This work demonstrates a novel linear-circular wideband transmission type polarization converter for K-and Ka-band applications. The unitcell comprises primarily two FSSs on both sides of a thin dielectric substrate. For a linear polarized wave incidence, the transmitted wave is circularly polarized with a minimum 3 dB Axial Ratio (AR) from 19.08-37.27 GHz with a relative bandwidth of 64.56% and near 0 dB AR at two frequencies, 24.4 GHz and 34.8 GHz. The response is angular stable, almost up to 45° for different oblique incidences under Transverse Electric (TE) and Transverse Magnetic (TM) modes. Electric field patterns are also investigated to visualize the circular polarization rotation sense. The unitcell is compact with a structural periodicity of 0.102?L×0.134?L and thickness of 0.051?L, where ?L is the free-space wavelength corresponding to the lowest operating frequency. In addition, this design offers a bandwidth tunability feature by adjusting the stub's length at the back FSS. Since the design is miniaturized with 0.697(?3L/ 1000) volume and wideband stable angular performance made this a potential candidate for real-time satellite applications. © 2022 The Institute of Electronics Information and Communication Engineers (IEICE) of Japan.