1. Wireless Radio Basics

2. Energy Losses / Gains
In all wireless communication systems there are several factors that contribute to the loss / gain of signal strength. Things that affect the signal strength include:
Choice of Cabling
Antenna Selection
Connectors
Environmental Obstructions

3. Radio Bands and Channels:
RADIO
CHANNEL
INCREASING
FREQUENCY :
RADIO
BAND
CHANNEL
WIDTH :

4. Frequency Spectrum Basic resource for wireless communications
practical radio communication between 3 KHz and 300 GHz
new systems designed tend to go higher in frequency providing larger bandwidth

5. Spectrum Allocation Chart
Mobile bands
Upper part of band for base Tx
lower part of band for base Rx

6. Radio Bands for Industrial Wireless
Licensed band - licensed by government authority
Specific frequency channel, only one user per area
“Narrow-band” - channel width 6.25, 12.5 or 25KHz
License-free - ISM - Industrial, scientific & medical
Spread spectrum technique, Allows wide-bandwidth

7. Radio Bands for Industrial Wireless -example
Examples
Licensed band to 470 MHz x 12.5KHz
License-free to 928 MHz, 26 x 1MHz or 1040 x 25KHz
GHz, extremely wide channels
Wider channels  Wider bandwidth  Higher data rates

8. Types of Spread Spectrum
Direct Sequence (DSSS)
Spreads data packet over wide band - effectively transmitting each bit on many channels. Higher data rates (> 1Mb/s), but vulnerable to interference.
Frequency Hopping (FHSS)
Change frequency after each data packet. Slower data rates (115.2Kbd), but more robust. Less vulnerable to interference.

9. Direct Sequence SS Each data bit is spread over multiple frequencies
Average power is reduced
Direct Sequence has a higher bit rate than Frequency Hopping
More vulnerable to interference

10. Frequency Hopping Power Watt Frequency Time/mSec 928MHz 869.65 MHz
Here it is in action verses time!
Frequency
902MHz
869.4 MHz
Time/mSec

11. Frequency Hopping
905U uses 50 x 250KHz channels
After 3 transmissions

12. Frequency Hopping
After 12 transmissions

13. Frequency Hopping
After 100 transmissions, all channels have been used once

14. Radio Variables Two main variables Frequency - Hertz - KHz, MHz, GHz
Power - linear measurement - Watts - mW, W
- log scale more common - dBm - referenced to 1mW
dBm = 10 log10 [RF signal in mW]
x 2 = +3dB x 4 = +6dB x 5 = +7dB x 10 = +10dB
x 1/2 = -3dB x 1/4 = -6dB x 1/5 = -7dB x 1/10 = -10dB
1mW = 0dBm 10mW = 10dBm mW = ? mW = ?
20dBm
23dBm

15. The real question should be: How far will a radio receive?
How far will the radio transmit?
The answer is...
The real question should be:
How far will a radio receive?

16. Receiver Sensitivity
A radio signal becomes unreliable when it’s strength falls below the Receiver Sensitivity or the background noise RF
Amplitude
Time
Noise
Average
level
Receiver sensitivity

17. Bit Error Ratio
BER - Ratio of the number of errors to total bits transmitted RF
Amplitude
Time
Noise
Receiver sensitivity
High BER Low BER
Received signal

18. Fade Margin
Fade margin is margin between Signal and Noise / Sensitivity
“Safety Margin” - normally 10dB on a “fine day” RF
Amplitude
Time
Noise
Receiver sensitivity
Fade margin
Received signal

19. Factors Affecting Distance
Frequency
as frequency increases, distance decreases proportionally
Receiver sensitivity, antenna gain, cable loss
despite manufacturers’ claims, most wireless products have similar sensitivities
Noise / interference
The noisier the environment the more careful you have to be with antenna placement
Transmitter power, antenna gain, cable loss
Attenuation of radio signal
Heights of antennas, Obstructions in radio path
Other factors
Atmospheric, Ground Mineralisation

20. Signal Attenuation A radio signal attenuates as it passes through air
Transmitter
30dBm = 1W
RF Power (dBm) along a radio path
Min. signal level for reliable operation
Receiver
-110dBm = 0.01pW
Distance

21. Transmit Power RF Power (dBm) along a radio path Distance
Increasing the power at the transmitter increases the distance
In “free-space”, distance doubles for 4x increase
in power (+6dB)
Power must reduce to 1/4 (-6dB) for
distance to halve
Transmitter
RF Power (dBm) along a radio path
Min. signal level for reliable operation
Distance

22. The effect of obstacles
miles
RF Power (dBm) along a radio path
Typical congested industrial path
Line-of-sight path
feet
Distance

23. The effect of obstacles
An obstacle has less blocking effect in the middle of the path
than close to one end
Radio path pattern between two antennas is a “football” envelope
The envelope is “less spread” as frequency increases  obstacles have more of a blocking effect at higher frequencies

