Oct. 16, 2006Oct. 16, 2006

Midterm Next ClassMidterm Next Class

Assignment #4 is MarkedAssignment #4 is Marked

Problem session in lab today – review for Problem session in lab today – review for midtermmidterm

More AntennasMore Antennas

Midterm OverviewMidterm Overview

Midterm Info:Midterm Info:– http://people.okanagan.bc.ca/dwilliams/coursehttp://people.okanagan.bc.ca/dwilliams/course

s/nten216/nten216_Quiz1.htms/nten216/nten216_Quiz1.htm

Sample questions:Sample questions:– http://people.okanagan.bc.ca/dwilliams/coursehttp://people.okanagan.bc.ca/dwilliams/course

s/nten216/Tests/NTEN216_Midterm1Samples/nten216/Tests/NTEN216_Midterm1SampleQuestions.pdfQuestions.pdf

Antenna CharacteristicsAntenna Characteristics

Gain and DirectivityGain and Directivity

Radiation PatternRadiation Pattern

PolarizationPolarization

Input ImpedanceInput Impedance

Antenna EfficiencyAntenna Efficiency

BandwidthBandwidth

ReciprocityReciprocity

BandwidthBandwidth

Range of frequencies over which antenna can Range of frequencies over which antenna can transmit or receive signals effectivelytransmit or receive signals effectivelyCan apply to a certain antennaCan apply to a certain antenna– Measurement is Measurement is

(Upper Frequency-Lower Frequency)/(Upper (Upper Frequency-Lower Frequency)/(Upper Frequency)Frequency)

– e.g. 2.4GHz Dipole antenna may be able to transmit e.g. 2.4GHz Dipole antenna may be able to transmit signals from 2.28 to 2.52GHz without significant loss signals from 2.28 to 2.52GHz without significant loss of signal power. BW = (2.52-2.28)/2.4 = 10%of signal power. BW = (2.52-2.28)/2.4 = 10%

Can apply to a certain type of antennaCan apply to a certain type of antenna– E.g. Half-wave dipole antennas in general have a E.g. Half-wave dipole antennas in general have a

bandwidth of 6GHz (0-6GHz) as long as the specific bandwidth of 6GHz (0-6GHz) as long as the specific dipole size is set to the half-wave lengthdipole size is set to the half-wave length

Antenna Input ImpedanceAntenna Input Impedance

Want input impedance to match Want input impedance to match impedance of incoming cableimpedance of incoming cable– Minimize reflectionsMinimize reflections– Maximize signal in to antennaMaximize signal in to antenna– Eliminate VSWREliminate VSWR

Impedance mismatch will reduce the Impedance mismatch will reduce the antenna efficiencyantenna efficiency

ReciprocityReciprocity

An antenna can be used for transmitting An antenna can be used for transmitting and receivingand receiving

If you know the transmit properties of an If you know the transmit properties of an antenna, you know the receive properties antenna, you know the receive properties of an antenna…they are the sameof an antenna…they are the same

Applies to: Gain, Radiation Pattern, Applies to: Gain, Radiation Pattern, Polarization, Input Impedance, Efficiency, Polarization, Input Impedance, Efficiency, and Bandwidthand Bandwidth

Cutoff for Midterm TopicsCutoff for Midterm Topics

Types of AntennasTypes of Antennas

OmnidirectionalOmnidirectional– Half-wave dipoleHalf-wave dipole– Quarter-wave monopoleQuarter-wave monopole

DirectionalDirectional– Yagi-Uda antennaYagi-Uda antenna– Patch antennaPatch antenna– Parabolic DishParabolic Dish– Phased ArrayPhased Array– Sector AntennasSector Antennas

Omnidirectional AntennasOmnidirectional Antennas

Ideally, radiates energy equally in all Ideally, radiates energy equally in all directionsdirections– Isotropic antennaIsotropic antenna

In reality, radiates energy equally in one In reality, radiates energy equally in one plane, but not in other planeplane, but not in other plane– Omnidirectional in one planeOmnidirectional in one plane

Half-Wave DipoleHalf-Wave Dipole

Dipole antenna consists of two conductors which Dipole antenna consists of two conductors which stretch out in opposite directionsstretch out in opposite directions

Best dipole is when length is equal to half the Best dipole is when length is equal to half the wavelength of EM being radiatedwavelength of EM being radiated

Half Wave Dipole CharacteristicsHalf Wave Dipole Characteristics

Gain: 2dBiGain: 2dBi

Typical Beamwidth: 80° x 360°Typical Beamwidth: 80° x 360°– Omnidirectional in horizontal planeOmnidirectional in horizontal plane– Beamwidth in vertical plane can varyBeamwidth in vertical plane can vary

Polarization: linear, and perpendicular to Polarization: linear, and perpendicular to antennaantenna

