In this paper we present a high-performance compact phased array antenna which is easy to integrate into mobile devices for 5G-and-beyond wireless telecommunications. The proposed design features high efficiency and wide-scan capabilities. The linear array consists of eight elements realized using substrate integrated waveguide technology in combination with two rows of metasurfaces that are used to optimize the transition towards free space for enhanced impedance matching characteristics. The integrated metasurface structure also enables a larger half-power beamwidth and wide-angle scanning at array level. A prototype has been realized using a dielectric substrate of Rogers RO4003C with relative permittivity of 3.55. The array is designed with an inter-element spacing of half-wavelength at 29.5 GHz and is characterized using dedicated millimeter-wave anechoic and reverberation chambers. The measurement results show that the proposed antenna array can scan from to with a gain fluctuation less than 3 dB in the frequency band of operation from 27 GHz to 29.5 GHz, and a measured total efficiency above 70 % with an uncertainty of 10% (95% confidence interval). Furthermore, when compared to the state-of-the-art, the proposed antenna provides a much wider scanning range while occupying a significantly smaller and compact volume.