Analog Modulation & It’s types

Analog modulation is further divided into three types:

 Amplitude modulation.

 Frequency modulation.

 Phase modulation.

Amplitude Modulation:

Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal. Amplitude modulation or AM as it is often called, is a form of modulation used for radio transmissions for broadcasting and two-way radio communication applications. Although one of the earliest used forms of modulation it is still used today, mainly for long, medium, and short-wave broadcasting and for some aeronautical point to point communications. Currently, this technique is used in many areas of communication such as in portable two-way radios, citizens band radio, VHF aircraft radio and in modems for computers. Amplitude modulation is also used to mention the mediumwave AM radio broadcasting.

One of the key reasons for the use of amplitude modulation was its ease of use. The system simply required the carrier amplitude to be modulated, but more usefully the detector required in the receiver could be a simple diode-based circuit. This meant that AM radios did not need complicated demodulators and costs were reduced - a key requirement for widespread use of radio technology, especially in the early days of radio when ICs were not available.

 

In general, amplitude modulation definition is given as a type of modulation where the amplitude of the carrier wave is varied in some proportion with respect to the modulating data or the signal.

Types of Amplitude Modulation:

o Double sideband-suppressed carrier modulation (DSB-SC).

o Single Sideband Modulation (SSB).

o Vestigial Sideband Modulation (VSB).

Advantages of Amplitude Modulation:

• Easier to implement.

• Simple demodulation circuit.

• Cheap receiver.

Disadvantages of Amplitude Modulation:

• AM signal is not efficient in terms of power usages.

• Use of bandwidth not efficient.

• Noise interference is high.

What is Modulation?

Modulation is a process through which audio, video, image or text information is added to an electrical or optical carrier signal to be transmitted over a telecommunication or electronic medium. 

Modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted. Most radio systems in the 20th century used frequency modulation (FM) or amplitude modulation (AM) for radio broadcast. 

Modulation enables the transfer of information on an electrical signal to a receiving device that demodulates the signal to extract the blended information.

Need for Modulation:

Baseband signals are incompatible for direct transmission. For such a signal, to travel longer distances, its strength must be increased by modulating with a high frequency carrier wave, which doesn’t affect the parameters of the modulating signal.

Modulator used for modulation and demodulator used for demodulating signals in its original form. A modem is a common example of a modulation technique in which the data is modulated with electrical signals and transmitted over telephone lines. It is later demodulated to receive the data.

There are basically two methods of modulations:

1.Analog Modulations Method

2.Digital Modulations Method

What is RF?

Radio frequency (RF) refers to the rate of oscillation of electromagnetic radio waves in the range of up to 300 GHz lower range exactly we can't define but we measured it from 9KHz, as well as the alternating currents carrying the radio signals. This is the frequency band that is used for communications transmission and broadcasting. Although RF really stands for the rate of oscillation of the waves, it is synonymous to the term "radio," or simply wireless communication.

 Radio frequency is being used in a lot of fields, but in the context of information and communications technology it refers to the frequency band at which wireless telecommunications signals are being transmitted and broadcast. The frequency band is being divided into different parts, which are then assigned to different technology industries. This is known as the radio spectrum. For example, the VHF (very high frequency) band, which ranges from 30-300 MHz, is being used for FM radio, TV broadcasts, and amateur radio and its counterparts. For a lot of electronic communication devices, the ultra-high frequency (UHF) band is being used. This is the space used by mobile phones, wireless LAN, Bluetooth, and TV and land radio.

Radio frequency is produced by oscillating current a specified number of times and then radiating it off a conductor, referred to as an antenna, into empty space (this refers to space occupied by air rather than solid objects and does not refer to outer space) as electromagnetic radio waves. RF signals are sent and received using conductors through the phenomenon known as the skin effect, where RF current latches itself and flows through the surface of conductors rather than penetrating and passing through them like it does with other non-conducting solids. This effect is the core and basis of radio technology.

