Optical phased array (OPA) based on silicon photonics is considered as a promising candidate for realizing solid-state beam steering. However, the high refractive index contrast of the silicon waveguides leads to conventional silicon based OPA suffering from large random phase errors, which require complex post-processing such as time-consuming phase calibration. We propose and demonstrate a calibration-free silicon OPA with optimized optical waveguides width as well as the compact 90° waveguide bends beyond the single mode regime. By using grouped cascaded phase shifters, it is able to reduce the number of control electrodes from N to log2(N). A 16-channel OPA has been demonstrated with continuous beam steering over the field of view controlled by only four control voltages without any calibration.