Design Of Filtering Antennas Based On Substrate Integrated Waveguide

Miniaturization,integration and multifunction are the inevitable development trend of the radio frequency front-end.The filtering antenna is a device that is compatible with the radiation performance of the antenna and the filtering performance of the filter,which is conducive to the miniaturization.Substrate Integrated Waveguide(SIW)has the advantages of high quality factor,low loss,small size,and easy to integrate with planar circuits.The SIW filtering antenna has potential application value in the wireless communication system.Therefore,a filtering antenna with a quasi-elliptic response based on the SIW H-plane horn,a dual-band and a tri-band filtering antenna based on the SIW technology are designed in this thesis.The main contributions of this thesis are summarized as follows.1.A filtering antenna with a quasi-elliptic response based on SIW H-plane horn is presented.By exploiting the cross-couplings of trapezoidal dual-mode cavity embedded into the horn,two radiation nulls are introduced on the gain curve,showing a quasi-elliptic filtering response without the increase of horn size.Then,a modified transition is printed in front of the horn aperture on both sides of the substrate,which acquires wider impedance bandwidth and maintains a low back-lobe radiation throughout the bandwidth.A wide impedance bandwidth of 12.2%and a large front-to-back ratio(FBR)of more than20 d B are measured.The gain at the center frequency of 16.1 GHz is 12.6 d Bi.Two radiation nulls are introduced at 14.02 GHz and 17.98 GHz,where the radiation efficiency drops significantly to near zero,leading to high frequency selectivity.To the best knowledge of the author,it is the first discussion about introducing radiation nulls in filtering horn antenna.2.Dual-band/tri-band filtering antennas integrated with two-layer SIW resonator cavities are designed.(1)The lower layer of dual-band filtering antenna is a square SIW dual-mode resonator cavity with the perturbation metallized via,which works in orthogonal diagonal TE₁₀₂ and diagonal TE₂₀₁ modes in low-band and high-band respectively.There are two SIW radiation cavities etched slot in upper layer,which are responsible for energy radiation and introducing radiation null.The position of the radiation slot determines its resonant frequency and radiation null.The coupling slots are etched on the ground plane.The electric field of TE₁₀₂ mode is strong and TE₂₀₁ mode is weak around the low-band coupling slot,while the high-band slot is the opposite.(2)By changing the perturbation method of the metallized via,the lower square resonator cavity of the tri-band filtering antenna works in perturbation TE₁₀₁,diagonal TE₁₀₂ and diagonal TE₂₀₁ modes.The upper layer is increased to three radiation cavities,realizing three bands of filtering and energy radiation.The physical model of the tri-band SIW filtering antenna is processed and tested.The results show that the three passbands are 4.43-4.57 GHz,4.93-5.07 GHz and 5.38-5.52GHz.There are four radiation nulls at the frequencies of 4.41 GHz,4.74 GHz,5.32 GHz and 5.65 GHz on the gain curve,which improve the frequency selectivity.The positions of the radiation nulls are controlled by the radiation cavities independently.The frequency ratio of multiple passband is controlled by the perturbation metallized vias.So the design is flexible and simple.