This paper proposes design of a cavity-backed patch antenna for broadband applications using substrate integrated waveguides (SIW). The actual antenna dimensions used for the design results in X-Band performance. By using a rectangular SIW based cavity under a square ring radiating element in the antenna and slightly optimising the width and length, the frequency band was reduced. This reduction in turn resulted in the miniaturization of the antenna. This leads to a multi-band performance with circularly polarised radiation in the Wi-Fi (802.11a) range specifically from 4 to 6 GHz, where the return loss is below -15dB. The antenna exhibits unidirectional radiation pattern and the SIW helps in reducing the side lobes and effectively increasing the efficiency. © 2019 IEEE.