29-06-2012, 06:17 PM
MICROSTRIP STACKED PATCH ANTENNA FOR NEXT GENERATION GSM
[attachment=26218]
MICROSTRIP ANTENNA
Introduction
Antennas play a very important role in the field of wireless communications. Some of them are Parabolic Reflectors, Patch Antennas, Slot Antennas, and Folded Dipole Antennas. Each type of antenna is good in their own properties and usage. We can say antennas are the backbone and almost everything in the wireless communication without which the world could have not reached at this age of technology. Patch antennas play a very significant role in today’s world of wireless communication systems. A Micro strip patch antenna (Fig 1) [1] is very simple in the construction using a conventional Micro strip fabrication technique. The most commonly used Micro strip patch antennas are rectangular and circular patch antennas. These patch antennas are used as simple and for the widest and most demanding applications. Dual characteristics, circular polarizations, dual frequency operation, frequency agility, broad band width, feed line flexibility, beam scanning can be easily obtained from these patch antennas.
Merits and Demerits of the Micro strip antennas
The Micro strip antennas have a lot of popularity based on their applications, which has some Merits and De-merits as any other.
The merits of these antennas have some similarities as of the conventional microwave antennas, as these cover a broader range of frequency from 100 MHz to 100 GHz, same is the case with these Micro strip antennas.
These are widely used in the handheld devices (wireless) such as pager, mobile phones, etc...
Some merits and demerits of these Microstrip antennas are: [2]
1.1 (a) Merits:
‐ Low weight, low volume and thin profile configurations which can be made conformal.
‐ Low fabrication cost, readily available to mass production.
‐ Required no cavity backing.
‐ Linear and circular polarizations are possible.
‐ Easily integrated with microwave integrated circuits (MICS).
‐ Capable of dual and triple frequency operations.
‐ Feed lines and matching network can be fabricated simultaneously.
-The telemetry and communication antennas on missiles need to be thin and conformal and are often in the form of Micro strip patch antennas.
-Another area where they have been used successfully is in Satellite communication.
- Mechanically robust when mounted on rigid surfaces.
(b) De Merits
Even though these Micro strip antennas are compared with conventional antennas these Micro strip antennas have some number of demerits:
‐ Low efficiency.
‐ Low grain.
‐ Lower gain ( some what → -6dB)
‐ Large ohmic loss in the feed structure of arrays.
‐ Poor end fire radiator except tapered slot antennas,
‐ Extraneous radiation from feeds and junctions.
-Low power handling capacity (approx 100W).
‐ Excitation of surface waves.
-Narrow bandwidth.
- Extraneous radiation from feeds and junctions.
-Low power handling capacity.
‐ Polarization purity is difficult to achieve.
‐ Complex feed structures require high performance arrays.
‐ There is reduced gain and efficiency as said before and also unacceptably high levels of cross polarization and mutual coupling within the array environment at high frequencies.
‐ Antennas are fabricated on a substrate with a high dielectric constant are strongly preferred for easy integration.
Micro strip patch antennas have a very high antenna quality factor (Q). It represents the losses associated with the antenna where a large Q leads to narrow bandwidth and low efficiency. Q can be reduced by increasing the thickness of the dielectric substrate. But as the thickness increases, an increasing fraction of the total power delivered by the source goes into a surface wave. This surface wave contribution can be counted as an unwanted power loss since it is ultimately scattered at the dielectric bends and causes degradation of the antenna characteristics. Other problems such as lower gain and lower power handling capacity can be overcome by using an array configuration for the elements.
Micro strip antenna falls into the category of printed antennas: radiating element that utilize printed circuit manufacturing process to develop the feed and radiating structure of all printed antenna is by far the most popular & adaptable .This is because of all its salient features: including ease of fabrication, good radiation control & low cost of production.
The Micro strip antenna is constructed from dielectric substrate and patch metal and that a portion of the metallization layer is responsible for radiation. Micro strip antenna was conceived in the 1950s, and then extensive investigations of the patch antennas followed in the 1970s and resulted in many useful design configurations. Through decades of research, it was identified that the performance and operation of a Micro strip antenna is driven mainly by the geometry of the printed patch and the material characteristics of the substrate onto which the antenna is printed.
