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The letter presents an extremely compact frequency-reconfigurable self-diplexing antenna based on fluidic channels for sub-6 GHz applications. The self-diplexing antenna is realized by using slot-loaded half-mode and quarter-mode substrate-integrated rectangular cavities, which takes an extremely compact size. The high isolation is obtained by employing the loading slot and the orthogonal feed lines, and three fluidic vias are bored from the bottom plane and filled with different dielectric liquids to enable frequency reconfigurability with little effect on the antenna radiation. To illustrate the antenna mechanism, the equivalent circuit, electric field distributions, and parameter studies are analyzed. For validation of the concept, an antenna diplexer is built and demonstrated. The constructed antenna prototype has a small footprint of 0.078$\lambda _{g}^{2}$ with 15% and 16% of reconfigurability in the lower and upper frequency bands, respectively. The measured results show 31.3 dB isolation, 3.28 dBi gain for the low band, and 4.5 dBi gain for the high band, respectively. A good consistency is obtained in between full-wave simulations and measurement.

This brief presents a novel design of a miniaturized self-triplexing antenna (STA) based on the shielded half-mode substrate integrated waveguide (S-HMSIW) for WiFi/WLAN/ISM-band applications. The S-HMSIW is constructed by assembling one row of vias and an open slot at the open-ended side of the conventional HMSIW. This configuration increases the quality factor and minimizes unwanted radiation loss, which allows for achieving high performance. A modified inverted U-shaped slot is created on the top plane of the cavity to form three different radiating patches, which are excited by three independent $50~\Omega $ microstrip feedlines to operate at three different frequencies. The proposed STA exhibits competitive features such as highly compact size ( $0.09\lambda _{g}^{2}$ ), high isolation (>33dB), and gain ( $>4.8$ dBi), which makes it suitable for handheld communication devices. The simulated and measured circuit responses are in good agreement.

This work introduces a novel frequency tunable self-diplexing antenna (SDA) design based on substrate integrated waveguide (SIW) technology. A modified A-shaped slot is employed on the cavity’s top plane, which is excited by two independent $50~\Omega $ microstrip feed lines to operate at each resonant frequency. The frequency flexibility of the proposed antenna allows for fine-tuning at each resonance frequency. The frequency flexibility has been achieved by employing the substrate’s air- and liquid-filled pockets. The proposed antenna can be configured to operate in the 3.5-3.8 GHz and 5.53-6.2 GHz bands, as demonstrated by the simulation results. With distilled water-filled pockets, the proposed antenna offers peak gains of 5.04 dBi and 5.26 dBi. The proposed SDA exhibits competitive features such as a highly compact size of $0.22\lambda _{g} ^{2}$ and high isolation (>27dB), which makes it suitable for handheld communication devices. The simulated and measured circuit responses are in good agreement.

This letter introduces a novel self-quadruplexing antenna (SQA) architecture using a substrate-integrated rectangular cavity (SIRC) for compact size, wide-frequency redesignability, and high isolation responses. The proposed SQA is developed by engraving two U-shaped slots (USSs) on the top conductor of the SIRC. The USSs are excited by employing four microstrip feedlines to achieve SQA characteristics. The operating frequencies can be tuned independently according to the assumed targets, with a wide tuning range from 2.3 to 7 GHz. The dimensions of USSs are meticulously chosen to achieve high isolation and compact size. An equivalent circuit is suggested to validate the proposed SQA. Finally, the SQA operating at 2.33, 2.96, 5.43, and 6.15 GHz is fabricated and validated. As compared to the earlier SQAs, the proposed antenna offers competitive performance with a compact size of 0.124λ2 (45.6% smaller than the most compact SQA reported in the literature), high isolation of 32.5 dB, and a wide tunable range from 2.3 to 7 GHz. Its measured gain is 4.31, 3.39, 6.12, and 4.34dBi at 2.33, 2.96, 5.43, and 6.15 GHz, respectively.

This paper communicates the design and experimental validation of dual-band SIW power dividers (single-stage and double-stage) with arbitrary power division. The dual-band power dividers are developed for WiMAX (3.5 GHz) and WLAN (5 GHz) applications. The proposed SIW power dividers are realized by a rectangular cavity, two rows of metallic-vias and one pair of unequal complementary split-ring resonators (CSRRs). Two resonating frequencies are produced below the waveguide cut-off frequency due to the unequal CSRRs etched-out on the top-surface of the cavity, which results in size reduction. To realize arbitrary power division, two output-ports are configured asymmetric with respect to input-port. The power division is varied by altering the distance between the two output-ports. Finally, two compact dual-frequency power dividers (single-stage and double-stage) working at 3.5 and 5 GHz are designed and validated through fabrication and measurement. The fabricated prototype exhibits dual-band operation, compact size (0.027λg2${\lambda }_{g}^{2}$), good magnitude imbalance, return loss and isolation.