Antennas and their communication parameters (B2-B3)

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Antennas and their communication parameters (B2-B3)

Course UNIK4700, UNIK9700
Title Antennas and their communication parameters
Lecture date 2017/10/03 1300-1600
presented by Josef Noll
Objective Discussion on Antennas and their communication parameters
Learning outcomes What will we learn today:
  • Reflection coefficient and impedance
  • Propagation and Absorption
  • Antenna types
  • Radiation patterns
  • Antenna gain
  • Interference
Pensum (read before) Antenna Parameters

TDMA, FDMA and CDMA in Mobile Communications

References (further info) References:
Keywords antennas, beamwidth, radiation pattern, gain, directivity, input impedance

this page was created by Special:FormEdit/Lecture, and can be edited by Special:FormEdit/Lecture/Antennas and their communication parameters (B2-B3).


Test yourself, answer these questions

  • What two functions are performed by antenna?
  • What is isotropic antenna?
  • What factors determine antenna gain?
  • What is meant by radiation pattern?
  • What is polarisation ? What are its types?
  • If a high frequency has a short wavelength, what wavelength does a low frequency have?
  • What is fading?
  • What is the difference between diffraction and fading?
  • What is the difference between fast and slow fading?
  • What is the difference between flat and selective fading?

Lecture notes

Earlier years


Title
UNIK4710/UNIK9710 Antennas
Author
Josef Noll
Footer
Antennas and their communication parameters (B2-B3)
Subfooter
UNIK4710/UNIK9710


Topic selection for next week

  • 10Oct: present your ideas
  • identify the parameters you will look at (prepare for sensitivity analysis and own evaluation)
  • don't simply present, but rather show your understanding of a "sub-set" og the topic
  • perform an evaluation towards the parameters used


⌘ B2-Antennas

Building .... Networks
History, Now and Future
History
Pioneers: Maxwell, Hertz,...
1G, 2G,... 5G networks
Frequencies and Standards
Future Challenges
A-Basics of Communication
Electromagnetic Signals
Radio Communication Principles
Digital communication: Signal/Noise Ratio
Signal strength and Capacity: Shannon
B-Antennas and Propagation
Free Space Propagation
Antennas, Gain, Radiation Pattern
Multipath Propagation, Reflection, Diffraction
Attenuation, Scattering
Interference and Fading (Rayleigh, Rician, …)
Mobile Communication dependencies
C-Propagation models
Environments (indoor, outdoor to indoor, vehicular)
Outdoor (Lee, Okumura, Hata, COST231 models)
Indoor (One-slope, multiwall, linear attenuation)
D-System Comparison
Proximity: RFID, NFC
Short Range: ZigBee, Bluetooth, ANT+,...
WLAN/Wifi/802.11...
Mobile: GSM, UMTS, IMT-A (WiMAX, LTE)
E-Mobility
Mobile Network mobility
IP mobility
F-Network Building
Future Networks
5G Heterogeneous Networks
Basic Internet
Video Distribution Networks
Coverage simulations
Coverage simulations
Traffic simulations
Network Capacity simulations
Building .... Networks

Keywords: Antennas, Hertz Dipol, Antenna Gain

⌘ B2-Antenna Basics

The gain is the radiation intensity of an antenna into the main direction as compared to an isotropic antenna (omnidirectional). For a perfect antenna without any losses, the gain G will be identical to the directivity D.

⌘ Antenna pattern

If the antenna pattern is known, then the gain can be easily calculated.

  • Isotropic antenna = point source:
  • Hertz Dipol = Short dipol:
  • -Dipol:
  • draw electrical field of dipole
  • Aperture antennas: , with , leads to gain of
  • examples of reflector antennas (effective aperture)

For more info, see intro course: http://www.cv.nrao.edu/course/astr534/AntennaTheory.html

⌘Example:

Gain calculation for a -antenna calculate the gain of a antenna, given that the electrical field can be described as:

AntennaGain.png

Practical measurement of antenna gain: Compare the value of the electromagnetic field in the main direction of radiation with the gain of an isotropic antenna (or the gain of a known antenna). Best interaction is for antennas with length l approx lambda/2 ... lambda. Examples are provided for stubb antennas on GSM phones and typical WLAN 802.11b antennas.


AntennaGainCalculation.png

Calculate the gain of a lambda/2 antenna, given that the electrical field of the antenna is given through a sin(theta) relation


DoublingAntennaGain.png

Doubling antenna gain (+3 dB) will decrease the antenna pattern by a factor of two. This might cause mobile phones to fall outside of the radiation range.

⌘Example

What happens if I move from 2.4 Unik/GHz (802.11b) band to 5.1 Unik/GHz (802.11a)?

  • Free space propagation
  • antenna gain
  • total power budget
  • other factors?



AntennaPattern.png

Increase frequency from 2.4 to 5.2 Unik/GHz will yield to an additional free-space attenuation of 5.5 dB. If the same antennas are used, then this attenuation will be overcompensated by the antenna gain of both the transmit and the receive antenna.