Theory of Micro strip Patch Antennas
Types of Micro strip Antennas
There are different types of Micro strip antennas which are classified based on their physical parameters. There different types of antennas have many different shapes and dimensions. The basic categories of these Micro strip antennas can be classified in to four [2], which are:
‐ Micro strip patch antennas
‐ Micro strip dipoles
‐ Printed slot antennas
‐ Micro strip travelling wave antennas
Going further let’s have a small description on each of the type of the Micro strip antennas as it will give us good sound knowledge on how each type is classified and on what basis:
[attachment=26218]
MICROSTRIP ANTENNA
Introduction
Antennas play a very important role in the field of wireless communications. Some of them are Parabolic Reflectors, Patch Antennas, Slot Antennas, and Folded Dipole Antennas. Each type of antenna is good in their own properties and usage. We can say antennas are the backbone and almost everything in the wireless communication without which the world could have not reached at this age of technology. Patch antennas play a very significant role in today’s world of wireless communication systems. A Micro strip patch antenna (Fig 1) [1] is very simple in the construction using a conventional Micro strip fabrication technique. The most commonly used Micro strip patch antennas are rectangular and circular patch antennas. These patch antennas are used as simple and for the widest and most demanding applications. Dual characteristics, circular polarizations, dual frequency operation, frequency agility, broad band width, feed line flexibility, beam scanning can be easily obtained from these patch antennas.
Merits and Demerits of the Micro strip antennas
The Micro strip antennas have a lot of popularity based on their applications, which has some Merits and De-merits as any other.
The merits of these antennas have some similarities as of the conventional microwave antennas, as these cover a broader range of frequency from 100 MHz to 100 GHz, same is the case with these Micro strip antennas.
These are widely used in the handheld devices (wireless) such as pager, mobile phones, etc...
Some merits and demerits of these Microstrip antennas are: [2]
1.1 (a) Merits:
‐ Low weight, low volume and thin profile configurations which can be made conformal.
‐ Low fabrication cost, readily available to mass production.
‐ Required no cavity backing.
‐ Linear and circular polarizations are possible.
‐ Easily integrated with microwave integrated circuits (MICS).
‐ Capable of dual and triple frequency operations.
‐ Feed lines and matching network can be fabricated simultaneously.
-The telemetry and communication antennas on missiles need to be thin and conformal and are often in the form of Micro strip patch antennas.
-Another area where they have been used successfully is in Satellite communication.
- Mechanically robust when mounted on rigid surfaces.
(b) De Merits
Even though these Micro strip antennas are compared with conventional antennas these Micro strip antennas have some number of demerits:
‐ Low efficiency.
‐ Low grain.
‐ Lower gain ( some what → -6dB)
‐ Large ohmic loss in the feed structure of arrays.
‐ Poor end fire radiator except tapered slot antennas,
‐ Extraneous radiation from feeds and junctions.
-Low power handling capacity (approx 100W).
‐ Excitation of surface waves.
-Narrow bandwidth.
- Extraneous radiation from feeds and junctions.
-Low power handling capacity.
‐ Polarization purity is difficult to achieve.
‐ Complex feed structures require high performance arrays.
‐ There is reduced gain and efficiency as said before and also unacceptably high levels of cross polarization and mutual coupling within the array environment at high frequencies.
‐ Antennas are fabricated on a substrate with a high dielectric constant are strongly preferred for easy integration.
Micro strip patch antennas have a very high antenna quality factor (Q). It represents the losses associated with the antenna where a large Q leads to narrow bandwidth and low efficiency. Q can be reduced by increasing the thickness of the dielectric substrate. But as the thickness increases, an increasing fraction of the total power delivered by the source goes into a surface wave. This surface wave contribution can be counted as an unwanted power loss since it is ultimately scattered at the dielectric bends and causes degradation of the antenna characteristics. Other problems such as lower gain and lower power handling capacity can be overcome by using an array configuration for the elements.
Micro strip antenna falls into the category of printed antennas: radiating element that utilize printed circuit manufacturing process to develop the feed and radiating structure of all printed antenna is by far the most popular & adaptable .This is because of all its salient features: including ease of fabrication, good radiation control & low cost of production.
The Micro strip antenna is constructed from dielectric substrate and patch metal and that a portion of the metallization layer is responsible for radiation. Micro strip antenna was conceived in the 1950s, and then extensive investigations of the patch antennas followed in the 1970s and resulted in many useful design configurations. Through decades of research, it was identified that the performance and operation of a Micro strip antenna is driven mainly by the geometry of the printed patch and the material characteristics of the substrate onto which the antenna is printed.
Theory of Micro strip Patch Antennas
Types of Micro strip Antennas
There are different types of Micro strip antennas which are classified based on their physical parameters. There different types of antennas have many different shapes and dimensions. The basic categories of these Micro strip antennas can be classified in to four [2], which are:
‐ Micro strip patch antennas
‐ Micro strip dipoles
‐ Printed slot antennas
‐ Micro strip travelling wave antennas
Going further let’s have a small description on each of the type of the Micro strip antennas as it will give us good sound knowledge on how each type is classified and on what basis: