A quarter-wavelength shorted microstrip antenna with a slot for dual-frequency operation

A novel dual-band internal antenna similar in size to the single-band internal antenna for cellular handsets is proposed. Our approach to realize a small and low-profile dual-band internal antenna is to use the dominant mode (TM10 mode) and the higher-order mode (TM30 mode). In order to use this approach for recent dual-band cellular systems it is necessary to lower the resonant frequency of the higher-order mode (TM30 mode). This motivated our development of a new antenna configuration with a slot on the radiation element of a quarter-wavelength shorted microstrip antenna to lower the resonant frequency of the TM30 mode. In this paper, the experimental and the analytical results for this antenna are presented. In the results, by adjusting the location and the length of the slot, the dual-frequency operation can be achieved with the frequency ratio (TM30 mode/TM10 mode) from 2 to 3. In addition, the enhancement of bandwidth is presented.