The application performance of Synthetic Aperture Radar (SAR) instruments is generally limited in their capability to acquire radar images with both high-resolution and wide swath coverage. The available swath width of Polarimetric SAR (PolSAR) systems is even more restricted. Recently, a new PolSAR architecture called the Hybrid-Polarity (HP) architecture has attracted worldwide attentions. Compared with conventional linearly-polarized PolSARs, HP architecture based PolSARs have significant advantages such as wider swath coverage and lower hardware requirement. In this paper, the principles of the HP architecture, including system designs, system models and calibration methods are first reviewed. Two implementation difficulties of the HP architecture, concerning calibration issue and transmit configuration are illustrated. In order to overcome these problems, an improved version of the HP architecture is proposed. A prototype system based on this improved HP architecture developed for experimental validation is also introduced. In the latter part of this paper, applications suitable for the HP architecture based PolSARs are reviewed. Since the quadrature-polarimetric (quad-pol) data provided by an HP architecture based PolSAR system may be directly transformed into conventional linearly-polarized quad-pol data, this part of review is mainly focused on the corresponding dual-pol applications, i.e. Compact Polarimetry (CP) applications.