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• Useful tool in DESIGNING ANTENNA.
• It approximates the pattern of a COMPLICATED array without making lengthy computations.

The total FIELD pattern of an ARRAY of NON isotropic but similar SOURCES is the product of the

• Individual source pattern and
• 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.

The total field pattern of an array of non isotropic but similar sources is the product of the

While the total phase pattern is the sum of the phase patterns of the individual source pattern and array pattern.

SIMILAR POINT SOURCES with equal MAXIMUM amplitudes are CALLED identical point sources.

Similar point sources with equal maximum amplitudes are called identical 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.

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.

Graphical representation of the radial COMPONENT of the POYNTING vector Sr at a constant radius as a function of ANGLE is called power DENSITY PATTERN or power pattern.

Graphical representation of the radial component of the poynting vector Sr at a constant radius as a function of angle is called power density pattern or power pattern.

The need for a BINOMIAL ARRAY is

• In uniform linear array as the array length is increased to increase the directivity, the SECONDARY lobes also occurs.
• For certain applications, it is highly desirable that secondary lobes should be eliminated completely or REDUCED to minimum desirable level compared to MAIN lobes.

The need for a binomial array is

• In Broad SIDE array antennas are fed in phase δ = 0, where as in end FIRE ARRAYS the antenna elements are fed out of phase i.e. δ = - β d.
• In broad side array the maximum RADIATION is perpendicular to the direction of array axis, where as in case of end fire array the maximum radiation is directed along the array axis.

For BROAD side ARRAY the expression for beam width between the FIRST nulls is given by,

BWFN = ( ( + / -) 2 λ / N d )

For End fire array the expression for beam width between the first nulls is given by,

BWFN = ( ( + / -) 2 ( 2 λ / n d ) )1/2

For broad side array the expression for beam width between the first nulls is given by,

BWFN = ( ( + / -) 2 λ / n d )

For End fire array the expression for beam width between the first nulls is given by,

BWFN = ( ( + / -) 2 ( 2 λ / n d ) )1/2

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.

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.

The normalized value of the total FIELD is given by,

E = ( 1 / N) ( SIN (n Ψ / 2) / sin ( Ψ / 2) )

The field is given by the expression E will be referred to as ARRAY factor.

The normalized value of the total field is given by,

E = ( 1 / n) ( sin (n Ψ / 2) / sin ( Ψ / 2) )

The field is given by the expression E will be referred to as array factor.

When δ = - β d, produces maximum field in the direction φ = 0 but DIES not give the maximum directivity. It has been shown by Hansen and woodyard that a LARGE directivity is obtained by INCREASING the PHASE change between the sources so that δ = - (βd + π / n ).

This condition will be referred to as the condition for increased directivity.

When δ = - β d, produces maximum field in the direction φ = 0 but dies not give the maximum directivity. It has been shown by Hansen and woodyard that a large directivity is obtained by increasing the phase change between the sources so that δ = - (βd + π / n ).

This condition will be referred to as the condition for increased directivity.

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.

EG. Yagi uda antenna.

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.

Eg. Yagi uda antenna.

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. 

EG. OMNIDIRECTIONAL antenna.

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. 

Eg. Omnidirectional antenna.

End FIRE array is defined as an arrangement in which the principal DIRECTION of RADIATION is coincides with the array AXIS. 

For end fire array δ = - β d 

where β = 2Π / λ and d = distance between the ELEMENTS.

End fire array is defined as an arrangement in which the principal direction of radiation is coincides with the array axis. 

For end fire array δ = - β d 

where β = 2Π / λ and d = distance between the elements.

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. 

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. 

• Broad SIDE ARRAY.
• End FIRE array
• Collinear array.
• Parasitic 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.

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.

An ANTENNA is a SYSTEM of SIMILAR ANTENNAS oriented similarly to get GREATER directivity in a desired direction.

An antenna is a system of similar antennas oriented similarly to get greater directivity in a desired direction.

It is the WAVES originate at a fictitious volume LESS EMITTER source at the center ‘O’ of the OBSERVATION circle.

