Various techniques can be used to increase the gain of an antenna. For example, two or more uniformly distributed radiating elements can be used to create an antenna array. Array antennas have been successfully used for several years, but, unfortunately, they still suffer from a fundamental disadvantage: their feeding structure is inevitably more complex and may generate considerable losses (Horng & Alexopoulos, 1993). This is especially true at millimeterwave frequencies, where losses of 40% to 50% are not uncommon (Uchimura et al., 2005; Huang & Wang, 2006; Weily & Guo, 2009). This type of antenna is also somewhat limited by the mutual coupling of its individual elements (Mohammadian et al., 1989; Malherbe, 1989). These factors, combined with the greater quantity of materials required to manufacture an array, can be responsible for a longer time-to-market and higher production costs. Nevertheless, array antennas can offer useful functionalities such as electronic beam steering, introduction of nulls in specific directions (to counter a source of interference, for example) and suppression of secondary lobes by adjusting the phase and/or amplitude of the signals feeding the individual elements. However, if these characteristics are not necessary for a given system, an array antenna might not be the best choice, especially if complexity and cost are issues. The single element hybrid microstrip antennas presented in this chapter rely on a large electrical size to increase the gain. This is achieved by exciting a higher order mode inside a dielectric ring resonator. Two hybrid antennas that were designed and fabricated using this approach will be presented in this chapter. The first antenna is linearly polarized and the second has two orthogonal linear polarizations.