A wideband curved patch antenna with coplanar microstrip feeding

We present a wideband curved patch antenna with direct coplanar microstrip feeding. The patch substrate is derived from a solid of revolution generated using a parabolic profile that rests on a planar substrate. The proposed antenna takes advantage of the local increase in substrate thickness in the patch region to improve the reflection coefficient bandwidth. This design reduces substrate losses in comparison with conventional patch antennas printed on a thick dielectric substrate (key for bandwidth improvement). Indeed, in our case, the thick (curved) substrate is limited to the patch region, whereas the surrounding substrate can be made as thin as necessary, depending on the operating frequency, dielectric permittivity, and loss tangent. The presented configuration exhibits a reflection coefficient bandwidth of 32%, increasing the bandwidth of state-of-the-art patch antennas fed by coplanar microstrip lines by over 50%. The achieved operating bandwidth is even comparable to that of several coaxial probe-fed configurations, which, although undesirable for integrated implementations, typically offer a larger bandwidth due to greater flexibility in accessing the optimal feeding point, as seen in stacked and suspended-substrate patch antennas. The proposed configuration represents a significant advancement for patch antennas suitable for integrated implementation and intended as elements in planar arrays with direct coplanar microstrip feeding.