AbstractIn this article, a circular substrate integrated waveguide (CSIW) antenna is proposed. Conventional log‐periodic antenna offers unidirectional and bidirectional radiation patterns that are used in two‐way communications provide moderate gain. The proposed antenna has the advantages of high gain, compact size, low loss, easy to integrate the high frequency components, and it also operates at L band and S band frequencies. To improve the gain and radiation characteristics, circular SIW is introduced and integrated with log‐periodic antenna. The comparison between simulated and measured results shows that the proposed antenna used for wireless communications both in L (1‐2 GHz) and in S (2‐4 GHz) frequency bands. It provides the bandwidth of 9.1%, 10%, 21.6%, and 11.03% and also the realized gain of 6.62 dB, 15.8 dB, 3.9 dB, and 8.3 dB is obtained in 1.2 GHz, 1.6 GHz, 2.4 GHz, and 2.9 GHz, respectively.