WIDE BAND RADIATORS, DESIGN OF HELICAL ANTENNAS FOR COMMUNICATION ,

2. RADIATION & PROPOGATION
-Broadband Antennas
AJAL.A.J
Assistant Professor –Dept of ECE,
UNIVERSAL ENGINEERING COLLEGE, THRISSUR- 680123 - INDIA
Mob: 8907305642
MAIL: ec2reach@gmail.com

3. Broadband Antennas

4. Overview
Typical antennas are designed for a specific
narrow band of operation
Broadband antennas are designed to operate
effectively over a wide range of frequencies



Public two-way-radio VHF covers 130-174Mhz
Public two-way-radio UHF 406-512Mhz
The challenge is to create an antenna which can
operate in both the VHF and UHF bands

5. Bandwidth
Definition for center frequency: f C =
fU − f L
2
Bandwidth can be expressed as a percentage of the
center frequency or as a ratio


The percentage is commonly used for small bandwidth
antennas:
f − fL
BP = U
× 100%
fC
The ratio is commonly used for large bandwidth antennas:
BR =
fU
fL

6. Broad Spectrum of Types
Helical
Log Periodic
Biconical
Sleeve
Spiral
6

7. Narrow Band Antennas
Circularly Polarized
Linearly Polarized
Feed
Horns
Dipole
Uniform Helical
Yagi-Uda

8. Broad Band Antennas
Circularly Polarized
Linearly Polarized
Array of narrow band
antennas
Tapered
Helical
Spiral
Planar
Tapered Yagi-Uda

9. Polarization
helical antennas have circular polarization

10. Parameters Varied
Conductor material
Size of conductor

11. Cont. Parameters Varied
SMA connector
Tuning
Feeding point

12. Biconical Antenna
Types of Biconical



Infinite Biconical
Finite Biconical
Discone

13. Log Periodic Antenna
The antenna is ideally suited for
reception of VHF/UHF point-topoint communication where its
directional characteristics can
significantly improve rejection of
interfering signals.
In professional applications, this
antenna is ideally suited for EMC
pre-testing, surveillance and
monitoring.
The antenna covers a frequency
range of 230 to 1600 MHz (a
much wider frequency range can
be received with reduced gain).
http://www.winradio.com/home/ax
31b.htm

14. Sleeve Antenna
The sleeve antenna is used
primarily as a receiving
antenna. It is a broadband,
vertically polarized,
omnidirectional antenna. Its
primary uses are in broadcast,
ship-to-shore, and ground-toair communications. Although
originally developed for shore
stations, there is a modified
version for shipboard use.
http://www.tpub.com/inch/32.ht
m
http://www.emartin.it/it9vky/Ris
orse/opensleeve.htm

15. Spiral Antenna
http://www.emi.dtu.dk/research/afg/research/gpr/spiral_antenna.html
http://www.naapo.org/Argus/docs/990702.htm
The spiral antenna is used
primarily as a receiving antenna
Vertically polarized
Frequency Independent

Designed to minimize finite lengths
and maximize angular dependence
http://www.ece.uiuc.edu/pubs/antenna/slide03.html

16. Helical Antenna
Helix antenna
was invented by J. D. Kraus.
two modes of operation,
normal
axial

17. Helix Antenna Story
Dr. John Kraus
Professor of Electrical
Engineering and
Astronomy Emeritus
Ohio State University

19. Radiation Patterns
NORMAL MODE

20. Radiation Patterns
AXIAL MODE

21. Geometrical Considerations
Matching Network
S
D1
D2
L

22. Building the First Prototype

23. Building the Array

24. Increasing the Diameter
Kapton Tape
D1
Matching Network
D2

25. Calculations

26. Measurements

27. Return Loss

28. VSWR

29. Resonance and Matching
Reflection




SWR
Return Loss
Smith Chart
Impedance
Transmission

30. Gain
Spectrum Analyzer
Signal
Generator

31. Helical Antenna
Directional
Circularly Polarized

Polarization changes
with time
Both high gain and
wide band

32. 
1989 ONWARDS

33. 1989
Early Helix – 2 x 10 Turns

34. 1991
2 x 15 Turn 70 cm Helix

35. About 1994
AO-13 Antennas

36. 2001
AO-40 Antennas

37. 2003
13 and 23 cm Helix Arrays

39. Geometry
D= diameter of helix
C= circumference of helix
Lo= length of one turn =
C2 + S2
S
)
α= pitch angle = tan (
πD
−1
S= spacing between turns
N= number of turns
Lw= length of helix
d= diameter of conductor
Antenna Theory, Constantine A. Balanis
Theory,

40. Normal Mode
Radiation pattern similar
to linear dipole
The dimensions of the
helix are small compared
to the wavelength
Narrow in bandwidth
Radiation efficiency is
small
Rarely used

42. Axial Mode
Circular Polarization



¾<C/λ<4/3
C/λ=1:near optimum
S= λ/4
Half-Power Beam width: 50 x 50 degrees
3
52λ 2
C NS
Directivity:
C 2S
15 N 3
λ
Typical Gain: 10dB
Bandwidth: 52%
Frequency limit: 100MHZ to 3GHz
http://www.mobile.ss.titech.ac.jp/~ken/broadband-antennas.pdf

43. Helix Applications
Space Telemetry Applications of satellites,
space probes, and ballistic missiles

Signals have undergone Faraday rotation
Directional applications

44. Adaptation of Single Antenna for
Multi-band Use.

45. Test Equipment Set Up

46. Antenna Test Range

47. Spiro-Helical Antenna

49. double helix gps antenna

50. GPS & GLONASS

51. thanks for your patient listening