, and satellite television. This type of modulation is used for signal generation in al synthesizers, such as the Yamaha DX7 to implement FM synthesis.

Types of Analog Modulation

Therefore, Analog modulation includes AM, FM and PM and these are more sensitive to noise. If noise enters into a system, it persists and gets carried up to the end receiver. So, this drawback can be overcome by the digital modulation technique.

Digital Modulation

For a better quality and efficient communication, digital modulation technique is employed. The main advantages of the digital modulation over analog modulation include available bandwidth , high noise immunity and permissible power. In digital modulation, a message signal is converted from analog to digital message, and then modulated by using a carrier wave.

Digital Modulation

The carrier wave is switched on and off to create pulses such that the signal is modulated. Similar to the analog, in this system, the type of the digital modulation is decided by the variation of the carrier wave parameters like amplitude, phase and frequency.

The most important digital modulation techniques are based on keying such as

Amplitude Shift Keying, Frequency Shift Keying, Phase Shift Keying, Differential Phase Shift Keying, Quadrature Phase Shift Keying, Minimum Shift Keying, Gaussian Minimum Shift Keying, Orthogonal Frequency Division Multiplexing, etc., as shown in the figure.

In an Amplitude shift keying, the amplitude of the carrier wave changes based on the message signal or on the base-band signal, which is in digital format. It is sensitive to noise and used for low-band requirements.

In frequency shift keying, the frequency of the carrier wave is varied for each symbol in the digital data. It needs larger bandwidths as shown in the figure. Similarly, the phase shift keying changes the phase of the carrier for each symbol and it is less sensitive to noise.

Types of Digital Modulation

Communication Based Project Ideas

Communication based projects mainly covers a wide range of areas such as GSM, GPS, Bluetooth, RFID, DTMF, Mobile, Ethernet, RF, XBEE, Networking, Data Acquisition and Smart Card. The following is a list of communication based projects for engineering students:

Communication Based Project

These are the different types of modulation in communication system and communication projects. Therefore, the readers, can share their ideas, suggestions and comments in the comment section below.

Filed Under: Communications, Electronics

In radio communication, the message signal wave (low frequency) is combined with a carrier signal (high frequency). In this combination, one or more characteristics of the carrier wave are varied with respect to message signal. This variation is termed as modulation and it is needed so that message can be transmitted over long distances and no undesired signal mixing takes place. Depending on several factors such as range, application and budget, modulation can be casted into three types: Amplitude Modulation, Frequency Modulation and Phase Modulation. Out of these three types, the former two are widely known as they form a major commercially applicative part of radio communication. In this article, we will discuss common difference between AM and FM which will enhance our learning in terms of these two technologies.

1.Evolution: Formulated in the 1870s, AM is a relatively older modulation process compared to FM which was found in the 1930s by Edwin Armstrong.

{      2.Technology:AM stands for amplitude modulation where the amplitude of the carrier is modulated as per the message signal. The other aspects of the carrier wave such as frequency phase etc. remain constant. On the other hand, FM means frequency modulation and in it only frequency of the carrier wave changes while amplitude, phase etc. remain constant.

     3.Frequency range of working: Amplitude modulation works between 540-1650 KHz while FM works at 88-108MHz. 

4. Power Consumption: FM based signal transmission consumes a higher amount of power than an equivalent AM based signal transmission system.

    All Metro and most Tier-2 Cities have their own commercial channels that work on FM

   5. AM vs FM: Signal Quality: Signal quality is a lot superior in FM than AM as amplitude based signals are more susceptible to noise than those which use frequency.  Moreover, noise signals are difficult to filter out in AM reception whereas FM receivers easily filter out noise using the capture effect and pre-emphasis, de-emphasis effects. In capture effect, the receiver locks itself to catch stronger signal so that signals received are more synced with that at the transmitting end.

In pre-emphasis, de-emphasis process, the signal is further amplified to a higher frequency at sending end (pre-emphasis) and vice versa at receiver end (de-emphasis). These two processes reduce down the chances of a signal to get mixed with other signals and make FM more immune to noise than AM.

6.Fading: Fading refers to power variation during signal transmission. Due to fading, the power with the signal received can vary significantly and reception wouldn’t be of a good quality. Fading is more prominent in amplitude modulation as compared to frequency modulation. That is why, AM radio channels often face the problem where sound intensity varies while FM radio channels have constant good reception.

7. Wavelength Difference between AM and FM: AM waves work in the range of KHz while in FM waves work in MHz range. As a result, AM waves have a higher wavelength than the FM ones. A higher wavelength increases the range of AM signals as compared to FM which have a limited area of coverage.

8.Bandwidth consumption: AM signals consume 30KHz of bandwidth for each while in FM 80KHz is the bandwidth consumed by each signal. Hence, over a limited range of bandwidth, more number of signals can be sent in AM than FM.

9.Circuit Complexity: Aforesaid, Amplitude Modulation is an older process and has a very simple circuitry. On the other hand, frequency modulation requires a complicated circuitry for transmission and reception of signal. The signals sent in FM are more modulated and emphasized at the transmitter and they are thoroughly checked and corrected at the receiving end. This is why circuitry for FM signals is very complicated.

10.Commercial Aspects: Setting up an AM based radio communication system is very economic as there is no complicated circuitry and processes are easy to understand.

A few radios come with AM and FM functionality

On the other hand, FM is a fairly complicated communication system and requires high capital investment and expertise at work.  Commercially FM based radio systems are more popular due to high signal quality (especially audio) and more immunity to noise.