Planar antennas are a type of antenna that uses a flat plate mounted over a substrate as a radiator. Popular for their advantages like low cost and ease of fabrication and integration. However, they have low efficiency and suffer from spurious radiation from feeds, junctions, and surface waves. With a pursuit in low-cost and low-profile devices and due to other useful properties of the planar antennas, substantial work has been expended to enhance performance and surpass their limitations. This work presents three new antenna designs. The designs pretend to different applications. The first design presents an antenna sensor of dielectric properties of liquids, which uses a differential feed, and it can work in standalone mode or in a wireless system as a tag. The second designs consist of a dual-polarized array that manages common and differential excitation with a single balanced feed to generate each polarization. The last design is an Archimedean spiral antenna that generates beams with different orbital angular momentum orders at the same frequency.