This article proposes an asymmetric dual-polarized microstrip antenna (DPMA) with single-dimension-constraint resonant frequencies for orthogonal polarizations. Different from regular DPMAs, the orthogonal modes of the proposed antenna are only determined by a single dimension, breaking the symmetry limitations of dual-polarized (DP) antennas and leading to the irrelevant dimension for optimized radiation properties of gain and beamwidth. The proposed antenna consists of a vertical-slot-etched rectangular patch with two groups of shorting vias and a horizontal slot on the ground. By feeding two ports with differential or common modes, the antiphase TM10 or antiphase epsilon-near-zero (ENZ) modes are excited for orthogonal polarizations in extremely asymmetric structures. As an application example for mobile terminals, a circular-polarized (CP) antenna with a 90°-phase-step two-way power divider is constructed and integrated onto the upper metal bezel with a high aspect ratio for satellite communications. The measured results show an overlapped bandwidth of 40 MHz and beamwidth beyond 80° in a volume of 0.39×0.026×0.0065 λ30 , exhibiting the unique design approach for DP or CP antennas in extremely asymmetric platforms.