oct. 16, 2006
DESCRIPTION
Oct. 16, 2006. Midterm Next Class Assignment #4 is Marked Problem session in lab today – review for midterm More Antennas. Midterm Overview. Midterm Info: http://people.okanagan.bc.ca/dwilliams/courses/nten216/nten216_Quiz1.htm Sample questions: - PowerPoint PPT PresentationTRANSCRIPT
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