VARIOUS FREQUENCIES USED IN ANTENNA DESIGN, GOLIATH ANTENNAS , REAL TIME SCENARIO

2. EC 09 RADIATION AND PROPAGATION
AJAL.A.J
Assistant Professor –Dept of ECE,
UNIVERSAL ENGINEERING COLLEGE
Mob: 8907305642 MAIL: ec2reach@gmail.com

3. VLF/ LF/ MF Antennas
&
Antenna Systems

4. Instrument Configuration
IDPU: Instrument Data Processor Unit
SPB : Spin Plane Booms (4x)
AXB : Axial Booms (2x)
SST : Solid State Telescope (2x)
ESA : Electrostatic Analyzer
FGM : Fluxgate Magnetometer
SCM : Search Coil Magnetometer
4

5. Probe Configuration
EFI Axial Booms (2, Stowed)
Antenna
ESA
Miniature Sun
Sensor
Fuel Tank
IDPU
EFI SPB
Thruster
A2
Repress
Tank
Fuel Tank
Transponder
Thruster T1
EFI SPB
Thruster A1
BAU
Battery
Gyros
Thruster T2
AEB
EFI SPB
5

6. EM Spectrum
ISM band
902 – 928 Mhz
2.4 – 2.4835 Ghz
5.725 – 5.785 Ghz
LF
30kHz
10km
MF
300kHz
1km
VHF
HF
3MHz
30MHz
100m
10m
UHF
300MHz
1m
SHF
3GHz
EHF

30GHz
300GHz
1cm
100mm
10cm

X rays

infrared visible UV
1 kHz
1 MHz
1 GHz
1 THz
1 PHz
Gamma rays
1 EHz
Propagation characteristics are different in each frequency band

7. Frequency Band Allocations
IR
RADIO
VISIBLE
UV
X-RAYS
GAMMA RAYS
RADIO
VLF
3k
LF
30k
MF
300k
HF
3M
VLF: Very Low Frequency
MF: Medium Frequency
VHF: Very High Frequency
SHF: Super High Frequency
VHF
30M
UHF SHF
300M 3G
EHF
30G
300GHz
LF: Low Frequency
HF: High Frequency
UHF: Ultra High Frequency
EHF: Extremely High Frequency
7

8. Wavelengths of Frequency Bands





c meters sec meters


f cycles sec
cycle

VLF, LF  long waves
Propagate well beyond line of sight
MF  medium waves
The distance the signal travels
HF, VHF  short waves
UHF, SHF  microwaves  Decreases
as the frequency increases

EHF  millimeter waves

Above microwave region, only certain windows of frequencies
propagate freely through air, rain, etc.
Infrared and visible light will not penetrate walls
X-rays and gamma rays interact with matter


8

9. TX
R=100 m
RX

10. VLF Antennas
•
They operates on VLF Band.
•
They are electrically small. This simplifies analysis.
•
They are physically large structures.
–
–
Generally have a number of towers 200-300 m high.
Generally cover areas of up to a square kilometer or
more.
•
Support worldwide communicatipn.
•
The principal objective is to radiate specified amount of
power over a sufficient bandwidth of frequency.

11. Problems with VLF Antennas
1.
Bandwidth is less than 200 Hz.
2.
Small radiation resistance.
3.
They are expensive structures.
4.
Antenna system covers a large area.
5.
Designing an efficient transmitting antenna is
difficult.
6.
High power levels are needed for transmission.

12. Vertical Electric Monopole Antenna
-Antenna Model-

13. Vertical Electric Monopole Antenna
-E and H FieldsAssume a uniform vertical electric current I along a monopole of effective
height he
rms vertical
electric field
rms tangentical
magnetic field

14. Vertical Electric Monopole Antenna
-Radiated Power-
The vertical electric field in terms of radiated power is:

15. Vertical Electric Monopole Antenna
-Equivalent Antenna Circuit-

16. Vertical Electric Monopole Antenna
-Radiation Efficiencywhere
and
antenna loss resistance
Effective power = (power capacity of the transmitter) x (antenna system efficiency)

17. Vertical Electric Monopole Antenna
-Antenna BandwidthThe 3 dB bandwidth b in (c/s) for a single resonant circuit is:
f : resonant frequency
Q: the circuit reactance resistance ratio X/R0
R0: Total series resistance

18. Multiple Tuned VLF Antennas
To have sufficient bandwidths:

Huge antenna systems can be built.
or

Several small multiple-tuned elements can be
used.

19. Multiple Tuned VLF Antennas
 Ground losses are reduced.
 Radiation resistance and efficiency are increased.
 Instead of one and vulnerable antenna, several and smaller elements can
achieve the same bandwidth-efficiency product.
 If one element is shunt off servicing, the others still can be operated.
 The effective ground loss with multiple-tuning will be less than for a
single element.
 Tuning and retuning after the system is disturbed is difficult.
 Each antenna has to be matched to a transmitter.

20. Multiple Tuned VLF Antennas
Goliath Antenna

21. Some Applications of VLF Antenna
1.Submarine:

Requires EM Wave at VLF because of skin effect.

Propagation in sea water is almost vertical so only electric and magnetic
type of dipoles can be used.

Transmitted wave will be attenuated in the sea-water so output power must
be high enough to reach receiver.

22. Some Applications of VLF Antenna (II)
2.Underground Mine Communication:

Especially it is designed for the event of mine disaster.

Provide wireless communication between earth’s surface and miner.

Normal radio frequency get attenuated rapidly so VLF Band is used.

VLF Loop antenna can be used for this purpose.

23. Some Other Applications
Water resource exploration.
 Geological mapping.
 Human body SAR detection.


24. Simplified VLF Transmitting Antenna

25. Pictures
Triatic Type Antenna

26. Maine Antenna Installation

27. Goliath Antenna

28. Goliath Antenna (2)

29. Goliath Antenna

30. Conclusion
@
VLF band

31. VLF Band
EM waves penetrate well into the sea water.
(Communications with submerged
submarines)
Low atmospheric attenuation.
Appropriate for long range communication.

32. VLF Antennas
•
Ground and Sky waves
•
Frequeny range: 3-30 KHz
•
Antennas : very large
•
Power: kW levels and even more

33. Some Problems Associated with VLF
Antenna Systems
•
Small Bandwidth (usually less than 200 Hz)
•
Small radiation resistance.
•
High cost.
•
Antenna system covers a large area.
•
Need for very high power levels for transmission.

34. LF Band

35. LF Antennas

Ground and Sky waves

Frequeny range: 30-300 KHz

Antennas: large

Power: kW levels and even more

36. Some Disadvantages
 High
cost
 Large
Dimensions
 Trouble
with efficiency, power capacity,
bandwidth

37. VLF and LF antennas are
“electrically small” antennas :

problem: high capacitive reactance and
small antenna radiation resistance

remedy: top loading

38. Top-loading
 Top-loading
increases gain bandwidth (by decreasing reactance)
 In
VLF large top-loading
supported by towers

39. 3/5/2014
39

40. INTRODUCTION
•
Usually: Vertical radiators operating in the
MF band (300-3000 kHz).
•
The towers may be guyed or selfsupporting.

41. APPLICATION AREAS
•
AM Broadcasting
•
Maritime Radio
•
Coast Guard Communication
•
Direction Finding

42. CHARACTERISTICS OF
RADIATORS
•
•
Maximum radiation in the horizontal plane
Antennas taller than one-half wavelength have a
minor lobe

43. Characteristics of the
Radiators

Requirement for metallic ground plane to
minimize losses

Vertical polarization is preferred due to
superior propagation characteristics

44. •
•
•
Other features of the
radiators
Shunt fed radiators
Top loaded radiators
Sectionalized radiators

45. Circuits for MF antenna systems
•
•
•
Antenna tuning units for matching purposes
Phase shifter networks for directional antenna systems
Power dividing networks
FROM
TRASMITTER
PHASE CONTROL
NETWORK
T-LINE
ANTENNA
TUNING
UNIT
T-LINE
ANTENNA
TUNING
UNIT
POWER
DIVIDER
NETWORK
PHASE CONTROL
NETWORK

46. Ground Systems
•
•
•
•
•
120 buried (1/4 length) copper wires
Extending radially outward
120-180 cm depth is sufficient
Individual ground systems are
required for each tower of the array.
Copper-mesh ground system may also be
used.

47. Ground Systems
A typical ground system for a two-element directional
antenna

48. HF Antennas &
Antenna Systems

49. HF Antennas and Antenna
Systems

Frequency Range: 3 to 30 MHz
( 10 to 100 meters; in wavelength)

For medium- and long- distance
communications and broadcoasting

50. Characteristics of HF Antennas:

Signals are distorted as the ionosphere is neither
regular nor smooth.

High powers and high antenna gains may be
needed for communication.

51. Types of HF Antennas:
Non-Resonant HF Antennas
Long-wire Antenna
Vee Antenna
Rhombic Antenna
Resonant HF Antennas
Monopole Antenna
Dipoles and Slot
Antennas
Loop Antennas
Log Periodic HF Antennas
Early Log-Periodic Antenna
Logarithmic Dipole Antenna
Directional HF Antennas
End-fire Arrays
Broadside Arrays
Circular Arrays

52. Non-Resonant HF Antennas:
•
wave propagates along the radiator in one
direction only
• remaining power is absorbed in a matched load
TYPES



Long-wire Antenna
Vee Antenna
Rhombic Antenna

53. Long-wire Antenna
A long terminated wire radiator
3/5/2014
53

54. Vee Antenna



Single mast (one wire radiator terminated in a resistive load
at the far end).
Radiation pattern exhibits large side lobes near the main beam.
The efficiency is low (almost half of the total input power may be
exhausted in the matched load.
3/5/2014
54

55. Rhombic Antenna
•
•
•
•
4 radiating wires of equal length mounted on four masts
one of the wires are load-matched.
high directivity
the large rhombics are used for long-range communications.
3/5/2014
55

56. Resonant HF Antennas:

Monopole Antenna
• Elevated-feed Monopole
• Double-cone Monopole
• Inverted-L and –T Antenna

Dipoles and Slot Antennas

Loop Antennas
3/5/2014
56

57. Monopole Antennas
Outside half-wave resonance, elevation pattern breaks up into main
lobes as input impedance becomes very high. Efficiency decreases
3/5/2014
57

58. Dipole Antennas

59. Loop Antennas
Usully used for reception and direction finding.

60. The Log-Periodic Antenna



Fed from the vertex.
Signal travells along the structure until reaches its resonant region.
The signal radiates from the resonant region

61. Directional HF Antennas:

End-fire Arrays
• Horizontal Array of Dipoles
• RCA Fishborne Antenna
• Series Phase Array

Broadside Arrays
• Broadside Dipole Array
• Wide-Band Curtain Array

Circular Arrays

62. End-fire Arrays





Higher directivity.
Provide increased directivity in
elevation and azimuth planes.
Generally used for reception.
Impedance match difficulty in
high power transmissions.
Variants are:

Horizontal Array of Dipoles

RCA Fishborne Antenna

Series Phase Array

63. Broadside Arrays
Beam steering by phase variation is possible.

64. Circular Arrays



Used for direction finding.
Consists of 30 – 100 elements, with equi-spaced and fed
from a central source – goniometer.
Band-width seperation is possible:

65. Ship’s Antenna Arrangement

66. Ship’s Antenna Arrangement
Watch keeping RX
Radar
VHF DSC RX
Scanner
E.B. Saturn 35
Radome
DSC RX
VHF T/RX no. 2
MF/HF Radio Telephone
RDF
loop
VHF DSC TX
Loran RX
Navtex RX
VHF
TX/RX

67. E-layer
F1-layer
D-layer
Night
F2-layer
Day

68. VHF
Direct Wave
TX
RX
Reflected Wave

69. MF
Reflected Wave
Ground Wave
TX
RX

70. HF
8 Mhz
16 Mhz

71. E- Layer’s Effect
F - Layer
E - Layer
DAY

72. E- Layer’s Effect
F - Layer
E - Layer
NIGHT

73. E- Layer’s Effect
F - Layer
E - Layer