Research Design

Research design can be thought of as the structure of research it is the glue that holds all of the elements in a research project together. We often describe a design using a concise notation that enables us to summarize a complex design structure efficiently. The elements that a design includes are:-

1.Observations or Measures:-

These are symbolized by an o in design notation . An o can refer to a single measure a single instrument with multiple items , a complex multi-part instrument , or a whole battery of tests or measures given out on one occasion. If you need to distinguish among specific measures, you can use subscripts with the o, as in o1, o2, and so on.

2.Treatments or Programs:-

These are symbolized with an x in design notations. The x can refer to a simple intervention or to a complex hodgepodge program . Usually, a no- treatment control or comparison group has no symbol for the treatment. As with observations, you can use subscripts to distinguish different programs or program variations.

3. Groups:-

Each group in a design is given its own line in the design structure , if the design notation has three lines, there are three groups in the design.

4.Assignment to Group:-

Assignment to group is  designated by a letter at the begninning of each line that describes how the group was assigned.

The major types of assignment are:

R=random assignment

N=nonequivalent groups

C=assignment by cutoff

Time time moves from left to right. Elements that are listed on the left occur before elements that are listed on the right.

Design Notation Examples-

Its always easier to explain design notation through examples than it is to describe it in words. The figure shows the design notation for a pretest - posttest treatment versus comparison group randomized experimental design each of the parts. There are two lines in the notation, so you should realize that the study has two groups. There are four os in the notation, two on each line and two for each group. When the os are stacked vertically on top of other it means they are collected at the same time. In the notation you can see that we have two os that are taken before any treatment is given - the pretest - and two os taken after the treatment is given - the posttest. The R at the beginning of each line signifies that the two groups are randomly assigned . The design is a treatment versus comparison group one because the top line has an x while the bottom line does not. You should be able to see why many of my students have called this type of notation the tic - tac - toe  method of design notation -  there are lots of xs and  sometimes we have to be more specific in describing the os or xs than just using a single letter. In the second figure, we have the identical research design with some subscripting of the os. What does this means?

Because all of the os have a subscript of 1 there is some measure or set of measures that is collected for both groups on both occasions. But the design also has two os with a subscript of 2 both taken at the posttest. This means that there was some measure or set of measures that were collected only at the posttest.

With this simple set of rules for describing a research design in notational form, you can concisely explain even complex design structures. And , using a notation helps to show common design sub - structures across different designs that we might not recognize as easily without the notation.

Generation of Amplitude Modulation (AM).

The device which is used to generate an amplitude modulation (AM) wave is known as amplitude modulator. The methods as amplitude modulator Generation may be broadly classified as following:-

1) Low level AM Modulation.

2)High level AM Modulation.

1)Low Level Amplitude Modulation:-

Figure shows  the block diagram of a low level AM modulation system. In a low level amplitude modulation system, the modulation is done at low power level. At low power levels, a very small power is associated with the carrier signal and the modulation signal. Because of this the output power of modulation is low. Therefore the power amplifiers are required to boost the amplitude modulated signals up to the desired output level.

 From block diagram in figure it is clear that modulation is done at low power level. After this the amplitude modulated signal is applied to a wide band power amplifier . A wide band power amplifier is used just to preserve the sidebands of the modulated signal. Amplitude modulated systems , employing modulation at low power levels are also called low level amplitude modulation transmitters.

Square-law diode modulation and switching modulation are examples of low-level modulation.

2)High level Amplitude Modulation:-

Figure  shows the block diagram of a high level AM modulation system. In a high-level amplitude -modulation system, the modulation is done at high power level. Therefore, to produce amplitude modulation at these high power levels, the base band signal and the carrier signal must be at high power levels. In block diagram of figure the modulating signal and carrier signal are first power amplified and then applied to AM  high level modulator. For modulating signal the wide band power amplifier is required just to preserve all the frequency components present in modulating signal.

On the other hand for carrier signal , the narrow band power amplifier is required because it is a fixed frequency signal. The collector modulation method is the example of high level modulation. Before we discuss low level and high level modulation methods in detail, we shall establish the fact that a non- linear resistance of non linear device can be made to produce amplitude modulation when two different frequencies are passed together through it.

Pulse Amplitude Modulation (PAM).

