Analysis and design of broadband planar antenna

A planar antenna is proposed that can be matched to the intrinsic impedance of an ordinary coaxial cable (50 /spl Omega/) without using parasitic elements or balun circuits. Specifically, modification of the internal notch shape of aperture of the rectangular loop antenna element is attempted without deforming the outline of the element; control of the input impedance becomes possible and bandwidth, for S11 less than or equal to -10 dB, can reach about 50% at the desire frequency, f/sub 0/. Moreover, the proposed antenna demonstrates gain more than equal to the one wavelength square loop antenna. An antenna was fabricated for trial and studied both by experiments and by FDTD analysis.