Dual frequency microstrip patch antenna, reduced in size by use of triangularly arranged peripheral slits

A technique for size-reducing a two-port, meandered-square patch antenna, which is intended for dual frequency operation, is investigated in this paper. Forty slits of varying height have been cut on the perimeter of the antenna, ten on each side, to reduce the operating frequency. In order to achieve dual-frequency operation, the central slits in the x- and y-dimensions of the antenna are unequal in height and so does the difference in height, i.e. the height step, between any two adjacent slits on the same side. The effectiveness of the aforesaid technique has been tested by simulating, designing, and measuring a prototype, square, patch antenna with two ports, which resonates at 1.75GHz and 2GHz. Measured results have verified that the return loss at port #1 is below -15dB, whereas at port #2 it is below -25dB; the isolation between the two ports is below -25dB. The slits do not affect the gain or the radiation pattern (co- and cross- polar) of the antenna. The area of our prototype, square, patch antenna, thus meandered, is 43.5% smaller than that of a two-port, orthogonal patch without slits, which resonates at the very same frequencies.