A novel compact all planer-fed self-triplexing patch antenna is designed and demonstrated for triple-band operation simultaneously. The model is comprised of one substrate integrated waveguide (SIW) cavity, three planar ports, and one modified I-shaped slot. The proposed antenna is designed in a simple three-step method to achieve improved self-triplexing property. In the first step, a rectangular slot is created and its position is altered to obtain initial isolation (> 20 dB) between any two ports. Secondly, the same slot is modified to an I-shape like, which creates three patches facing three different ports and radiates at three different frequencies (4.14 GHz, 6.1 GHz, and 8.32 GHz) with minimum isolations above 28.4 dB. In the third step one input-port is off centered to obtain port isolation trade-off so that isolation between any two ports is better than 30.8 dB. Importantly the proposed design also supports easy individual frequency tuning using single variable. For demonstration purpose the antenna is fabricated and characterized. The proposed planar antenna is very simple, compact and feasible for handheld microwave devices.

In this letter, a shielded quarter-mode substrate integrated waveguide (S-QMSIW)-based self-diplexing antenna for closely spaced bands and high isolation is proposed. A ${\rm Y}$ -shaped slot is engraved on the top of the metal to enhance the extra capacitance of the QMSIW cavity resonator; thus, it helps to reduce its size as well as achieve dual-band characteristics. The S-QMSIW resonator is then excited by two orthogonal microstrip feed lines in the full-wave electromagnetic simulator (high-frequency structure simulator) to operate at two distinct frequencies (3.47 and 3.84 GHz). A transmission zero is generated at 3.56 GHz to provide port isolation better than 47 dB. In addition, a lumped circuit model is predicted to validate the antenna structure. To demonstrate the proposed concept, an S-QMSIW-based self-diplexing antenna is designed, fabricated, and tested. The recorded peak gains of the antenna are 4.8 and 5.7 dBi at 3.47 and 3.84 GHz, respectively. At each band, the antenna front-to-back ratio is greater than 20 dB. The circuit size of the proposed antenna is very compact (0.15 $\lambda _g^{2}$ ).

In this communication a compact planar-fed substrate integrated waveguide (SIW)-based self-multiplexing (SM) antenna for hexa-band operation is proposed for the first time. Six different patches with planar $50~\Omega $ feed lines are designed and attached to the top side of the rectangular SIW cavity. The antenna operates at six different frequencies (5.33, 5.76, 6.31, 6.86, 7.34, and 7.8 GHz) simultaneously. The antenna attains 4.5, 4.94, 4.9, 5.12, 6.12, and 6.6 dBi peak gain at respective resonant frequencies. Port relocation, stepped patches, and additional vias are exploited to maintain isolation (>23 dB) between any two ports. The front-to-back ratios (FTBRs) are between 10 and 20 dB and Co-pol to Cross-pol ratios are between 10 and 29 dB. The design supports single-variable independent frequency tuning for all six patches and eligible for wide range of applications. The proposed design is fabricated and results are validated through measurement. The antenna is suitable for planar microwave devices.

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 Ω 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 0.22λg and high isolation (>27dB), which makes it suitable for handheld communication devices. The simulated and measured circuit responses are in good agreement.

This article presents two novel architectures of dual-band substrate-integrated waveguide (SIW) bandpass filters (BPFs). Initially, two identical open-loop ring resonators (OLRRs) were coupled face-to-face on the top of the SIW cavity to realize a dual-band single-pole BPF. To obtain two-pole dual-band characteristics, two OLRRs resonant units were assembled horizontally within the top metal layer of the SIW, which is a technique used for the first time in the literature. For demonstration purposes, two types of SIW filters loaded with OLRRs were designed and fabricated. The proposed filters feature an extremely compact size, a low insertion loss, and good selectivity. The single- and two-pole filters have an overall size of 0.012${\lambda }_g$${}^2$ and 0.041${\lambda }_g$${}^2$, respectively. The simulated and measured circuit responses are in good agreement.

This letter presents the design of compact triple- and quad-band power dividers (PDs) based on substrate integrated waveguide (SIW) technology. The proposed PDs are designed as a rectangular cavity, one pair of unequal complementary split-ring resonators (CSRRs) and U-shaped slots (USSs). Initially, a dual-frequency SIW PD is implemented using unequal CSRRs on the top surface of the SIW cavity. This dual-frequency PD is converted into triple-band and quad-band operations by employing USSs on the bottom surface of the cavity. The center frequencies of the proposed PDs are controlled by varying the dimensions of CSRRs and USS. To demonstrate the proposed concept, triple- and quad-band PDs are designed, fabricated, and tested. The measured responses are very much consistent with the simulated one. The overall sizes of the proposed triple- and quad-band PDs are 0.03λ _g ² and 0.02λ _g ² , respectively. The proposed PDs feature compact size, triple- and quad-band operation, good return loss, and isolation.