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A compact millimeter-wave (mm-wave) dual-band filtering patch antenna is presented. It is fed by a new multinull resonator, composed of a single-layer substrate integrated waveguide (SIW) cavity-backed slot. This multinull resonator can produce two resonant modes and three radiation nulls. With the load of a radiating patch, another radiation null can be generated between the two operating bands. In addition, the radiating patch produces two patch modes by introducing an H-shaped slot and four shorting pins. Therefore, a second-order bandpass filtering response is obtained for each operating band. Owing to this new multinull resonator, two controllable radiation nulls are realized beside each band, showing high-frequency selectivity and an out-of-band suppression level of more than 18 dB. The antenna prototype, with only two substrate layers, has antenna gains of 8 and 7.5 dBi in the 28- and 39-GHz bands. Furthermore, the dual-band filtering patch antenna is extended to a $2\times 2$ multiple input/multiple output (MIMO) antenna. With the aid of $\pi $ -/L-shaped parasitic strips, the isolation of the E-plane MIMO is enhanced by 5 dB. The isolations between any two-antenna elements are higher than 20 dB for the two passbands.

To improve the appearance and performance of consumer WiFi routers, the polarization-diversity omnidirectional glass antenna is used in place of the traditional space-diversity monopole antenna. Different images are engraved on the glass antenna to attract consumers. Since the cost is a major concern of consumer electronics, a new feeding circuit design that needs only a single PCB is investigated, which is in contrast to the reported design that requires two PCBs. For the first time, this paper studies the throughput performance of the glass antenna in a real indoor environment. Its throughput is compared with that of a conventional commercial space-diversity monopole antenna in our lab environment. Experimental results show that our design has an average improvement of more than 10%, with the maximum improvement given by 87.5%. Measurements were done to verify the simulations, and good agreement between the measured and simulated results is obtained. Also, a 3D-printed casing is used to package the WiFi router. The design details are given in the paper.

A single-layer filtering microstrip patch antenna with gain enhancement in the boresight direction is proposed. The antenna mainly consists of an outer ring patch and an inner rectangular patch with six shorting vias. Operating at the higher order TM12 mode, the rectangular ring patch is used for the first time to simultaneously provide an enhanced gain in the passband and a radiation null at the lower band edge. On the other hand, the rectangular patch placed inside the ring patch introduces another radiation null at the upper band edge due to the embedded structure (topology). In addition, the fundamental TM10 mode of the rectangular patch is excited, desirably increasing the bandwidth of the passband. Consequently, both good radiation and filtering performance is achieved, without using any filtering circuits. For demonstration, an antenna prototype is designed, fabricated, and measured, which operates at the 5.2 GHz WiFi band and suppresses the interference of 5.9 GHz Internet of Vehicles band. The prototype features an impedance bandwidth of 6.9%, a peak gain of 9.0 dBi, and an out-of-band radiation suppression level of over 16 dB.

A wideband and high-gain millimeter-wave (mm-wave) filtering antenna is proposed for 5G applications. The antenna mainly consists of a substrate-integrated waveguide (SIW) cavity with a rectangular slot, four identical rectangular patches with metallic vias, and a parasitic strip. Due to the perturbation of the slot, the SIW cavity is able to generate two resonant modes in the passband and simultaneously a radiation null at the lower bandedge. The via-loaded patch can generate an additional resonant mode to increase the operating bandwidth and further enhance the in-band gain of the antenna. In addition, the parasitic strip can offer the fourth resonance in the passband and, in the meantime, generate another radiation null at the upper bandedge due to its interaction with the rectangular patches. Consequently, a quasi-elliptic bandpass filtering response is achieved, along with enhanced impedance bandwidth and boresight gain. For demonstration, a prototype operating in the 5G mm-wave band is fabricated and measured. The prototype shows an impedance bandwidth of 18.4%, an average gain of 10.1 dBi, and an out-of-band suppression level of about 20 dB in the stopbands.