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A broadband antenna with simultaneous flat gain and filtering characteristic is proposed in this paper. To achieve a flat gain response, rectangle slots and a bandpass filter are loaded on the antipodal Vivaldi antenna. The loaded rectangle slots adjust the phase of the surface currents to widen the operating bandwidth, as well as reduce the far-field radiation cancellation of the reverse currents in the end-fire direction, thus improving the gain. In addition, a bandpass filter is added to the antenna to further equalize the currents amplitude and suppress out-of-band signals. The measured results show that the proposed antenna achieves an impedance bandwidth of 101.9% (3.99–12.28 GHz) and an out-of-band suppression level of 15.5 dBi in the upper stopband. What is more, an extremely low gain fluctuation of ± 0.464 dBi is realized in the 4–12 GHz. Compared with conventional broadband antennas, the antenna features simple structure and better performance, which achieves broadband with simultaneous flat gain response and filtering characteristic. The proposed antenna may be applied in high-precision radar sensing system. [ABSTRACT FROM AUTHOR]

In this paper, a dual-band filtering antenna with independent predetermined frequencies and low cross-polarization levels is proposed. In order to realize the independent control of frequencies of two radiation passbands, multiple additional structures such as rectangular slots, rectangular parasitic patches, and U-shaped slots are integrated on the traditional rectangular patch antenna to introduce new resonant modes and radiation nulls to the antenna, simultaneously. Since the generation structures of each frequency point are different, they do not affect each other. Besides, to obtain low cross-polarization levels, each additional structure is carefully adjusted such that the current vectors of each resonant frequency along the cross-polarized direction are quite weak. The proposed antenna operates in the 5G sub-6G (4050–4294 MHz) and the Wi-Fi 5.8 GHz band (5700–5920 MHz), and achieves cross-polarization levels of −37.8 and −36.8 dB in the lower and higher frequency bands, respectively. Compared to other multi-band filtering antennas, the proposed one has the advantages of independent predetermined frequencies and lower cross-polarization levels. [ABSTRACT FROM AUTHOR]