2. What is an antenna???
• Antenna is an electrical device which converts electrical power into radio waves
and vice versa
• It is usually used with a radio transmitter .
• Different types of antennas are
1)Microstrip antenna
2)Conventional micro wave antennas
3. Microstrip Antenna
• Microstrip antennas consists of a radiating
patch on one side of dielectric substrate
(Єr≤10), which has a ground plane on other
side.
• The micro strip antennas are the present day
antenna designer’s choice.
• A micro strip antenna is characterized by its
Length, Width, Input impedance, and Gain
and radiation patterns
6. Micro strip patch antenna
• Micro strip antennas consists of a
radiating patch on one side of dielectric
substrate (Єr≤10), which has a ground
plane on other side.
• The patch is generally made of
conducting material such as copper or
gold and can take any possible shape.
• The radiating patch and the feed lines
are usually photo etched on the
dielectric substrate.
7. Disadvantages
• Lightweight construction
• Versatility of possible
geometries
• Low cost manufacturing
• Simplicity of structure
Advantages
• Narrow bandwidth,
typically 3%
• Have low directivity /
broad beam width
• Low radiating power
efficiency
.
9. Rectangular Patch Antenna
• For a rectangular patch, the length L
of the patch is usually 0.3333λo< L <
0.5 λo, where λo is the free-space
wavelength. The patch is selected to
be very thin such that t << λo
(where t is the patch thickness).
• The height h of the dielectric
substrate is usually 0.003λo≤h≤0.05
λo.
• The dielectric constant of the
substrate (εr) is typically in the
range 2.2 ≤εr≤ 12.
10. Feed line techniques
• A feed line is radiate by direct or indirect contact.
• There are many different techniques of feeding and four most popular
techniques are
1. coaxial probe feed
2. micro strip line
3. aperture coupling and
4. proximity coupling
11. coaxial probe feed
• Coaxial probe feeding is feeding method in
which that the inner conductor of the
coaxial is attached to the radiation patch of
the antenna while the outer conductor is
connected to the ground plane
• Advantages of coaxial feeding is easy of
fabrication, easy to impedance match, low
spurious radiation
• disadvantages is narrow bandwidth,
Difficult to model specially for thick
substrate.
12. Proximity Coupled Feed
• This type of feed technique is also called as
the electromagnetic coupling scheme.
• two dielectric substrates are used such that
the feed line is between the two substrates
and the radiating patch is on top of the
upper substrate.
• The main advantage of this feed technique
is that it provides very high bandwidth
• the disadvantage of this method is that as
substrate thickness increases
13. Microstrip Line Feed
• In this type of feed technique, a conducting
strip is connected directly to the edge of the
Microstrip patch
• The conducting strip is smaller in width as
compared to the patch and this kind of feed
arrangement has the advantage that the feed
can be etched on the same substrate to
provide a planar structure
• The purpose of the inset cut in the patch is
to match the impedance of the feed line to
the patch without the need for any
additional matching element.
15. Mobile and satellite communication
• Mobile communication requires
small low cost ,low profile antennas
• Rectangular micro strip patch
antenna meets all requirements
and various types of micro strip
antennas have been designed to
use in mobile communication
• In case of satellite communication
Circularly polarized patterns are
required and can be realized using
either circular or square patch
Internal Integrated Microstrip Antenna
External Retractable Antenna
Internal Integrated Antenna
16. Real World Examples cont…_________
• Used at Johnson Space Center to
measure pre-launch ice buildup on
orbiter
• Measure thickness of ice on
roadway
• Measure thickness of uncut coal in
a mine
Microstrip Antenna as a sensor
17. conclusion
• A microstrip patch GPS antenna thinner and cheaper than the thick ceramic
patch antenna usually employed for automotive applications was proposed and
analyzed.
• This configuration allows to easily integrate a low noise amplifier on the
substrate used for the feeding circuitry.
18.
19. Return loss
• Return Loss:
• Return loss is the difference, in dB,
between forward and reflected power
measured at any given point in an RF
system and, like SWR, does not vary
with the power level at which it is
measured. A return loss of -30dB is
obtained at the desired frequency.
20. Input Impedance
• An antenna's impedance relates the voltage to
the current at the input to the antenna. The
magnitude of 0.82 is obtained from the input
impedance smith chart.