Pulse amplitude modulation may be defined as that type of modulation in which the amplitudes of regularly spaced rectangular pulses vary according to instantaneous value of the modulating or message signal . In fact the pulses in a PAM signal may be of flat top type or natural type or ideal type. Actually all the sampling methods which have been discussed in last sections are basically pulse amplitude modulation methods. Out of these three pulse amplitude modulation methods the flat top PAM is most popular and is widely used. 

The reason for using flat top PAM is that during the transmission the noise interferes with the top of the transmitted pulses and this noise can be easily removed if the PAM pulse has flat top. However , in case of natural samples PAM signal the pulse has varying top in accordance with the signal variation. Now when such type of pulse is received at the receiver it is always contaminated by noise. Then it becomes quite difficult to determine the shape of the top of the pulse ans thus amplitude detection of the pulse is not exact. Due to this errors are introduced in the received signal. Therefore, flat top sampled PAM is widely used signal. 

Working Principle:- 

A sample and hold circuit shown in fig. is used to produce flat top sampled PAM . The working principle of this circuit is quite easy. The sample and Hold circuit consists of two field 

effect transistors (FET) switches and a capacitor. The sampling switch is closed for a short duration by a short pulse applied to the gate G1 of the transistor . During this period the capacitor C is quickly charged up to a voltage equal to the instantaneous sample value of the incoming signal x(t) . Now the sampling switch is opened and the capacitor C holds the charge. The discharge switch is then closed by a pulse applied to gate G2 of the other transistor . Due to this the capacitor C is discharged to zero volts. The discharges switch is then opened and thus capacitor has no voltage.

Hence the output of the sample and hold circuit consists of a sequence of flat top samples .

Research Process

Research process consists of series of actions or steps necessary to carry out research and the desired sequencing of these steps:-

A brief description of these steps is as follows-

1.Formulation

2.Review of Literature

3.Formulation of hypothesis

4.Research Design

5.Determining Sample design

6.Collection of Data

7.Execution of project

8.Analysis of Hypothesis

9.Testing of Hypothesis

10.Generations and Interpretations

11.Preparation of Research Report

1.Formulation  of research problem-

the first step in any research is to formulate a research problem

There are basically 2 steps of research problem:

1.problem which relates to state of nature.

2.problem which relates to relationship between variables

At the very beginning researcher must identity the problem be wants to study.

Essentially two steps are involve in formulation a research problem

1.Understanding the problem thoroughly and the best way of it is to discuss it with ones own colleagues or the experts in that matter.

2.Rephrasing the problem in to meaningful terms from an analytical point of view.
2.Review of Literature-

 After the problem is formulated, a brief summary of it should be written down and this summary is known as synopsis an for getting phd degree it is necessary to submit it to the committee or research board for approval. At this time the researcher should undertake extensive literature survey connected

with the problem. For this purpose journals and published / unpublished bibliographies are first place to go to. The other things that can be referred are academic journals, conference proceedings, Government reports, books, internet sites etc.

3.Formulation of Hypothesis-

 After extensive literature survey, the next step is to formulate working hypothesis. Hypothesis is a tentative assumption made in order to draw out and test its logical consequences. Hypothesis should be very specific and limited to the piece of research in hand because it has to be tested. The role of hypothesis is to guide the researcher by delimiting the area of research and to keep him on the right track. It sharpens the thinking of researcher & focuses attention on more important facts of the problem.

4.Preparation of Research Design-

The next step is to prepare a conceptual structure within which research would be conducted. The function of research design is to provide for the collection of relevant information and evidence with minimum expenditure of effort , time and money.

research objective / purpose may be grouped into 4 categories..