However, the antenna characteristic will change significantly when doubling the frequency. Assuming that no mismatch occurs at the antenna feed, the width of the antenna beam will be reduced by a factor of two (relation lambda/l). This means that if receive and transmit antennas don't point towards each other, significant antenna gain loss might be seen.

Antenna interaction

  • from antenna design, what have we learned?
  • which length/area is best (as compared to to interact with an electromagnetic wave)?

⌘ Further Reading

  • Media:Antennas_for_communications_Haavard.pdf (by Håvard Austad)
  • Book: Stallings; Wireless Communications & networks
  • Book:Thorvaldsen & Henne; Planning of line-of-sight radio relay system
  • Book:Balanis: Antenna Therory: Analysis and Design

⌘ B3-Multipath Propagation

Building .... Networks
History, Now and Future
History
Pioneers: Maxwell, Hertz,...
1G, 2G,... 5G networks
Frequencies and Standards
Future Challenges
A-Basics of Communication
Electromagnetic Signals
Radio Communication Principles
Digital communication: Signal/Noise Ratio
Signal strength and Capacity: Shannon
B-Antennas and Propagation
Free Space Propagation
Antennas, Gain, Radiation Pattern
Multipath Propagation, Reflection, Diffraction
Attenuation, Scattering
Interference and Fading (Rayleigh, Rician, …)
Mobile Communication dependencies
C-Propagation models
Environments (indoor, outdoor to indoor, vehicular)
Outdoor (Lee, Okumura, Hata, COST231 models)
Indoor (One-slope, multiwall, linear attenuation)
D-System Comparison
Proximity: RFID, NFC
Short Range: ZigBee, Bluetooth, ANT+,...
WLAN/Wifi/802.11...
Mobile: GSM, UMTS, IMT-A (WiMAX, LTE)
E-Mobility
Mobile Network mobility
IP mobility
F-Network Building
Future Networks
5G Heterogeneous Networks
Basic Internet
Video Distribution Networks
Coverage simulations
Coverage simulations
Traffic simulations
Network Capacity simulations
Building .... Networks

⌘Multipath and how to use it

Multipath propagation Multipath propagation can be used through
  1. ) specific receivers (rake receivers)
  2. ) Multiple-input, multiple-output antenna systems (MIMO)

Note: The mobile phone users will typically not have a direct link between the mobile phone and the antennas of the base station in a typical environment. Such a situation, where the mobile communication has to go "around a building" or "around the corner" are called NLOS, non Line-of-Sight connection. As compared to a Line-of-Sight LOS connection the signal is typically reduced by some 20-30 dB.

⌘ Boundary conditions

  • What is happening on electrical walls, magnetic walls?
Figure: Reflection of an electromagnetic wave at the ground plane

Scattering, reflection and diffraction (explain differences) are the three major components in wave propagation. Ideal reflection environments are characterised through


⌘Comments

ReceiverCharacteristics.png

Receiver characteristics for usage of reflections in impulse response

  • sliding 16 mu s window and integration of power in this window (typical GSM)
  • Rake receiver, where each finger of the receiver points to one reflection (typical enhanced GSM, UMTS)
  • MIMO (Multiple input, multiple output) or smart antenna arrays. Here we use spatial filtering, assuming that radiation comes in from different directions (typical 802.11n, smart antennas for UMTS)


⌘ Reflection

Reflection at a perfectly plane gives a reflection coefficient r= -1. When the surface gets rougher, reflection is still in the main direction, but the reflected power is spread around the main reflection angle. Assuming that no absorption takes place, then the total reflected power is constant.

When the surface becomes extremely rough, and with roughness >> lambda, then the reflected wave will be scattered into any direction.

ReflectionScattering.png

Related physics

Free Space impedance as connection of permeability and permittivity .

. The unit of is


.

The unit of is Farad/m:

Diffraction

Diffraction is the transforming of a wave at an object, typical edge of a house ("edge diffraction") or the roof-top

Scattering

Interaction with object being about the same size as the wavelength,


⌘ Interaction of electromagnetic waves with the Environment

InteractionNatural.png

Interaction with a natural target, here: a tree. The tree will interact with the electromagnetic wave both when it comes to thickness of objects and dimension of objects. Thickness typically influences attenuation, while the dimension of the object contributes to the reflection.

Examples are:

  • leaves will mainly interact around 6 Unik/GHz: thickness will attenuate, whereas reflection is due to diameter of leaves
  • branches will have main interaction at about 1 Unik/GHz
  • the tree trunk will interact with almost all frequencies at 30 Unik/MHz and above.

⌘ Attenuation in walls

Attenuation in material follows typical an exponential behaviour. Wallattenuation.png

⌘Attenuation parameters for 2.4 GHz

Obstacle Attenuation [dB]
Brick wall with window 2
Brick wall next to metal door 3
Cinder Block wall 4
Office wall 6
Metal door in office wall 6
Metall door in brick wall 12.4
Floor 30

Measurements performed for European building

(Source:Hydra Deliverable D5.4, p 12)

⌘ Path loss calculation

TableWirelessISM.png

Hydra pass loss approximation

  • relation between fading margin and receiver sensitivity


PathLossHydra.png