Investigation of inner shorted annular microstrip antennas

Ali Hussain Ali Yawer
Dr. AbdulKareem Abd Ali

Abstract: The inner shorted annular microstrip antenna (ISAMSA) is one of the different types of microstrip patches which are widely-used for their numerous advantages. These antennas have the advantage of controlling the radiation pattern by varying the inner and outer radius in the same mode .This thesis presents a study of the design parameters of inner shorted annular microstrip antennas such as the input impedance, the bandwidth, the radiation pattern and the modes that can be excited in this type of antennas using EM-Sight of Microwave Office 2000. The thesis also covers the subject of bandwidth enhancement using three methods:
• Using thick substrate
• Using a capacitive element to feed the patch
• Using capacitively-fed stacked patches.
It is suggested using of other methods of bandwidth enhancement such as slots method which has an advantage of the small size in comparison to the other methods.The maximum achievable bandwidth for ISAMSA was 21.88 % with respect to the resonance frequency which is 900 MHz using capacitively-fed stacked configuration. The bandwidth enhancement of inner shorted annular microstrip antennas presented in this thesis is considered as an attempt of bandwidth improving for these antennas.