24. Typical industrial radio path
No direct path
Multiple reflected paths Tx
There is more signal loss on reflection or passing through buildings as frequency increases Rx

25. Radiated Power Transmitter power = Power generated by transmitter
Radiated power = Power radiated by antenna in desired direction
ERP = Effective Radiated Power
= Transmitter power * Antenna gain * Cable loss
Cable loss is less than 1 and reduces radiated power.
Antenna gain should be more or less than 1
In dB terms,
ERP = Transmitter dBm + Antenna gain dB - Cable loss dB

26. Radiated Power Same effect at Receiver Effective radiated
Transmitter Power = 30dBm
= 1W
Effective radiated
power = 36dBm
= 4W
cable loss
- 4dB
Antenna gain
= 10dB
Signal at Receiver
= -94dBm
cable loss
- 4dB
Received Signal = -100dBm
Antenna gain
= 10dB
Same effect at Receiver

27. Power Losses
All wireless communication systems have several factors that contribute to the loss of signal strength. Cabling, connectors, and lightning arrestors can all impact the performance of your system if not installed properly.
In a ‘low power’ system every dB you can save is important!! Remember the “3 dB Rule”.
For every 3 dB gain you will double your power
For every 3 dB loss you will halve your power

28. 3 dB Rule -3 dB = 1/2 power -6 dB = 1/4 power +3 dB = 2x power
Sources of loss in a wireless system: free space, cables, connectors, jumpers, obstructions

29. Propagation Mechanisms
Propagation mechanisms are very complex and diverse.
First, because of the separation between the receiver and the transmitter, attenuation of the signal strength occurs.
In addition, the signal propagates by means of diffraction, scattering, reflection, transmission, refraction, etc.

30. Propagation Mechanisms - LOS (Line of Sight)
Site A
Site B
Antenna to Antenna
This maximizes the distance and reliability of the signal.

31. Propagation Mechanisms - Diffraction
Diffraction occurs when the direct line-of-sight (LOS) between the transmitter and the receiver is obstructed by an obstacle whose dimensions are much larger than the signal wavelength (67cm for 450 MHz radio wave).
Waves bend around the obstacle, even when LOS does not exist
Site A
Site B

32. Propagation Mechanisms - Scattering
Scattering occurs when the path contains obstacles that’s are comparable in size to the wavelength (67cm for 450 MHz radio wave). E.g., foliage, street signs, lamp posts
Similar to diffraction, except that the radio waves are scattered in a greater number of directions.
Of all the mentioned effects, scattering is the most difficult to be predicted.
Site A
Site B

33. Propagation Mechanisms - Reflection
Occurs when the radio wave encroaches an obstacle which is larger than the wavelength (67cm for 450 MHz radio wave).
A reflected wave can increase or decrease the signal level at the receiver. In many cases, the received signal level tends to be very unstable. This is commonly referred to as Multipath Fading.
E.g., the surface of the Earth, buildings, walls, etc.
Site A
Site B

34. Penetrating Objects 900Mhz 2.4Ghz
Higher frequencies have higher attenuation on penetrating obstacles
900Mhz
2.4Ghz

35. Reflections
900Mhz
2.4Ghz
Higher frequencies lose more signal strength on reflection

36. Effects of Obstructions
Radio path does not have to be line-of-sight - only for maximum range
Obstacles reduce radio signal, witch reduces reliable range
Metal and wet obstacles reduce signal more than non-metal and dry
An obstacle has more affect when it is closer to the antenna
TEST THE RADIO PATH

37. Antennas - How They Work
The antenna converts radio frequency electrical energy fed to it (via the transmission line) to an electromagnetic wave propagated into space.
The physical size of the radiating element is proportional to the wavelength. The higher the frequency, the smaller the antenna size.
Assuming that the operating frequency in both cases is the same, the antenna will perform identically in Transmit or Receive mode

38. Antenna Pattern Reference - Isotropic Antenna
Isotropic Source - spherical radiation
This is a hypothetical point source antenna that serves as a reference for the measurement of antenna gain
Gain = 0 dB
Elevation View
Plan View

39. Antenna Types Omni-Directional
The type of system you are installing will help determine the type of antenna used. Generally speaking, there are two ‘types’ of antennas:
Omni-Directional
This type of antenna has a wide beamwidth and radiates 3600; with the power being more spread out, shorter distances are achieved but greater coverage attained
Dipole antenna
This type of antenna is typically used for shorter distances

40. Light is omni-directional
Omni Antenna - Example
Light is omni-directional

41. Omni Antenna Radiation Pattern
Horizontal Pattern
Vertical Pattern

42. Dipole Antenna
Dipole Pattern
Isotropic Pattern
Dipole is made of two 1/4-wave conductors joined in the middle
Elevation
Gain = 2.14 dB
Plan