What is anAntenna

An Antenna is a transducer, which converts electrical power into electromagnetic waves
and vice versa.
An Antenna can be used either as a transmitting antenna or a receiving antenna.
 A transmitting antenna is one, which converts electrical signals into
electromagnetic waves and radiates them.
 A receiving antenna is one, which converts electromagnetic waves from the
received beam into electrical signals.
 In two-way communication, the same antenna can be used for both transmission
and reception.
Antenna can also be termed as an Aerial. Plural of it is, antennae or antennas. Now-a-
days, antennas have undergone many changes, in accordance with their size and shape.
There are many types of antennas depending upon their wide variety of applications.

Transistor

A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor’s terminals controls the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal.

How it works

A transistor is really simple and really complex. Let’s start with the simple part. A transistor is a miniature electronic component that can do two different jobs. It can work either as an amplifier or a switch:

• When it works as an amplifier, it takes in a tiny electric current at one end (an input current) and produces a much bigger electric current (an output current) at the other. In other words, it's a kind of current booster. That comes in really useful in things like hearing aids, one of the first things people used transistors for. A hearing aid has a tiny microphone in it that picks up sounds from the world around you and turns them into fluctuating electric currents. These are fed into a transistor that boosts them and powers a tiny loudspeaker, so you hear a much louder version of the sounds around you. William Shockley, one of the inventors of the transistor, once explained transistor-amplifiers to a student in a more humorous way: "If you take a bale of hay and tie it to the tail of a mule and then strike a match and set the bale of hay on fire, and if you then compare the energy expended shortly thereafter by the mule with the energy expended by yourself in the striking of the match, you will understand the concept of amplification."
• Transistors can also work as switches. A tiny electric current flowing through one part of a transistor can make a much bigger current flow through another part of it. In other words, the small current switches on the larger one. This is essentially how all computer chips work. For example, a memory chip contains hundreds of millions or even billions of transistors, each of which can be switched on or off individually. Since each transistor can be in two distinct states, it can store two different numbers, zero and one. With billions of transistors, a chip can store billions of zeros and ones, and almost as many ordinary numbers and letters (or characters, as we call them). More about this in a moment.

PLC (Programmable Logic Controller)

A programmable logic controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile memory. A PLC is an example of a hard real time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result.

                                                            

Programmable logic controllers provide dependable, high speed control and monitoring demanded

by a wide variety of automated applications. Before the automotive industry discovered the advantages of PLC’s, the process of modifying relay circuitry was a headache inducing endeavor. In the past, annual car model changes forced plant engineers to constantly modify production equipment managed by relay circuitry. In some cases, the engineers had to scrap entire relay controlled panels and replace them with completely redesigned systems. Now, PLC’s allow engineers to implement numerous manufacturing changes with relative ease, which reduces changeover costs and downtime.  Prior to PLC’s, cont-actor or relay controls solved many of these control tasks. This is often referred to as hardwired control. Electricians had to design circuit diagrams, specify and install electrical components, and create wiring lists before wiring the components necessary to perform a specific task. Design errors would force the electrician to trace the wires to identify the problem and then reconnect the wires. A change in function or a system expansion required extensive component changes and rewiring. Now, PLC software programming makes wiring changes between devices and relay contacts easier. Although hard wiring is still necessary for connecting field devices, it’s less intensive than before.

Door Open Sensor

Each Door Open Sensor is made up of two parts. A magnet and a switch. The magnet will be attached to the door. The switch will be attached to the door frame. Depending on the relative position of magnet and switch, the switch will open or close. With the proper placement, this will allow the detection of the door being opened or closed Once the switch is wired to an input of the Frotcom GPS/GPRS device; these changes will be detected and communicated to the Frotcom Data Center. Then, Frotcom will update the door open status for that vehicle and check for alarm conditions.

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Main features

Here are some of the main features of the Door Open Sensor:

• Thermoplastic enclosure
• Flat design
• Long life
• Non-contacting principle
• 1 reed contact
• Actuating distance up to 60mm
• Actuating surface marked by protrusion
• Pre-wired cable with length 1m
• Protection class IP 67