Stacked Microstrip Patch Antenna With Defected Ground Structures For WLAN and WIMAX applications

Abstract

During the last few years wireless technology has gained so much importance and has been rapidly and widely developed in the modern world. For further development in future the aim of the communication devices is to provide speech, image and data communications anywhere and anytime all over the world. This shows that for communication purpose in future the antennas must be able to cover all the possible frequency bands. For this it should meet the requirements of wideband or multi-band. With the increase in number of frequency bands the design of antennas become more difficult. For miniaturisation in wireless technology the size of the antenna should be so small that it can be easily placed in the system. For the transmission and reception of more information there is requirement of large bandwidth. Therefore researchers are working to improve the bandwidth of the antenna. The presented work includes the simulation of aperture coupled microstrip patch antenna using transmission line model. The effect of various antenna parameters is studied such as length (L), width (W) and effective dielectric constant of the material. The effect of using stacked antennas is also studied. The substrates with lower dielectric constant are preferred over substrates having high dielectric constant because the lower dielectric constant substrates give more bandwidth which is the main necessity. The patch is placed on the substrate layer and has different shapes like rectangular and circular etc. but rectangular shape is generally preferred. The antenna length is nearly half of the wavelength in dielectric and it gives the resonant frequency of the antenna. For the designing procedure, the selection of the length and width of the patch and the dimensions of feedline are the major parameters. Therefore, in the following thesis the design of simple aperture coupled microstrip antenna operating at 5.8 GHz having bandwidth 340 MHz for WLAN application is discussed and simulated using CST (Computer Simulation Technology) Microwave Studio 2010. The parametric study of antenna is done and the physical parameters are examined such as stub length and slot in the ground plane. Also comparison of a stacked patch aperture coupled microstrip antenna and single layered aperture coupled microstrip antenna resonating at 5.8GHz providing 80% bandwidth enhancement is discussed. A dual band aperture coupled microstrp stacked patch antenna with DGS covering the WLAN and WiMAX bands is simulated and then fabricated in this thesis. Various parameters like return loss, Gain, Directivity, VSWR, Bandwidth, input impedance and iv operating frequency are discussed. The dual band antenna is fabricated and it has been tested using VNA. The results of testing are compared with results of fabricated antenna. In future tests can be carried out to implement the designed antenna in practical scenario