This document provides an overview of microstrip patch antennas, also known as patch antennas. It defines patch antennas as consisting of a metal patch on top of a grounded dielectric substrate, which are useful at microwave frequencies above 1 GHz. The document discusses the geometry, advantages, disadvantages, feeding techniques, basic properties including resonance frequency and bandwidth, radiation pattern, and applications of microstrip patch antennas. The main applications mentioned are in mobiles, satellites, GPS, WiMAX, medical devices, and radar.

2. OVERVIEW
• DEFINITION
• GEOMETRY
• ADVANTAGES AND DISADVANTAGES
• FEEDING TECHNIQUES
• BASIC PROPERTIES
• BANDWIDTH IMPROVEMENT
• RADIATION PATTERN
• IMPROVING PERFORMANCE
• MAIN APPLICATIONS
• CONCLUSIONS
• REFERENCES

3. WHAT IS MICROSTRIP ANTENNA
ALSO CALLED AS ‘PATCH ANTENNAS’
 One of the most useful antennas at microwave
frequencies( f>1 Ghz)
 It consists of a metal ‘patch’ on top of a grounded
dielectric substrate
 The patch may be in variety of shapes but circular
and rectangular are the most common

4. OVERVIEW OF MICROSTRIP ANTENNA (CONT.)

5. GEOMETRY OF RECTANGULAR PATCH ANTENNA
Typically h is much smaller than operating wavelength but not smaller than .05 of
wavelength

6. ADVANTAGES OF PATCH ANTENNA
 Light weight and low volume
 Easy to fabricate(use etching & photolithography)
 Easy to feed(coaxial cable,microstrip line etc.)
 Easy to use in an array or incorporate with other
microstrip circuit elements
 Mechanically robust when mounted on a rigid
surface

7. DISADVANTAGES OF PATCH ANTENNA
 Narrow bandwidth
 Low efficiency limited by *conductor & dielectric and **surface
wave losses
 Low gain
 Radiation from feeds and junctions
 Low power handling capacity
*Conductor and dielectric losses are more severe for thinner
substrates
**Surface wave losses become more severe for thicker
substrates(unless air or foam is used)

8. FEEDING TECHNIQUES
MICROSTRIP FEED :
• EASY TO FABRICATE
• SIMPLE TO MATCH BY
CONTROLLING THE INSET POSITION
• RELATIVELY SIMPLE TO MODEL

9. FEEDING TECHNIQUES(CONTD.)
QUARTER WAVELENGTH FEED
Z1 CAN BE ALTERED BY
CHANGING WIDTH OF
QUARTER WAVELENGTH
STRIP

10. FEEDING TECHNIQUES(CONTD.)
COAXIAL OR PROBE FEED
• EASY TO FABRICATE
• LOW SPURIOUS RADIATION
• FEED CAN BE PLACE AT ANY DESIRED
LOCATION TO MATCH IMPUT
IMPEDANCE
• NARROW BANDWIDTH
• FOR THICKER SUBSTRATES,THE
INCREASED PROBE LENGTH MAKES
Zin MORE INDUCTIVE

11. FEEDING TECHNIQUES(CONTD.)
APERTURE COUPLING FEED
• THE RADIATING PATCH AND THE MICROSTRIP FEED
LINE ARE SEPARATED BY THE GROUND PLANE
• THE AMOUNT OF COUPLING FROM
THE FEED LINE TO THE PATCH IS
DETERMINED BY THE SHAPE, SIZE
AND LOCATION OF THE APERTURE.
• LOW SPURIOUS RADIATION
• DIFFICULT TO FABRICATE
• NARROW BANDWIDTH

12. FEEDING TECHNIQUES(CONTD.)
PROXIMITY COUPLING
• FEED LINE IS BETWEEN THE TWO SUBSTRATES AND THE RADIATING PATCH IS
ON TOP OF THE UPPER SUBSTRATE.
• ELIMINATES SPURIOUS RADIATION
• HIGH BANDWIDTH
• DIFFICULT TO FABRICATE
• Length of feeding stub and
width-to-length ratio of patch
is used to control the match

13. BASIC PROPERTIES OF PATCH ANTENNA
RESONANCE FREQUENCY
The resonance frequency is controlled by the patch length and the substrate
permittivity.
The calculation can be improved by adding a“fringing length extension” ΔL to each
edge of the patch to get an “effective length” Le .

14. RESONANT FREQUENCY(CONTD.)

15. BANDWIDTH
• The bandwidth is directly proportional to substrate
thickness h.
• The bandwidth is inversely proportional to εr (a foam
substrate gives a high bandwidth).
• The bandwidth is directly proportional to the width W.
RESULTS:
• By using a thick foam substrate, bandwidth of about
10% can be achieved.
• By using special feeding techniques (aperture coupling)
and stacked patches, bandwidth of over 50% have been
achieved.

16. BANDWIDTH IMPROVEMENT
U-SLOT
The introduction of a U-shaped slot
can give a significant bandwidth
(10%-40%).
DOUBLE U-SLOT
A 44% bandwidth was achieved.

17. BANDWIDTH IMPROVEMENT(CONTD.)
A bandwidth of 34% was achieved

18. RESONANT INPUT RESISTANCE
• The resonant input resistance is almost independent of the
substrate thickness h.
• The resonant input resistance is proportional to εr.
• The resonant input resistance is directly controlled by the
location of the fed point. (maximum at edges , zero at center
of patch.)

19. RADIATION PATTERN
• The E-plane pattern is typically broader than the H-
plane pattern.
• The truncation of the ground plane will cause edge
diffraction, which tends to degrade the pattern

20. RADIATION PATTERN(CONTD.)
E - P L A N E
PAT T E R N
H - P L A N E
PAT T E R N

21. IMPROVING PERFORMANCE
By Reducing Surface-Wave Excitation and LateraL Radiation by
decreasing dielectric thickness and permittivity

22. IMPROVING PERFORMANCE(CONTD.)
Reducing surface-wave excitation and lateral radiation
reduces mutual coupling.

23. MAIN APPLICATIONS
1. MOBILES AND SATELLITES
2. GLOBAL POSITIONING SYSTEM(GPS)
3. RADIO FREQUENCY
IDENTIFICATION(RFID)
4. WORLDWIDE INTEROPERABILITY
FOR MICROWAVE ACCESS(WiMAX)
5. MEDICAL APPLICATIONS
6. RADAR APPLICATIONS

24. CONCLUSION
• A THEORITICAL AS WELL AS PRACTICAL ASPECT OF MICROSTRIP
PATCH ANTENNA IS PRESENTED
• Lower gain and low power handling capacity can be
overcome through an array configuration.
• Particular microstrip patch antenna can be designed for each
application and different merits are compared with
conventional microwave antenna.

25. REFERENCES
• C.A. Balanis, Antenna theory: analysis and design, 2nd ed., John Willey and
& Son, Inc., 1997
• James j., and P.S. Hall (Eds), Handbook of microstrip antenna, Peter
Peregrinus, London, UK, 1989.
• J. D. Kraus, R. J. Marhefka, “Antenna for all applications” 3rd Ed., McGraw-
Hill, 2002.
• P.Subbulakshmi , R.Rajkumar : “ Design and characterization of corporate
feed rectangular microstrip patch antenna array antenna”,IEEE International
Conference on Emerging Trends in Computing, Communication and
Nanotechnology,549-552, (ICECCN 2013)
• WWW.ANTENNA-THEORY.COM