Showing posts with label Communication Systems. Show all posts
Showing posts with label Communication Systems. Show all posts

Semi Conductor Electronics and Communication Systems Complete Lesson

Semiconducting material has conducting nature in between conductors and insulators. At absolute zero temperature the behaves like insulators and at increased temperature they can be have like conducting materials. Silicon and germanium are simple examples of the semiconducting materials which are also called as intrinsic type of semiconducting materials as well as called as pure semiconducting materials. 

 We can modify them as per requirement by adding a small amount of impurities and that phenomena is called as dooping. When you add impurities,we will be getting two types of semiconducting materials called P type and N type. Using this materials we can make electronic devices like diodes, transistors and integrated chips. Here we are going to identify how they are going to work. We are also going to discuss a little bit of digital electronics and  some discussion about logic Gates.

Communication system is a way of communicating information from one place to another place using a channel. There are basically three different types of communications like ground wave communication, sky wave communication and space wave communication.

Here we are going to list out all the posts that are linked with this topics is given below in a systematic order .

Intrinsic and Extrinsic Semi Conducting Materials

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Sky Wave and Space Wave Propagation and Modulation

Sky wave propagation

There are different ways of propagation in this sky wave propagation. The first possibility is to use a particular tower who can communicate with the help of a tower of a particular height. 

 This kind of the signals are released into the space are to be further communicated to a specific region. The distance up to with the signal can reach depend on the height of the tower as well as the radius of the earth which is of course a constant value.

Once if you know the distance up to where it can travel, taking the point of the tower as a reference and the distance is a radius we can draw a circle and that is the area up to where the signal can be reached.

 If you know the number of the people existing in the given place per unit area which is also called as population density,we can calculate the total number of the people that can receive the signal with the help of this tower. This is simply done by multiplying the area with the population density.



We can use line of sight concept by using the two Towers as a part of a sky wave propagation. Here instead of one tower we will use two towers therefore we can increase the range of the signal communication significantly.

 The concept is actually the same but just at the ending of the transmitting range of the one tower we are going to put another tower who is having a beginning of the receiving range. Thus we are able to cover the double area that what we have covered in the previous case therefore it is more reachable to people. The maximum possible distance between the two Towers shall be the sum of the distances up to where the first tower can send the signal and the second tower can receive the signal.



Problem and Solution One

Here we are going to solve small problem basing on the concept of the height of the tower  or  the transmitting antenna. When the distance up to where the signal has to be reached is given,we can calculate the corresponding requirement of the height of the tower as shown below.



Problem Two and Solution

Consider solving one more problem basing on the concept of the line of sight as shown below. In this problem we would like to calculate the height of the transmitting antenna as well as the receiving antenna when the maximum distance between the towers is given to you and the ratio of the heights of the towers is given as shown below.



There is a third possibility in the sky wave propagation that is by using the particular layer of the atmosphere that is there. Above the surface of the earth we have different layers.We can use ionosphere as a reference which can reflect a particular signal frequency. Of course this can do the job only for a particular frequency and once if that frequency range is crossed, the signal is going to overshoot the layer therefore it will never reach the destination and the receiving antenna.



Space wave communication

In this kind of communication we are going to depend on satellites rather than depending on the nature like ground and space. An artificial satellite is a man-made satellite that is being sent into the space for the particular needs and satisfactions of the communications and for some other purposes.Now a days we are having a satellites called as geostationary satellites.They always appear stationary from the surface of the earth. It is just because they have the time period similar to the  earth  that is 24 hours and rotating from west to east.

This kind of satellites will have dedicated transponders who can receive and send the signals of particular frequency ranges. Using a transmitting antenna on the ground and the receiving antenna in the devices we can use a satellites very effectively for a very nice communication.This is the most dependable communication kind of the system  as of now and are used very much widely for Telephonic  communications  like cell phone communications, Internet communications and the TV.



When you are sending the signal via the space wave communication there is one important issue that the signal itself is not good enough to travel for that much longer distance and come back via the satellite.We need to give enough strength for the signal to travel to this much long distances by adding extra career to that and the phenomenon of adding a career like this is called as modulation.

