2-GHz-Band Highly Accurate On-chip Polyphase filters is presented. A rotational asymmetric configuration is adopted to improve the gain mismatches and phase errors of quadrature signals. Shielded metal layer, which is between polyphase filters and substrate of wafers, could reduce the substrate crosstalk, which causes the gain mismatches of quadrature signals. The measured amplitude mismatches and phase errors of the polyphase filters are 0.05 dB and 1 degree, respectively. An image rejection mixer, which composed of a quadrature mixer and the polyphase filters, achieves 40dB image rejection.