1.Exploration

2.Description 

3.Diagnosis

4.Experimental/Hypothesis

The research design should be flexible and it should provide apportunity for considering many different aspects of a problem fit is of exploratory nature.
The following points should be considered while preparing a research design:
1.The means of obtaining information.
2.The availability and skill of researcher and his staff.
3.The time available for research.
4.The cost factor relating to research i.e finance available for research . There are number of research design such as: Experiment and non Experiment research design.
5.Determining Sample Design:-
All the items under consideration in any field of enquiry or research constitute a universe or population. If all these items are included in our study then it is known as census method of enquiry.
For example
1.Random Sampling
2.Systematic Sampling
3.Stratified Sampling
Non probability samples are those in which there is some bias on the part of researcher.
6.Collection of Data:-
For carreing out any research successfully data collected should be adequate and should be based on nature of enquiry.
There are several ways of collecting data and these differ on the basis of time cost money cost and other resources at the disposal of research.
The data to be collected is of 2 types.
1.Primary data is data which is collected for the first time by researcher himself.
2.Secondary data is data which has been collected by someone else earlier and is used by research for his research.
7.Execution of Project:-
It is a very important step in research process. The data collected would be adequate and dependable if project is executed in right manner. The research should see that project is executed in a systematic manner and within prescribed time.
If data is to be collected by interviews then steps should be taken for selection of right person and proper training should be given to him. Occasional field check should be made to ensure that interviewers are doing their assigned job efficiently and sincerely.If details to be collected by means of structure questionarie then questions as well as answers should be coded so the data can be readily matching processed.
8. Analysis of data:-
Analysis of data refers to computation of certain measures along with serearching for pattrens of relationship that exist among data groups.It requires editing classification and codification of data tabulation and then drawing statistical interference out of arranged data. After tabulation of data analysis process involves calculation of various percentages coefficient etc. By applying various statical methods and tools so as to find out whether observation support theory on not . In this case our problem will be whether the two means value differ significantly or the difference  just due to fluctuations of sampling.

 9.Testing of Hypothesis:-
After data has been analysed the research is in a position to test the hypothesis formed earlier. He has to test whether the facts support the hypothesis or not? The various test such as t test z test chi sequar test f test have been designed for this purpose . Hypothesis may be tested either by using one test or one or more test depending upon the object and significance of research study.
10.Generalization and interpretations:-
When Hypothesis is tested and up held several times then it is possible for researcher to build a theory . This is known as Generalization.
If there is no hypothesis then researcher might explain his findings on the basis of some theory . This process is known as interpretation.
11.Preparation of research report:-
The last step in research process is to prepare report of what has been done or achieved by him .It is not an easy task and proper care should be kept while preparing it.
It may stood as follows .
1.Preliminary pages-
Title page
Acknowledgment
Preface
Table of contents
List of tables and charts etc.
2.Main text
Introduction
Main report
Summary of findings
Conclusion
Suggestions
3.The End matter.
Appendics
Bibliography etc.

555 Timer.

The 555 IC  is available as an 8-pin metal can, an 8-pin mini DIP(dual-in-package) or a 14-pin DIP, This IC consists of 23 transistors , 2 diodes and 16 resistors. The explanation of terminals coming out of the timer IC is as follows. The pin number is used in the following discussion refer to the 8-pin DIP and 8-pin metal can packages.

Pin1: grounded Terminal-

All the voltages are measured w.r.t this terminal.

Pin2: Trigger Terminal-

This pin is an inverting input to a comparator that is responsible for transition of flip-flop from set or reset. The output of the timer depends on the amplitude of the external trigger pulse applied to this pin.

Pin3: Output Terminal-

Output of the timer is available at this pin. There are two ways in which a load can be connected to the output terminal either between pin3 and ground pin or between pin3 and supply pin .The load connects between pin3 and supply in is called the normally  on load and that connected between pin 3 and ground pin is called the normally off load.

Pin4: Reset Terminal-

To disable or reset the timer a negative pulse is applied to this pin due to which it is referred to as reset terminal. When this pin is not to be used for reset purpose. It should be connected to +vcc to avoid any possibility of false triggering.

Pin5: Control Voltage Terminal-

The function of this terminal is to control the threshold and trigger levels. Thus either the external voltage or a pot connected to this pin determines the pulse width of the output waveform. The external voltage applied to this pin can be used to modulate the output waveform. When this pin is not in used , it should be connected to ground through a 0.01uf to avoid any noise problem.

Pin6: Threshold Terminal-

This is the non-inverting input terminal of comparator 1, which compares the voltage applied to this terminal with s reference voltage of +2/3 vcc . The amplitude of voltage applied to this terminal is responsible for the state of flip-flop.

Pin7: Discharge Terminal-

This pin is connected internally to the collector of transistor and mostly a capacitor is connected between this terminal and ground. It is called discharge terminal because when transistor saturates ,capacitor discharges through the transistor. When transistor is cutoff, the capacitor charges at a rate determined by external resistor and capacitor.

Pin8: Supply Terminal-

 A supply voltage of +5v to   +18v is applied to this terminal with respect to ground .

