some basics

sin 0 = 0

sin 90 = 1

cos 0 = 1

cos 90 = 0

sine is a ratio. a ratio of the vertical height (altitude/perpendicular) to the slant height (slope/hypotenuse). co-tangent is reciprocal of sine.

co-sine is a ratio. a ratio of the horizontal height (length or base) to the slant height (slope/hypotenuse). secant* is reciprocal of co-sine.

tangent is a ratio of the vertical height (altitude) to the horizontal height (length or base). co-secant is reciprocal of tangent.

reciprocal of tangent is co-secant i.e. cosec

inverse of tangent is arc-tangent i.e. arctan or atan or tan^(-1)

_____________ of tangent is hyperbolic-tangent i.e. tanh

inverse of ______________ of tangent is area-hyperbolic-tangent i.e. artanh or atanh or arctanh

*secant, in geometry, is a straight line that intersects a curve at two or more points. 

sine or sinus means 'cavity'

tangent means 'to touch lightly'

secant means 'to cut' 

co- means 'mutual'

higher the frequency - higher the energy - shorter be the wavelength - shorter be the communication range - weaker be the noise immunity - sharper the beamwidth - higher the directivity

red light has greater wavelength, hence it is used for long-distance communication. (most often, to alert the person at a distance)

violet light is much energetic than red, hence it is used as fog light in vehicles.

myth buster: red is the least energetic wave.

even leaves are a kind of antenna, which receives all the colors from the white sunlight wave, except the green. it reflect back the 510nm green color

Poynting vector measures the rate of flow of energy. P=ExH

Poynting vector corresponds to the power density.

isotropic: equal in magnitude in each'n'every direction.

magnitude of the Poynting vector varies inversely as the sq. of distance from a point-source antt.

radiation intensity is measured in watts per unit solid-angle.

radiation intensity is independent of radius of the isotropic source

path difference is function of the distance between two power sources. 

greater the distance, larger be the path-difference 

phase angle is around six times of path difference

major lobe is @ principle maxima

minor lobe is @ principle minima

HPPD: Half Power Point Directions

BWFN: Beam Width between First Nulls
HPBW: Half Power Beam Width

AF: Array Factor

BWFN varies directly for twice of wavelength and inversely for the number of elements in the array and the spacing between them.

i.e.

longer the wavelength, wider be the BWFN or higher the frequency, sharper be the BWFN

more the array elements (n), sharper be the BWFN

spacious the array elements (d), sharper be the BWFN 

    

HPBW = BWFN/ 2

let, initially BWFN be 120° for an array of 1m,

if we stretched the array to 2m, the BWFN will get reduced to 60°. (120°/2)


Directivity (D) is the ratio of array length to wavelength

array length (L) = n * d