In this article, a novel design approach to tripleresonant, circular sector patch antenna with wideband null frequency scanning functionality is advanced. At first, the operation principle of null frequency scanning functionality is revealed by the simplest, straight electric dipole under multiple resonances. Then, a triple-resonant circular sector patch antenna is designed based on a double-wavelength prototype magnetic dipole by synthesizing it usable resonant modes. As synthesized, the resonant TM12/17,1, TM36/17,1, and TM60/17,1 modes within a 255◦ circular sector patch radiator can be simultaneously excited, properly perturbed, and then used to realize a wideband null frequency scanning functionality. Next, different prototype antennas are designed and fabricated and experimentally verified the design approach on a single layered air substrate. As finally demonstrated, the antenna can exhibit a null frequency scanning range from θ = +35◦ to −60◦ within an available radiation bandwidth (ARB) of 24% (i.e., 2.20–2.80 GHz) for null depth smaller than −10 dB.