Abstract
A fourth-order filtering patch antenna with a novel coupling structure is presented in this paper. Using the proposed coupling structure, both the balanced coupling feed and cross-coupling are realized. Two identical slots etched on the ground plane are utilized to excite the radiating patch with the reduced cross-polarization level. A short slot etched on the ground plane is employed for cross-coupling, which introduces two controllable radiation nulls with a steep roll-off rate. In addition, owing to the split-ring resonators and hairpin resonators, the improved impedance bandwidth is achieved with the fourth-order filtering response. To demonstrate the proposed design techniques, both the filtering antenna element and the low-sidelobe array are designed, fabricated, and measured. The measured results show that the proposed antenna has the impedance bandwidth of 12% (4.78–5.39 GHz) with the total height of $0.06\lambda _{0}$ , the cross-polarization level lower than −31 dB, and two radiation nulls with the suppression higher than 31 dB. For the low-sidelobe antenna array, wide impedance bandwidth is also obtained with the sidelobe level below −28.7 dB, the cross-polarization level below −34 dB, and the out-of-band suppression better than 25 dB.
Highlights
Filtering antennas have been widely researched owing to their advantages of integrated filtering characteristics, including the improved in-band selection, skirt roll-off rate, and high out-of-band suppression
While the upper radiation null moves to lower frequency compared to the simulated result, which is probably caused by the PCB fabrication and the assembly errors
This paper presents a balanced feed filtering patch antenna and its low-sidelobe array with a novel coupling structure
Summary
Filtering antennas have been widely researched owing to their advantages of integrated filtering characteristics, including the improved in-band selection, skirt roll-off rate, and high out-of-band suppression. To improve the in-band selectivity and out-of-band suppression of the filtering antennas, quasi-elliptic response with multiple radiation nulls are investigated by using some novel techniques [13]–[19] Inspired by the previous research works in [11] and [12], split ring resonators and hairpin resonators are used to excite the antenna radiating patch with improved impedance bandwidth Different from these works, by using the proposed novel coupling structure, balanced coupling feed method is used to reduce the cross-polarization of the antenna, which overcomes the problem of the cross-polarization deterioration due to the resonators and slots loading effects. Both of the filtering antenna element and the antenna array are designed, fabricated, and measured to validate the antenna design concept
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