43. Collinear Antenna Collinears Dipole Collinear 2 Dipoles Stacked Dipole

44. Typical Omni Antenna Gains
Dipole Whip 2dB
Collinears 5 / 8 / 10 dB
1/4 wave whips to 0dB

45. Antenna Types Directional
This type of antenna has a narrow beam-width; with the power being more directional, greater distances are usually achieved but area coverage is sacrificed
Yagi, Panel, Sector and Parabolic antennas
This type of antenna in is used in both Point to Point and Point to Multipoint

46. Light is focussed in a particular direction
Typical Omni Antenna Gains
YAGI Antennas
Reflector / mirror
Light is focussed in a particular direction

47. YAGI Antennas
Reflector
Folded Dipole
Director

48. YAGI Radiation Pattern

49. 2 Element YAGI
Isotropic Antenna
Gain = 3 dB

50. YAGI Bandwidth Yagi Antennas direct almost all power in one direction
Higher gain antennas direct power into a tighter beam
6 Element Yagi
450
9 Element Yagi
350

51. Typical YAGI Gains 16 Element 16dB 9 Element 14dB 6 Element 11dB

52. Parabolic, Grid-pack Antennas
only for very high frequency > 2 GHz
used in medium to long links
gains of 18 to 28 dBi

53. Sectoral Antennas
directional in nature, but can be adjusted anywhere from 450 to 1800
typical gains vary from 10 to 19 dBi
very commonly seen at cell phone base stations

54. Antenna Polarization
Polarization can be Vertical or Horizontal - depend on how antenna is installed.
Omni-directional antennas have Vertical polarity when mounted vertically
Polarity of Yagis is based on direction of elements - can be Vertical or Horizontal
All antennas in the same RF network must be polarized identically regardless of the antenna type.

55. Polarity - Vertical
Yagi
Omni-directional

56. Horizontal Polarity is known as ‘E’ Plane
Polarity - Horizontal
Horizontal Polarity is known as ‘E’ Plane
Two Yagis can form a Horizontal polarity link
Not compatible with Omni-directional antennas
Can be used for “radio isolation” from another system with Vertical polarity

57. Coaxial Cables
Data wireless uses 50 ohm cables - RF impedance is based on inner : outer diameters
Loss increases with cable length and frequency
Larger diameter cables have lower loss, but are much harder to install - bending radius

58. Attenuation Table - Cables
Attenuation Table for 900Mhz should be added too as follows:
-12.9dB/100meters (LMR-400)
-8.3dB/100meters (LMR-600)
-4.1dB/100meters (7/8” Heliax)
-7.55dB/100meters(1/2” Heliax)

59. Connector Types
N-male
BNC
N-female
SMA

60. Connectors – Good Practices
Have someone experienced install them
Poor fitting results in high RF losses
Best to buy pre-made cables
Do not splice connections in the antenna lines
Buy one cable that reaches the entire distance
Exposed connections need to be well taped
Antennas – usually Female
Lightning Arrestors – usually Female

61. Cable Connection Protection
Stretch to elongate sealant tape while wrapping over the connection
Scotch® 23 Rubber Splicing Tape
For proper UV protection Electrical Tape should then be wrapped over the Vulcanising Tape
All outside coax connections should be wrapped in a Rubber Vulcanising Tape to stop moisture ingress.

62. The Lightning Arrestor
Use a lightning arrestor when the antenna is not protected by surrounding steelwork
Connect antenna bracket, wireless unit and the lightning arrestor to same earth point.
Typically structural steel is OK for ground connection
Do not use Gas Lines or Water pipes for discharge.
Check Electrical Code for grounding recommendations.

63. Redundancy This is one of the main concerns with wireless systems.
Our products do support redundancy for
Radio path
I/O
Total redundancy
Stand-by

64. Wireless Redundancy – Radio Path
Radio Path redundancy between same modules via a repeater
Suitable if primary radio path is variable – e.g. construction site
Simple to achieve, and only need one radio channel
Doesn’t protect equipment failure
Two sets of outputs
Two comms-fail outputs -
one for each path
Radio Path Redundancy

65. Wireless Redundancy – Outputs
Redundancy for outputs in different locations
Suitable when connected to common system via existing LAN
Protects equipment failure & RF interference at output module
Doesn’t protect equipment failure at input end
Output Redundancy
input

66. Wireless Redundancy – Total
Complete redundancy
Two separate wireless systems on two separate radio channels
Protects equipment failure and RF interference at both ends
Special set-up to ensure radio channels don’t “block” each other
Hot Redundancy

67. Wireless Redundancy – Standby
Standby Redundancy
Protects equipment failure, but not RF interference
Intelligent devices (e.g. PLC) must be at both ends
Intelligent device switches power upon comms-fail
Standby Redundancy
input
comms-fail output

68. Rules For Best Performance
Line of Sight whenever possible – Always the best
Antenna outside of the cabinet - Always
Antenna away from Noisy sources – As far away as possible
other antennas, VFDs, Welders, computers, etc
Antenna as high as possible
Coax Cable as short as possible
Use pre-made tested hi-quality cables, this will lower the loses in the system
Ground ALL equipment to the earth system properly
This will reduce the noise level