Bandwidth: 10%.Bandwidth: 10%.– Effective from 0-6GHzEffective from 0-6GHz

Half Wave Dipole Radiation PatternHalf Wave Dipole Radiation Pattern

Quarter Wave MonopoleQuarter Wave Monopole

One conductor One conductor carrying the signal carrying the signal referenced to a referenced to a ground planeground planeVirtual mirror image of Virtual mirror image of conductor created on conductor created on opposite side of planeopposite side of plane2 x 2 x λλ/4 = /4 = λλ/2. This is /2. This is effectively a half-wave effectively a half-wave dipoledipole

λλ/4 Monopole Characteristics/4 Monopole Characteristics

Gain: 2-6dBiGain: 2-6dBi

Typical Beamwidth: 45° x 360°Typical Beamwidth: 45° x 360°– Omnidirectional in horizontal planeOmnidirectional in horizontal plane– Beamwidth in vertical plane can varyBeamwidth in vertical plane can vary

Polarization: linear, and perpendicular to Polarization: linear, and perpendicular to antennaantenna

Bandwidth: 10%.Bandwidth: 10%.– Effective from 0 to very highEffective from 0 to very high

λλ/4 Monopole Radiation pattern/4 Monopole Radiation pattern

Directional AntennasDirectional Antennas

Focus coverage more in one direction than Focus coverage more in one direction than othersothers

Refers to all antennas that are not Refers to all antennas that are not omnidirectional. Wide range of degrees of omnidirectional. Wide range of degrees of directionalitydirectionality– Semidirectional: smaller gain, wider coverage Semidirectional: smaller gain, wider coverage

regionregion– Highly directional: high gain, focused strongly Highly directional: high gain, focused strongly

in one direction, long distance rangein one direction, long distance range

Yagi AntennaYagi Antenna

One radiating dipole, one reflector to reflect One radiating dipole, one reflector to reflect signal in opposite direction, several directors to signal in opposite direction, several directors to focus energyfocus energySize and number of directors determines Size and number of directors determines directivity and gaindirectivity and gain

Yagi Antenna CharacteristicsYagi Antenna Characteristics

Gain: 5-15dBiGain: 5-15dBi

Typical Beamwidth: 50° x50°Typical Beamwidth: 50° x50°

Polarization: HorizontalPolarization: Horizontal

Bandwidth: 5%Bandwidth: 5%– Effective from 50MHz to 2.5GHzEffective from 50MHz to 2.5GHz

Yagi Antenna Radiation PatternYagi Antenna Radiation Pattern

Patch or Panel AntennaPatch or Panel Antenna

Consists of metallic plate Consists of metallic plate and base sandwiching an and base sandwiching an insulating materialinsulating material

Easy to manufactureEasy to manufacture

Easy to mountEasy to mount

Similar to Yagi Antennas Similar to Yagi Antennas in terms of performancein terms of performance

Better than Yagis for cost, Better than Yagis for cost, ease of use and ease of use and aestheticsaesthetics

Patch/Panel Antenna Patch/Panel Antenna CharacteristicsCharacteristics

Gain: 5-18dBiGain: 5-18dBi

Typical Beamwidth: 50° x50°Typical Beamwidth: 50° x50°

Polarization:Polarization:

Bandwidth:Bandwidth:– Effective from XXXHz to XXX HzEffective from XXXHz to XXX Hz

Patch/Panel Antenna Radiation Patch/Panel Antenna Radiation PatternPattern

Parabolic Dish or Grid AntennaParabolic Dish or Grid Antenna

Highly directional Highly directional antennas, beamwidth can antennas, beamwidth can be as small as a couple be as small as a couple of degreesof degreesUsed for fixed location, Used for fixed location, long distance long distance communicationscommunications– E.g. satellite, microwave E.g. satellite, microwave

towerstowers

Parabolic dish or grid Parabolic dish or grid focuses energy in one focuses energy in one direction.direction.

Dish Antenna CharacteristicsDish Antenna Characteristics

Gain: 20-30dBiGain: 20-30dBi

Beamwidth: 1-10 degreesBeamwidth: 1-10 degrees

Polarization: can be linear or circularPolarization: can be linear or circular

Bandwidth: 30%Bandwidth: 30%– Effective from 400MHz to 13GHzEffective from 400MHz to 13GHz

Parabolic Dish Radiation PatternParabolic Dish Radiation Pattern

Phased Array AntennasPhased Array Antennas

Group of Group of independently fed independently fed active elementsactive elementsInput signals can be Input signals can be controlled to cause controlled to cause required required constructive/deconstrconstructive/deconstructive waveformsuctive waveformsResult: antenna can Result: antenna can be aimed without any be aimed without any moving partsmoving parts

Phased Array Antenna Phased Array Antenna CharacteristicsCharacteristics

Gain: Varies widelyGain: Varies widely

Beamwidth: Varies WidelyBeamwidth: Varies Widely

Polarization: depends on array.Polarization: depends on array.

