Characteristics of fundamental and first higher-order modes of microstrip-fed slot antennas

Detailed characteristics of the fundamental and the first higher order modes of the microstrip-fed slot antenna are presented. By means of an example, it is shown that for both of these modes the antenna´s operating frequencies cannot be simply determined from the electrical length of the slot antenna. These frequencies are also dependent on the length of the microstrip open stub and the coupling between the slot and microstrip line. The slot field distribution (including the magnitude and phase distributions) and the radiation patterns are given for the two modes. These information are significant in the design of slot antennas