Environment Antenna And Wave Propagation By Kd Prasad Pdf


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Documents Similar To Digital Signal Processing by Ramesh Babu. Uploaded by. ajay. EC Antenna Wave Propagation. Uploaded by. Antenna and wave propagation /​ K.D. Prasad. Author. Prasad, K.D.. Other Authors. Handa, Deepak. Edition. 3rd ed. Published. New Delhi: Satya Prakashan. Radio Wave Propagation And Antennas lesson 1 identify characteristics of wave propagation task: identify the characteristics of wave.

If you know any book which is not present in. Far field radiation field : electromagnetic field created by the antenna that extends throughout all space.

If you are looking for basics on Microwave and Antennas, it is OK. D prasad? I am struggling with an antenna. Pre requisites: EM waves and Transmission lines. Jordan and K. Mithal GK : Electromagnetic Fields. Prasad, Satyaprakash publications. Mobile test. EC Antenna and Wave Propagation. Prasad L. They are Elliptical polarization ,circular polarization and linear polarization. What is meant by front to back ratio.? It is defined as the ratio of the power radiated in desired direction to the power radiated in the opposite direction.

Define antenna efficiency.? The efficiency of an antenna is defined as the ratio of power radiated to the total input power supplied to the antenna.

What is radiation resistance? The antenna is a radiating device in which power is radiated into space in the form of electromagnetic wave. Antenna beamwidth is a measure of directivity of an antenna.

Antenna beam width is an angular width in degrees, measured on the radiation pattern major lobe between points where the radiated power has fallen to half its maximum value. What is meant by reciprocity Theorem.? If an e. What is meant by isotropic radiator?

A isotropic radiator is a fictitious radiator and is defined as a radiator which radiates fields uniformly in all directions. It is also called as isotropic source or omni directional radiator or simply unipole. Define gain The ratio of maximum radiation intensity in given direction to the maximum radiation intensity from a reference antenna produced in the same direction with same input power. Define self impedance Self impedance of an antenna is defined as its input impedance with all other antennas are completely removed i.

Define mutual impedance The presence of near by antenna no. This effect is called mutual coupling and results in mutual impedance. What is meant by cross field.?

Normally the electric field E is perpendicular to the direction of wave propagation. In some situation the electric field E is parallel to the wave propagation that condition is called Cross field.

Define axial ratio The ratio of the major to the minor axes of the polarization ellipse is called the Axial Ratio. What is meant by Beam Area.? The beam area or beam solid angle or WA of an antenna is given by the normalized power pattern over a sphere. What is duality of antenna.? It is defined as an antenna is a circuit device with a resistance and temperature on the one hand and the space device on the other with radiation patterns, beam angle ,directivity gain and aperture.

State Poynting theorem.

It states that the vector product of electric field intensity vector E and the magnetic filed intensity vector H at any point is a measure of the rate of energy flow per unit area at that point. The direction of power flow is perpendicular to both the electric field and magnetic field components.

What is point source? What is meant by array.? An antenna is a system of similar antennas oriented similarly to get greater directivity in a desired direction. What is meant by uniform linear array.? An array is linear when the elements of the array are spaced equally along the straight line. If the elements are fed with currents of equal magnitude and having a uniform progressive phase shift along the line, then it is called uniform linear array. What are the types of array.?

Broad side array. End fire array c. Collinear array.

Parasitic array. What is Broad side array.? Broad side array is defined as an arrangement in which the principal direction of radiation is perpendicular to the array axis and also the plane containing the array element. Define End fire array.? End fire array is defined as an arrangement in which the principal direction of radiation is coincides with the array axis.

What is collinear array.? In this array the antenna elements are arranged coaxially by mounting the elements end to end in straight line or stacking them one over the other with radiation pattern circular symmetry.

Omnidirectional antenna. What is Parasitic array.? In this array the elements are fed parasitically to reduce the problem of feed line. The power is given to one element from that other elements get by electro magnetic coupling.

Yagi uda antenna. What is the condition on phase for the end fire array with increased directivity.? Define array factor. Define beam width of major lobe? It is defined the angle between the first nulls or it is defined as twice the angle between the first null and the major lobe maximum direction.

List out the expression of beam width for broad side array and end fire array. Differentiate broad side and End fire array.? Broad side array End fire array 1. Antennas fed in Phase 2.

2 antennas and wave propagation kd prasad satya

Maximum Radiation is perpendicular to the direction of array axis. Beam width of major lobe is twice the Antenna elements are fed of out of Phase - G Maximum Radiation is directed along the array axis. What is the need for the Binomial array.?

The need for a binomial array is i. In uniform linear array as the array length is increased to increase the directivity, the secondary lobes also occurs. Define power pattern.? What is meant by similar Point sources.?

Whenever the variation of the amplitude and the phase of the field with respect to the absolute angle for any two sources are same then they are called similar point sources. The maximum amplitudes of the individual sources may be unequal. What is meant by identical Point sources.?


Similar point sources with equal maximum amplitudes are called identical point sources. What is the principle of the pattern multiplication?

The total field pattern of an array of non isotropic but similar sources is the product of the i individual source pattern and ii The array pattern of isotropic point sources each located at the phase center of the individual source having the same amplitude and phase. While the total phase pattern is the sum of the phase patterns of the individual source pattern and array pattern. What is the advantage of pattern multiplication?

What is tapering of arrays? Tapering of array is a technique used for reduction of unwanted side lobes. The amplitude of currents in the linear array source is non-uniform; hence the central source radiates more energy than the ends. Tapering is done from center to end. What is a binomial array?

It is an array in which the amplitudes of the antenna elements in the array are arranged according to the coefficients of the binomial series. What are the advantages of binomial array?

Define Side Lobe Ratio Side Lobe Ratio is defined as the ratio of power density in the principal or main lobe to the power density of the longest minor lobe. What is a Short Dipole? Ans: A short dipole is one in which the field is oscillating because of the oscillating voltage and current.

It is also called as Hertzian Dipole which is a hypothetical antenna and is defined as a short isolated conductor carrying uniform alternating current. How radiations are created from a short Dipole?

Ans:The dipole has two equal charges of opposite sign oscillating up and down in a harmonic motion. The charges will move towards each other and electric filed lines were created. When the charges meet at the midpoint, the field lines cut each other and new field are created. This process is spontaneous and so more fields are created around the antenna. This is how radiations are obtained from a short dipole.

See Figure from John. Kraus Book Why a short dipole is also called an elemental dipole? A short dipole that does have a uniform current will be known as the elemental dipole.

Such a dipole will generally be considerably shorter than the tenth wave length maximum specified for a short dipole. Elemental dipole is also called as elementary dipole,elementary doublet and hertzian dipole. What is a Infinitesimal Dipole? When the length of the short dipole is vanishingly small,then such a dipole is called a infinitesimal dipole. If dl be the infinitesimally small length and I be the current,then Idl is called as the current element. Why a short dipole is called a oscillating dipole?

A short dipole is initially in neutral condition and the moment a current starts to flow in one direction,one half of the dipole require an excess of charge and the other a deficit because a current is a flow of electrical charge. Then ,there will be a voltage between the two halves of the dipole. When the current changes its direction this charge unbalance will cause oscillations.

Hence an oscillating current will result in an oscillating voltage.

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Since,in such dipole,electric charge oscillates ,it may be called as Oscilllating electric dipole. What do you understand by retarded current? Since,the short electric dipole is so short,the current which is flowing through the dipole is assumed to be constant throughtout its length. Define induction field The induction field will predominate at points close to the current element ,where the distance from the centre of the dipole to the particular point is less.

This field is more effective in the vicinity of the current element only. It represents the energy stored in the magnetic field surrounding the current element or conductor. This field is also known as near field. Define Radiation field The radiation field will be produced at a larger distance from the the current element ,where the distance from the centre of the dipole to the particular point is very large.

It is also called as distant field or far field. At what distance from the dipole is the induction field equal to the radiation field? However,a distance reaches from the conductor at which both the induction and radiation field becomes equal and the particular distance depends upon the wavelength.

The two fields will thus have equal amplitude at that particular distance. This distance is given by U Define Radiation Resistance It is defined as the fictitious resistance which when inserted in series with the antenna will consume the same amount of power as it is actually radiated. The antenna appears to the transmission line as a resistive component and this is known as the radiation resistance.

What is a dipole antenna? A dipole antenna may be defined as a symmetrical antenna in which the two ends are at equal potential relative to the midpoint. What is a half wave dipole? A half wave antenna is the fundamental radio antenna of metal rod or tubing or thin wire which has a physical length of half wavelength in free space at the frequency of operation What is a loop antenna?

How to increase the radiation resistance of a loop antenna The radiation resistance of a loop antenna can be increased by: 1. What are the types of loop antennas? Loop antennas are classified into: 1. What are Electrically Small loop antennas? Electrically Small loop antennas have small radiation resistances that are usually smaller than their loop resistances.

They are very poor radiators and seldom employed for transmission in radio communication. What are Electrically large loop antennas? Electrically Large loop antennas is one in which the overall length of the loop approaches the wavelength. What are the parameters to be considered for the design of an helical antenna?

Bandwidth 2. Gain 3. Impedance 4. Axial Ratio What are the types of radiation modes of operation for an helical antenna The two types of radiation modes of operation possible for an helical antenna are: 1. Normal mode of operation 2. Axial mode of operation Which antenna will produce circularly polarized waves Helical antenna radiates circularly polarized wave.

Define Sky wave. Waves that arrive at the receiver after reflection in the ionosphere is called sky wave. Define Tropospheric wave.

Waves that arrive at the receiver after reflection from the troposphere region is called Tropospheric wave. Define Ground wave.

Waves propagated over other paths near the earth surface is called ground wave propagation. What are the type of Ground wave. Ground wave classified into two types. Space wave ii. Surface wave. It is made up of direct wave and ground reflected wave. Also includes the portion of energy received as a result of diffraction around the earth surface and the reflection from the upper atmosphere.

What is meant by Surface Wave.? Attenuation of this wave is directly affected by the constant of earth along which it travels. What is meant by fading.? Variation of signal strength occur on line of sight paths as a result of the atmospheric conditions and it is called. It can not be predicted properly. What are the type of fading.?What is meant by identical Point sources.? Sky wave. Determine its radiation resistance and directivity. This book anrenna essential for students pursuing electronics engineering at various technical universities of India.

Elliptical polarization The electric field vector rotates and form a ellipse called polarization ellipse. Refer Page no fn. Also, there are numerous exercises which help students understand different. Define Side Lobe Ratio Side Lobe Ratio is defined as the ratio of power density in the principal or main lobe to the power density of the longest minor lobe. See Figure from John. The ratio of the main beam area to the total beam area is called beam efficiency.