Two types of antennas based on the open-ended substrate integrated waveguide (SIW) resonator are presented and investigated in this study. To understand the operation mechanism of these antennas, the open-ended SIW resonator is analysed by two different approaches. The waveguides theory is used in the first approach and the transmission line-based metamaterials theory is used in the second approach. Using the above-mentioned resonator and with regard to its analysed characteristics, two antennas are designed, simulated and fabricated. Both of them operate at the TM110 mode of the resonator. The measured operating frequency, bandwidth and peak gain of the first antenna are 8.46 GHz, 2.7% and 7.3 dBi, respectively. The second antenna which is the compact version of the first one has nearly the same operating frequency with smaller size. Its measured operating frequency, bandwidth and peak gain are 8.38 GHz, 5.9% and 4.8 dBi, respectively. The proposed antennas have advantages of low cross-polarisation radiation, low profile, compact size, easy fabrication and easy integration with other circuits.

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