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In this paper, a new vertical half disc-loaded monopole antenna (VHDMA) with a horizontally top-loaded small disc is investigated. This antenna provides a similar radiation pattern compared to that of the simple monopole antenna, a wide input impedance bandwidth, and a very small size. The radiation pattern of the proposed VHDMA in the azimuthal direction is almost omnidirectional, which is usually required for the design of conventional monopole antennas. In addition, the simulation and measured results show that the return loss characteristic of the VHDMA provides a considerably large bandwidth even with a small radiating area. Comparing the measured results of a circular and a half-circular disc-loaded monopole antenna with a small disc mounted on the top, it is found that the half-circular disc-loaded monopole antenna with a mounted disc is comparable to the circular disc-loaded monopole antenna with respect to size and electrical performance. Surface wave and dielectric loss are often caused by the printed antenna with a high dielectric constant, whereas they are not generated by metallic planar antennas by realizing a good impedance matching and avoiding lossy matching units. This implies that antenna return loss is directly related to antenna radiation efficiency.