Design of Arrays of Linearly Polarized Patch Antennas on an FR4 Substrate: Design of a probe-fed electrically equivalent microstrip radiator.

A new strategy for designing probe-fed electrically equivalent microstrip radiators based on their electrical dimensions is discussed in this article. Radiators on a Flame Retardant 4 (FR4) substrate are synthesized for equivalent performance, aiming at lower H-plane cross polarization over the bandwidth and resistive input impedance at the operating frequency. The effect of mutual coupling is analyzed for two classical arrangements: side-by-side and collinear configurations. With the proposed strategy, a broadside collinear array of linearly polarized rectangular patches is designed to operate at the center frequency of the industrial, scientific, and medical (ISM) band (2.45 GHz) on a moderately thick FR4 substrate. The array is designed for low cross polarization in the H-plane and to comply with the specified directivity and side lobe level (SLL). Special attention to the beamforming circuit design leads to a radiation efficiency near 70%.