Microstrip Patch Antenna

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Abstract

The basic Microstrip patch antenna consists of a thin metallic patch separated from the ground plane by a dielectric layer usually used at microwave frequencies. The Microstrip antenna, because of its small size, light weight, low profile, and low manufacturing cost is finding increasing applications in the industry. This paper briefly describes some of the features of the patch antenna and presents several examples of the antenna’s commercial applications such as Mobile satellite communication, Direct broadcast system, Global positioning system, Medical hypherthermia etc.


INTRODUCTION

1. Antenna:
An antenna is defined as a device for the radiation and reception of the electromagnetic waves. An antenna is of paramount importance in any communication system. It acts as a transducer (transitional structure) between the transmission line and the free space. An important property of an antenna is the ability to focus and shape the radiated power in space. It enhances the power in some wanted directions and suppresses the power in other directions.
The present communication scenario uses microwave frequencies for efficient transmission and reception. The term microwave is used for the radiations with frequencies 1 to 300GHz. However, microwave really indicates the wavelengths are in the micron ranges. This means microwave frequencies are up to infrared and visible light regions. In this region microwave frequencies refer to those from 1 to 106 GHz.
The antennas used in such microwave systems are called microwave antennas.
Microstrip patch antenna is one of the types of microwave antennas.

2. Microstrip antenna:

A microstrip patch antenna consists of a radiating patch on one side of the dielectric substrate with a ground plane on the other side. These antennas are characterized by,

• Radiation polar pattern
• Directivity
• Efficiency
• Gain
• Equivalent area
• Reciprocity
• Noise power (receiving)
• Terminal impedance, including radiation resistance
• Bandwidth and Q-factor

These antennas have found increasing applications in different fields like, mobile communication system, Global Positioning System, medicine, military applications, Direct Broadcast Satellite (DBS) system, etc. because of its advantages like low profile, small size, light weight, low manufacturing cost etc.


. Historical development

The microstrip patch antenna is dated back to as 1950s where famous figures like Professor Deschamp and Gutton invented the first microstrip patch antenna. The first prototype can be imagined as a thin radiating metal piece of arbitrary shape, separated from a ground plane by a dielectric substrate



3 Capability of adopting modern printed circuit technology:

The microstrip antenna approach has become rather popular and widely used because of the fact that they can be easily fabricated by photolithographic processes. This idea is similar to printed circuits operating at high microwave frequency in terms of GHz as compared to a simple printed circuit board for electronics at low frequency. Microstrip feed lines and radiating patch elements can thus be photoetched with ease on the dielectric substrate.

4 Compatible with modular design:

Research and development over the years have led to many variations for ease of integration with solid state devices like amplifiers, oscillators, modulators, attenuators, switches, mixer etc. these elements can be added to the substrate board without any difficulties. The microstrip antennas are also conformable to planar and non-planar surfaces.