It is the waves originate at a fictitious volume less emitter source at the center ‘O’ of the observation circle.

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.

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.

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, beamangle, directivity gain and APERTURE.

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, beamangle, directivity gain and aperture.

The beam area or beam solid angle or WA of an ANTENNA is given by the normalized power pattern over a SPHERE. 

WA = ò ò4p Pn ( Q,f ) DW

Where dW = SIN q dq.df 

The beam area or beam solid angle or WA of an antenna is given by the normalized power pattern over a sphere. 

WA = ò ò4p Pn ( q,f ) dW

Where dW = Sin q dq.df 

The RATIO of the MAJOR to the minor axes of the POLARIZATION ellipse is CALLED the AXIAL Ratio (AR). 

The ratio of the major to the minor axes of the polarization ellipse is called the Axial Ratio (AR). 

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. 

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. 

The presence of near by antenna no.2 induces a current in the antenna no.1 indicates that presence of antenna no.2 changes the IMPEDANCE of the antenna no.1. This effect is called mutual COUPLING and results in mutual impedance.

The presence of near by antenna no.2 induces a current in the antenna no.1 indicates that presence of antenna no.2 changes the impedance of the antenna no.1. This effect is called mutual coupling and results in mutual impedance.

SELF impedance of an ANTENNA is DEFINED as its input impedance with all other antennas are completely REMOVED i.e away from it.

Self impedance of an antenna is defined as its input impedance with all other antennas are completely removed i.e away from it.

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. i.e Maximum radiation intensity from test antenna (G)= Maximum radiation intensity from the reference antenna with same input power.

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. i.e Maximum radiation intensity from test antenna (G)= Maximum radiation intensity from the reference antenna with same input power.

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.

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.

If an e.m.f is applied to the terminals of an ANTENNA no.1 and the current MEASURED at the terminals of the ANOTHER antenna no.2, then an EQUAL current both in amplitude and phase will be obtained at the terminal of the antenna no.1 if the same emf is applied to the terminals of antenna no.2.

If an e.m.f is applied to the terminals of an antenna no.1 and the current measured at the terminals of the another antenna no.2, then an equal current both in amplitude and phase will be obtained at the terminal of the antenna no.1 if the same emf is applied to the terminals of antenna no.2.

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. This is called as "beam width" between half power points or half power beam width.(HPBW).

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. This is called as "beam width" between half power points or half power beam width.(HPBW).

The antenna is a radiating device in which power is RADIATED into SPACE in the form of ELECTROMAGNETIC wave. W’ = I2 R RR = W’/ I2 Where Rr is a fictitious resistance called called as radiation resistance.

The antenna is a radiating device in which power is radiated into space in the form of electromagnetic wave. W’ = I2 R Rr = W’/ I2 Where Rr is a fictitious resistance called called as radiation resistance.

The efficiency of an ANTENNA is DEFINED as the RATIO of power radiated to the total input power supplied to the antenna. Antenna efficiency = Power radiated / Total input Power.

The efficiency of an antenna is defined as the ratio of power radiated to the total input power supplied to the antenna. Antenna efficiency = Power radiated / Total input Power.

It is DEFINED as the ratio of the power RADIATED in DESIRED direction to the power radiated in the opposite direction. i.e FBR = Power radiated in desired direction / power radiated in the opposite direction.

It is defined as the ratio of the power radiated in desired direction to the power radiated in the opposite direction. i.e FBR = Power radiated in desired direction / power radiated in the opposite direction.

The polarization of the radio wave can be DEFINED by direction in which the electric vector E is aligned during the PASSAGE of ATLEAST one full cycle.ALSO polarization can also be defined the physical ORIENTATION of the radiated electromagnetic waves in space. The polarization are three types. They are Elliptical polarization ,circular polarization and linear polarization.

The polarization of the radio wave can be defined by direction in which the electric vector E is aligned during the passage of atleast one full cycle.Also polarization can also be defined the physical orientation of the radiated electromagnetic waves in space. The polarization are three types. They are Elliptical polarization ,circular polarization and linear polarization.

The FIELDS around an ANTENNA MAY be divided into two principal REGIONS.

• Near field zone (Fresnel zone)
• Far field zone (Fraunhofer zone)

The fields around an antenna may be divided into two principal regions.

The effective height h of an antenna is the parameter related to the aperture. It may be DEFINED as the ratio of the INDUCED voltage to the incident field.i.E H= V / E.

The effective height h of an antenna is the parameter related to the aperture. It may be defined as the ratio of the induced voltage to the incident field.i.e H= V / E.

The RATIO of the effective APERTURE to the physical aperture is the aperture EFFICIENCY. i.e Aperture efficiency = hap = Ae / Ap (DIMENSIONLESS).

The ratio of the effective aperture to the physical aperture is the aperture efficiency. i.e Aperture efficiency = hap = Ae / Ap (dimensionless).

Effective aperture (Ae): It is the area over which the power is extracted from the INCIDENT wave and delivered to the load is CALLED effective aperture. 

Scattering aperture (As): It is the ratio of the reradiated power to the power DENSITY of the incident wave.

Loss aperture (Ae): It is the area of the antenna which dissipates power as heat. 

Collecting aperture (Ae): It is the addition of above three APERTURES.

PHYSICAL aperture (Ap): This aperture is a measure of the physical size of the antenna.

Effective aperture (Ae): It is the area over which the power is extracted from the incident wave and delivered to the load is called effective aperture. 

Scattering aperture (As): It is the ratio of the reradiated power to the power density of the incident wave.

Loss aperture (Ae): It is the area of the antenna which dissipates power as heat. 

Collecting aperture (Ae): It is the addition of above three apertures.

Physical aperture (Ap): This aperture is a measure of the physical size of the antenna.

• EFFECTIVE APERTURE.
• Scattering aperture.
• Loss aperture.
• COLLECTING aperture.
• PHYSICAL aperture.

<P>The directivity of an ANTENNA is equal to the ratio of the maximum power density P (q,F)max to its average value over a sphere as OBSERVED in the FAR field of an antenna.

D = P (q,f)max / P(q,f)av. Directivity from Pattern.

D = 4p / WA. Directivity from beam area (WA).

The directivity of an antenna is equal to the ratio of the maximum power density P (q,f)max to its average value over a sphere as observed in the far field of an antenna.

D = P (q,f)max / P(q,f)av. Directivity from Pattern.

D = 4p / WA. Directivity from beam area (WA).

The TOTAL beam area (WA) consists of the main beam area (WM) PLUS the minor lobe area (Wm). 

Thus WA = WM+ Wm.

The ratio of the main beam area to the total beam area is called beam EFFICIENCY.

Beam efficiency (SM) = WM / WA.

The total beam area (WA) consists of the main beam area (WM) plus the minor lobe area (Wm). 

Thus WA = WM+ Wm.

The ratio of the main beam area to the total beam area is called beam efficiency.

Beam efficiency (SM) = WM / WA.

The POWER radiated from an antenna per UNIT solid ANGLE is CALLED the RADIATION intensity U (watts per steradian or per square degree). The radiation intensity is independent of distance.

The power radiated from an antenna per unit solid angle is called the radiation intensity U (watts per steradian or per square degree). The radiation intensity is independent of distance.

Radiation pattern is the relative distribution of radiated POWER as a function of distance in SPACE .It is a graph which shows the VARIATION in actual field strength of the EM wave at all points which are at EQUAL distance from the antenna. The energy radiated in a particular direction by an antenna is measured in terms of FIELD STRENGTH. (E Volts/m)

Radiation pattern is the relative distribution of radiated power as a function of distance in space .It is a graph which shows the variation in actual field strength of the EM wave at all points which are at equal distance from the antenna. The energy radiated in a particular direction by an antenna is measured in terms of FIELD STRENGTH. (E Volts/m)

ANTENNA is a transition device or a transducer between a guided wave and a free SPACE wave or vice-versa. Antenna is ALSO said to be an impedance TRANSFORMING device.

Antenna is a transition device or a transducer between a guided wave and a free space wave or vice-versa. Antenna is also said to be an impedance transforming device.