An embodiment of an antenna array includes a cavity, signal couplers, and antenna elements. The cavity is configured to reinforce a reference signal (e.g., a standing reference wave) having a wavelength λ, and each of the signal couplers is configured to generate a respective intermediate signal in response to the reference signal at a respective location of the cavity. And each of the antenna elements (e.g., conductive patches) is configured to radiate a respective elemental signal in response to an intermediate signal from a respective one of the signal couplers. In operation, the elemental signals interfere with one another to form a transmission beam. Controlling the cavity to introduce phase differences between the antenna elements can allow a wider pitch between adjacent antenna elements without the need for large, costly phase shifters, where the pitch can approach its theoretical limit of approximately λ/2.