This paper presents an innovative switched-beam architecture for a low-cost mobile-terminal antenna, suitable for linear-polarized satellite communications systems. This antenna concept can produce twelve adjacent sector beams that cover the full azimuth field of view with a directivity of 11 dB, using the same physical aperture. This radiating aperture consists of slot-coupled patch antennas arranged in a specific lattice, inspired by the so-called tri-hexagonal tiling of the plane. An innovative beamforming-network layout, based on series feeding, is devised to reduce the circuit-board real estate required by the different beams. A prototype producing two beams has been built, and its radiation pattern has been measured, in order to demonstrate the feasibility of the approach.