CHAPTER NO: 5

Q1: Micro strip antenna?

A Microstrip Antenna (also known as a patch antenna) is a type of
antenna commonly used in wireless communication systems due to
its low profile, lightweight, and ease of fabrication.
Structure:
A typical microstrip antenna consists of:
Radiating patch – usually made of a conducting metal like copper or
gold.
Dielectric substrate – an insulating material that separates the patch
from the ground plane.
Ground plane – a metallic sheet beneath the substrate.
How it Works:
The patch radiates electromagnetic waves when excited by a signal.
The patch and ground plane form a resonant cavity, and the
dimensions of the patch determine the frequency at which it
resonates.
Common Shapes:
Rectangular (most common)
Circular
Elliptical
Triangular
Advantages:
Lightweight and low-profile
Easy to integrate into circuit boards
Cost-effective for mass production
Disadvantages:
Narrow bandwidth
Low power handling
Lower gain compared to other antennas like parabolic dishes
Applications:
Mobile and satellite communication
GPS systems
Radar systems
Wireless LANs and RFID
Q2: What are the basic characteristics of micro strip
antennas?
Microstrip antennas, often referred to as patch antennas, are
widely used in wireless communication systems. Here are the
basic characteristics of microstrip antennas:
Structure:
Consist of a radiating patch on one side of a dielectric
substrate, with a ground plane on the other side.
The patch is usually made of conductive material like copper
or gold.
Low Profile:
They are thin and lightweight, making them ideal for compact
and portable devices.
Ease of Fabrication:
Can be easily fabricated using printed circuit board (PCB)
technology.
Suitable for mass production.
Frequency Range: Typically operate in the GHz range (e.g., 1–
10 GHz), though designs exist for higher or lower frequencies.
Narrow Bandwidth: One major limitation is their narrow
bandwidth (usually 1–5%), although techniques exist to
improve it.
Low Gain: Generally have low to moderate gain (about 6–9
dBi).
Gain can be enhanced using arrays or other structures.
Directional Radiation Pattern: Usually exhibit a broadside
radiation pattern (perpendicular to the surface).
Suitable for point-to-point communication.
Polarization: Can support linear or circular polarization,
depending on the patch shape and feeding technique.
Variety of Shapes: Common shapes include rectangular,
circular, triangular, and more, each affecting performance
characteristics.
Feeding Techniques: Several methods like microstrip line
feed, coaxial probe feed, aperture coupling, and proximity
coupling.
Would you like a diagram or more technical details (e.g.,
formulas for resonance or bandwidth).
Q3: Explain Feeding mechanism of micro strip
antennas?
The feeding mechanism of microstrip antennas refers to how the
antenna is supplied with the RF (radio frequency) signal. It is a critical
part of antenna design because it affects performance like impedance
matching, bandwidth, radiation efficiency, and ease of fabrication.
There are four main types of feeding mechanisms used in microstrip
antennas:
1. Microstrip Line Feed (Edge Feed):
Description: A microstrip transmission line is directly connected to the
radiating patch.
Advantages:
 Simple to design and fabricate
 Easy to match impedance

Disadvantages:
 Poor isolation between feed and radiating element
 Increased radiation from the feed line
2. Coaxial Probe Feed (Coaxial Connector Feed):
Description: A coaxial cable is used to feed the patch through the
substrate. The inner conductor connects to the patch, and the outer
conductor is grounded.
Advantages:
 Easy to fabricate
 Good isolation between the feed and patch
Disadvantages:
  Difficult to fabricate for thick substrates
 Matching can be complex
3. Aperture Coupled Feed:
Description: The feed line is located on a separate substrate beneath
the patch and couples energy to the patch through a small aperture
(slot) in the ground plane.
Advantages:
 Good isolation between feed and radiator
 Better bandwidth and radiation performance
Disadvantages:
 More complex design and fabrication
 Increased overall antenna thickness
4. Proximity Coupled Feed (Electromagnetic Coupling):
Description: The patch and feed line are on two different substrates
stacked on top of each other. Coupling occurs through
electromagnetic fields.
Advantages:
 Excellent bandwidth
 No physical connection to the patch
Disadvantages:
 Complex to fabricate
 Harder to control the coupling

Q4: What are the methods of analysis of micro strip

antennas?
The analysis of microstrip antennas (MSAs) can be approached
through various methods, depending on the level of accuracy
required and the complexity of the antenna structure. Here are the
main methods of analysis:
1. Transmission Line Model:
Simplest and most intuitive method.
Treats the microstrip patch as a resonant cavity with two radiating
slots.
Models the patch as a parallel plate transmission line.
Suitable for rectangular and circular patch antennas.
Advantages:
1) Simple and easy to use.
Disadvantages:
1) Less accurate, especially for complex shapes or higher
frequencies.
2. Cavity Model:
Assumes the patch is a cavity with perfect electric conductor (PEC)
on top and bottom and perfect magnetic conductor (PMC) on the
sides.
Analyzes the resonant modes inside the cavity.
More accurate than the transmission line model, especially for
calculating fields and radiation patterns.
Used for: Gain, efficiency, and field distribution analysis.
3. Full-Wave Electromagnetic Methods:
These are more rigorous and accurate, based on solving Maxwell’s
equations.
a). Method of Moments (MoM):
 Integral equation-based method.
Very accurate for planar structures like microstrip antennas.
Used in software like IE3D, FEKO, HFSS (in MoM mode).
b). Finite Element Method (FEM):
Solves the antenna structure by discretizing it into small elements.
Excellent for complex geometries and inhomogeneous substrates.
Used in tools like ANSYS HFSS.
c. Finite Difference Time Domain (FDTD):
Time-domain method; good for wideband and transient analysis.
Solves Maxwell’s equations over a grid in both space and time.
Powerful for broadband antennas and nonlinear materials.
4. Hybrid Methods:
Combine multiple techniques for better accuracy and
computational efficiency.
Example: MoM for radiation and FEM for internal fields
Q5: Explain rectangular patch and circular patch in micro
strip antenna?
In microstrip antenna design, rectangular patch and circular patch
are two common shapes used for the radiating elements. Here's a
simple explanation of both.
1. Rectangular Patch Antenna:
Shape: A flat rectangular-shaped metallic patch placed over a
dielectric substrate, backed by a ground plane.
Popular because: It's the easiest to design and analyze
mathematically.
Resonant Frequency: Determined by the length of the patch, which is
usually about half the wavelength in the dielectric medium.
Polarization: Can support linear or circular polarization depending on
feed technique.
Feed Methods: Commonly uses microstrip line, coaxial probe, or
aperture coupling.
Applications: Widely used in satellite communication, GPS, and
wireless devices.
Pros:
 Easy to fabricate.
 Simple analysis and modeling.
 Compact and low-profile.
Cons:
 Narrow bandwidth.
 Low gain (though arrays can improve this).
2. Circular Patch Antenna:
Shape: A flat circular metallic patch on a dielectric substrate with a
ground plane underneath.
Resonant Frequency: Based on the radius of the patch and dielectric
properties.
Polarization: Supports both linear and circular polarization.
Feed Methods: Coaxial probe or inset microstrip feed is commonly
used.
Applications: Often used in applications requiring circular
polarization, such as satellite communications and radar.
Pros:
 Better symmetry – good for circular polarization.
  Slightly better radiation efficiency in some cases.
Cons:
 More complex analysis compared to rectangular.
 Slightly harder to fabricate with precision.