The timer combines a relaxation oscillator, two comparators, an R-S flip-flop and a discharge capacitor.R-S flip -flop A pair  of cross-coupled transistors each collector drives the opposite base through resistance.On the other hand if transistor Q1 is cut off, its collector voltage , which is approximately equal to _vcc . drives the transistor Q2 into saturation. The low collector voltage of this transistor then keeps the transistor Q1 in cutoff.

Depending on which transistor is saturated, the Q output is either low or high. By adding more components to the circuit , an R-S flip-flop is obtained , R-S flip-flop is a circuit that can set the Q output to high or reset it low. The circuit latches in either two states. A high S input sets Q to high a high R input  resets Q To low. Output Q remain in given state until it is triggered into the opposite state.

Noise Analysis.

Electrical noise is defined as any undesirable electrical energy that falls within the pass band of the signal. For example in audio recording any unwanted electrical signal that fall within the audio frequency band of o hz to 15khz will interfere with the music and therefore be considered noise. The effect that noise has on an electrical signal. A sin wave without noise same signal except in the presence of noise. The grassy-looking squiggles superimposed on the sine wave are electrical noise, which contains a multitude of frequencies and amplitudes that can interfere with the quality of the signal.

Noise can be divided into general categories ; correlated and uncorrelated . Correlation implies a relationship between the signal and the noise. Therefore correlated noise exists only when a signal is present . Uncorrelated noise on the other hand is present all the time whether there is a signal or not.

Uncorrelated noise is present regardless of whether of there is a signal present or not. Uncorrelated noise can be further subdivided into two general categories: external and internal.

External noise is noise that is generated outside the device or circuit . The three primary sources of external noise are atmospheric, extraterrestrial, and man-made. Atmospheric noise is naturally occurring electrical disturbances that originate within earth s atmosphere. Atmospheric noise is commonly called static electricity and is the familiar sputtering , crackling , and so on often heard from a speaker when there is no signal present. The source of most static electricity is naturally occurring electrical conditions, such as lighting. static electricity is often in the form of impulses that spread energy throughout a wide range of frequency. The magnitude of this energy however is in inversely proportional to its frequency. Consequently at frequencies above 30 Mhz or so , atmospheric noise is relatively insignificant.

Extraterrestrial noise; Extraterrestrial noise consists of electrical signals that originate from outside earth s atmosphere and is therefore sometimes called deep-space noise. Extraterrestrial noise originates from the milky way, other galaxies, and the sun. Extraterrestrial noise is subdivided into two categories: solar and cosmic.

Solar noise is generated directly from the sun s heat. There are two parts to solar noise :  quiet condition , when a relatively constant radiation intensity exists, and high intensity , sporadic disturbances caused by sunspot activity and solar flare-ups. The magnitude of the sporadic noise caused by sunspot activity follows a cyclic pattern that repeats every 11 years.

Cosmic noise, sources are continuously distributed throughout the  galaxies. because the sources of galactic noise are located much farther away than our sun, their noise intensity is relatively small. Cosmic noise is often called black-body noise and is distributed fairly evenly throughout the sky.

Man-made noise man made noise is simply noise that is produced by mankind . The predominant sources of man made are spark producing mechanisms, such as commutators in electric motors, automobile ignition systems . ac power generating and switching equipment , and fluorescent lights.

Man made noise is impulsive in nature and contains a wide range of frequencies that are propagated through space in the same manner as radio waves. Man made noise is most intense in the more densely populated metropolitan and industrial areas and is therefore sometimes called industrial noise.

Internal noise: Internal noise is electrical interference generated within a device or circuit . There are three primary kinds of internally generated noise; shot transit time and thermal. Short noise is caused by the random arrival of carries at the output element of an electronic device ,such as a diode , field -effect transistor, or bipolar transistor . Short noise was first observed in the anode current of a vacuum-tube amplifier and was described mathematically by W.Schottky in 1918. The current carriers are not moving in a continuous, steady flow as the distance they travel varies because of their random paths of motion. Short noise is randomly varying and is superimposed onto any signal present.

When amplified short noise sounds similar to metal pellets falling on a tin roof . Short noise is sometimes called transistor noise and is additive with thermal noise.Transit-time noise and modification to a stream of carriers as they pass from the input to the output of a device produces an irregular, random variation categorized as transit-time noise . When the time it takes for a carrier to propagate through a device is an appreciable part of the time of one of the signal the noise becomes noticeable. Transit-time noise in transistor is determined by carrier mobility, bias voltage and transistor construction.

