A dual-resonant, semi-circular sector patch antenna is properly incorporated to a planar self-balanced magnetic dipole antenna and lead to a novel triple-resonant, dual-band planar antenna which has characteristics of wide E-plane beam width and stable gain at both bands in this work. Design approach with a group of approximate closed-form formulas is proposed to initially calculate value of the main parameters of the antenna. In the numerical and experimental verifications, it is demonstrated that the antenna operates at 2.4–2.48 and 4.75–5.95 GHz for reflection coefficient smaller than −10 dB. The antenna exhibits unique characteristics of wide E-plane half-power beamwidths of 91°/115°, and stable in-band average gain of about 4–5 dBi at both bands owing to the nearly complementary frequency dispersive characteristic of the radiation pattern in both principal-cut planes. As seen, the antenna can cover wide wireless communication spectra, which makes it promising to get applications in future developments of multi-functional WLAN/RFID antennas, C2C communication antennas, and light-weight, compact UAV antennas without bulky reflectors.