Lecture 1 Television Antenna. Parts of antenna

Lecture 1Lecture 1

Television AntennaTelevision Antenna

Parts of antennaParts of antenna

FormulaFormula

Frequency

3,000,000,000=

=Wavelength in metersf= frequency in hertz

WavelengthWavelength

Lambda (meters)Lambda (meters)Velocity (300,000,000 Velocity (300,000,000

meters/sec.)meters/sec.)Frequency (Hz)Frequency (Hz)

= v/f= v/f

Antenna SystemsAntenna Systems

Radio Energy in SpaceRadio Energy in Space–300 million meters per 300 million meters per secondsecond

E = MCE = MC22

Speed of LightSpeed of Light

Wavelength conversion

Meters: Lambda = 300/211.25 = 1.46 meters

Miles: Lambda = .186/211.25 = .00088 miles

Feet: 1 meter = 3.28 feet

Lambda = 1.46 meters x 3.28 = 4.79 feet

SpectrumSpectrum

TV StationTV Station

WTHR-TV

WTHR-TV

Ch.13 (210-216 MHz)

WAVELENGTH IN:

A. Meters

B. Miles

C. Feet

Types of AntennaTypes of Antenna

Dipole

Vertical Vertical Plane Plane

Radiation Radiation PatternPattern

MonopoleMonopole

Folded DipoleFolded Dipole

Mobile antennasMobile antennas

Reflector Reflector AntennaAntenna

Yagi AntennasYagi Antennas

Coax Linear Coax Linear ArrayArray

Single elements radiation Single elements radiation patternpattern

Radio WavesRadio Waves

Three important features of radio Three important features of radio waveswaves– amplitude, frequency, and polarizationamplitude, frequency, and polarization

Modulation by amplitude and Modulation by amplitude and frequency (AM and FM) is commonfrequency (AM and FM) is common

PolarizationPolarization– rarely used at allrarely used at all– essentially never to modulateessentially never to modulate

PolarizationPolarization

Polarization - the orientation of the electric field of an electromagnetic wave.

Linearly Polarized Wave Circularly Polarized Wave

Won’t we pick up both Won’t we pick up both signals?signals?

Polarization is related to antenna Polarization is related to antenna geometrygeometry– Horizontal antennae won’t pick up vertical Horizontal antennae won’t pick up vertical

waves and vise versawaves and vise versa Circular antennaeCircular antennae

– 50% of linear waves50% of linear waves– 100% of a correctly oriented circular wave100% of a correctly oriented circular wave– none of a circular wave of opposite none of a circular wave of opposite

polarizationpolarization

Current Uses of PolarizationCurrent Uses of Polarization

Satellite TVSatellite TV– Binary circularly polarized signalBinary circularly polarized signal– Maybe PMMaybe PM

Military communication--Military communication--particularly air to sea particularly air to sea communicationcommunication– Circularly polarized FM signalCircularly polarized FM signal

Antenna DesignAntenna Design

Sample AntennaSample Antenna Basic Design ComponentsBasic Design Components EquationsEquations CalculationsCalculations

EquationsEquations

= c/= c/ D =D = Gain in dB = 11.8 + 10 Gain in dB = 11.8 + 10

log(Clog(C22 * n * S) * n * S) C= C= for helical for helical

antennaeantennae

= wavelength= wavelength c = speed of lightc = speed of light = frequency= frequency D = diameter of helixD = diameter of helix n = # of turnsn = # of turns C = circumferenceC = circumference S = axial distance S = axial distance

between turnsbetween turns

Equations with NumbersEquations with Numbers

= c/= c/x10^8 m/s)/(2.4GHz)=.125 mx10^8 m/s)/(2.4GHz)=.125 m D =D = cm cm S = 3.924 cmS = 3.924 cm n = 6n = 6 Gain = 11.8 + 10 log(CGain = 11.8 + 10 log(C22 * n * S) = 7.46 dB for an * n * S) = 7.46 dB for an

antenna with approx. 4 cm diameter.antenna with approx. 4 cm diameter.

Antenna SafetyAntenna Safety

Think before actingThink before acting Do not erect an antenna structure near Do not erect an antenna structure near

enough to a power line allow distance enough to a power line allow distance between the twobetween the two

Do not try to throw-in lead wire from one Do not try to throw-in lead wire from one point to the another where there is even a point to the another where there is even a remote chance of power line contact.remote chance of power line contact.

Ground all antenna structures properlyGround all antenna structures properly Safety check receivers for power line Safety check receivers for power line

leakage to the antenna.leakage to the antenna.

continuationcontinuation

Use standard antenna system Use standard antenna system connectors and equipmentconnectors and equipment

Use power climbing equipmentUse power climbing equipment Dress correctly hard hat rubber sole Dress correctly hard hat rubber sole

etcetc Obtain help to handle heavy or hard Obtain help to handle heavy or hard

manage equipment.manage equipment.

ExperimentationExperimentation

TV Tuner

Amplifiers

Mixer

Frequency Synthesizer

IF filter

AmplifierEnvelope Detector

Non-coherent detector prototype