Technically there are different types of modulations like amplitude modulation, frequency modulation and phase modulation. In the case of the amplitude modulation we are going to add a particular signal who is having a higher amplitude to the massage signal, in the case of a frequency modulation we are going to add a high-frequency signal to pass the massage signal.  Phase modulation is a way of modulation such that will be passing the message from one place to another place by adding a specific phase.

At the input level,with the message signal this modulation signal is also attached with a device called modulator.This will add the required carrier signal to you the strength for communication and then further passed to a transmitting antenna. At the receiving level there will be another demodulator which can eliminate the carrier signal therefore the original message signal can be reached without any serious loss.



Amplitude modulation

The phenomenon of adding a higher amplitude to the original message signal as a carrier signal is called as a amplitude modulation. The impact of the message signal on the carrier signal is as shown below.The amplitude modulated signal will have a range of angular velocity as the sum and difference of the angular velocity of the message signal and the carrier signal as shown below.




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Intrinsic and Extrinsic Semi Conducting Materials
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Communication systems Overview

Communication is one of the very important part of a human being’s evolution.Without having a proper communication among the human beings, we cannot imagine the evolution of the world to the bitter place like that is existing right now. That is why,from the beginning human beings has put is a sustained and serious effort in developing a communication system from one person to another person from one place to another place.

Language is the first way of communication among the people. People tried very hard to make up a language which is understandable for everybody.Right from the human birth,we struggle a lot to learn a language so that we can communicate. There are broadly two types of communications like one-to-one communication and one to many communication.Telephonic conversation is a simple example of a one-to-one communication whereas a TV and the radio is a one to many communication systems.

Communication simply is a act of transmission of information from one place to another place. If you want to communicate with a large gathering we can simply use a microphone which will make you are able better when compared with the solo voice. But anyway this way of communication is limited to a very small region and if you want to communicate to a very large area like a big city, any kind of big Microphone is not going to be sufficient. This kind of a communication system needs a particular process which requires a transmitter which emits the signal, a channel which acts like a media to communicate the signal from one place to another place and a receiver who can receive the information.

At the level of the channel there is always a possibility of getting a noise added and this kind of the phenomena is called distortion. To eliminate this kind of the problems we will fine-tune the circuit. It is done with the filter circuits.The channel could be a wired one or a wireless one depending on the type of the communication.



There are different ways of the messages that you can communicate from one place to another place like it could be a speech, music  or a  video. To communicate each of this kind of information a particular frequency will be more suitable.The table is being given below.




Ground Wave communication

There are broadly three ways of communication from one place to another place.The oldest type of the communication system is ground wave communication or ground wave propagation. This kind of a communication system will be having a particular antenna ,which will release the signal into the air and that signal is going to travel over the surface of the earth taking the earth as a reference.

Ground wave communication has broadly two issues. The first one is the size of the antenna. As for the practical observations.the height of the antenna required shall be at least equal to 1 by fourth of the wavelength of the signal that we want to pass. In all practical ways, we can thus send only low wave length and hence this kind of propagation is not possible.




The other serious issue that this ground wave communication has is having a clean surface. The signal that has to pass be passed on the surface of the ground can reach the destination only when the surface is in a comfortable mode such that there is no obstructions .But in a day-to-day life,all these surfaces are filled with buildings, trees, towers, minerals, hills and hence all these obstacles will absorb a portion of the  signal.Hence it will be never able to reach the destination successfully without any serious  loss. Because of this two basic reasons,now a days people are not using a ground wave communication system.

Sky wave propagation

There are different ways of propagation in this sky wave propagation. The first possibility is use a particular tower who can communicate and shall have certain height. This kind of the signals are released into the space.They will be  further communicated to a specific region. The distance up to with the signal can reach depend on the height of the tower as well as the radius of the earth  is of course a constant value.

Once if you know the distance up to where the signal can travel,taking that tip of the tower as a reference and the distance as a radius,we can draw a circle and that is the area up to where the signal can be reached. If you know the number of the people existing in the given place per area which is also called as population density we can calculate the total number of the people that can receive the signal with the help of this tower. This is simply done by multiplying the area with the population density.


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Intrinsic and Extrinsic Semi Conducting Materials
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