Claims:Claims:
1. A design structure of Aperture-Coupled Microstrip Antenna has been fabricated.
2. The antenna has been simulated for different resonant frequencies for di-electric constants 2.4,4 and 9.8.
3. The experimental data have been collected using the fabricated antenna. Similar return loss plot found experimentally proves legitimacy of the work.
4. The proposed approach can be carried to fabricate microstrip fed antenna with any di-electric and any resonant frequencies with adequate success. , Description:Background of invention:
The concept of aperture coupled microstrip was first introduced by D.M.Pozar antenna to compare the bandwidth of standard probe fed microstrip antennas. Various methods of analysis of this structure have been reported in literature. The cavity Q has been computed considering dominant TM10 mode to be present only. The field radiated by a Horizontal Electric Dipole (HED) on a grounded substrate has been used to compute radiated power assuming the patch being replaced by a surface current corresponding to dominant TM10 mode. This formulation takes into consideration the surface wave losses and therefore patches of relatively thicker substrate can be modelled without much error committed. Conductor and dielectric losses can be computed by modeling the cavity as lossy cavity. Many techniques have been suggested related to design and analyze impedance matching and radiation pattern of aperture coupled microstrip antenna. As it has got a number of adjustable parameters, its performance optimization is an interesting problem, which, when carried out properly may result in considerable improvement of bandwidth.
Advantages of Aperture Coupling:
1. The aperture coupling configuration is well suited for monolithic phased arrays wherein various active devices can be integrated.
2. The antenna is shielded from any spurious radiation from the feed line.
3. Problems such as large probe reactance or wide micro strip line, which are critical at microwave frequencies, are avoided as the feed line is electromagnetically coupled to the antenna elements.
4. Theoretically zero cross polarization in principle planes.
The present work presents a method for resonant frequencyoptimization of such type of antenna where the optimization
parameters are aperture length, aperture width and stub length. The length & width of thepatch is obtained initially using suitable softwaretool. Particle Swarm Optimization algorithm1,2 has been used for determining the parameters that provides accurate value of the resonant frequency.
Summary of the Invention:
In aperture coupled microstrip antenna the feed line is electromagnetically coupled to the antenna elements. This feeding
technique has many adjustable parameters in the form of aperture and stub dimensions. It consists of a rectangular patch of
dimensions a x b (a is the length of the patch and b is the width) fabricated on a substrate of thickness h and dielectric constant er. The patch is fed by a microstrip line through an aperture etched in the common ground plane of patch and microstrip feed as shown in the figure. This work presents a design structure of Aperture-Coupled Microstrip Antenna.The structure of Aperture-Coupled Microstrip Antenna has been fabricated for a desired frequency and its results
showing the convergence of return loss at exactly the same target frequency. Same structure procedure can be applied for different frequencies ranging from (2-18 GHz). The authenticity of the work is verified by the measured result obtained experimentally which are very similar to the simulated results.

Detailed description of the proposed approach:

This work presents a design structure of Aperture-Coupled Microstrip Antenna. The investigation is made at different microwave frequency ranges (2-18 GHz) and for different dielectric constant of antenna and feed substrate (er= 2.4,4, 9.8).The dimension of the antenna in the simulation results for resonant frequency=8GHz and dielectric constant=2.4 are coming out to be aperture length= 0.6 cm, aperture width = 0.1 cm, stub length=2.19 cm and for resonant frequency=8 Ghz and dielectric constant 4 the results are coming out to be aperture length=0.55 cm, aperture width=0.07 cm and stub length=1.5 cm. Similarly for dielectric constant 9.8 and 8 GHz resonant frequency the dimensions of the antenna come out to be apertaure length=0.21 cm, aperture width=0.04 cm and stub length=1.05 cm. The structure of Aperture-Coupled Microstrip Antenna has been fabricated for this desired frequency and dielectric constant 2.4 and its result is showing the convergence of return loss at exactly the same target frequency.