Key-shaped slot loaded circular microstrip antenna for multi-band and broadband response

A novel design and analysis of circular microstrip antenna loaded with a key-shaped slot is presented. The introduction of key-shaped slot in the microstrip patch excites the additional modes which are orthogonal to each other, thus demonstrating multi-band dual polarized antenna characteristics. Also the next higher order modes manifest the broadband antenna response. For the optimization of the input impedance at the excited patch modes, a rectangular slot is incorporated in the patch design which realizes optimum bandwidth of 1 to 2% at each of the frequencies in 1000 MHz frequency range. The proposed dual-polarized antenna configuration yields broadside radiation pattern over all the resonant patch modes.