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This work presents a dual‐band (3.5/26 GHz) shared‐aperture antenna with high aperture reuse ratio and high isolation. The proposed 26‐GHz 4 × 4 substrate integrated waveguide (SIW) cavity‐backed slot array antenna consists of four hybrid TE130–TE310‐mode SIW cavities, which can simplify the design of feeding network. The radiating slots are unequally offset and inductance windows are added for good impedance matching. The entire structure of the 4 × 4 slot array antenna also functions as an equivalent TM10‐mode patch antenna at 3.5 GHz. The resonant frequency of the patch is fine‐tuned by inserting an air gap instead of enlarging the patch length, thus ensuring high aperture reuse ratio. To enhance channel isolation, the patch is designed with a bandpass filtering response centered at 3.5 GHz by introducing a stub‐loaded resonator feeding structure. For demonstration, a prototype of the proposed dual‐band antenna was fabricated and measured. The measured results show that the proposed antenna achieves excellent dual‐band performance, and its aperture reuse ratio and channel isolation are as high as 87.5% and 62 dB, respectively. [ABSTRACT FROM AUTHOR]

This letter presents a wideband sequential-rotated (SR) circularly polarized (CP) 2 × 2 filtenna array with multiple radiation nulls for high out-of-band rejection level. A pair of arc-shaped via walls is introduced to split the degenerate modes TE120/TE210 of the substrate integrated waveguide (SIW) cavity for achieving CP characteristics. SIW cavity modes TE110 and TE220 are generated at the lower and upper band edges, respectively, to form a bandpass filtering response. A CP patch is embedded to enhance the AR bandwidth and create an additional radiation null near the upper band edge. Four filtering slots are further introduced around the radiation aperture to create another radiation null in the upper stopband. This compact filtenna element can achieve high stopband rejection without external filtering circuits. A SR feed network is designed for 2 × 2 array implementation with enhanced gain and AR bandwidth. By integrating a simple filtering structure in the SR feed network, the out-of-band rejection level in the lower stopband can be significantly improved. For demonstration, a 2 × 2 SR filtenna array was fabricated and tested. Good agreements between the measured and simulated results are observed, with a wide AR bandwidth of 18% (centered at 10 GHz), a peak gain of 13.2 dBic, and out-of-band rejection levels of 33 dB and 23 dB in the lower and upper stopbands, respectively. [ABSTRACT FROM AUTHOR]

A compact T-complementary split-ring resonator (CSRR) antenna was developed. Different from traditional designs, the proposed CSRR functioned not only as a loading structure but also as a radiator. The operation of the T-CSRR antenna was similar to that of a slot antenna with a gain of 3.1 dBi. Because of the loading effect of the CSRR, the size of the radiator of the proposed antenna was only 0.14λ0 × 0.26λ0. The circuit sizes of the proposed T-CSRR antenna were 50% and 74% smaller than those of the traditional half-wavelength slot and T-shaped monopole antennas, respectively. For further gain enhancement, the performance of two feasible array arrangements, namely collinear and parallel arrays with 1 × 4 T-CSRR elements, were compared, which revealed that the parallel 1 × 4 T-CSRR antenna array can achieve a gain of 9 dBi at 2.45 GHz. [ABSTRACT FROM AUTHOR]

This paper presents a wideband 60-GHz antenna array with a dual-resonant slot-patch structure. A multilayered low-temperature co-fired ceramic substrate was used for antenna fabrication. A half-wavelength resonant slot was designed with a backed substrate-integrated waveguide (SIW) cavity to enhance the front radiation. The inverted microstrip center-fed structure was designed for easy signal excitation and superior impedance matching. A parasitic patch was also applied to enhance for bandwidth and gain enhancement. The effects of the SIW cavity-backed slot antenna with and without parasitic patches were empirically examined. The simulated results show that adding parasitic patches increased the resonance of the poles and improved antenna gain by 1.85 dB and bandwidth by 9%. A 2\,\times\,2 dual-resonant slot-patch antenna array was designed to further enhance the gain and bandwidth. The equipment setup for on-chip measurements of gain and radiation patterns was established. The measured S11 showed a wide bandwidth of 23%. The measured gain for the four-element antenna array was 9 dBi with slight fluctuations over the 57–64-GHz frequency range. [ABSTRACT FROM AUTHOR]