Bandwidth: depends on array.Bandwidth: depends on array.– Effective from 10MHz to 10GHzEffective from 10MHz to 10GHz

Radiation Pattern: depends on arrayRadiation Pattern: depends on array

Sector AntennasSector Antennas

Generate “Pie Slice” radiation patternsGenerate “Pie Slice” radiation patterns

““Pie Slice” width depends on particular Pie Slice” width depends on particular antennaantenna

Because of predictability of slice, multiple Because of predictability of slice, multiple antennas may be mounted together to antennas may be mounted together to give larger coverage areagive larger coverage area

E.g. want 270° of coverage, but have only E.g. want 270° of coverage, but have only 90° sector antennas, what do you do.90° sector antennas, what do you do.

Sector Antenna CharacteristicsSector Antenna Characteristics

Gain: 10-21dBi.Gain: 10-21dBi.– A 90° sector antenna can still have variable A 90° sector antenna can still have variable

gain by changing the vertical patterngain by changing the vertical pattern

Beamwidth: Depends on Pie Slice sizeBeamwidth: Depends on Pie Slice size

Polarization: linearPolarization: linear

Bandwidth:Bandwidth:– Effective from Effective from

Sector Antenna Radiation PatternSector Antenna Radiation Pattern

Increase coverage area by joining three 120° Increase coverage area by joining three 120° antennas together.antennas together.

Omnidirectional in horizontal plane, controllable Omnidirectional in horizontal plane, controllable in vertical plane.in vertical plane.

AntennaAntenna GainGain

(dBi)(dBi)

BeamBeamwidthwidth

PolariPolarizationzation

BandBandwidthwidth

Lower Lower FF

Upper Upper FF

λλ/2 Dipole/2 Dipole 22 80x36080x360 LinearLinear 10%10% NoneNone 6GHz6GHz

λλ/4 /4 MonopoleMonopole

2-62-6 45x36045x360 LinearLinear 10%10% NoneNone NoneNone

ParabolicParabolic 20-3020-30 1-101-10 LinearLinear 33%33% 400MHz400MHz 13GHz13GHz

YagiYagi 5-155-15 50x5050x50 LinearLinear 5%5% 50MHz50MHz 2GHz2GHz

PatchPatch 8-188-18 VariesVaries LinearLinear

ArrayArray variesvaries VariesVaries LinearLinear 10MHz10MHz 10GHz10GHz

SectorSector 8-218-21 VariesVaries LinearLinear

ReviewReviewWhat are lobes and nulls?What are lobes and nulls?If you have a right handed circularly polarized If you have a right handed circularly polarized transmission antenna, what is the best kind of transmission antenna, what is the best kind of antenna to use as the reception antenna?antenna to use as the reception antenna?If the gain of an antenna is 5dBi for If the gain of an antenna is 5dBi for transmission, and its beamwidth for transmission transmission, and its beamwidth for transmission is 90°x45°, what would the gain and beamwidth is 90°x45°, what would the gain and beamwidth be if it was used for reception? What is this be if it was used for reception? What is this principle called?principle called?A 1 watt signal is input to an antenna, but A 1 watt signal is input to an antenna, but 200mW is reflected. The gain of the antenna is 200mW is reflected. The gain of the antenna is 10dBi, and the loss of power due to resistance is 10dBi, and the loss of power due to resistance is 50mW. What is the efficiency of this antenna?50mW. What is the efficiency of this antenna?

ReviewReview

What happens if there is an impedance What happens if there is an impedance mismatch between the antenna, and the cable mismatch between the antenna, and the cable coming into the antenna?coming into the antenna?

The center frequency of an antenna is The center frequency of an antenna is 104.7MHz, and at 104.7MHz it radiates 50 Watts 104.7MHz, and at 104.7MHz it radiates 50 Watts of power. If it radiates a 100MHz signal, it can of power. If it radiates a 100MHz signal, it can only output 12.5W of power, and at 110MHz, it only output 12.5W of power, and at 110MHz, it can only output 12.5W of power. What is the can only output 12.5W of power. What is the bandwidth of this antenna?bandwidth of this antenna?

ReviewReview

In terms of In terms of directionality, what directionality, what kind of antenna is this kind of antenna is this ??

What are the What are the horizontal and vertical horizontal and vertical beamwidths?beamwidths?

In the vertical plane, In the vertical plane, what is the signal what is the signal strength at 45° if the strength at 45° if the strength at 90° is strength at 90° is 50mW?50mW?

ReviewReviewDescribe at least two ways to provide full Describe at least two ways to provide full wireless coverage to a large rectangularly wireless coverage to a large rectangularly shaped warehouse. Explain the types of shaped warehouse. Explain the types of antennas you would use and why.antennas you would use and why.

If you have need for long distance point to If you have need for long distance point to point communications, what kind of point communications, what kind of antenna would you use.antenna would you use.

What would you use a Yagi antenna for?What would you use a Yagi antenna for?

ResourcesResources

http://www.arrl.org/tis/info/whyantradiates.http://www.arrl.org/tis/info/whyantradiates.htmlhtml

http://www.hp.com/rnd/pdf_html/antenna.hhttp://www.hp.com/rnd/pdf_html/antenna.htmtm

http://www.connect802.com/wcu_articles.hhttp://www.connect802.com/wcu_articles.htmtm