This communication presents a simplified approach to design compact, wideband resonant-cavity antennas (RCAs) with partially reflecting surfaces (PRSs) made out of only a single dielectric material. Gain enhancement over a large bandwidth is obtained by using a high-permittivity dielectric PRS, which is flat at the bottom and has a stair-case profile on the top. The resulting RCA demonstrates a measured directivity-bandwidth product (DBP) of 5990 and a DBP per unit area of 1222. To the best of our knowledge, these figures are comparable to the figures for RCAs with transverse permittivity gradient PRSs, which require multiple dielectric materials. The measured radiation patterns of this RCA demonstrate low sidelobe levels (<−15 dB in the E-plane and −20 dB in the H-plane, with a peak directivity of 20.3 dBi), which are consistent across the half-power directivity bandwidth.