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In this paper, a design of a low profile cavity backed antenna consisting of bilateral slots is developed for generating two frequencies. Here, the whole antenna including substrate integrated waveguide (SIW) cavity is constructed from only one substrate with the height of 0.026λ 0. The long transversal slot at the ground plane is excited by TE 210 mode of the cavity and produces one hybrid mode resonance at 9.85 GHz. When the short transversal slot cut is incorporated in the top portion of the cavity, TE 310 mode is perturbed, which results in generating an additional hybrid mode resonance at 14 GHz. Both these hybrid modes help to create a dual-band response. A sample of the proposed design is fabricated, and it has been verified experimentally that the bandwidths of the proposed design are 530 MHz (5.48%) and 440 MHz (3.15%) at lower and higher resonant frequencies, respectively. The antenna renders measured peak gains of 6.62 dBi and 6.44 dBi at 9.85 GHz and 14 GHz, respectively. The cross-polarization level of maximum −20 dB and same polarization planes are obtained at both the operating frequencies.

In this article, a new approach has been demonstrated for the bandwidth enlargement of a substrate integrated waveguide (SIW) cavity-backed antenna. The proposed structure employs bilateral slots, instead of unilateral slots, which is a distinct approach, in contrast to traditional cavity antennas. The proposed antenna embodies SIW cavity with a height less than 0.017λ 0 and thus holds a low-profile planar geometry, while retaining lower losses and light weight. The non-resonant slot, at the bottom plate, produces two-hybrid modes (odd TE 210 and even TE 210 ). The quality factor (Q) of these hybrid modes is greatly reduced by loading the resonant slot cut at the top metallic plate of the SIW cavity which leads to achieving a wideband response. A sample is fabricated and investigated at X-band. It is shown that the experimental results are well-matched with the simulated ones. The measured impedance bandwidth of the proposed antenna is 860 MHz, (8.6%). Moreover, it renders a maximum gain of 6.56 dBi at 9.78 GHz and 6.75 dBi at 10.35 GHz, within the operating bandwidth. The cross-polarization radiation levels of maximum −26 dB and −28 dB are obtained at the corresponding resonant frequencies, respectively.

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In this paper, a half-mode substrate integrated waveguide (HMSIW) semi-circular cavity backed antenna, using two higher order modes (TM 210 and TM 020), has been proposed for dual-band operation. A semicircular slot is engraved on the top of the HMSIW structure forming a cavity that is fed by co-axial feeding to get impedance matching with the line. The theoretical operation of TM 210 and TM 020 modes is explained using the simulation tool. The antenna parameters such as reflection coefficient, gain, and radiation patterns have been measured for the fabricated antenna. The antenna radiates in two bands, in which the first band center frequency is 8.5 GHz, and the second band center frequency is 10.6 GHz. Peak gains at boresight direction are around 7.5 dBi and 6 dBi, respectively.