Fig. 1. Structure of designed antenna

Fig. 2. Designed process of proposed antenna. (a) SIW cavity; (b) antenna 1; (c) antenna 2

Fig. 3. Variation in reflection coefficient of different structures with frequency

Fig. 4. Variation in real part of the input impedance with frequency

Fig. 5. Electric field distribution in SIW cavity. (a) Frequency of 13.04 GHz; (b) frequency of 15.00 GHz

Fig. 6. Electric field distribution in antenna 1 cavity. (a) Frequency of 12.26 GHz; (b) frequency of 14.47 GHz

Fig. 7. Electric field distribution in antenna 2 cavity. (a) Frequency of 12.16 GHz; (b) frequency of 14.86 GHz

Fig. 8. Variation in reflection coefficient with feed gap width of embed microstrip line

Fig. 9. Variation in reflection coefficient with insert length of microstrip line

Fig. 10. Variation in reflection coefficient with length of triangular complementary ring groove

Fig. 11. Variation in reflection coefficient with width of triangular complementary ring groove

Fig. 12. Radiation direction of proposed antenna at 12.00 GHz

Fig. 13. Radiation direction of proposed antenna at 14.80 GHz