Carriers traveling from emitter to collector suffer from emitter time delays, base transit time delays and collector recombination time and propagation time delay . If transmit delays are excessive at high frequencies the device may add more noise than amplification to the signal. Thermal noise thermal noise is associated with the rapid and random movement of electrons within a conductor due to thermal agitation. The English botanist Robert Brown first noted this random movement . Brown first observed evidence for the moving particle nature of matter in pollen grains and later noticed that the same phenomenon occurred with smoke particles.

Thermal noise is present in all electronic components and communications systems. Because thermal noise is uniformly distributed across the entire electromagnetic frequency spectrum , it is often referred to as white noise. Thermal noise is a form of additive noise , meaning that it cannot be eliminated , and it increase in intensity with the number of devices in a circuit and with circuit length.

Therefore thermal noise sets the upper bound on the performance of a communication system.

Propagation of electromagnetic waves.

Electromagnetic waves traveling within earth s atmosphere are called terrestrial waves and communications between two or more points on earth is called terrestrial radio communications. Terrestrial waves are influenced by the atmosphere and earth itself. In terrestrial radio communications, electromagnetic waves can be propagate in several ways , depending on the type of system and the environment. As previously explained electromagnetic waves travels in straight lines except when earth and its atmosphere alter their path. Essentially there are three ways of propagating electromagnetic waves within earths  atmosphere ground wave space wave and sky wave propagation.

The three modes of propagation possible between two radio terrestrial antennas. Path 1 a direct or free-space wave, path 2 a ground - reflected wave. Direct and ground - reflected waves together are called space waves. Path 3 a surface wave which consists of the electric and magnetic fields associated with the currents induced in the ground. The magnitude of the ground current depends on the constants of the ground and the electromagnetic waves propagation. The cumulative sum of the direction ground - reflected , and surface waves is sometimes referred to as the ground wave, which is confusing because a surface wave by itself is also sometimes called a ground wave. Path 4 is called the sky wave which depends on the presence of the ionized layers above earth that returns some of the energy that otherwise would be lost in outer space.

Each of the four propagation modes exists in every radio system;however some are negligible in certain frequency ranges or over a particular type of terrain. At frequencies below approximately 2mhz , surface waves provide the best coverage because ground losses increase rapidly with frequency .Sky waves are used for high frequency applications , and apace are used for very high frequencies and above.

A surface wave propagation is an earth guided electromagnetic wave that travels over the surface of earth. As a surface wave moves over earth s surface , it is accompanied by charges induced in the earth. The charges move with the wave producing a current . Since the earth offers resistance to the flow of current , energy is dissipated in a manner very similar to those in a transmission line. Earth s surface also has dielectric losses. Therefore surface waves are attenuated as they propagate . because energy is absorbed from the surface wave , the portion of the wave in contact with earth s surface is continuously wiped out. The energy is replenished by diffraction of energy downward from the portion of the ground wave immediately above earth s surface. This phenomenon produces a slight forward tilt in the wavefront .

Attenuation of the surface wave due to absorption depends on the conductivity of earths surface and the frequency of the electromagnetic wave. Surface waves propagate best over a good conductor. It is apparent that the best surface wave transmission occurs over seawater and that the highest degree of attenuation is over jungle areas. Attenuation over all types of terrain increases rapidly with frequency . Extremely high losses make it impractical to use surface waves for long -distance transmission of high-frequency electromagnetic waves.

Ground wave must be vertically polarized because the electric field in a horizontally polarized wave woulds be parallel to earth s surface and such waves would be short circuited by the conductivity of the ground. Earth s atmosphere has a gradient density which also causes the wavefront to tilt progressively forward. Therefore the wave propagates around the earth remaining close to its surface , and if enough power is transmitted, the wavefront could propagate beyond the horizon or even around the entire circumference of the earth.

However , care must be taken when selecting the frequency and terrain over which surface waves will propagate to ensure that the wavefront does not tilt excessively and simply turn over , lie flat the ground and case to propagate.Surface wave propagation is commonly used for ship-to-ship ans ship-to-shore communications, for radio navigation and for maritime mobile communications. Surface waves are used at frequencies as low as 15khz.