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A cylindrical open-ended substrate-integrated waveguide (SIW) cavity is studied and analyzed in this work. Two orthogonally oriented gaps are used to shrink the dimension of the cylindrical open-ended SIW cavity. Then, the miniaturized cylindrical open-ended SIW cavity is used to construct dual-band antennas. One dual-band antenna is realized by a composite structure that supports two independent modes: they are the half-circular loop mode for the lower band and the half quasi TE11(1/2) mode for the upper band. The other dual-band antenna is an aperture-shared structure: the lower band is related to the miniaturized cylindrical open-ended SIW cavity which works at the quasi TE11(1/2) mode; the upper band is characterized by suspending a concentric slot-loaded circular patch which works at the TM11 patch mode over the empty space of the miniaturized cylindrical open-ended SIW cavity. All modes involved in the two dual-band antennas, the half-circular loop mode, the half quasi TE11(1/2) mode, the quasi TE11(1/2) mode, and TM11 mode, are featured by broadside radiation. The structures of the two dual-band antennas are easy to fabricate by using conventional printed circuit board (PCB) techniques and can be integrated with other planar circuits. Compared to other open-ended cavity antennas, the proposed cylindrical counterpart shows a more compact size and lower profile. [ABSTRACT FROM AUTHOR]

A low pulling effect self-isolated harmonic active radiator operating around 28 GHz is proposed, investigated, and demonstrated in this article. Thanks to the inherent self-isolation property of a feedback loop of the proposed active radiator, a superiority of pulling effect mitigation, harmonic output, and simple structure is achieved. As part of the loop, a partially air-filled dual-mode substrate integrated waveguide cavity with a dielectric-loaded broadside slot is designed to realize the functions of resonators, harmonic diplexers, and antennas concurrently. The radiator oscillates at a fundamental frequency which is set by the first mode of the cavity resonator, and the generated second harmonic signal is extracted and radiated by the diplexer and antenna functions, respectively. Self-isolation is achieved because a pulling signal is attenuated by the synergetic effect of the reverse isolation and harmonic separation of the loop amplifier and diplexer, respectively. Measured results of a fabricated prototype show a maximum equivalent isotropic radiated power of 15 dBm at 28.15 GHz and a phase noise of −108 dBc/Hz at 1 MHz offset. Load pulling and injection pulling are reduced by a factor of 10 and 17, respectively, compared with an active radiator transmitting a fundamental signal around 28 GHz. Such a robust and compactly integrated structure is a good candidate for low-cost millimeter-wave Internet-of-Things applications in connection with identification, sensing, tracking, and communication. [ABSTRACT FROM AUTHOR]

A new decoupling scheme called dual-band coupled resonator decoupling network (CRDN) is presented. By properly designing the coupling coefficients between two pairs of coupled resonators, the network can effectively reduce the mutual couplings between two coupled dual-band antennas in two bands simultaneously. The new scheme is proved by a practical microstrip version of the device for two dual-band antennas working at 2.4 and 5.2 GHz frequency bands. A compact planar dual-band CRDN consisting of a pair of dual-band open-loop square ring resonators is proposed. The measured scattering parameters of two coupled antennas with and without the dual-band CRDN in free space (FS) and with hand phantom demonstrate that the isolation between the two antennas in both the low and high bands can be improved from 8 to 10 dB, respectively, to below 20 dB while maintaining a good matching performance. The total efficiency and envelop correlation coefficient for the decoupled antennas show a significant improvement as compared to the coupled antenna case. The proposed dual-band CRDN scheme is easy to be implemented in an integrated device, and is very attractive for practical multiple input and multiple output (MIMO) applications. [ABSTRACT FROM PUBLISHER]

A new microwave device called the cascaded type of coupled resonator decoupling network (C-CRDN) is proposed in this paper. The four-port device can be used to reduce the interference between two radio systems that work in adjacent or even contiguous frequency bands. A C-CRDN is cascaded between the two antennas to be decoupled and the I/O ports of their radio systems, respectively. The coupling matrix of a C-CRDN can be designed to meet the required isolation and return-loss specifications. To prove the concept, a fourth- and sixth-order C-CRDN using coaxial combline cavities are designed, fabricated, and measured according to the characteristics of a testing array that consists of two high-gain sleeve dipoles working in the adjacent time-division long-term evolution and wireless fidelity bands. The measured results have demonstrated that the proposed C-CRDN can effectively mitigate the coexistence interference between the two collocated systems by providing at least 20-dB isolation improvement and enhanced matching performance. The proposed technique is general and can find many applications in heterogeneous wireless systems. [ABSTRACT FROM AUTHOR]